animals

Article

Environmental Impact and Relative Invasiveness ofFree-Roaming Domestic Carnivoresmdasha NorthAmerican Survey of Governmental Agencies

Ana Lepe 1 Valerie Kaplan 1 Alirio Arreaza 1 Robert Szpanderfer 1 David Bristol 2 andM Scott Sinclair 1

1 SeaSearch Biological Surveys 1275 S Lee Street St David AZ 85630 USA analepeoutlookcom (AL)shinyhappygothgmailcom (VK) alirioarreazagmailcom (AA) rszpandoutlookcom (RS)

2 Statistical Consulting Services Winston-Salem NC 27127 USA davidstatistical-consulting-servicescom Correspondence pancotverizonnet

Received 21 August 2017 Accepted 9 October 2017 Published 14 October 2017

Simple Summary This paper reports on a survey that explores the impact of three non-nativedomestic carnivoresmdashdogs cats and ferretsmdashon the native wildlife of the United States (US) andCanada Government agencies were asked to document the number and frequency of sightings andthe degree of concern resulting from free-roaming animals on urban suburban rural recreationalareas and wildlands in their jurisdictions Results confirm the existence of free-roaming cats anddogs throughout North America as well as their profound impact on native wildlife with cats beingthe major offenders Except for an occasional stray free-roaming ferrets were ldquoneverrdquo or ldquorarelyseenrdquo no agency reported that ferrets caused environmental harm This is the first study to comparethe relative impact of free-roaming dogs cats and ferrets It shows differences in how these threeanimals react to novel environments For the US and Canada free roaming cats and dogs meet thedefinition of an ldquoinvasiverdquo species whereas ferrets do not However the way we as a society viewthese animals our attitudes and perceptions may influence how governmental agencies manage andcontrol them

Abstract A survey of the United States and Canadian governmental agencies investigatedthe environmental impact and relative invasiveness of free-roaming domestic non-nativecarnivoresmdashdogs cats and ferrets Agencies represented wildlife fish game natural orenvironmental resources parks and recreation veterinary and human health animal controland agriculture Respondents were asked to document the number and frequency of sightingsof unconfined animals evidence for environmental harm and the resulting ldquodegree of concernrdquoin their respective jurisdictions Results confirmed the existence of feral (breeding) cats and dogsdocumenting high levels of concern regarding the impact of these animals on both continental andsurrounding insular habitats Except for occasional strays no free-roaming or feral ferrets werereported nor were there reports of ferrets impacting native wildlife including ground-nesting birdsor sensitive species This is the first study to report the relative impact of free-roaming domesticcarnivores Dogs and cats meet the current definition of ldquoinvasiverdquo species whereas ferrets do notDifferences in how each species impacts the North American environment highlights the complexinteraction between non-native species and their environment Public attitudes and perceptionsregarding these species may be a factor in their control and agency management priorities

Keywords cat dog domestic carnivore ferret environmental impact government invasivenon-native species North America survey

Animals 2017 7 78 doi103390ani7100078 wwwmdpicomjournalanimals

Animals 2017 7 78 2 of 18

1 Introduction

Concern over the impact of non-native species on novel ecosystems has been a major focus ofboth conservationists and governmental agencies world-wide which has resulted in the mandatedmonitoring and management of non-native species [1] Historically humans migrating to newgeographic locations brought their animals and plants with them resulting in large-scale introductionsof non-native species to novel ecosystems These activities created both competition with and in manycases destruction of native species and habitats Concepts of ldquonativenessrdquo and ldquoalienrdquo species did notarise however until the 19th century later engendering a global discussion of ldquobiologic invasionsrdquoexemplified by Charles Eltonrsquos 1958 treatise The Ecology of Invasion by Animals and Plants [23] Currentlyan ldquoinvasiverdquo species is defined as ldquoany species not native to the ecosystem likely to cause economic orenvironmental harm or harms human healthrdquo [4] Today Canada and the United States are among thenations to develop positions regarding ldquoinvasiverdquo species along with mandates to control them [45]

With the exception of the Alaskan malamute the domestic carnivoresmdashthe dog (Canis lupusfamiliaris) cat (Felis silvestris catus) and ferret (Mustela putorius furo)mdasheach meet the definition ofldquononnativerdquo species [6ndash11] The ferret (also ldquoEuropeanrdquo ferret) should not be confused with the wildblack-footed ferret (Mustela nigripes) one of North Americarsquos most endangered mammals [12]

In 1993 a US Congressional report ldquoHarmful Non-Indigenous Species in the United Statesrdquo namedferal dogs and cats as ldquotwo of the three most common subjects of wildlife control effortsrdquo of US nationalparks and wildlife reserves the ferret was not mentioned [13] In the US alone cats reportedly kill13ndash40 billion birds and 63ndash223 billion mammals annually resulting in economic damages around$14 billion (USD) [14ndash24] All 50 states report the existence of feral dogs with resultant damage to bothnatural and agricultural resources estimated at more than $620 million annually [212225] In a 10-yearreview by Bergman et al the impact from feral dogs was seen not only in their predation but also intheir causing behavioral changes in both wildlife and livestock and their role in disease transmissionto other animals and to humans [25]

Although it is legal to own a dog or cat throughout the North American continent and thesurrounding islands some jurisdictions prohibit ferrets These include the states of Hawaii andCalifornia and certain cities [26ndash29] As a basis for restricting the ferret government agencies citereports from New Zealand and other island nations where European settlers released thousandsof ferrets cats and other domestic species in the late 19th century resulting in a disruption oflocal ecosystems [3031] In response to a Citizen Petition to California regarding its ban on ferretsa nation-wide survey was conducted in 1996ndash1997 by the California Department of Fish and GameHabitat Conservation and Planning Branch Although state agencies reported urban sightings of ldquostrayrdquoferrets as ldquononerdquo (15ndash30) or ldquorare or ldquosporadicrdquo (28ndash56) and no state suspected or documentedldquobreedingrdquo (feral) ferrets California continued its ban on domestic ferrets [32]

SeaSearch Biological Surveys (SeaSearch) became interested in the discrepancy in regulatoryresponse Therefore the purpose of this study was to examine the evidence for invasiveness from thethree domestic carnivores using a survey to assess their relative levels of impact on the North Americanenvironment and agriculture The survey was designed to document the existence of free-roaming(ldquounconfinedrdquo) animalsmdashthose outside of the direct control of humans and the evidence for ldquoharmrdquocaused to native wildlife and agricultural species It also elicited the ldquodegree of concernrdquo generated bythe presence and impact of these three animals when in the unconfined state This article focuses onthe impact to native wildlife and the environment including parks and recreational areas The impacton agriculture is being reported separately

2 Materials and Methods

State agencies of the US (including Washington DC) and provincial agencies of Canada were selectedthat had roles in the control management or impact of domestic or wild animals Agencies representednatural or environmental resources fish game and wildlife agriculture parks and recreational areasand human and veterinary health departments (eg ldquoState Veterinarianrdquo) where such a department or

Animals 2017 7 78 3 of 18

position existed Due to Californiarsquos statewide ban on ferrets both the state and county agencies werequeried County agencies represented parks and recreation health agriculture and animal control

The survey was disseminated in the form of a questionnaire (see Supplementary MaterialsFigure S1) It addressed agency and responder demographics terminology used by the agenciesto classify dogs cats and ferrets (eg ldquohouse-petcompanionrdquo ldquodomesticdomesticatedrdquo ldquoexoticrdquoldquowildrdquondashrdquowildliferdquo etc) ldquosightingsrdquo and ldquoexistencerdquo of unconfined animalsrdquo ldquofrequency of unconfinedanimal sightingsrdquo and estimates of ldquonumber of animalsrdquo at each sighting ldquoeffects (impact)rdquo on wildlifeparks-recreational areas and agriculture and ldquoactions takenrdquo (eg ldquononerdquo ldquolive traprdquo ldquorefer toanother agencyrdquo etc) Rating systems varied depending on the question Responses requiringestimates were presented in a discrete ratings system to reduce open-ended responses and decreasethe response variability Each question included a ldquocommentsrdquo section to allow for clarification ordocumentation of the ratings given Respondents were also asked to rank their ldquodegree of concernrdquoand to provide any ldquospecial concernsrdquo regarding unconfined animals in urban rural-agricultureparks-recreational and wildlands-undeveloped settings

Initial agency contacts were identified using the Internet When no comparable agency was foundthe highest jurisdictional level was contacted by telephone in an attempt to identify the responsibleorganizational unit or individual Using a script potential respondents were then contacted bytelephone to invite their participation

In the initial telephone calls participants were asked how they wished to receive the surveyBased on their requests the survey was distributed to agencies in electronic format (pdfmdashAdobeAcrobatreg) by facsimile or mailed in ldquohard-copyrdquo Delivery receipt and correspondence were trackedand recorded Completed surveys and correspondence were saved in or converted to electronic mediaAt least six attempts were made to reach non-responding jurisdictions and results of these efforts wererecorded Data collection included both coded ratings and text All data were periodically updatedand maintained in a database (Microsoft Accessreg) Analyses were performed on individual agencycategories and in combination with other agency categories

Responses were categorized as a ldquocompleted surveyrdquo (S) or a ldquononsurvey responserdquo (NS) whensome information responsive to the questionnaire was provided Failure or refusal to respond in theabsence of any responsive information was recorded as a ldquononresponserdquo (NR) For NRs the nextorganizational level was contacted to determine whether another individual or organizational unitwould be more appropriate Results reported herein reflect all responding state or provincial agencieswith a separate set of analyses performed on the combined CA county agencies

The Mann-Whitney test was used to compare responses for dogs cats and ferrets with respect tofrequency of sightings (0 = ldquoNeverrdquo 1 = ldquoHistoricalrdquo 2 = ldquoRarerdquo 3 = ldquoCommonrdquo or 4 = ldquoFrequentrdquo)degree of concern regarding sightings (minus2 = ldquoDefinite Concernrdquo minus1 = ldquoSome Concernrdquo 0 = ldquoNoConcernrdquo 1 = ldquoSome Benefitrdquo or 2 = ldquoDefinite Benefitrdquo) and the number of animals per sightingMeans and standard error of the mean (sem) are presented for each comparison Pairwise comparisonsare designated as lsquoarsquo dogs vs cats lsquobrsquo ferrets vs dogs and lsquocrsquo ferrets vs cats p-values between 00001and 0001 are presented as ldquop lt 0001rdquo p-values between 0001 and 001 are presented as ldquop lt 001rdquop-values between 001 and 005 are presented as ldquop lt005rdquo and p-values exceeding 005 presented as ldquonsrdquo

3 Results

Responses were received from 967 (59 of 61) jurisdictions at the stateprovincial levelrepresenting 108 agencies (85 S 23 NS) The majority of responding agencies (S + NS) were wildlife fishgame natural or environmental resources (58 537) with the remaining from parks and recreation(13 120) State Veterinarian (15 139) health (12 111) and agriculture (10 93) Included amongthe NS were those claiming ldquono datardquo (103) or that they were not the ldquocorrectrdquo agency but gavereferrals to other agencies (83) One hundred sixty-four agencies were NRs no agency responded fromArizona and Kansas When reasons were given NRs stated that they did not wish to participate lackedthe funding or time to participate or refused to participate unless they knew more about the surveyor

Animals 2017 7 78 4 of 18

Demographics showed that respondents represented a wide range of organizational levels andexpertise Of the 69 US agencies providing sufficient organizational information 290 were agencyor department heads (level 1) 304 were supervisors (level 2) and 406 had no supervisoryresponsibility (level 3) Of the 10 Canadian provincial agency responders 182 were level 1 182 level 2 and 636 level 3

Thirty-five (6034) of Californiarsquos 58 counties responded Not all counties had agenciescomparable to those at the state level and no county agency represented wildlife fish game naturalor environmental resources Instead of a veterinary unit most counties had an animal control divisionForty-five county agencies responded (S + NS) 36 S (800) and 9 NS (200) Of responders (S + NS)23 (511) were animal control 6 (133)-parks (beaches)-recreation 12 (267)-agriculture and 4(89)-health departments One hundred forty-eight county agencies were NR which either failed orrefused to respond or provided no information responsive to the survey Of the 31 counties completingthe demographics section 387 were level 1 individuals 419 level 2 and 193 level 3

31 Sightings of Unconfined Animals

Respondents were asked to estimate the ldquofrequency of sightingrdquo of unconfined dogs cats andferrets the number of animals seen at each sighting and ldquodegree of concernrdquo regarding unconfinedanimals in the following areas urban-suburban rural-agricultural parks-recreational areas wildlandsand the existence of ldquofree-living (surviving gt 1 week)rdquo ldquoferal (breeding)rdquo or ldquonaturalizedrdquo animals

The ldquofrequency of sightingsrdquo of an unconfined dog cat or ferret was reported covering specifiedtime periods (Figure 1) In most areas sightings of ldquostrayrdquo dogs and cats were rated ldquocommon(gt1 time per year)rdquo whereas ferret sightings were rated as either ldquohistoricalrdquo (ldquonot in the past10 yearsrdquo) or ldquoneverrdquo Unconfined cats were sighted more frequently than dogs in most locationshowever both species had ratings for ldquocommonly seen (gt1 time per year)rdquo ldquofree-livingrdquo ldquoferalrdquoor ldquonaturalizedrdquo animals Similar results were reported from responding California county agenciesUnconfined cats the most frequently observed animal except for a slight majority of dogs spottedin parks and recreational areas and in wildlands No county agency reported ldquofree-livingrdquo ldquoferalrdquoor ldquonaturalizedrdquo ferrets

Animals 2017 7 78 4 of 18

Demographics showed that respondents represented a wide range of organizational levels and

expertise Of the 69 US agencies providing sufficient organizational information 290 were agency

or department heads (level 1) 304 were supervisors (level 2) and 406 had no supervisory

responsibility (level 3) Of the 10 Canadian provincial agency responders 182 were level 1 182

level 2 and 636 level 3

Thirty-five (6034) of Californiarsquos 58 counties responded Not all counties had agencies

comparable to those at the state level and no county agency represented wildlife fish game natural

or environmental resources Instead of a veterinary unit most counties had an animal control

division Forty-five county agencies responded (S + NS) 36 S (800) and 9 NS (200) Of responders

(S + NS) 23 (511) were animal control 6 (133)-parks (beaches)-recreation 12 (267)-agriculture

and 4 (89)-health departments One hundred forty-eight county agencies were NR which either

failed or refused to respond or provided no information responsive to the survey Of the 31 counties

completing the demographics section 387 were level 1 individuals 419 level 2 and 193 level

3

31 Sightings of Unconfined Animals

Respondents were asked to estimate the ldquofrequency of sightingrdquo of unconfined dogs cats and

ferrets the number of animals seen at each sighting and ldquodegree of concernrdquo regarding unconfined

animals in the following areas urban-suburban rural-agricultural parks-recreational areas

wildlands and the existence of ldquofree-living (surviving gt 1 week)rdquo ldquoferal (breeding)rdquo or

ldquonaturalizedrdquo animals

The ldquofrequency of sightingsrdquo of an unconfined dog cat or ferret was reported covering specified

time periods (Figure 1) In most areas sightings of ldquostrayrdquo dogs and cats were rated ldquocommon (gt1

time per year)rdquo whereas ferret sightings were rated as either ldquohistoricalrdquo (ldquonot in the past 10 yearsrdquo)

or ldquoneverrdquo Unconfined cats were sighted more frequently than dogs in most locations however both

species had ratings for ldquocommonly seen (gt1 time per year)rdquo ldquofree-livingrdquo ldquoferalrdquo or ldquonaturalizedrdquo

animals Similar results were reported from responding California county agencies Unconfined cats

the most frequently observed animal except for a slight majority of dogs spotted in parks and

recreational areas and in wildlands No county agency reported ldquofree-livingrdquo ldquoferalrdquo or

ldquonaturalizedrdquo ferrets

Figure 1 Frequency of sighting for unconfined dogs cats and ferrets for (A) United States andCanada (B) California counties Rating mean plusmn standard error of the mean (sem) Asterisk representssignificant difference p lt 005 p lt 001 p lt 0001

Animals 2017 7 78 5 of 18

For ldquoaverage numbers of unconfined animalsrdquo reported at each sighting (Figure 2 Table 1)dogs were most often sighted as single animals whereas cats were seen in groups of three or morewith increasing numbers of cats observed as ldquofree-livingrdquo ldquoferal (breeding)rdquo and ldquonaturalizedrdquo animalsIn ldquourban-suburbanrdquo and rural-agricultural settings state and provincial agencies reported dogs andcats in equal numbers whereas the California county agencies observed increased numbers of cats inthese areas For most other areas cats were seen in greater numbers than dogs and large numbers offeral cats were observed by all of the agencies Except for occasional strays in areas of human activityno California agency reported ferrets as ldquonaturalizedrdquo ldquoferal (breeding)rdquo or ldquofree-livingrdquo

Animals 2017 7 78 5 of 18

Figure 1 Frequency of sighting for unconfined dogs cats and ferrets for (a) United States and

Canada (b) California counties Rating mean plusmn standard error of the mean (sem) Asterisk represents

significant difference p lt 005 p lt 0001

For ldquoaverage numbers of unconfined animalsrdquo reported at each sighting (Figure 2 Table 1) dogs

were most often sighted as single animals whereas cats were seen in groups of three or more with

increasing numbers of cats observed as ldquofree-livingrdquo ldquoferal (breeding)rdquo and ldquonaturalizedrdquo animals

In ldquourban-suburbanrdquo and rural-agricultural settings state and provincial agencies reported dogs and

cats in equal numbers whereas the California county agencies observed increased numbers of cats

in these areas For most other areas cats were seen in greater numbers than dogs and large numbers

of feral cats were observed by all of the agencies Except for occasional strays in areas of human

activity no California agency reported ferrets as ldquonaturalizedrdquo ldquoferal (breeding)rdquo or ldquofree-livingrdquo

Figure 2 Average number of animals per sighting of (a) United States Canada and (b)

California counties Rating mean plusmn standard error of the mean (sem) Asterisk represents

significant difference p lt 005 p lt 001

Table 1 Number of animals per sighting

Animal Sightings Dogs Cats Ferrets

p-Value Mean plusmn sem Mean plusmn sem Mean plusmn sem

United States and Canada

Straymdashurbansuburban 106 plusmn 018 086 plusmn 014 038 plusmn 018 ac ns

b p lt 005

Straymdashruralagricultural 112 plusmn 017 086 plusmn 014 029 plusmn 018 a ns

bc p lt 005

Straymdashparks amp recreational areas 067 plusmn 016 213 plusmn 128 014 plusmn 014 abc ns

Straymdashwildlands 086 plusmn 018 100 plusmn 039 014 plusmn 014 a ns

bc p lt 005

Free-living (surviving gt 1 week) 067 plusmn 014 225 plusmn 162 014 plusmn 014 a ns

bc p lt 005

Figure 2 Average number of animals per sighting of (A) United States Canada and (B) Californiacounties Rating mean plusmn standard error of the mean (sem) Asterisk represents significant difference p lt 005

Table 1 Number of animals per sighting

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem Mean plusmn sem Mean plusmn sem

United States and Canada

Straymdashurbansuburban 106 plusmn 018 086 plusmn 014 038 plusmn 018ac ns

b p lt 005

Straymdashruralagricultural 112 plusmn 017 086 plusmn 014 029 plusmn 018a ns

bc p lt 005Straymdashparks amp recreational areas 067 plusmn 016 213 plusmn 128 014 plusmn 014 abc ns

Straymdashwildlands 086 plusmn 018 100 plusmn 039 014 plusmn 014a ns

bc p lt 005

Free-living (surviving gt 1 week) 067 plusmn 014 225 plusmn 162 014 plusmn 014a ns

bc p lt 005

Feral (breeding) 073 plusmn 027 240 plusmn 196 000 plusmn 000ac ns

b p lt 005Naturalized 025 plusmn 016 288 plusmn 0245 000 plusmn 000 abc ns

Animals 2017 7 78 6 of 18

Table 1 Cont

Animal Sightings Dogs Cats Ferrets p-ValueMean plusmn sem Mean plusmn sem Mean plusmn sem

California CountiesStray Animalsmdashurbansuburban 127 plusmn 020 313 plusmn 160 075 plusmn 048 abc ns

Stray Animalsmdashruralagricultural 150 plusmn 029 229 plusmn 080 033 plusmn 033 abc ns

Stray animalsmdashparks amp recreational areas 142 plusmn 047 377 plusmn 176 033 plusmn 033ac ns

b p lt 005

Stray Animalsmdashwildlands 140 plusmn 052 144 plusmn 056 000 plusmn 000ac ns

b p lt 005Free-living animals (surviving gt 1 week) 079 plusmn 021 136 plusmn 052 000 plusmn 000 abc ns

Feral (Breeding) Animals 138 plusmn 068 425 plusmn 103 000 plusmn 000ac p lt 005

b nsNaturalized animals 000 plusmn 000 040 plusmn 040 000 plusmn 000 ac ns

Statistical comparisons a dogs vscats b ferrets vs dogs c ferrets vs cats sem standard error of the meanns nonsignificant

32 Sighting of Unconfined AnimalsmdashrdquoDegree of Concernrdquo

Respondents were asked to rank their ldquodegree of concernrdquo regarding the existence of unconfineddogs cats and ferrets Ratings were quantified as follows ldquodefinite concernrdquo (minus2) ldquosome concernrdquo(minus1) ldquono concernrdquo (0) ldquosome benefitrdquo (+1) or ldquodefinite benefitrdquo (+2) For state and provincial agenciescats and dogs engendered ldquosome concernrdquo to ldquodefinite concernrdquo (Table 2) Feral cats were ranked thehighest ldquodegree of concernrdquo (minus183) Overall unconfined cats ranked higher than dogs with ferretsgiven the lowest level of concern (Overall Means cats minus173 dogs minus147 ferrets minus056)

Ratings from the California county agencies were somewhat lower than those given by states andprovinces (Overall Means cats minus123 dogs minus121 ferrets minus043) The greatest ldquodegree of concernrdquowas from unconfined dogs in recreational (minus174) and agricultural (minus169) areas and from unconfinedstray cats in urban-suburban (minus158) and in agricultural areas (minus144) and in the feral state (minus144)County agencies which ranked ferrets lowest overall most notably had the least concerns over ldquoferalrdquo(minus036) or ldquonaturalizedrdquo (minus022) ferrets which conformed to agenciesrsquo lack of sightings or reports offerrets existing in these states

33 Impact Existence of Incidents on Wildlife from Unconfined Animals and Degree of Concern

Respondents were also asked to identify the existence of incidents or impact from unconfineddomestic carnivores on native wildlife (Figure 3 see also Supplementary Materials Table S1) Stateand provincial agencies ranked incidents from unconfined dogs and cats as ldquoreported to existrdquoor ldquopreviously existedrdquo regarding ldquotree-dwelling andor nesting birdsrdquo ldquoground-dwelling andornesting birdsrdquo ldquowaterfowlrdquo ldquotree-dwellingrdquo animals ldquoground-dwellingrdquo animalsrdquo ldquoaquatic animalsrdquoldquothreatened endangered andor sensitive speciesrdquo with Hawaii listing dogs as aggravating ldquomonkrdquoseals With the exception of the ldquomonkrdquo seal (Hawaii) and ldquobig gamerdquo animals cats received thehighest levels of incidents representing the greatest negative impact on wildlife for all categories (cats253 dogs 219) In contrast ferrets ranged from ldquoprobably does not existrdquo to ldquodefinitely does notexistrdquo (ferrets 059) Results from the California county agencies followed a similar pattern withferret-related incidents ranked the lowest (cats 155 dogs 115 ferrets 015)

State and provincial agencies ranked ldquodegree of concernrdquo highest for cats for their impact onldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs as aldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) (Table 3) The California county agenciesalso ranked cats the highest with regard to the ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo

Animals 2017 7 78 7 of 18

Table 2 ldquoDegree of concernrdquo regarding sightings of unconfined dogs cats ferrets

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Stray-urbansuburban minus158 plusmn 009 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus050 plusmn 012 (minus2)ndash0a ns

bc p lt 0001

Stray-rural agricultural minus161 plusmn 009 (minus2)ndash0 minus172 plusmn 009 (minus2)ndash1 minus054 plusmn 014 (minus2)ndash1a ns

bc p lt 0001

Stray-parks amp recreational areas minus157 plusmn 008 (minus2)ndash0 minus170 plusmn 009 (minus2)ndash1 minus056 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Stray-wildlands minus149 plusmn 010 (minus2)ndash0 minus170 plusmn 007 (minus2)ndash(minus1) minus058 plusmn 014 (minus2)ndash0a ns

bc p lt 0001

Free-living (surviving gt 1 week) minus150 plusmn 010 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus054 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Feral (Breeding) minus153 plusmn 010 (minus2)ndash0 minus183 plusmn 006 (minus2)ndash(minus1) minus054 plusmn 013 (minus2)ndash0a p lt 005

bc p lt 0001

Naturalized minus103 plusmn 018 (minus2)ndash2 minus161 plusmn 013 (minus2)ndash0 minus065 plusmn 015 (minus2)ndash0

a p lt 005b ns

c p lt 0001Overall Means minus147 minus173 minus056

California Counties

Stray-urbansuburban minus100 plusmn 019 (minus2)ndash0 minus158 plusmn 016 (minus2)ndash1 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-ruralagricultural minus174 plusmn 011 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash2 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-parks amp recreational areas minus169 plusmn 013 (minus2)ndash0 minus136 plusmn 016 (minus2)ndash1 minus050 plusmn 020 (minus2)ndash0

a nsbc p lt 0001

c p lt 001

Stray-wildlands minus128 plusmn 016 (minus2)ndash0 ndash108 plusmn 019 (minus2)ndash1 minus046 plusmn 022 (minus2)ndash0

a nsb p lt 001c p lt 005

Free-living (surviving gt 1 week) minus116 plusmn 018 (minus2)ndash0 minus119 plusmn 020 (minus2)ndash1 minus050 plusmn 023 (minus2)ndash0a ns

bc p lt 005

Feral (Breeding) minus129 plusmn 018 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash1 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 001Naturalized minus033 plusmn 026 (minus2)ndash1 minus050 plusmn 025 (minus2)ndash1 minus022 plusmn 022 (minus2)ndash0 abc ns

Overall Means minus121 minus123 minus0431 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 8 of 18

1

Figure 3 ldquoExistencerdquo of incidents (impact) on wildlife from unconfined dogs cats ferrets (A) UnitedStates Canada and (B) California counties Rating mean plusmn standard error of the mean (sem) Asteriskrepresents significant difference p lt 005 p lt 001 and p lt 0001

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals andDegree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to theother environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured moreprominently than dogs in all of the wildlife categories for state and provincial agencies as well as theCalifornia county agencies with the exception of ldquootherrdquo animals Dogs were listed as having a greaterimpact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California counties notedthat both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impacton ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogsas a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California countyagencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo (Table 4)

Animals 2017 7 78 9 of 18

Animals 2017 7 x 9 of 18

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals and

Degree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to the

other environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured

more prominently than dogs in all of the wildlife categories for state and provincial agencies as well

as the California county agencies with the exception of ldquootherrdquo animals Dogs were listed as having

a greater impact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California

counties noted that both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impact

on ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs

as a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California county

agencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at least

ldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andor

sensitive speciesrdquo (Table 4)

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from

unconfined dogs cats ferrets (a) United States Canada and (b) California counties Rating mean plusmn

standard error of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and

p lt 0001

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from unconfineddogs cats ferrets (A) United States Canada and (B) California counties Rating mean plusmn standarderror of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and p lt0001

Animals 2017 7 78 10 of 18

Table 3 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife

Effects on WildlifeDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus068 plusmn 013 (minus2)ndash0 minus178 plusmn 007 (minus2)ndash(minus1) minus033 plusmn 014 (minus2)ndash0ac p lt 0001

b nsGround-dwelling andorndashnesting birds minus143 plusmn 010 (minus2)ndash0 minus190 plusmn 005 (minus2)ndash(minus1) minus056 plusmn 018 (minus2)ndash0 abc p lt 0001

Waterfowl minus109 plusmn 011 (minus2)ndash0 minus141 plusmn 011 (minus2)ndash0 minus033 plusmn 011 (minus1)ndash0a p lt 005

bc p lt 0001

Tree-dwelling animals minus075 plusmn 011 (minus2)ndash0 minus128 plusmn 014 (minus2)ndash0 minus044 plusmn 015 (minus2)ndash0

a p lt 001b ns

c p lt 0001

Ground-dwelling animals minus136 plusmn 010 (minus2)ndash0 minus162 plusmn 009 (minus2)ndash0 minus056 plusmn 018 (minus2)ndash0a ns

bc p lt 0001

Aquatic animals minus054 plusmn 011 (minus2)ndash0 minus063 plusmn 012 (minus2)ndash0 minus022 plusmn 010 (minus1)ndash0ab ns

c p lt 005

Threatened Endangered andor Sensitive species minus113 plusmn 013 (minus2)ndash0 minus163 plusmn 013 (minus2)ndash0 minus063 plusmn 021 (minus2)ndash0

a p lt 001b p lt 005

c p lt 0001Other (Monk Seal Big Game Animals) minus133 plusmn 033 (minus2)ndash(minus1) 0 0 0 0 b ns

Overall Means minus104 minus128 minus038

California Counties

Tree-Dwelling andormdashnesting birds minus011 plusmn 035 (minus2)ndash2 minus164 (minus2)ndash(minus1) minus033 (minus1)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andormdashnesting birds minus109 plusmn 028 (minus2)ndash0 minus146 plusmn 018 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0ab ns

c p lt 005Waterfowl minus109 plusmn 028 (minus2)ndash0 minus130 plusmn 026 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Tree-dwelling animals minus078 plusmn 032 (minus2)ndash0 minus125 plusmn 037 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsGround-dwelling animals minus131 plusmn 021 (minus2)ndash0 minus140 plusmn 022 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abcns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus086 plusmn 034 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsThreatened Endangered andor Sensitive species minus130 plusmn 030 (minus2)ndash0 minus144 plusmn 029 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Other (Monk Seal Big Game Animals) 0 0 0 0 0 0 -Overall Means minus077 minus117 minus029

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 3 of 18

position existed Due to Californiarsquos statewide ban on ferrets both the state and county agencies werequeried County agencies represented parks and recreation health agriculture and animal control

The survey was disseminated in the form of a questionnaire (see Supplementary MaterialsFigure S1) It addressed agency and responder demographics terminology used by the agenciesto classify dogs cats and ferrets (eg ldquohouse-petcompanionrdquo ldquodomesticdomesticatedrdquo ldquoexoticrdquoldquowildrdquondashrdquowildliferdquo etc) ldquosightingsrdquo and ldquoexistencerdquo of unconfined animalsrdquo ldquofrequency of unconfinedanimal sightingsrdquo and estimates of ldquonumber of animalsrdquo at each sighting ldquoeffects (impact)rdquo on wildlifeparks-recreational areas and agriculture and ldquoactions takenrdquo (eg ldquononerdquo ldquolive traprdquo ldquorefer toanother agencyrdquo etc) Rating systems varied depending on the question Responses requiringestimates were presented in a discrete ratings system to reduce open-ended responses and decreasethe response variability Each question included a ldquocommentsrdquo section to allow for clarification ordocumentation of the ratings given Respondents were also asked to rank their ldquodegree of concernrdquoand to provide any ldquospecial concernsrdquo regarding unconfined animals in urban rural-agricultureparks-recreational and wildlands-undeveloped settings

Initial agency contacts were identified using the Internet When no comparable agency was foundthe highest jurisdictional level was contacted by telephone in an attempt to identify the responsibleorganizational unit or individual Using a script potential respondents were then contacted bytelephone to invite their participation

In the initial telephone calls participants were asked how they wished to receive the surveyBased on their requests the survey was distributed to agencies in electronic format (pdfmdashAdobeAcrobatreg) by facsimile or mailed in ldquohard-copyrdquo Delivery receipt and correspondence were trackedand recorded Completed surveys and correspondence were saved in or converted to electronic mediaAt least six attempts were made to reach non-responding jurisdictions and results of these efforts wererecorded Data collection included both coded ratings and text All data were periodically updatedand maintained in a database (Microsoft Accessreg) Analyses were performed on individual agencycategories and in combination with other agency categories

Responses were categorized as a ldquocompleted surveyrdquo (S) or a ldquononsurvey responserdquo (NS) whensome information responsive to the questionnaire was provided Failure or refusal to respond in theabsence of any responsive information was recorded as a ldquononresponserdquo (NR) For NRs the nextorganizational level was contacted to determine whether another individual or organizational unitwould be more appropriate Results reported herein reflect all responding state or provincial agencieswith a separate set of analyses performed on the combined CA county agencies

The Mann-Whitney test was used to compare responses for dogs cats and ferrets with respect tofrequency of sightings (0 = ldquoNeverrdquo 1 = ldquoHistoricalrdquo 2 = ldquoRarerdquo 3 = ldquoCommonrdquo or 4 = ldquoFrequentrdquo)degree of concern regarding sightings (minus2 = ldquoDefinite Concernrdquo minus1 = ldquoSome Concernrdquo 0 = ldquoNoConcernrdquo 1 = ldquoSome Benefitrdquo or 2 = ldquoDefinite Benefitrdquo) and the number of animals per sightingMeans and standard error of the mean (sem) are presented for each comparison Pairwise comparisonsare designated as lsquoarsquo dogs vs cats lsquobrsquo ferrets vs dogs and lsquocrsquo ferrets vs cats p-values between 00001and 0001 are presented as ldquop lt 0001rdquo p-values between 0001 and 001 are presented as ldquop lt 001rdquop-values between 001 and 005 are presented as ldquop lt005rdquo and p-values exceeding 005 presented as ldquonsrdquo

3 Results

Responses were received from 967 (59 of 61) jurisdictions at the stateprovincial levelrepresenting 108 agencies (85 S 23 NS) The majority of responding agencies (S + NS) were wildlife fishgame natural or environmental resources (58 537) with the remaining from parks and recreation(13 120) State Veterinarian (15 139) health (12 111) and agriculture (10 93) Included amongthe NS were those claiming ldquono datardquo (103) or that they were not the ldquocorrectrdquo agency but gavereferrals to other agencies (83) One hundred sixty-four agencies were NRs no agency responded fromArizona and Kansas When reasons were given NRs stated that they did not wish to participate lackedthe funding or time to participate or refused to participate unless they knew more about the surveyor

Animals 2017 7 78 4 of 18

Demographics showed that respondents represented a wide range of organizational levels andexpertise Of the 69 US agencies providing sufficient organizational information 290 were agencyor department heads (level 1) 304 were supervisors (level 2) and 406 had no supervisoryresponsibility (level 3) Of the 10 Canadian provincial agency responders 182 were level 1 182 level 2 and 636 level 3

Thirty-five (6034) of Californiarsquos 58 counties responded Not all counties had agenciescomparable to those at the state level and no county agency represented wildlife fish game naturalor environmental resources Instead of a veterinary unit most counties had an animal control divisionForty-five county agencies responded (S + NS) 36 S (800) and 9 NS (200) Of responders (S + NS)23 (511) were animal control 6 (133)-parks (beaches)-recreation 12 (267)-agriculture and 4(89)-health departments One hundred forty-eight county agencies were NR which either failed orrefused to respond or provided no information responsive to the survey Of the 31 counties completingthe demographics section 387 were level 1 individuals 419 level 2 and 193 level 3

31 Sightings of Unconfined Animals

Respondents were asked to estimate the ldquofrequency of sightingrdquo of unconfined dogs cats andferrets the number of animals seen at each sighting and ldquodegree of concernrdquo regarding unconfinedanimals in the following areas urban-suburban rural-agricultural parks-recreational areas wildlandsand the existence of ldquofree-living (surviving gt 1 week)rdquo ldquoferal (breeding)rdquo or ldquonaturalizedrdquo animals

The ldquofrequency of sightingsrdquo of an unconfined dog cat or ferret was reported covering specifiedtime periods (Figure 1) In most areas sightings of ldquostrayrdquo dogs and cats were rated ldquocommon(gt1 time per year)rdquo whereas ferret sightings were rated as either ldquohistoricalrdquo (ldquonot in the past10 yearsrdquo) or ldquoneverrdquo Unconfined cats were sighted more frequently than dogs in most locationshowever both species had ratings for ldquocommonly seen (gt1 time per year)rdquo ldquofree-livingrdquo ldquoferalrdquoor ldquonaturalizedrdquo animals Similar results were reported from responding California county agenciesUnconfined cats the most frequently observed animal except for a slight majority of dogs spottedin parks and recreational areas and in wildlands No county agency reported ldquofree-livingrdquo ldquoferalrdquoor ldquonaturalizedrdquo ferrets

Animals 2017 7 78 4 of 18

Demographics showed that respondents represented a wide range of organizational levels and

expertise Of the 69 US agencies providing sufficient organizational information 290 were agency

or department heads (level 1) 304 were supervisors (level 2) and 406 had no supervisory

responsibility (level 3) Of the 10 Canadian provincial agency responders 182 were level 1 182

level 2 and 636 level 3

Thirty-five (6034) of Californiarsquos 58 counties responded Not all counties had agencies

comparable to those at the state level and no county agency represented wildlife fish game natural

or environmental resources Instead of a veterinary unit most counties had an animal control

division Forty-five county agencies responded (S + NS) 36 S (800) and 9 NS (200) Of responders

(S + NS) 23 (511) were animal control 6 (133)-parks (beaches)-recreation 12 (267)-agriculture

and 4 (89)-health departments One hundred forty-eight county agencies were NR which either

failed or refused to respond or provided no information responsive to the survey Of the 31 counties

completing the demographics section 387 were level 1 individuals 419 level 2 and 193 level

3

31 Sightings of Unconfined Animals

Respondents were asked to estimate the ldquofrequency of sightingrdquo of unconfined dogs cats and

ferrets the number of animals seen at each sighting and ldquodegree of concernrdquo regarding unconfined

animals in the following areas urban-suburban rural-agricultural parks-recreational areas

wildlands and the existence of ldquofree-living (surviving gt 1 week)rdquo ldquoferal (breeding)rdquo or

ldquonaturalizedrdquo animals

The ldquofrequency of sightingsrdquo of an unconfined dog cat or ferret was reported covering specified

time periods (Figure 1) In most areas sightings of ldquostrayrdquo dogs and cats were rated ldquocommon (gt1

time per year)rdquo whereas ferret sightings were rated as either ldquohistoricalrdquo (ldquonot in the past 10 yearsrdquo)

or ldquoneverrdquo Unconfined cats were sighted more frequently than dogs in most locations however both

species had ratings for ldquocommonly seen (gt1 time per year)rdquo ldquofree-livingrdquo ldquoferalrdquo or ldquonaturalizedrdquo

animals Similar results were reported from responding California county agencies Unconfined cats

the most frequently observed animal except for a slight majority of dogs spotted in parks and

recreational areas and in wildlands No county agency reported ldquofree-livingrdquo ldquoferalrdquo or

ldquonaturalizedrdquo ferrets

Figure 1 Frequency of sighting for unconfined dogs cats and ferrets for (A) United States andCanada (B) California counties Rating mean plusmn standard error of the mean (sem) Asterisk representssignificant difference p lt 005 p lt 001 p lt 0001

Animals 2017 7 78 5 of 18

For ldquoaverage numbers of unconfined animalsrdquo reported at each sighting (Figure 2 Table 1)dogs were most often sighted as single animals whereas cats were seen in groups of three or morewith increasing numbers of cats observed as ldquofree-livingrdquo ldquoferal (breeding)rdquo and ldquonaturalizedrdquo animalsIn ldquourban-suburbanrdquo and rural-agricultural settings state and provincial agencies reported dogs andcats in equal numbers whereas the California county agencies observed increased numbers of cats inthese areas For most other areas cats were seen in greater numbers than dogs and large numbers offeral cats were observed by all of the agencies Except for occasional strays in areas of human activityno California agency reported ferrets as ldquonaturalizedrdquo ldquoferal (breeding)rdquo or ldquofree-livingrdquo

Animals 2017 7 78 5 of 18

Figure 1 Frequency of sighting for unconfined dogs cats and ferrets for (a) United States and

Canada (b) California counties Rating mean plusmn standard error of the mean (sem) Asterisk represents

significant difference p lt 005 p lt 0001

For ldquoaverage numbers of unconfined animalsrdquo reported at each sighting (Figure 2 Table 1) dogs

were most often sighted as single animals whereas cats were seen in groups of three or more with

increasing numbers of cats observed as ldquofree-livingrdquo ldquoferal (breeding)rdquo and ldquonaturalizedrdquo animals

In ldquourban-suburbanrdquo and rural-agricultural settings state and provincial agencies reported dogs and

cats in equal numbers whereas the California county agencies observed increased numbers of cats

in these areas For most other areas cats were seen in greater numbers than dogs and large numbers

of feral cats were observed by all of the agencies Except for occasional strays in areas of human

activity no California agency reported ferrets as ldquonaturalizedrdquo ldquoferal (breeding)rdquo or ldquofree-livingrdquo

Figure 2 Average number of animals per sighting of (a) United States Canada and (b)

California counties Rating mean plusmn standard error of the mean (sem) Asterisk represents

significant difference p lt 005 p lt 001

Table 1 Number of animals per sighting

Animal Sightings Dogs Cats Ferrets

p-Value Mean plusmn sem Mean plusmn sem Mean plusmn sem

United States and Canada

Straymdashurbansuburban 106 plusmn 018 086 plusmn 014 038 plusmn 018 ac ns

b p lt 005

Straymdashruralagricultural 112 plusmn 017 086 plusmn 014 029 plusmn 018 a ns

bc p lt 005

Straymdashparks amp recreational areas 067 plusmn 016 213 plusmn 128 014 plusmn 014 abc ns

Straymdashwildlands 086 plusmn 018 100 plusmn 039 014 plusmn 014 a ns

bc p lt 005

Free-living (surviving gt 1 week) 067 plusmn 014 225 plusmn 162 014 plusmn 014 a ns

bc p lt 005

Figure 2 Average number of animals per sighting of (A) United States Canada and (B) Californiacounties Rating mean plusmn standard error of the mean (sem) Asterisk represents significant difference p lt 005

Table 1 Number of animals per sighting

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem Mean plusmn sem Mean plusmn sem

United States and Canada

Straymdashurbansuburban 106 plusmn 018 086 plusmn 014 038 plusmn 018ac ns

b p lt 005

Straymdashruralagricultural 112 plusmn 017 086 plusmn 014 029 plusmn 018a ns

bc p lt 005Straymdashparks amp recreational areas 067 plusmn 016 213 plusmn 128 014 plusmn 014 abc ns

Straymdashwildlands 086 plusmn 018 100 plusmn 039 014 plusmn 014a ns

bc p lt 005

Free-living (surviving gt 1 week) 067 plusmn 014 225 plusmn 162 014 plusmn 014a ns

bc p lt 005

Feral (breeding) 073 plusmn 027 240 plusmn 196 000 plusmn 000ac ns

b p lt 005Naturalized 025 plusmn 016 288 plusmn 0245 000 plusmn 000 abc ns

Animals 2017 7 78 6 of 18

Table 1 Cont

Animal Sightings Dogs Cats Ferrets p-ValueMean plusmn sem Mean plusmn sem Mean plusmn sem

California CountiesStray Animalsmdashurbansuburban 127 plusmn 020 313 plusmn 160 075 plusmn 048 abc ns

Stray Animalsmdashruralagricultural 150 plusmn 029 229 plusmn 080 033 plusmn 033 abc ns

Stray animalsmdashparks amp recreational areas 142 plusmn 047 377 plusmn 176 033 plusmn 033ac ns

b p lt 005

Stray Animalsmdashwildlands 140 plusmn 052 144 plusmn 056 000 plusmn 000ac ns

b p lt 005Free-living animals (surviving gt 1 week) 079 plusmn 021 136 plusmn 052 000 plusmn 000 abc ns

Feral (Breeding) Animals 138 plusmn 068 425 plusmn 103 000 plusmn 000ac p lt 005

b nsNaturalized animals 000 plusmn 000 040 plusmn 040 000 plusmn 000 ac ns

Statistical comparisons a dogs vscats b ferrets vs dogs c ferrets vs cats sem standard error of the meanns nonsignificant

32 Sighting of Unconfined AnimalsmdashrdquoDegree of Concernrdquo

Respondents were asked to rank their ldquodegree of concernrdquo regarding the existence of unconfineddogs cats and ferrets Ratings were quantified as follows ldquodefinite concernrdquo (minus2) ldquosome concernrdquo(minus1) ldquono concernrdquo (0) ldquosome benefitrdquo (+1) or ldquodefinite benefitrdquo (+2) For state and provincial agenciescats and dogs engendered ldquosome concernrdquo to ldquodefinite concernrdquo (Table 2) Feral cats were ranked thehighest ldquodegree of concernrdquo (minus183) Overall unconfined cats ranked higher than dogs with ferretsgiven the lowest level of concern (Overall Means cats minus173 dogs minus147 ferrets minus056)

Ratings from the California county agencies were somewhat lower than those given by states andprovinces (Overall Means cats minus123 dogs minus121 ferrets minus043) The greatest ldquodegree of concernrdquowas from unconfined dogs in recreational (minus174) and agricultural (minus169) areas and from unconfinedstray cats in urban-suburban (minus158) and in agricultural areas (minus144) and in the feral state (minus144)County agencies which ranked ferrets lowest overall most notably had the least concerns over ldquoferalrdquo(minus036) or ldquonaturalizedrdquo (minus022) ferrets which conformed to agenciesrsquo lack of sightings or reports offerrets existing in these states

33 Impact Existence of Incidents on Wildlife from Unconfined Animals and Degree of Concern

Respondents were also asked to identify the existence of incidents or impact from unconfineddomestic carnivores on native wildlife (Figure 3 see also Supplementary Materials Table S1) Stateand provincial agencies ranked incidents from unconfined dogs and cats as ldquoreported to existrdquoor ldquopreviously existedrdquo regarding ldquotree-dwelling andor nesting birdsrdquo ldquoground-dwelling andornesting birdsrdquo ldquowaterfowlrdquo ldquotree-dwellingrdquo animals ldquoground-dwellingrdquo animalsrdquo ldquoaquatic animalsrdquoldquothreatened endangered andor sensitive speciesrdquo with Hawaii listing dogs as aggravating ldquomonkrdquoseals With the exception of the ldquomonkrdquo seal (Hawaii) and ldquobig gamerdquo animals cats received thehighest levels of incidents representing the greatest negative impact on wildlife for all categories (cats253 dogs 219) In contrast ferrets ranged from ldquoprobably does not existrdquo to ldquodefinitely does notexistrdquo (ferrets 059) Results from the California county agencies followed a similar pattern withferret-related incidents ranked the lowest (cats 155 dogs 115 ferrets 015)

State and provincial agencies ranked ldquodegree of concernrdquo highest for cats for their impact onldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs as aldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) (Table 3) The California county agenciesalso ranked cats the highest with regard to the ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo

Animals 2017 7 78 7 of 18

Table 2 ldquoDegree of concernrdquo regarding sightings of unconfined dogs cats ferrets

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Stray-urbansuburban minus158 plusmn 009 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus050 plusmn 012 (minus2)ndash0a ns

bc p lt 0001

Stray-rural agricultural minus161 plusmn 009 (minus2)ndash0 minus172 plusmn 009 (minus2)ndash1 minus054 plusmn 014 (minus2)ndash1a ns

bc p lt 0001

Stray-parks amp recreational areas minus157 plusmn 008 (minus2)ndash0 minus170 plusmn 009 (minus2)ndash1 minus056 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Stray-wildlands minus149 plusmn 010 (minus2)ndash0 minus170 plusmn 007 (minus2)ndash(minus1) minus058 plusmn 014 (minus2)ndash0a ns

bc p lt 0001

Free-living (surviving gt 1 week) minus150 plusmn 010 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus054 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Feral (Breeding) minus153 plusmn 010 (minus2)ndash0 minus183 plusmn 006 (minus2)ndash(minus1) minus054 plusmn 013 (minus2)ndash0a p lt 005

bc p lt 0001

Naturalized minus103 plusmn 018 (minus2)ndash2 minus161 plusmn 013 (minus2)ndash0 minus065 plusmn 015 (minus2)ndash0

a p lt 005b ns

c p lt 0001Overall Means minus147 minus173 minus056

California Counties

Stray-urbansuburban minus100 plusmn 019 (minus2)ndash0 minus158 plusmn 016 (minus2)ndash1 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-ruralagricultural minus174 plusmn 011 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash2 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-parks amp recreational areas minus169 plusmn 013 (minus2)ndash0 minus136 plusmn 016 (minus2)ndash1 minus050 plusmn 020 (minus2)ndash0

a nsbc p lt 0001

c p lt 001

Stray-wildlands minus128 plusmn 016 (minus2)ndash0 ndash108 plusmn 019 (minus2)ndash1 minus046 plusmn 022 (minus2)ndash0

a nsb p lt 001c p lt 005

Free-living (surviving gt 1 week) minus116 plusmn 018 (minus2)ndash0 minus119 plusmn 020 (minus2)ndash1 minus050 plusmn 023 (minus2)ndash0a ns

bc p lt 005

Feral (Breeding) minus129 plusmn 018 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash1 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 001Naturalized minus033 plusmn 026 (minus2)ndash1 minus050 plusmn 025 (minus2)ndash1 minus022 plusmn 022 (minus2)ndash0 abc ns

Overall Means minus121 minus123 minus0431 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 8 of 18

1

Figure 3 ldquoExistencerdquo of incidents (impact) on wildlife from unconfined dogs cats ferrets (A) UnitedStates Canada and (B) California counties Rating mean plusmn standard error of the mean (sem) Asteriskrepresents significant difference p lt 005 p lt 001 and p lt 0001

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals andDegree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to theother environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured moreprominently than dogs in all of the wildlife categories for state and provincial agencies as well as theCalifornia county agencies with the exception of ldquootherrdquo animals Dogs were listed as having a greaterimpact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California counties notedthat both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impacton ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogsas a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California countyagencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo (Table 4)

Animals 2017 7 78 9 of 18

Animals 2017 7 x 9 of 18

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals and

Degree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to the

other environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured

more prominently than dogs in all of the wildlife categories for state and provincial agencies as well

as the California county agencies with the exception of ldquootherrdquo animals Dogs were listed as having

a greater impact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California

counties noted that both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impact

on ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs

as a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California county

agencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at least

ldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andor

sensitive speciesrdquo (Table 4)

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from

unconfined dogs cats ferrets (a) United States Canada and (b) California counties Rating mean plusmn

standard error of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and

p lt 0001

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from unconfineddogs cats ferrets (A) United States Canada and (B) California counties Rating mean plusmn standarderror of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and p lt0001

Animals 2017 7 78 10 of 18

Table 3 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife

Effects on WildlifeDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus068 plusmn 013 (minus2)ndash0 minus178 plusmn 007 (minus2)ndash(minus1) minus033 plusmn 014 (minus2)ndash0ac p lt 0001

b nsGround-dwelling andorndashnesting birds minus143 plusmn 010 (minus2)ndash0 minus190 plusmn 005 (minus2)ndash(minus1) minus056 plusmn 018 (minus2)ndash0 abc p lt 0001

Waterfowl minus109 plusmn 011 (minus2)ndash0 minus141 plusmn 011 (minus2)ndash0 minus033 plusmn 011 (minus1)ndash0a p lt 005

bc p lt 0001

Tree-dwelling animals minus075 plusmn 011 (minus2)ndash0 minus128 plusmn 014 (minus2)ndash0 minus044 plusmn 015 (minus2)ndash0

a p lt 001b ns

c p lt 0001

Ground-dwelling animals minus136 plusmn 010 (minus2)ndash0 minus162 plusmn 009 (minus2)ndash0 minus056 plusmn 018 (minus2)ndash0a ns

bc p lt 0001

Aquatic animals minus054 plusmn 011 (minus2)ndash0 minus063 plusmn 012 (minus2)ndash0 minus022 plusmn 010 (minus1)ndash0ab ns

c p lt 005

Threatened Endangered andor Sensitive species minus113 plusmn 013 (minus2)ndash0 minus163 plusmn 013 (minus2)ndash0 minus063 plusmn 021 (minus2)ndash0

a p lt 001b p lt 005

c p lt 0001Other (Monk Seal Big Game Animals) minus133 plusmn 033 (minus2)ndash(minus1) 0 0 0 0 b ns

Overall Means minus104 minus128 minus038

California Counties

Tree-Dwelling andormdashnesting birds minus011 plusmn 035 (minus2)ndash2 minus164 (minus2)ndash(minus1) minus033 (minus1)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andormdashnesting birds minus109 plusmn 028 (minus2)ndash0 minus146 plusmn 018 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0ab ns

c p lt 005Waterfowl minus109 plusmn 028 (minus2)ndash0 minus130 plusmn 026 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Tree-dwelling animals minus078 plusmn 032 (minus2)ndash0 minus125 plusmn 037 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsGround-dwelling animals minus131 plusmn 021 (minus2)ndash0 minus140 plusmn 022 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abcns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus086 plusmn 034 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsThreatened Endangered andor Sensitive species minus130 plusmn 030 (minus2)ndash0 minus144 plusmn 029 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Other (Monk Seal Big Game Animals) 0 0 0 0 0 0 -Overall Means minus077 minus117 minus029

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 4 of 18

Demographics showed that respondents represented a wide range of organizational levels andexpertise Of the 69 US agencies providing sufficient organizational information 290 were agencyor department heads (level 1) 304 were supervisors (level 2) and 406 had no supervisoryresponsibility (level 3) Of the 10 Canadian provincial agency responders 182 were level 1 182 level 2 and 636 level 3

Thirty-five (6034) of Californiarsquos 58 counties responded Not all counties had agenciescomparable to those at the state level and no county agency represented wildlife fish game naturalor environmental resources Instead of a veterinary unit most counties had an animal control divisionForty-five county agencies responded (S + NS) 36 S (800) and 9 NS (200) Of responders (S + NS)23 (511) were animal control 6 (133)-parks (beaches)-recreation 12 (267)-agriculture and 4(89)-health departments One hundred forty-eight county agencies were NR which either failed orrefused to respond or provided no information responsive to the survey Of the 31 counties completingthe demographics section 387 were level 1 individuals 419 level 2 and 193 level 3

31 Sightings of Unconfined Animals

Respondents were asked to estimate the ldquofrequency of sightingrdquo of unconfined dogs cats andferrets the number of animals seen at each sighting and ldquodegree of concernrdquo regarding unconfinedanimals in the following areas urban-suburban rural-agricultural parks-recreational areas wildlandsand the existence of ldquofree-living (surviving gt 1 week)rdquo ldquoferal (breeding)rdquo or ldquonaturalizedrdquo animals

The ldquofrequency of sightingsrdquo of an unconfined dog cat or ferret was reported covering specifiedtime periods (Figure 1) In most areas sightings of ldquostrayrdquo dogs and cats were rated ldquocommon(gt1 time per year)rdquo whereas ferret sightings were rated as either ldquohistoricalrdquo (ldquonot in the past10 yearsrdquo) or ldquoneverrdquo Unconfined cats were sighted more frequently than dogs in most locationshowever both species had ratings for ldquocommonly seen (gt1 time per year)rdquo ldquofree-livingrdquo ldquoferalrdquoor ldquonaturalizedrdquo animals Similar results were reported from responding California county agenciesUnconfined cats the most frequently observed animal except for a slight majority of dogs spottedin parks and recreational areas and in wildlands No county agency reported ldquofree-livingrdquo ldquoferalrdquoor ldquonaturalizedrdquo ferrets

Animals 2017 7 78 4 of 18

Demographics showed that respondents represented a wide range of organizational levels and

expertise Of the 69 US agencies providing sufficient organizational information 290 were agency

or department heads (level 1) 304 were supervisors (level 2) and 406 had no supervisory

responsibility (level 3) Of the 10 Canadian provincial agency responders 182 were level 1 182

level 2 and 636 level 3

Thirty-five (6034) of Californiarsquos 58 counties responded Not all counties had agencies

comparable to those at the state level and no county agency represented wildlife fish game natural

or environmental resources Instead of a veterinary unit most counties had an animal control

division Forty-five county agencies responded (S + NS) 36 S (800) and 9 NS (200) Of responders

(S + NS) 23 (511) were animal control 6 (133)-parks (beaches)-recreation 12 (267)-agriculture

and 4 (89)-health departments One hundred forty-eight county agencies were NR which either

failed or refused to respond or provided no information responsive to the survey Of the 31 counties

completing the demographics section 387 were level 1 individuals 419 level 2 and 193 level

3

31 Sightings of Unconfined Animals

Respondents were asked to estimate the ldquofrequency of sightingrdquo of unconfined dogs cats and

ferrets the number of animals seen at each sighting and ldquodegree of concernrdquo regarding unconfined

animals in the following areas urban-suburban rural-agricultural parks-recreational areas

wildlands and the existence of ldquofree-living (surviving gt 1 week)rdquo ldquoferal (breeding)rdquo or

ldquonaturalizedrdquo animals

The ldquofrequency of sightingsrdquo of an unconfined dog cat or ferret was reported covering specified

time periods (Figure 1) In most areas sightings of ldquostrayrdquo dogs and cats were rated ldquocommon (gt1

time per year)rdquo whereas ferret sightings were rated as either ldquohistoricalrdquo (ldquonot in the past 10 yearsrdquo)

or ldquoneverrdquo Unconfined cats were sighted more frequently than dogs in most locations however both

species had ratings for ldquocommonly seen (gt1 time per year)rdquo ldquofree-livingrdquo ldquoferalrdquo or ldquonaturalizedrdquo

animals Similar results were reported from responding California county agencies Unconfined cats

the most frequently observed animal except for a slight majority of dogs spotted in parks and

recreational areas and in wildlands No county agency reported ldquofree-livingrdquo ldquoferalrdquo or

ldquonaturalizedrdquo ferrets

Figure 1 Frequency of sighting for unconfined dogs cats and ferrets for (A) United States andCanada (B) California counties Rating mean plusmn standard error of the mean (sem) Asterisk representssignificant difference p lt 005 p lt 001 p lt 0001

Animals 2017 7 78 5 of 18

For ldquoaverage numbers of unconfined animalsrdquo reported at each sighting (Figure 2 Table 1)dogs were most often sighted as single animals whereas cats were seen in groups of three or morewith increasing numbers of cats observed as ldquofree-livingrdquo ldquoferal (breeding)rdquo and ldquonaturalizedrdquo animalsIn ldquourban-suburbanrdquo and rural-agricultural settings state and provincial agencies reported dogs andcats in equal numbers whereas the California county agencies observed increased numbers of cats inthese areas For most other areas cats were seen in greater numbers than dogs and large numbers offeral cats were observed by all of the agencies Except for occasional strays in areas of human activityno California agency reported ferrets as ldquonaturalizedrdquo ldquoferal (breeding)rdquo or ldquofree-livingrdquo

Animals 2017 7 78 5 of 18

Figure 1 Frequency of sighting for unconfined dogs cats and ferrets for (a) United States and

Canada (b) California counties Rating mean plusmn standard error of the mean (sem) Asterisk represents

significant difference p lt 005 p lt 0001

For ldquoaverage numbers of unconfined animalsrdquo reported at each sighting (Figure 2 Table 1) dogs

were most often sighted as single animals whereas cats were seen in groups of three or more with

increasing numbers of cats observed as ldquofree-livingrdquo ldquoferal (breeding)rdquo and ldquonaturalizedrdquo animals

In ldquourban-suburbanrdquo and rural-agricultural settings state and provincial agencies reported dogs and

cats in equal numbers whereas the California county agencies observed increased numbers of cats

in these areas For most other areas cats were seen in greater numbers than dogs and large numbers

of feral cats were observed by all of the agencies Except for occasional strays in areas of human

activity no California agency reported ferrets as ldquonaturalizedrdquo ldquoferal (breeding)rdquo or ldquofree-livingrdquo

Figure 2 Average number of animals per sighting of (a) United States Canada and (b)

California counties Rating mean plusmn standard error of the mean (sem) Asterisk represents

significant difference p lt 005 p lt 001

Table 1 Number of animals per sighting

Animal Sightings Dogs Cats Ferrets

p-Value Mean plusmn sem Mean plusmn sem Mean plusmn sem

United States and Canada

Straymdashurbansuburban 106 plusmn 018 086 plusmn 014 038 plusmn 018 ac ns

b p lt 005

Straymdashruralagricultural 112 plusmn 017 086 plusmn 014 029 plusmn 018 a ns

bc p lt 005

Straymdashparks amp recreational areas 067 plusmn 016 213 plusmn 128 014 plusmn 014 abc ns

Straymdashwildlands 086 plusmn 018 100 plusmn 039 014 plusmn 014 a ns

bc p lt 005

Free-living (surviving gt 1 week) 067 plusmn 014 225 plusmn 162 014 plusmn 014 a ns

bc p lt 005

Figure 2 Average number of animals per sighting of (A) United States Canada and (B) Californiacounties Rating mean plusmn standard error of the mean (sem) Asterisk represents significant difference p lt 005

Table 1 Number of animals per sighting

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem Mean plusmn sem Mean plusmn sem

United States and Canada

Straymdashurbansuburban 106 plusmn 018 086 plusmn 014 038 plusmn 018ac ns

b p lt 005

Straymdashruralagricultural 112 plusmn 017 086 plusmn 014 029 plusmn 018a ns

bc p lt 005Straymdashparks amp recreational areas 067 plusmn 016 213 plusmn 128 014 plusmn 014 abc ns

Straymdashwildlands 086 plusmn 018 100 plusmn 039 014 plusmn 014a ns

bc p lt 005

Free-living (surviving gt 1 week) 067 plusmn 014 225 plusmn 162 014 plusmn 014a ns

bc p lt 005

Feral (breeding) 073 plusmn 027 240 plusmn 196 000 plusmn 000ac ns

b p lt 005Naturalized 025 plusmn 016 288 plusmn 0245 000 plusmn 000 abc ns

Animals 2017 7 78 6 of 18

Table 1 Cont

Animal Sightings Dogs Cats Ferrets p-ValueMean plusmn sem Mean plusmn sem Mean plusmn sem

California CountiesStray Animalsmdashurbansuburban 127 plusmn 020 313 plusmn 160 075 plusmn 048 abc ns

Stray Animalsmdashruralagricultural 150 plusmn 029 229 plusmn 080 033 plusmn 033 abc ns

Stray animalsmdashparks amp recreational areas 142 plusmn 047 377 plusmn 176 033 plusmn 033ac ns

b p lt 005

Stray Animalsmdashwildlands 140 plusmn 052 144 plusmn 056 000 plusmn 000ac ns

b p lt 005Free-living animals (surviving gt 1 week) 079 plusmn 021 136 plusmn 052 000 plusmn 000 abc ns

Feral (Breeding) Animals 138 plusmn 068 425 plusmn 103 000 plusmn 000ac p lt 005

b nsNaturalized animals 000 plusmn 000 040 plusmn 040 000 plusmn 000 ac ns

Statistical comparisons a dogs vscats b ferrets vs dogs c ferrets vs cats sem standard error of the meanns nonsignificant

32 Sighting of Unconfined AnimalsmdashrdquoDegree of Concernrdquo

Respondents were asked to rank their ldquodegree of concernrdquo regarding the existence of unconfineddogs cats and ferrets Ratings were quantified as follows ldquodefinite concernrdquo (minus2) ldquosome concernrdquo(minus1) ldquono concernrdquo (0) ldquosome benefitrdquo (+1) or ldquodefinite benefitrdquo (+2) For state and provincial agenciescats and dogs engendered ldquosome concernrdquo to ldquodefinite concernrdquo (Table 2) Feral cats were ranked thehighest ldquodegree of concernrdquo (minus183) Overall unconfined cats ranked higher than dogs with ferretsgiven the lowest level of concern (Overall Means cats minus173 dogs minus147 ferrets minus056)

Ratings from the California county agencies were somewhat lower than those given by states andprovinces (Overall Means cats minus123 dogs minus121 ferrets minus043) The greatest ldquodegree of concernrdquowas from unconfined dogs in recreational (minus174) and agricultural (minus169) areas and from unconfinedstray cats in urban-suburban (minus158) and in agricultural areas (minus144) and in the feral state (minus144)County agencies which ranked ferrets lowest overall most notably had the least concerns over ldquoferalrdquo(minus036) or ldquonaturalizedrdquo (minus022) ferrets which conformed to agenciesrsquo lack of sightings or reports offerrets existing in these states

33 Impact Existence of Incidents on Wildlife from Unconfined Animals and Degree of Concern

Respondents were also asked to identify the existence of incidents or impact from unconfineddomestic carnivores on native wildlife (Figure 3 see also Supplementary Materials Table S1) Stateand provincial agencies ranked incidents from unconfined dogs and cats as ldquoreported to existrdquoor ldquopreviously existedrdquo regarding ldquotree-dwelling andor nesting birdsrdquo ldquoground-dwelling andornesting birdsrdquo ldquowaterfowlrdquo ldquotree-dwellingrdquo animals ldquoground-dwellingrdquo animalsrdquo ldquoaquatic animalsrdquoldquothreatened endangered andor sensitive speciesrdquo with Hawaii listing dogs as aggravating ldquomonkrdquoseals With the exception of the ldquomonkrdquo seal (Hawaii) and ldquobig gamerdquo animals cats received thehighest levels of incidents representing the greatest negative impact on wildlife for all categories (cats253 dogs 219) In contrast ferrets ranged from ldquoprobably does not existrdquo to ldquodefinitely does notexistrdquo (ferrets 059) Results from the California county agencies followed a similar pattern withferret-related incidents ranked the lowest (cats 155 dogs 115 ferrets 015)

State and provincial agencies ranked ldquodegree of concernrdquo highest for cats for their impact onldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs as aldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) (Table 3) The California county agenciesalso ranked cats the highest with regard to the ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo

Animals 2017 7 78 7 of 18

Table 2 ldquoDegree of concernrdquo regarding sightings of unconfined dogs cats ferrets

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Stray-urbansuburban minus158 plusmn 009 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus050 plusmn 012 (minus2)ndash0a ns

bc p lt 0001

Stray-rural agricultural minus161 plusmn 009 (minus2)ndash0 minus172 plusmn 009 (minus2)ndash1 minus054 plusmn 014 (minus2)ndash1a ns

bc p lt 0001

Stray-parks amp recreational areas minus157 plusmn 008 (minus2)ndash0 minus170 plusmn 009 (minus2)ndash1 minus056 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Stray-wildlands minus149 plusmn 010 (minus2)ndash0 minus170 plusmn 007 (minus2)ndash(minus1) minus058 plusmn 014 (minus2)ndash0a ns

bc p lt 0001

Free-living (surviving gt 1 week) minus150 plusmn 010 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus054 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Feral (Breeding) minus153 plusmn 010 (minus2)ndash0 minus183 plusmn 006 (minus2)ndash(minus1) minus054 plusmn 013 (minus2)ndash0a p lt 005

bc p lt 0001

Naturalized minus103 plusmn 018 (minus2)ndash2 minus161 plusmn 013 (minus2)ndash0 minus065 plusmn 015 (minus2)ndash0

a p lt 005b ns

c p lt 0001Overall Means minus147 minus173 minus056

California Counties

Stray-urbansuburban minus100 plusmn 019 (minus2)ndash0 minus158 plusmn 016 (minus2)ndash1 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-ruralagricultural minus174 plusmn 011 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash2 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-parks amp recreational areas minus169 plusmn 013 (minus2)ndash0 minus136 plusmn 016 (minus2)ndash1 minus050 plusmn 020 (minus2)ndash0

a nsbc p lt 0001

c p lt 001

Stray-wildlands minus128 plusmn 016 (minus2)ndash0 ndash108 plusmn 019 (minus2)ndash1 minus046 plusmn 022 (minus2)ndash0

a nsb p lt 001c p lt 005

Free-living (surviving gt 1 week) minus116 plusmn 018 (minus2)ndash0 minus119 plusmn 020 (minus2)ndash1 minus050 plusmn 023 (minus2)ndash0a ns

bc p lt 005

Feral (Breeding) minus129 plusmn 018 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash1 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 001Naturalized minus033 plusmn 026 (minus2)ndash1 minus050 plusmn 025 (minus2)ndash1 minus022 plusmn 022 (minus2)ndash0 abc ns

Overall Means minus121 minus123 minus0431 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 8 of 18

1

Figure 3 ldquoExistencerdquo of incidents (impact) on wildlife from unconfined dogs cats ferrets (A) UnitedStates Canada and (B) California counties Rating mean plusmn standard error of the mean (sem) Asteriskrepresents significant difference p lt 005 p lt 001 and p lt 0001

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals andDegree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to theother environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured moreprominently than dogs in all of the wildlife categories for state and provincial agencies as well as theCalifornia county agencies with the exception of ldquootherrdquo animals Dogs were listed as having a greaterimpact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California counties notedthat both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impacton ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogsas a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California countyagencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo (Table 4)

Animals 2017 7 78 9 of 18

Animals 2017 7 x 9 of 18

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals and

Degree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to the

other environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured

more prominently than dogs in all of the wildlife categories for state and provincial agencies as well

as the California county agencies with the exception of ldquootherrdquo animals Dogs were listed as having

a greater impact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California

counties noted that both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impact

on ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs

as a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California county

agencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at least

ldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andor

sensitive speciesrdquo (Table 4)

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from

unconfined dogs cats ferrets (a) United States Canada and (b) California counties Rating mean plusmn

standard error of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and

p lt 0001

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from unconfineddogs cats ferrets (A) United States Canada and (B) California counties Rating mean plusmn standarderror of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and p lt0001

Animals 2017 7 78 10 of 18

Table 3 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife

Effects on WildlifeDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus068 plusmn 013 (minus2)ndash0 minus178 plusmn 007 (minus2)ndash(minus1) minus033 plusmn 014 (minus2)ndash0ac p lt 0001

b nsGround-dwelling andorndashnesting birds minus143 plusmn 010 (minus2)ndash0 minus190 plusmn 005 (minus2)ndash(minus1) minus056 plusmn 018 (minus2)ndash0 abc p lt 0001

Waterfowl minus109 plusmn 011 (minus2)ndash0 minus141 plusmn 011 (minus2)ndash0 minus033 plusmn 011 (minus1)ndash0a p lt 005

bc p lt 0001

Tree-dwelling animals minus075 plusmn 011 (minus2)ndash0 minus128 plusmn 014 (minus2)ndash0 minus044 plusmn 015 (minus2)ndash0

a p lt 001b ns

c p lt 0001

Ground-dwelling animals minus136 plusmn 010 (minus2)ndash0 minus162 plusmn 009 (minus2)ndash0 minus056 plusmn 018 (minus2)ndash0a ns

bc p lt 0001

Aquatic animals minus054 plusmn 011 (minus2)ndash0 minus063 plusmn 012 (minus2)ndash0 minus022 plusmn 010 (minus1)ndash0ab ns

c p lt 005

Threatened Endangered andor Sensitive species minus113 plusmn 013 (minus2)ndash0 minus163 plusmn 013 (minus2)ndash0 minus063 plusmn 021 (minus2)ndash0

a p lt 001b p lt 005

c p lt 0001Other (Monk Seal Big Game Animals) minus133 plusmn 033 (minus2)ndash(minus1) 0 0 0 0 b ns

Overall Means minus104 minus128 minus038

California Counties

Tree-Dwelling andormdashnesting birds minus011 plusmn 035 (minus2)ndash2 minus164 (minus2)ndash(minus1) minus033 (minus1)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andormdashnesting birds minus109 plusmn 028 (minus2)ndash0 minus146 plusmn 018 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0ab ns

c p lt 005Waterfowl minus109 plusmn 028 (minus2)ndash0 minus130 plusmn 026 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Tree-dwelling animals minus078 plusmn 032 (minus2)ndash0 minus125 plusmn 037 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsGround-dwelling animals minus131 plusmn 021 (minus2)ndash0 minus140 plusmn 022 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abcns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus086 plusmn 034 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsThreatened Endangered andor Sensitive species minus130 plusmn 030 (minus2)ndash0 minus144 plusmn 029 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Other (Monk Seal Big Game Animals) 0 0 0 0 0 0 -Overall Means minus077 minus117 minus029

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 5 of 18

For ldquoaverage numbers of unconfined animalsrdquo reported at each sighting (Figure 2 Table 1)dogs were most often sighted as single animals whereas cats were seen in groups of three or morewith increasing numbers of cats observed as ldquofree-livingrdquo ldquoferal (breeding)rdquo and ldquonaturalizedrdquo animalsIn ldquourban-suburbanrdquo and rural-agricultural settings state and provincial agencies reported dogs andcats in equal numbers whereas the California county agencies observed increased numbers of cats inthese areas For most other areas cats were seen in greater numbers than dogs and large numbers offeral cats were observed by all of the agencies Except for occasional strays in areas of human activityno California agency reported ferrets as ldquonaturalizedrdquo ldquoferal (breeding)rdquo or ldquofree-livingrdquo

Animals 2017 7 78 5 of 18

Figure 1 Frequency of sighting for unconfined dogs cats and ferrets for (a) United States and

Canada (b) California counties Rating mean plusmn standard error of the mean (sem) Asterisk represents

significant difference p lt 005 p lt 0001

For ldquoaverage numbers of unconfined animalsrdquo reported at each sighting (Figure 2 Table 1) dogs

were most often sighted as single animals whereas cats were seen in groups of three or more with

increasing numbers of cats observed as ldquofree-livingrdquo ldquoferal (breeding)rdquo and ldquonaturalizedrdquo animals

In ldquourban-suburbanrdquo and rural-agricultural settings state and provincial agencies reported dogs and

cats in equal numbers whereas the California county agencies observed increased numbers of cats

in these areas For most other areas cats were seen in greater numbers than dogs and large numbers

of feral cats were observed by all of the agencies Except for occasional strays in areas of human

activity no California agency reported ferrets as ldquonaturalizedrdquo ldquoferal (breeding)rdquo or ldquofree-livingrdquo

Figure 2 Average number of animals per sighting of (a) United States Canada and (b)

California counties Rating mean plusmn standard error of the mean (sem) Asterisk represents

significant difference p lt 005 p lt 001

Table 1 Number of animals per sighting

Animal Sightings Dogs Cats Ferrets

p-Value Mean plusmn sem Mean plusmn sem Mean plusmn sem

United States and Canada

Straymdashurbansuburban 106 plusmn 018 086 plusmn 014 038 plusmn 018 ac ns

b p lt 005

Straymdashruralagricultural 112 plusmn 017 086 plusmn 014 029 plusmn 018 a ns

bc p lt 005

Straymdashparks amp recreational areas 067 plusmn 016 213 plusmn 128 014 plusmn 014 abc ns

Straymdashwildlands 086 plusmn 018 100 plusmn 039 014 plusmn 014 a ns

bc p lt 005

Free-living (surviving gt 1 week) 067 plusmn 014 225 plusmn 162 014 plusmn 014 a ns

bc p lt 005

Figure 2 Average number of animals per sighting of (A) United States Canada and (B) Californiacounties Rating mean plusmn standard error of the mean (sem) Asterisk represents significant difference p lt 005

Table 1 Number of animals per sighting

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem Mean plusmn sem Mean plusmn sem

United States and Canada

Straymdashurbansuburban 106 plusmn 018 086 plusmn 014 038 plusmn 018ac ns

b p lt 005

Straymdashruralagricultural 112 plusmn 017 086 plusmn 014 029 plusmn 018a ns

bc p lt 005Straymdashparks amp recreational areas 067 plusmn 016 213 plusmn 128 014 plusmn 014 abc ns

Straymdashwildlands 086 plusmn 018 100 plusmn 039 014 plusmn 014a ns

bc p lt 005

Free-living (surviving gt 1 week) 067 plusmn 014 225 plusmn 162 014 plusmn 014a ns

bc p lt 005

Feral (breeding) 073 plusmn 027 240 plusmn 196 000 plusmn 000ac ns

b p lt 005Naturalized 025 plusmn 016 288 plusmn 0245 000 plusmn 000 abc ns

Animals 2017 7 78 6 of 18

Table 1 Cont

Animal Sightings Dogs Cats Ferrets p-ValueMean plusmn sem Mean plusmn sem Mean plusmn sem

California CountiesStray Animalsmdashurbansuburban 127 plusmn 020 313 plusmn 160 075 plusmn 048 abc ns

Stray Animalsmdashruralagricultural 150 plusmn 029 229 plusmn 080 033 plusmn 033 abc ns

Stray animalsmdashparks amp recreational areas 142 plusmn 047 377 plusmn 176 033 plusmn 033ac ns

b p lt 005

Stray Animalsmdashwildlands 140 plusmn 052 144 plusmn 056 000 plusmn 000ac ns

b p lt 005Free-living animals (surviving gt 1 week) 079 plusmn 021 136 plusmn 052 000 plusmn 000 abc ns

Feral (Breeding) Animals 138 plusmn 068 425 plusmn 103 000 plusmn 000ac p lt 005

b nsNaturalized animals 000 plusmn 000 040 plusmn 040 000 plusmn 000 ac ns

Statistical comparisons a dogs vscats b ferrets vs dogs c ferrets vs cats sem standard error of the meanns nonsignificant

32 Sighting of Unconfined AnimalsmdashrdquoDegree of Concernrdquo

Respondents were asked to rank their ldquodegree of concernrdquo regarding the existence of unconfineddogs cats and ferrets Ratings were quantified as follows ldquodefinite concernrdquo (minus2) ldquosome concernrdquo(minus1) ldquono concernrdquo (0) ldquosome benefitrdquo (+1) or ldquodefinite benefitrdquo (+2) For state and provincial agenciescats and dogs engendered ldquosome concernrdquo to ldquodefinite concernrdquo (Table 2) Feral cats were ranked thehighest ldquodegree of concernrdquo (minus183) Overall unconfined cats ranked higher than dogs with ferretsgiven the lowest level of concern (Overall Means cats minus173 dogs minus147 ferrets minus056)

Ratings from the California county agencies were somewhat lower than those given by states andprovinces (Overall Means cats minus123 dogs minus121 ferrets minus043) The greatest ldquodegree of concernrdquowas from unconfined dogs in recreational (minus174) and agricultural (minus169) areas and from unconfinedstray cats in urban-suburban (minus158) and in agricultural areas (minus144) and in the feral state (minus144)County agencies which ranked ferrets lowest overall most notably had the least concerns over ldquoferalrdquo(minus036) or ldquonaturalizedrdquo (minus022) ferrets which conformed to agenciesrsquo lack of sightings or reports offerrets existing in these states

33 Impact Existence of Incidents on Wildlife from Unconfined Animals and Degree of Concern

Respondents were also asked to identify the existence of incidents or impact from unconfineddomestic carnivores on native wildlife (Figure 3 see also Supplementary Materials Table S1) Stateand provincial agencies ranked incidents from unconfined dogs and cats as ldquoreported to existrdquoor ldquopreviously existedrdquo regarding ldquotree-dwelling andor nesting birdsrdquo ldquoground-dwelling andornesting birdsrdquo ldquowaterfowlrdquo ldquotree-dwellingrdquo animals ldquoground-dwellingrdquo animalsrdquo ldquoaquatic animalsrdquoldquothreatened endangered andor sensitive speciesrdquo with Hawaii listing dogs as aggravating ldquomonkrdquoseals With the exception of the ldquomonkrdquo seal (Hawaii) and ldquobig gamerdquo animals cats received thehighest levels of incidents representing the greatest negative impact on wildlife for all categories (cats253 dogs 219) In contrast ferrets ranged from ldquoprobably does not existrdquo to ldquodefinitely does notexistrdquo (ferrets 059) Results from the California county agencies followed a similar pattern withferret-related incidents ranked the lowest (cats 155 dogs 115 ferrets 015)

State and provincial agencies ranked ldquodegree of concernrdquo highest for cats for their impact onldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs as aldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) (Table 3) The California county agenciesalso ranked cats the highest with regard to the ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo

Animals 2017 7 78 7 of 18

Table 2 ldquoDegree of concernrdquo regarding sightings of unconfined dogs cats ferrets

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Stray-urbansuburban minus158 plusmn 009 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus050 plusmn 012 (minus2)ndash0a ns

bc p lt 0001

Stray-rural agricultural minus161 plusmn 009 (minus2)ndash0 minus172 plusmn 009 (minus2)ndash1 minus054 plusmn 014 (minus2)ndash1a ns

bc p lt 0001

Stray-parks amp recreational areas minus157 plusmn 008 (minus2)ndash0 minus170 plusmn 009 (minus2)ndash1 minus056 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Stray-wildlands minus149 plusmn 010 (minus2)ndash0 minus170 plusmn 007 (minus2)ndash(minus1) minus058 plusmn 014 (minus2)ndash0a ns

bc p lt 0001

Free-living (surviving gt 1 week) minus150 plusmn 010 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus054 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Feral (Breeding) minus153 plusmn 010 (minus2)ndash0 minus183 plusmn 006 (minus2)ndash(minus1) minus054 plusmn 013 (minus2)ndash0a p lt 005

bc p lt 0001

Naturalized minus103 plusmn 018 (minus2)ndash2 minus161 plusmn 013 (minus2)ndash0 minus065 plusmn 015 (minus2)ndash0

a p lt 005b ns

c p lt 0001Overall Means minus147 minus173 minus056

California Counties

Stray-urbansuburban minus100 plusmn 019 (minus2)ndash0 minus158 plusmn 016 (minus2)ndash1 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-ruralagricultural minus174 plusmn 011 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash2 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-parks amp recreational areas minus169 plusmn 013 (minus2)ndash0 minus136 plusmn 016 (minus2)ndash1 minus050 plusmn 020 (minus2)ndash0

a nsbc p lt 0001

c p lt 001

Stray-wildlands minus128 plusmn 016 (minus2)ndash0 ndash108 plusmn 019 (minus2)ndash1 minus046 plusmn 022 (minus2)ndash0

a nsb p lt 001c p lt 005

Free-living (surviving gt 1 week) minus116 plusmn 018 (minus2)ndash0 minus119 plusmn 020 (minus2)ndash1 minus050 plusmn 023 (minus2)ndash0a ns

bc p lt 005

Feral (Breeding) minus129 plusmn 018 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash1 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 001Naturalized minus033 plusmn 026 (minus2)ndash1 minus050 plusmn 025 (minus2)ndash1 minus022 plusmn 022 (minus2)ndash0 abc ns

Overall Means minus121 minus123 minus0431 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 8 of 18

1

Figure 3 ldquoExistencerdquo of incidents (impact) on wildlife from unconfined dogs cats ferrets (A) UnitedStates Canada and (B) California counties Rating mean plusmn standard error of the mean (sem) Asteriskrepresents significant difference p lt 005 p lt 001 and p lt 0001

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals andDegree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to theother environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured moreprominently than dogs in all of the wildlife categories for state and provincial agencies as well as theCalifornia county agencies with the exception of ldquootherrdquo animals Dogs were listed as having a greaterimpact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California counties notedthat both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impacton ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogsas a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California countyagencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo (Table 4)

Animals 2017 7 78 9 of 18

Animals 2017 7 x 9 of 18

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals and

Degree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to the

other environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured

more prominently than dogs in all of the wildlife categories for state and provincial agencies as well

as the California county agencies with the exception of ldquootherrdquo animals Dogs were listed as having

a greater impact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California

counties noted that both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impact

on ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs

as a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California county

agencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at least

ldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andor

sensitive speciesrdquo (Table 4)

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from

unconfined dogs cats ferrets (a) United States Canada and (b) California counties Rating mean plusmn

standard error of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and

p lt 0001

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from unconfineddogs cats ferrets (A) United States Canada and (B) California counties Rating mean plusmn standarderror of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and p lt0001

Animals 2017 7 78 10 of 18

Table 3 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife

Effects on WildlifeDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus068 plusmn 013 (minus2)ndash0 minus178 plusmn 007 (minus2)ndash(minus1) minus033 plusmn 014 (minus2)ndash0ac p lt 0001

b nsGround-dwelling andorndashnesting birds minus143 plusmn 010 (minus2)ndash0 minus190 plusmn 005 (minus2)ndash(minus1) minus056 plusmn 018 (minus2)ndash0 abc p lt 0001

Waterfowl minus109 plusmn 011 (minus2)ndash0 minus141 plusmn 011 (minus2)ndash0 minus033 plusmn 011 (minus1)ndash0a p lt 005

bc p lt 0001

Tree-dwelling animals minus075 plusmn 011 (minus2)ndash0 minus128 plusmn 014 (minus2)ndash0 minus044 plusmn 015 (minus2)ndash0

a p lt 001b ns

c p lt 0001

Ground-dwelling animals minus136 plusmn 010 (minus2)ndash0 minus162 plusmn 009 (minus2)ndash0 minus056 plusmn 018 (minus2)ndash0a ns

bc p lt 0001

Aquatic animals minus054 plusmn 011 (minus2)ndash0 minus063 plusmn 012 (minus2)ndash0 minus022 plusmn 010 (minus1)ndash0ab ns

c p lt 005

Threatened Endangered andor Sensitive species minus113 plusmn 013 (minus2)ndash0 minus163 plusmn 013 (minus2)ndash0 minus063 plusmn 021 (minus2)ndash0

a p lt 001b p lt 005

c p lt 0001Other (Monk Seal Big Game Animals) minus133 plusmn 033 (minus2)ndash(minus1) 0 0 0 0 b ns

Overall Means minus104 minus128 minus038

California Counties

Tree-Dwelling andormdashnesting birds minus011 plusmn 035 (minus2)ndash2 minus164 (minus2)ndash(minus1) minus033 (minus1)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andormdashnesting birds minus109 plusmn 028 (minus2)ndash0 minus146 plusmn 018 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0ab ns

c p lt 005Waterfowl minus109 plusmn 028 (minus2)ndash0 minus130 plusmn 026 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Tree-dwelling animals minus078 plusmn 032 (minus2)ndash0 minus125 plusmn 037 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsGround-dwelling animals minus131 plusmn 021 (minus2)ndash0 minus140 plusmn 022 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abcns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus086 plusmn 034 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsThreatened Endangered andor Sensitive species minus130 plusmn 030 (minus2)ndash0 minus144 plusmn 029 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Other (Monk Seal Big Game Animals) 0 0 0 0 0 0 -Overall Means minus077 minus117 minus029

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 6 of 18

Table 1 Cont

Animal Sightings Dogs Cats Ferrets p-ValueMean plusmn sem Mean plusmn sem Mean plusmn sem

California CountiesStray Animalsmdashurbansuburban 127 plusmn 020 313 plusmn 160 075 plusmn 048 abc ns

Stray Animalsmdashruralagricultural 150 plusmn 029 229 plusmn 080 033 plusmn 033 abc ns

Stray animalsmdashparks amp recreational areas 142 plusmn 047 377 plusmn 176 033 plusmn 033ac ns

b p lt 005

Stray Animalsmdashwildlands 140 plusmn 052 144 plusmn 056 000 plusmn 000ac ns

b p lt 005Free-living animals (surviving gt 1 week) 079 plusmn 021 136 plusmn 052 000 plusmn 000 abc ns

Feral (Breeding) Animals 138 plusmn 068 425 plusmn 103 000 plusmn 000ac p lt 005

b nsNaturalized animals 000 plusmn 000 040 plusmn 040 000 plusmn 000 ac ns

Statistical comparisons a dogs vscats b ferrets vs dogs c ferrets vs cats sem standard error of the meanns nonsignificant

32 Sighting of Unconfined AnimalsmdashrdquoDegree of Concernrdquo

Respondents were asked to rank their ldquodegree of concernrdquo regarding the existence of unconfineddogs cats and ferrets Ratings were quantified as follows ldquodefinite concernrdquo (minus2) ldquosome concernrdquo(minus1) ldquono concernrdquo (0) ldquosome benefitrdquo (+1) or ldquodefinite benefitrdquo (+2) For state and provincial agenciescats and dogs engendered ldquosome concernrdquo to ldquodefinite concernrdquo (Table 2) Feral cats were ranked thehighest ldquodegree of concernrdquo (minus183) Overall unconfined cats ranked higher than dogs with ferretsgiven the lowest level of concern (Overall Means cats minus173 dogs minus147 ferrets minus056)

Ratings from the California county agencies were somewhat lower than those given by states andprovinces (Overall Means cats minus123 dogs minus121 ferrets minus043) The greatest ldquodegree of concernrdquowas from unconfined dogs in recreational (minus174) and agricultural (minus169) areas and from unconfinedstray cats in urban-suburban (minus158) and in agricultural areas (minus144) and in the feral state (minus144)County agencies which ranked ferrets lowest overall most notably had the least concerns over ldquoferalrdquo(minus036) or ldquonaturalizedrdquo (minus022) ferrets which conformed to agenciesrsquo lack of sightings or reports offerrets existing in these states

33 Impact Existence of Incidents on Wildlife from Unconfined Animals and Degree of Concern

Respondents were also asked to identify the existence of incidents or impact from unconfineddomestic carnivores on native wildlife (Figure 3 see also Supplementary Materials Table S1) Stateand provincial agencies ranked incidents from unconfined dogs and cats as ldquoreported to existrdquoor ldquopreviously existedrdquo regarding ldquotree-dwelling andor nesting birdsrdquo ldquoground-dwelling andornesting birdsrdquo ldquowaterfowlrdquo ldquotree-dwellingrdquo animals ldquoground-dwellingrdquo animalsrdquo ldquoaquatic animalsrdquoldquothreatened endangered andor sensitive speciesrdquo with Hawaii listing dogs as aggravating ldquomonkrdquoseals With the exception of the ldquomonkrdquo seal (Hawaii) and ldquobig gamerdquo animals cats received thehighest levels of incidents representing the greatest negative impact on wildlife for all categories (cats253 dogs 219) In contrast ferrets ranged from ldquoprobably does not existrdquo to ldquodefinitely does notexistrdquo (ferrets 059) Results from the California county agencies followed a similar pattern withferret-related incidents ranked the lowest (cats 155 dogs 115 ferrets 015)

State and provincial agencies ranked ldquodegree of concernrdquo highest for cats for their impact onldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs as aldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) (Table 3) The California county agenciesalso ranked cats the highest with regard to the ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo

Animals 2017 7 78 7 of 18

Table 2 ldquoDegree of concernrdquo regarding sightings of unconfined dogs cats ferrets

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Stray-urbansuburban minus158 plusmn 009 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus050 plusmn 012 (minus2)ndash0a ns

bc p lt 0001

Stray-rural agricultural minus161 plusmn 009 (minus2)ndash0 minus172 plusmn 009 (minus2)ndash1 minus054 plusmn 014 (minus2)ndash1a ns

bc p lt 0001

Stray-parks amp recreational areas minus157 plusmn 008 (minus2)ndash0 minus170 plusmn 009 (minus2)ndash1 minus056 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Stray-wildlands minus149 plusmn 010 (minus2)ndash0 minus170 plusmn 007 (minus2)ndash(minus1) minus058 plusmn 014 (minus2)ndash0a ns

bc p lt 0001

Free-living (surviving gt 1 week) minus150 plusmn 010 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus054 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Feral (Breeding) minus153 plusmn 010 (minus2)ndash0 minus183 plusmn 006 (minus2)ndash(minus1) minus054 plusmn 013 (minus2)ndash0a p lt 005

bc p lt 0001

Naturalized minus103 plusmn 018 (minus2)ndash2 minus161 plusmn 013 (minus2)ndash0 minus065 plusmn 015 (minus2)ndash0

a p lt 005b ns

c p lt 0001Overall Means minus147 minus173 minus056

California Counties

Stray-urbansuburban minus100 plusmn 019 (minus2)ndash0 minus158 plusmn 016 (minus2)ndash1 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-ruralagricultural minus174 plusmn 011 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash2 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-parks amp recreational areas minus169 plusmn 013 (minus2)ndash0 minus136 plusmn 016 (minus2)ndash1 minus050 plusmn 020 (minus2)ndash0

a nsbc p lt 0001

c p lt 001

Stray-wildlands minus128 plusmn 016 (minus2)ndash0 ndash108 plusmn 019 (minus2)ndash1 minus046 plusmn 022 (minus2)ndash0

a nsb p lt 001c p lt 005

Free-living (surviving gt 1 week) minus116 plusmn 018 (minus2)ndash0 minus119 plusmn 020 (minus2)ndash1 minus050 plusmn 023 (minus2)ndash0a ns

bc p lt 005

Feral (Breeding) minus129 plusmn 018 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash1 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 001Naturalized minus033 plusmn 026 (minus2)ndash1 minus050 plusmn 025 (minus2)ndash1 minus022 plusmn 022 (minus2)ndash0 abc ns

Overall Means minus121 minus123 minus0431 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 8 of 18

1

Figure 3 ldquoExistencerdquo of incidents (impact) on wildlife from unconfined dogs cats ferrets (A) UnitedStates Canada and (B) California counties Rating mean plusmn standard error of the mean (sem) Asteriskrepresents significant difference p lt 005 p lt 001 and p lt 0001

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals andDegree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to theother environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured moreprominently than dogs in all of the wildlife categories for state and provincial agencies as well as theCalifornia county agencies with the exception of ldquootherrdquo animals Dogs were listed as having a greaterimpact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California counties notedthat both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impacton ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogsas a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California countyagencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo (Table 4)

Animals 2017 7 78 9 of 18

Animals 2017 7 x 9 of 18

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals and

Degree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to the

other environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured

more prominently than dogs in all of the wildlife categories for state and provincial agencies as well

as the California county agencies with the exception of ldquootherrdquo animals Dogs were listed as having

a greater impact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California

counties noted that both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impact

on ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs

as a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California county

agencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at least

ldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andor

sensitive speciesrdquo (Table 4)

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from

unconfined dogs cats ferrets (a) United States Canada and (b) California counties Rating mean plusmn

standard error of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and

p lt 0001

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from unconfineddogs cats ferrets (A) United States Canada and (B) California counties Rating mean plusmn standarderror of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and p lt0001

Animals 2017 7 78 10 of 18

Table 3 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife

Effects on WildlifeDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus068 plusmn 013 (minus2)ndash0 minus178 plusmn 007 (minus2)ndash(minus1) minus033 plusmn 014 (minus2)ndash0ac p lt 0001

b nsGround-dwelling andorndashnesting birds minus143 plusmn 010 (minus2)ndash0 minus190 plusmn 005 (minus2)ndash(minus1) minus056 plusmn 018 (minus2)ndash0 abc p lt 0001

Waterfowl minus109 plusmn 011 (minus2)ndash0 minus141 plusmn 011 (minus2)ndash0 minus033 plusmn 011 (minus1)ndash0a p lt 005

bc p lt 0001

Tree-dwelling animals minus075 plusmn 011 (minus2)ndash0 minus128 plusmn 014 (minus2)ndash0 minus044 plusmn 015 (minus2)ndash0

a p lt 001b ns

c p lt 0001

Ground-dwelling animals minus136 plusmn 010 (minus2)ndash0 minus162 plusmn 009 (minus2)ndash0 minus056 plusmn 018 (minus2)ndash0a ns

bc p lt 0001

Aquatic animals minus054 plusmn 011 (minus2)ndash0 minus063 plusmn 012 (minus2)ndash0 minus022 plusmn 010 (minus1)ndash0ab ns

c p lt 005

Threatened Endangered andor Sensitive species minus113 plusmn 013 (minus2)ndash0 minus163 plusmn 013 (minus2)ndash0 minus063 plusmn 021 (minus2)ndash0

a p lt 001b p lt 005

c p lt 0001Other (Monk Seal Big Game Animals) minus133 plusmn 033 (minus2)ndash(minus1) 0 0 0 0 b ns

Overall Means minus104 minus128 minus038

California Counties

Tree-Dwelling andormdashnesting birds minus011 plusmn 035 (minus2)ndash2 minus164 (minus2)ndash(minus1) minus033 (minus1)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andormdashnesting birds minus109 plusmn 028 (minus2)ndash0 minus146 plusmn 018 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0ab ns

c p lt 005Waterfowl minus109 plusmn 028 (minus2)ndash0 minus130 plusmn 026 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Tree-dwelling animals minus078 plusmn 032 (minus2)ndash0 minus125 plusmn 037 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsGround-dwelling animals minus131 plusmn 021 (minus2)ndash0 minus140 plusmn 022 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abcns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus086 plusmn 034 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsThreatened Endangered andor Sensitive species minus130 plusmn 030 (minus2)ndash0 minus144 plusmn 029 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Other (Monk Seal Big Game Animals) 0 0 0 0 0 0 -Overall Means minus077 minus117 minus029

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 7 of 18

Table 2 ldquoDegree of concernrdquo regarding sightings of unconfined dogs cats ferrets

Animal SightingsDogs Cats Ferrets

p-ValueMean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Stray-urbansuburban minus158 plusmn 009 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus050 plusmn 012 (minus2)ndash0a ns

bc p lt 0001

Stray-rural agricultural minus161 plusmn 009 (minus2)ndash0 minus172 plusmn 009 (minus2)ndash1 minus054 plusmn 014 (minus2)ndash1a ns

bc p lt 0001

Stray-parks amp recreational areas minus157 plusmn 008 (minus2)ndash0 minus170 plusmn 009 (minus2)ndash1 minus056 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Stray-wildlands minus149 plusmn 010 (minus2)ndash0 minus170 plusmn 007 (minus2)ndash(minus1) minus058 plusmn 014 (minus2)ndash0a ns

bc p lt 0001

Free-living (surviving gt 1 week) minus150 plusmn 010 (minus2)ndash0 minus176 plusmn 008 (minus2)ndash0 minus054 plusmn 013 (minus2)ndash0a ns

bc p lt 0001

Feral (Breeding) minus153 plusmn 010 (minus2)ndash0 minus183 plusmn 006 (minus2)ndash(minus1) minus054 plusmn 013 (minus2)ndash0a p lt 005

bc p lt 0001

Naturalized minus103 plusmn 018 (minus2)ndash2 minus161 plusmn 013 (minus2)ndash0 minus065 plusmn 015 (minus2)ndash0

a p lt 005b ns

c p lt 0001Overall Means minus147 minus173 minus056

California Counties

Stray-urbansuburban minus100 plusmn 019 (minus2)ndash0 minus158 plusmn 016 (minus2)ndash1 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-ruralagricultural minus174 plusmn 011 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash2 minus047 plusmn 019 (minus2)ndash0a ns

bc p lt 0001

Stray-parks amp recreational areas minus169 plusmn 013 (minus2)ndash0 minus136 plusmn 016 (minus2)ndash1 minus050 plusmn 020 (minus2)ndash0

a nsbc p lt 0001

c p lt 001

Stray-wildlands minus128 plusmn 016 (minus2)ndash0 ndash108 plusmn 019 (minus2)ndash1 minus046 plusmn 022 (minus2)ndash0

a nsb p lt 001c p lt 005

Free-living (surviving gt 1 week) minus116 plusmn 018 (minus2)ndash0 minus119 plusmn 020 (minus2)ndash1 minus050 plusmn 023 (minus2)ndash0a ns

bc p lt 005

Feral (Breeding) minus129 plusmn 018 (minus2)ndash0 minus144 plusmn 020 (minus2)ndash1 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 001Naturalized minus033 plusmn 026 (minus2)ndash1 minus050 plusmn 025 (minus2)ndash1 minus022 plusmn 022 (minus2)ndash0 abc ns

Overall Means minus121 minus123 minus0431 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 8 of 18

1

Figure 3 ldquoExistencerdquo of incidents (impact) on wildlife from unconfined dogs cats ferrets (A) UnitedStates Canada and (B) California counties Rating mean plusmn standard error of the mean (sem) Asteriskrepresents significant difference p lt 005 p lt 001 and p lt 0001

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals andDegree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to theother environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured moreprominently than dogs in all of the wildlife categories for state and provincial agencies as well as theCalifornia county agencies with the exception of ldquootherrdquo animals Dogs were listed as having a greaterimpact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California counties notedthat both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impacton ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogsas a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California countyagencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo (Table 4)

Animals 2017 7 78 9 of 18

Animals 2017 7 x 9 of 18

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals and

Degree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to the

other environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured

more prominently than dogs in all of the wildlife categories for state and provincial agencies as well

as the California county agencies with the exception of ldquootherrdquo animals Dogs were listed as having

a greater impact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California

counties noted that both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impact

on ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs

as a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California county

agencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at least

ldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andor

sensitive speciesrdquo (Table 4)

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from

unconfined dogs cats ferrets (a) United States Canada and (b) California counties Rating mean plusmn

standard error of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and

p lt 0001

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from unconfineddogs cats ferrets (A) United States Canada and (B) California counties Rating mean plusmn standarderror of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and p lt0001

Animals 2017 7 78 10 of 18

Table 3 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife

Effects on WildlifeDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus068 plusmn 013 (minus2)ndash0 minus178 plusmn 007 (minus2)ndash(minus1) minus033 plusmn 014 (minus2)ndash0ac p lt 0001

b nsGround-dwelling andorndashnesting birds minus143 plusmn 010 (minus2)ndash0 minus190 plusmn 005 (minus2)ndash(minus1) minus056 plusmn 018 (minus2)ndash0 abc p lt 0001

Waterfowl minus109 plusmn 011 (minus2)ndash0 minus141 plusmn 011 (minus2)ndash0 minus033 plusmn 011 (minus1)ndash0a p lt 005

bc p lt 0001

Tree-dwelling animals minus075 plusmn 011 (minus2)ndash0 minus128 plusmn 014 (minus2)ndash0 minus044 plusmn 015 (minus2)ndash0

a p lt 001b ns

c p lt 0001

Ground-dwelling animals minus136 plusmn 010 (minus2)ndash0 minus162 plusmn 009 (minus2)ndash0 minus056 plusmn 018 (minus2)ndash0a ns

bc p lt 0001

Aquatic animals minus054 plusmn 011 (minus2)ndash0 minus063 plusmn 012 (minus2)ndash0 minus022 plusmn 010 (minus1)ndash0ab ns

c p lt 005

Threatened Endangered andor Sensitive species minus113 plusmn 013 (minus2)ndash0 minus163 plusmn 013 (minus2)ndash0 minus063 plusmn 021 (minus2)ndash0

a p lt 001b p lt 005

c p lt 0001Other (Monk Seal Big Game Animals) minus133 plusmn 033 (minus2)ndash(minus1) 0 0 0 0 b ns

Overall Means minus104 minus128 minus038

California Counties

Tree-Dwelling andormdashnesting birds minus011 plusmn 035 (minus2)ndash2 minus164 (minus2)ndash(minus1) minus033 (minus1)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andormdashnesting birds minus109 plusmn 028 (minus2)ndash0 minus146 plusmn 018 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0ab ns

c p lt 005Waterfowl minus109 plusmn 028 (minus2)ndash0 minus130 plusmn 026 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Tree-dwelling animals minus078 plusmn 032 (minus2)ndash0 minus125 plusmn 037 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsGround-dwelling animals minus131 plusmn 021 (minus2)ndash0 minus140 plusmn 022 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abcns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus086 plusmn 034 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsThreatened Endangered andor Sensitive species minus130 plusmn 030 (minus2)ndash0 minus144 plusmn 029 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Other (Monk Seal Big Game Animals) 0 0 0 0 0 0 -Overall Means minus077 minus117 minus029

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 8 of 18

1

Figure 3 ldquoExistencerdquo of incidents (impact) on wildlife from unconfined dogs cats ferrets (A) UnitedStates Canada and (B) California counties Rating mean plusmn standard error of the mean (sem) Asteriskrepresents significant difference p lt 005 p lt 001 and p lt 0001

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals andDegree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to theother environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured moreprominently than dogs in all of the wildlife categories for state and provincial agencies as well as theCalifornia county agencies with the exception of ldquootherrdquo animals Dogs were listed as having a greaterimpact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California counties notedthat both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impacton ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogsas a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California countyagencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at leastldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andorsensitive speciesrdquo (Table 4)

Animals 2017 7 78 9 of 18

Animals 2017 7 x 9 of 18

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals and

Degree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to the

other environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured

more prominently than dogs in all of the wildlife categories for state and provincial agencies as well

as the California county agencies with the exception of ldquootherrdquo animals Dogs were listed as having

a greater impact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California

counties noted that both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impact

on ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs

as a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California county

agencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at least

ldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andor

sensitive speciesrdquo (Table 4)

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from

unconfined dogs cats ferrets (a) United States Canada and (b) California counties Rating mean plusmn

standard error of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and

p lt 0001

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from unconfineddogs cats ferrets (A) United States Canada and (B) California counties Rating mean plusmn standarderror of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and p lt0001

Animals 2017 7 78 10 of 18

Table 3 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife

Effects on WildlifeDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus068 plusmn 013 (minus2)ndash0 minus178 plusmn 007 (minus2)ndash(minus1) minus033 plusmn 014 (minus2)ndash0ac p lt 0001

b nsGround-dwelling andorndashnesting birds minus143 plusmn 010 (minus2)ndash0 minus190 plusmn 005 (minus2)ndash(minus1) minus056 plusmn 018 (minus2)ndash0 abc p lt 0001

Waterfowl minus109 plusmn 011 (minus2)ndash0 minus141 plusmn 011 (minus2)ndash0 minus033 plusmn 011 (minus1)ndash0a p lt 005

bc p lt 0001

Tree-dwelling animals minus075 plusmn 011 (minus2)ndash0 minus128 plusmn 014 (minus2)ndash0 minus044 plusmn 015 (minus2)ndash0

a p lt 001b ns

c p lt 0001

Ground-dwelling animals minus136 plusmn 010 (minus2)ndash0 minus162 plusmn 009 (minus2)ndash0 minus056 plusmn 018 (minus2)ndash0a ns

bc p lt 0001

Aquatic animals minus054 plusmn 011 (minus2)ndash0 minus063 plusmn 012 (minus2)ndash0 minus022 plusmn 010 (minus1)ndash0ab ns

c p lt 005

Threatened Endangered andor Sensitive species minus113 plusmn 013 (minus2)ndash0 minus163 plusmn 013 (minus2)ndash0 minus063 plusmn 021 (minus2)ndash0

a p lt 001b p lt 005

c p lt 0001Other (Monk Seal Big Game Animals) minus133 plusmn 033 (minus2)ndash(minus1) 0 0 0 0 b ns

Overall Means minus104 minus128 minus038

California Counties

Tree-Dwelling andormdashnesting birds minus011 plusmn 035 (minus2)ndash2 minus164 (minus2)ndash(minus1) minus033 (minus1)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andormdashnesting birds minus109 plusmn 028 (minus2)ndash0 minus146 plusmn 018 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0ab ns

c p lt 005Waterfowl minus109 plusmn 028 (minus2)ndash0 minus130 plusmn 026 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Tree-dwelling animals minus078 plusmn 032 (minus2)ndash0 minus125 plusmn 037 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsGround-dwelling animals minus131 plusmn 021 (minus2)ndash0 minus140 plusmn 022 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abcns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus086 plusmn 034 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsThreatened Endangered andor Sensitive species minus130 plusmn 030 (minus2)ndash0 minus144 plusmn 029 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Other (Monk Seal Big Game Animals) 0 0 0 0 0 0 -Overall Means minus077 minus117 minus029

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 9 of 18

Animals 2017 7 x 9 of 18

34 Impact Existence of Incidents on Wildlife in ParksmdashRecreational Areas from Unconfined Animals and

Degree of Concern

Impact ratings on the wildlife in parks and recreational areas followed a pattern similar to the

other environmental regions (Figure 4 see also Supplementary Materials Table S2) Cats featured

more prominently than dogs in all of the wildlife categories for state and provincial agencies as well

as the California county agencies with the exception of ldquootherrdquo animals Dogs were listed as having

a greater impact on the ldquomonkrdquo seal and ldquobig gamerdquo Interestingly under ldquootherrdquo the California

counties noted that both cats dogs (ldquoon leashesrdquo) and humans as having impact in recreational areas

State and provincial agencies also ranked ldquodegree of concernrdquo highest for cats for their impact

on ldquotree-dwellingrdquo and ldquoground dwellingrdquo birds with the exception of Hawaii which ranked dogs

as a ldquodefinite concernrdquo with respect to the ldquomonkrdquo seal (ldquootherrdquo) Similarly the California county

agencies ranked cats the highest with regard to ldquodegree of concernrdquo although they expressed at least

ldquosome concernrdquo for all three species when unconfined with regard to ldquothreatened endangered andor

sensitive speciesrdquo (Table 4)

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from

unconfined dogs cats ferrets (a) United States Canada and (b) California counties Rating mean plusmn

standard error of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and

p lt 0001

Figure 4 ldquoExistencerdquo of incidents (impact) on wildlife in parks and recreational areas from unconfineddogs cats ferrets (A) United States Canada and (B) California counties Rating mean plusmn standarderror of the mean (sem) Asterisk represents significant difference p lt 005 p lt 001 and p lt0001

Animals 2017 7 78 10 of 18

Table 3 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife

Effects on WildlifeDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus068 plusmn 013 (minus2)ndash0 minus178 plusmn 007 (minus2)ndash(minus1) minus033 plusmn 014 (minus2)ndash0ac p lt 0001

b nsGround-dwelling andorndashnesting birds minus143 plusmn 010 (minus2)ndash0 minus190 plusmn 005 (minus2)ndash(minus1) minus056 plusmn 018 (minus2)ndash0 abc p lt 0001

Waterfowl minus109 plusmn 011 (minus2)ndash0 minus141 plusmn 011 (minus2)ndash0 minus033 plusmn 011 (minus1)ndash0a p lt 005

bc p lt 0001

Tree-dwelling animals minus075 plusmn 011 (minus2)ndash0 minus128 plusmn 014 (minus2)ndash0 minus044 plusmn 015 (minus2)ndash0

a p lt 001b ns

c p lt 0001

Ground-dwelling animals minus136 plusmn 010 (minus2)ndash0 minus162 plusmn 009 (minus2)ndash0 minus056 plusmn 018 (minus2)ndash0a ns

bc p lt 0001

Aquatic animals minus054 plusmn 011 (minus2)ndash0 minus063 plusmn 012 (minus2)ndash0 minus022 plusmn 010 (minus1)ndash0ab ns

c p lt 005

Threatened Endangered andor Sensitive species minus113 plusmn 013 (minus2)ndash0 minus163 plusmn 013 (minus2)ndash0 minus063 plusmn 021 (minus2)ndash0

a p lt 001b p lt 005

c p lt 0001Other (Monk Seal Big Game Animals) minus133 plusmn 033 (minus2)ndash(minus1) 0 0 0 0 b ns

Overall Means minus104 minus128 minus038

California Counties

Tree-Dwelling andormdashnesting birds minus011 plusmn 035 (minus2)ndash2 minus164 (minus2)ndash(minus1) minus033 (minus1)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andormdashnesting birds minus109 plusmn 028 (minus2)ndash0 minus146 plusmn 018 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0ab ns

c p lt 005Waterfowl minus109 plusmn 028 (minus2)ndash0 minus130 plusmn 026 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Tree-dwelling animals minus078 plusmn 032 (minus2)ndash0 minus125 plusmn 037 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsGround-dwelling animals minus131 plusmn 021 (minus2)ndash0 minus140 plusmn 022 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abcns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus086 plusmn 034 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsThreatened Endangered andor Sensitive species minus130 plusmn 030 (minus2)ndash0 minus144 plusmn 029 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Other (Monk Seal Big Game Animals) 0 0 0 0 0 0 -Overall Means minus077 minus117 minus029

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 10 of 18

Table 3 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife

Effects on WildlifeDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus068 plusmn 013 (minus2)ndash0 minus178 plusmn 007 (minus2)ndash(minus1) minus033 plusmn 014 (minus2)ndash0ac p lt 0001

b nsGround-dwelling andorndashnesting birds minus143 plusmn 010 (minus2)ndash0 minus190 plusmn 005 (minus2)ndash(minus1) minus056 plusmn 018 (minus2)ndash0 abc p lt 0001

Waterfowl minus109 plusmn 011 (minus2)ndash0 minus141 plusmn 011 (minus2)ndash0 minus033 plusmn 011 (minus1)ndash0a p lt 005

bc p lt 0001

Tree-dwelling animals minus075 plusmn 011 (minus2)ndash0 minus128 plusmn 014 (minus2)ndash0 minus044 plusmn 015 (minus2)ndash0

a p lt 001b ns

c p lt 0001

Ground-dwelling animals minus136 plusmn 010 (minus2)ndash0 minus162 plusmn 009 (minus2)ndash0 minus056 plusmn 018 (minus2)ndash0a ns

bc p lt 0001

Aquatic animals minus054 plusmn 011 (minus2)ndash0 minus063 plusmn 012 (minus2)ndash0 minus022 plusmn 010 (minus1)ndash0ab ns

c p lt 005

Threatened Endangered andor Sensitive species minus113 plusmn 013 (minus2)ndash0 minus163 plusmn 013 (minus2)ndash0 minus063 plusmn 021 (minus2)ndash0

a p lt 001b p lt 005

c p lt 0001Other (Monk Seal Big Game Animals) minus133 plusmn 033 (minus2)ndash(minus1) 0 0 0 0 b ns

Overall Means minus104 minus128 minus038

California Counties

Tree-Dwelling andormdashnesting birds minus011 plusmn 035 (minus2)ndash2 minus164 (minus2)ndash(minus1) minus033 (minus1)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andormdashnesting birds minus109 plusmn 028 (minus2)ndash0 minus146 plusmn 018 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0ab ns

c p lt 005Waterfowl minus109 plusmn 028 (minus2)ndash0 minus130 plusmn 026 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Tree-dwelling animals minus078 plusmn 032 (minus2)ndash0 minus125 plusmn 037 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsGround-dwelling animals minus131 plusmn 021 (minus2)ndash0 minus140 plusmn 022 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abcns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus086 plusmn 034 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc nsThreatened Endangered andor Sensitive species minus130 plusmn 030 (minus2)ndash0 minus144 plusmn 029 (minus2)ndash0 minus033 plusmn 033 (minus1)ndash0 abc ns

Other (Monk Seal Big Game Animals) 0 0 0 0 0 0 -Overall Means minus077 minus117 minus029

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 11 of 18

Table 4 ldquoDegree of concernrdquo regarding the effects (impact) of unconfined animal on wildlife in parks and recreational areas

Effects on ParksRecreational AreasDogs Cats Ferrets p-Value

Mean plusmn sem 1 Rating Range Mean plusmn sem Rating Range Mean plusmn sem Rating Range

United States DC and Canada

Tree-Dwelling andorndashnesting birds minus054 plusmn 012 (minus2)ndash0 minus135 plusmn 016 (minus2)ndash0 minus064 plusmn 017 (minus2)ndash0

a p lt 0001b ns

c p lt 001

Ground-dwelling andorndashnesting birds minus125 plusmn 014 (minus2)ndash0 minus157 plusmn 013 (minus2)ndash0 minus036 plusmn 020 (minus2)ndash0a ns

bc p lt 0001

Waterfowl minus096 plusmn 014 (minus2)ndash0 minus115 plusmn 015 (minus2)ndash0 minus007 plusmn 007 (minus1)ndash0a ns

bc p lt 0001

Tree-dwelling animals minus043 plusmn 012 (minus2)ndash0 minus120 plusmn 015 (minus2)ndash0 minus023 plusmn 017 (minus2)ndash0ac p lt 0001

b ns

Ground-dwelling animals minus119 plusmn 012 (minus2)ndash0 minus142 plusmn 014 (minus2)ndash0 minus029 plusmn 016 (minus2)ndash0a ns

bc p lt 0001Aquatic animals minus045 plusmn 014 (minus2)ndash0 minus045 plusmn 014 (minus2)ndash0 minus013 plusmn 009 (minus1)ndash0 abc ns

Threatened Endangered andor Sensitive species minus112 plusmn 017 (minus2)ndash0 minus144 plusmn 016 (minus2)ndash0 minus043 plusmn 020 (minus2)ndash0

a nsb p lt 005c p lt 001

Other (monk sealhumansdomesticated dogs) minus200 minus2 - - - - -Overall Mean minus099 minus123 minus031

California CountiesTree-Dwelling andor- nesting birds minus033 plusmn 033 (minus2)ndash0 minus111 plusmn 031 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Ground-dwelling andor- nesting birds minus089 plusmn 031 (minus2)ndash0 minus133 plusmn 029 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsWaterfowl minus071 plusmn 036 (minus2)ndash0 minus117 plusmn 040 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Tree-dwelling animals minus033 plusmn 033 (minus2)ndash0 minus100 plusmn 045 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc nsGround-dwelling animals minus089 plusmn 026 (minus2)ndash0 minus113 plusmn 030 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Aquatic animals minus050 plusmn 034 (minus2)ndash0 minus071 plusmn 036 (minus2)ndash0 minus050 plusmn 050 (minus2)ndash0 abc nsThreatened Endangered andor Sensitive species minus100 plusmn 038 (minus2)ndash0 minus129 plusmn 036 (minus2)ndash0 minus067 plusmn 067 (minus2)ndash0 abc ns

Other (monk sealhumansdomesticated dogs) - - - - - - -Overall Mean minus067 minus111 minus064

1 Rating scale ldquodefinite concernrdquo minus2 ldquosome concernrdquo minus1 ldquono concernrdquo 0 ldquosome benefitrdquo +1 ldquodefinite benefitrdquo +2 Statistical comparisons a dogs vs cats b ferrets vs dogs c ferrets vscats sem standard error of the mean ns nonsignificant

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 12 of 18

35 Classifications

Table 5 shows the terms used by agencies to classify dogs cats and ferrets Overwhelmingly dogsand cats were classified as ldquohouse-petrdquo or ldquocompanionrdquo animal by both state and provincial agencies(gt76) and county agencies of California (90) in contrast to ferrets (54 and 10 respectively)There was much greater recognition of dogs and cats as ldquodomesticrdquo or ldquodomesticatedrdquo (gt80) versusferrets (statesprovinces 61 California counties 14) Ferrets were frequently identified as ldquoexoticrdquoanimals (statesprovinces 26 California counties 59) whereas dogs and cats were not (0ndash3)A minority of state and provincial agencies classified ferrets as ldquolisted restricted not permittedrdquo(7) or ldquorestricted except under permitrdquo (3) whereas most but not all California county agenciesclassified ferrets as such (38 and 41 respectively)

Table 5 Terms used by agencies to classify dogs cats ferrets

Classification Dogs Cats Ferrets

United States DC and CanadaldquoHouse-petrdquo or ldquoCompanionrdquo 56 (78) 55 (76) 39 (54)ldquoDomesticrdquo or ldquoDomesticatedrdquo 59 (82) 58 (81) 44 (61)

ldquoExotic animalrdquo 1 (1) 2 (3) 19 (26)ldquoNon-gamerdquo 9 (13) 9 (13) 10 (14)

ldquoFur-bearingrdquo 0 1 (1) 8 (11)ldquoLaboratoryrdquo or ldquoResearchrdquo 13 (18) 13 (18) 9 (13)

ldquoWildrdquo or Wildliferdquo 2 (3) 2 (3) 7 (10)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 10 (14) 9 (13) 14 (19)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 3 (4) 2 (3) 2 (3)

ldquoRestricted except under a permitrdquo 0 0 5 (7)Other (Please specify in Comments) 1 (1) 2 (3) 2 (3)

No Classification 9 (13) 11 (15) 12 (17)

California CountiesldquoHouse- petrdquo or ldquoCompanionrdquo 26 (90) 26 (90) 3 (10)ldquoDomesticrdquo or ldquoDomesticatedrdquo 26 (90) 25 (86) 4 (14)

ldquoExotic animalrdquo 0 1 (3) 17 (59)ldquoNon-gamerdquo 12 (41) 11 (38) 9 (31)

ldquoFur-bearingrdquo 2 (7) 2 (7) 8 (28)ldquoLaboratoryrdquo or ldquoResearchrdquo 8 (28) 7 (24) 3 (10)

ldquoWildrdquo or Wildliferdquo 2 (7) 1 (3) 8 (28)ldquoUnlistedrdquo or ldquoUnrestrictedrdquo or ldquoPermittedrdquo 6 (21) 6 (21) 2 (7)ldquoListedrdquo or ldquoRestrictedrdquo or ldquoNot permittedrdquo 1 (3) 1 (3) 11 (38)

ldquoRestricted except under a permitrdquo 1 (3) 0 12 (41)Other (Please specify in Comments) 0 0 1 (3)

No Classification 3 (10) 3 (10) 2 (7)

36 Actions Taken

Agencies were asked to list the actions undertaken when a free-roaming animal is found in theirjurisdiction Overall agencies reported a wide-range of actions taken (Table 6) California countyagencies reported that free-roaming dogs and cats were assumed to be lost pets (dogs 67 cats 55)that were trapped and then taken to shelters At the state-provincial level 40 of responders reportedmaking ldquoreferrals to another agencyrdquo which likely may have included animal control at a morelocal level Despite reports of negative effects from free-roaming dogs and cats on wildlife and a highldquodegree of concernrdquo a small number of agencies reported that they would not take action as it was ldquonotconsidered to be importantrdquo For free-roaming cats 21 stateprovincial agencies and 12 Californiacounty agencies reported that no action would be taken as it was ldquodesirable but not feasiblerdquo to do so

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 13 of 18

Table 6 Actions taken by agencies for unconfined dogs cats ferrets

Action Taken Dogs Cats Ferrets

United States DC and CanadaNone not considered to be important 2 (3) 3 (4) 8 (11)

None desirable but not feasible 12 (17) 15 (21) 9 (13)Live traptake to shelter (assumed lost pet) 17 (24) 15 (21) 8 (11)

Live trapeuthanize 8 (11) 10 (14) 7 (10)Live traptransport (specify destination in Comments) 7 (10) 9 (13) 4 (6)

Take by any means 10 (14) 5 (7) 4 (6)Refer to another agency (specify in Comments) 27 (38) 24 (34) 19 (27)

Attempt eradication 3 (4) 4 (6) 4 (6)Unknown 3 (4) 4 (6) 8 (11)

California CountiesNone not considered to be important 1 (3) 3 (9) 2 (6)

None desirable but not feasible 0 4 (12) 0Live traptake to shelter (assumed lost pet) 22 (67) 18 (55) 6 (18)

Live trapeuthanize 7 (21) 7 (21) 5 (15)Live traptransport (specify destination in Comments) 4 (12) 3 (9) 2 (6)

Take by any means 5 (15) 2 (6) 4 (12)Refer to another agency (specify in Comments) 4 (12) 4 (12) 13 (40)

Attempt eradication 2 (6) 1 (3) 2 (6)Unknown 0 0 1 (3)

37 ldquoSpecial Concernsrdquo

ldquoSpecial concernsrdquo were provided by 52 (35-stateprovincial 17 California county) agenciesThe majority of commenters at the state and provincial levels represented fish and wildlife agenciesand at the county level animal control Cats were mentioned most often (22ndash43) with ldquoferalrdquocats listed as a major concern based on their impact on wildlife and disease transmission such asrabies followed by dogs (13ndash25) and specifically dogs ldquooff-leashrdquo Only six (3-stateprovincial and3-county) agencies mentioned ferrets Commenters from stateprovincial agencies called out thatno ldquoferalrdquo or ldquowild ferretsrdquo existed within their jurisdiction or that ferrets posed little or no concernOne California county agency expressed concerns that unconfined ferrets and cats could potentiallycause harm to native animals two counties commented that ferrets were ldquonot legalrdquo in the state

4 Discussion

This is the first survey to compare the environmental impact of three non-native domesticcarnivores While other surveys have addressed the impact of free-roaming dogs cats or ferretsnone has conducted a head-to-head comparison nor described the relative impact of these carnivoreson the wildlife of North America [143233] A key advantage of this survey over those conductedby governmental bodies or well-known organizations is the anonymity of SeaSearch which holdsno public position or political agenda that would influence the responder Due to the uniformityof the respondents who had similar roles and backgrounds in their respective agencies as wellas the relatively small number of nonresponders concern regarding ldquonon-responserdquo bias wasminimized [3435] Limitations to this study however include the inherent inaccuracies of retrospectivereporting (ldquorecall errorrdquo) intra-observer variation due to individual bias or experience potential impactof local laws regulation and practices as well as a lack of documentation from respondents supportingtheir ratings [3637]

The results from the current study showed remarkable consistency with prior reports In thissurvey the existence of feral cats and dogs was consistently reported as well as their profound impacton local wildlife Free-roaming cats were identified as having the greatest environmental impactUnder ldquospecial concernsrdquo Hawaii stated ldquoThere are significantly more cats than there are dogs infree roaming populationsrdquo One of the biologists estimates a 91 ratio Iowa reported ldquoOur biggest

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 14 of 18

concerns would be free-ranging or feral cats and their potential impact on wildliferdquo New York voiceda concern of many of the states ldquoIn the case of dogs and cats these animals directly kill and injurecountless numbers of small mammals and birds up to and including white-tailed deer rdquo Quebecdescribed its management efforts ldquoIn the past years we have had problems with racoon (sic) rabiesIn an operation to control the disease in southern Quebec in 2007 we have captured 10000 racoons(sic) and 3500 domestic cats and only a few dogs rdquo

Aside from an occasional ldquostrayrdquo there were no reports of ldquoferal (breeding)rdquo ferrets nor werethere reports that of ldquofree-livingrdquo or ldquonaturalizedrdquo ferrets anywhere in the continental United Statesor Canada including California More importantly no jurisdiction reported ferrets impacting local(native) wildlife including ground-nesting birds or threatened endangered and sensitive species

Except for state requirements for licensing and routine immunization most animal controlactivities are at the level of local government and the private sector Cities county parks and recreationand housing and homeownersrsquo associations often impose ldquonuisancerdquo and ldquoleashrdquo laws limits onthe number of allowable animals and restrictions on ownership of certain dog breeds such as pitbulls [3839] However California under a 1933 law regulates ferrets as ldquowildliferdquo prohibiting theirsale or possession within the state [40] Concern over the ferretrsquos invasive potential has been largelybased on reports from island nations where deliberate introductions of species resulted in feral ferretsand other domestic species which caused harm to the local ecosystems [303140] In its response tothe current survey neither the state nor its county agencies reported feral ferrets or environmentalharm caused by ferrets confirming the statersquos own nation-wide survey [32] The sum of the resultscalls into question the relevancy of insular experiences to a state that is contiguous with the NorthAmerican continent

Regardless demands that ldquosolid scientific evidence demonstrating no risk to our native wildlifeand their habitatsrdquo regarding the ferret have continued [41] whereas most government agencies havetaken little action to curtail free-roaming cats and dogs in the face of irrefutable evidence of profoundnegative environmental impact Such regulatory bias may have less to do with objective data andmore to do with human nature [4243] Public attitudes and opinions towards various animals havebeen shown to be affected by ldquothe perceived attractiveness and usefulness of the species involvedindigenous or non-indigenousrdquo [44] The current study appears to support this conclusion As ldquospecialconcernsrdquo New York writes ldquo If pesticides were the cause of the numbers of wild animals and birdsinjured or killed each year by domestic and feral house cats the public would demand action to haltthis destruction However when there is direct evidence of such wanton waste by domestic and feralhouse cats the cat-lovers effectively threaten the elected officials from taking any actions to rid theenvironment of these introduced predatorsrdquo

Terminology used by agencies in describing these animals is also revealing In the present studydogs and cats are recognized as ldquohouse petsrdquomdashldquocompanionrdquo animals and ldquodomesticrdquomdashldquodomesticatedrdquospecies (Table 3) whereas the ferret is considered ldquoexoticrdquo ldquoExoticrdquo means ldquoforeignrdquo and ldquonot-nativerdquowhich makes the ferret no more ldquoexoticrdquo than the cat or dog (with the sole exception of the Alaskanmalamute) The fact that the veterinary community refers to all small animals that are ldquonot dogs or catsrdquoas ldquoexotic animalsrdquo undoubtedly contributes to the publicrsquos view of these respective carnivores [45]

Moreover in its current state code California lists the ferret as a ldquodetrimentalrdquo animalldquonot normally domesticated in this staterdquo whereas the Asian water buffalo (Bubalus bubalis) a relativelyrecent introduction to the state is considered a ldquowelfare animalrdquo a mammal so ldquolisted to prevent thedepletion of wild populations and to provide for animal welfarerdquo [4647] Such distinction reflectson societal values that go far beyond scientific principles to our cultural roots and perceptions andon a more pragmatic level to hardline economics it is the water buffalo that produces a sought-aftermozzarella cheesemdashnot so for the ferret [48] The labeling of the ferret as not domestic hence ldquowildrdquo isnot without consequence Palmer argues that it changes the human-animal social contract from oneof caring and protection extended to domestic and companion animals to a hands-off ldquolaissez faire

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

1 Executive Order of the President 81 FR 88609ndashSafeguarding the nation from the impacts of invasive speciesFed Regist 2016 81 88609ndash88614

2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 15 of 18

intuitionrdquo that as humans intuitively we do not experience the same moral obligation towards ananimal that by nature is ldquowildrdquo [49]

The global policy initiatives to prevent and eradicate non-native species which arose overconcerns of ldquobiological invasionrdquo are only recently undergoing re-examination [35051] Not onlyis there growing disagreement over what constitutes ldquoharmrdquo arguably some species can be bothldquogoodrdquo and ldquobadrdquo for their new environment ldquodepending on the location and the perceptions of theobserversrdquo [1350] In 2006 the US National Invasive Species Council (NISC) cautioned ldquoMany alienspecies are non-invasive and support human livelihoods or a preferred quality of liferdquo [44] Undercertain conditions even native organisms have been shown to exhibit ldquoinvasivenessrdquo within theirown natural habitats [43] More importantly introduction of nonnative species has in some instancesresulted in an increase in overall biodiversity [52]

NISC provides additional cautions ldquoBecause invasive species management is difficult and oftenvery expensive (the) worst offenders are the most obvious and best targets for policy attention andmanagementrdquo [53] Based on current evidence for the North American continent the ferret is a lowprobability target whereas unconfined dogs and cats particularly in the feral state should rank highamong the list of management priorities The true target however may be management of publicattitudes and perceptions regarding these and other non-native species

5 Conclusions

This survey confirms the negative impact from free-roaming cats and dogs on native NorthAmerican wildlife while demonstrating the absence of any discernible impact from the ferret Basedon evidence of substantial environmental impact and harm unconfined cats and the dogs meet thedefinition for ldquoinvasiverdquo species whereas the ferret does not on this continent Results from this studydisplay the differences among three carnivore species and their relative impact on the North Americanecosystem Public attitudes and perceptions regarding these species however may play a role inagency control efforts and management priorities

Supplementary Materials The following are available online at httpwwwmdpicom2076-261571078s1 the supplementary questionnaire Table S1 Existence of incidents of unconfined dogs cats ferretsimpact on wildlife Table S2 Existence of incidents of unconfined dogs cats ferrets impact on wildlife inparts-recreational areas

Acknowledgments SeaSearch Biological Surveys is a privately-owned consultancy that selects and funds itsown research for scientific purposes SeaSearch wishes to thank Cynthia Sinclair and Carmen Tamayo for theirassistance in preparation of this document and for its editorial review

Author Contributions M Scott Sinclair a wild-life biologist identified funded and directed the projectThe team identified the agency contacts disseminated the questionnaires received and organized the responsedata Valerie Kaplan was instrumental in the design of the questionnaire developed the electronic versionand set up the initial database with the assistance of Robert Szpanderfer IT director Alirio Arreaza revised thedatabase and prepared in the initial figures and tables Ana Lepe finalized the database with the assistance ofRobert Szpanderfer performed the analyses with the help of the team and drafted the manuscripts for publicationDavid Bristol conducted the final statistical analyses and prepared the statistical section of the manuscriptAll authors read and approved the final manuscript

Conflicts of Interest The authors declare no conflict of interest

References

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2 Elton CS The Ecology of Invasions by Animals and Plants University of Chicago Press Chicago IL USA 19583 Davis MA Chew MK Hobbs RJ Lugo AE Ewel JJ Vermeji GJ Brown JH Rosenzweig ML

Gardener MR Carroll SP et al Donrsquot judge species on their origins Nature 2011 474 153ndash154 [CrossRef][PubMed]

4 Executive Order of the President 64 FR 6183ndashInvasive species Fed Regist 1999 64 6183ndash61865 Canada Invasive Alien Species No CW66ndash3942004E Environment Canada Quebec Canada 2004

Animals 2017 7 78 16 of 18

6 Sato JJ Hosoda T Wolsan M Tsuchiya K Yamaoto M Suzuki H Phylogenetic relationships anddivergence times among Mustelids (Mammalia Carnivora) based on nucleotide sequences of the nuclearinterphotoreceptor retinoid binding protein and mitochondrial cytochrome b genes Zool Sci 2003 20243ndash264 [CrossRef] [PubMed]

7 Vigne JD Guilaine J Debue K Haye L Gerard P Early taming of the cat in Cyprus Science 2004 304259ndash264 [CrossRef] [PubMed]

8 Handwerk B House Cat Origin Traced to Middle Eastern Wildcat Ancestor 2007 National GeographicNews Available online httpnewsnationalgeographiccomnews200706070628-cat-ancestorhtml(accessed on 8 September 2017)

9 Thalmann O Shapiro B Cui P Schuenemann VJ Sawyer SK Greenfield DL Germonpreacute MBSablin MV Loacutepez-Giraacuteldez F Domingo-Roura X et al Complete mitochondrial genomes of ancientcanids suggest a European origin of domestic dogs Science 2013 342 871ndash874 [CrossRef] [PubMed]

10 Fox JG Marini RP Biology and Diseases of the Ferret 3rd Edition John Wiley amp Sons Inc Ames IA USA 201411 American Kennel Club Available online httpwwwakcorgdog-breedsalaskan-malamutedetail

(accessed on 8 September 2017)12 Godbey J Biggins D Recovery of the black-footed ferret Looking back looking forward End Species

Tech Bull 1994 19 10ndash1313 US Congress Office of Technology Assessments Harmful Non-Indigenous Species in the United States

OTA-F-565 US Government Printing Office Washington DC USA 199314 Dauphineacute N Cooper RJ Impacts of free-ranging domestic cats (Felis catus) on birds in the United States

A review of recent research with conservation and management recommendations In Tundra to TropicsProceedings of the Fourth International Partners in Flight Conference McAllen TX USA 13ndash16 February 2008Rich TD Arizmendi C Demarest DW Thompson C Eds PICCC Honolulu Hawaii 2009 pp 205ndash219

15 Green JS Gipson PS Feral dogs In The Handbook Prevention and Control of Wildlife Damage Hygnstrom SETimm RM Larson GE Eds University of Nebraska-Lincoln Lincoln NE USA 1994 p 35

16 Coleman JS Temple SA Craven SR Cats and Wildlife A Conservation Dilemma University of WisconsinCooperative Extension Publications Madison WI USA 1997 Available online httpswebextensionillinoiseduwildlifefilescats_and_wildlifepdf (accessed on 8 September 2017)

17 Ogan CV Jurek RM Biology and ecology of feral free-roaming and stray cats In Mesocarnivores ofNorthern California Biology Management and Survey Techniques Workshop Manual Harris JE Ogan CVEds Humbolt State University Arcata CA USA 1997 pp 87ndash92

18 Baker PJ Bentley AJ Ansell RJ Harris S Impact of predation by domestic cats Felis catus in an urbanarea Mammal Rev 2005 35 302ndash312 [CrossRef]

19 National Park Service (NPS) Available online httpswwwnpsgoveverlearneducationuploadbackgroundinformationpdf (accessed on 8 September 2017)

20 Mcruer DL Gray LC Horne L-A Clark EE Free-roaming cat interactions with wildlife admitted to awildlife hospital J Wildl Manag 2016 81 163ndash173 [CrossRef]

21 Mott M National Geographic News Available online httpnewsnationalgeographiccomnews2003080821_030821_straydogshtml (accessed on 8 September 2017)

22 Pimental D Environmental and economic costs of vertebrate species invasions into the United StatesIn Managing Vertebrate Invasive Species Proceedings of an international symposium Fort Collins CO USA 7ndash9August 2007 Witmer GW Pitt WC Fagerstone KA Eds USDAAPHIS Wildlife Services NationalWildlife Research Center Fort Collins CO USA 2007 pp 1ndash8

23 Loss SR Will T Marra PP The impact of free-ranging domestic cats on wildlife of the United StatesNat Commun 2013 4 [CrossRef]

24 Mott M National Geographic News Available online httpnewsnationalgeographiccomnews2004090907_040907_feralcatshtml (accessed on 8 September 2017)

25 Bergman DS Breck S Bender S Dogs gone wild Feral dog damage in the United States In NationalWildlife Research CentermdashStaff Proceedings of the 13th WDM Conference Saratoga Springs New York USA 4ndash6May 2009 Boulanger JR Ed USDAAPHIS Wildlife Services National Wildlife Research Center FortCollins CO USA 2009 pp 177ndash183

26 Demarest DW Thompson C Animal Law in Canada Available online httpwwwanimallawca(accessed on 8 September 2017)

Animals 2017 7 78 17 of 18

27 Wisch RF Overview of Local and State Dog Laws 2014 Available online httpswwwanimallawinfointrostate-and-local-dog-laws (accessed on 8 September 2017)

28 Wisch RF Detailed Discussion of State Cat Laws 2005 Available online httpswwwanimallawinfoarticledetailed-discussion-state-cat-laws (accessed on 8 September 2017)

29 American Ferret Association Home Page Gaines D Summary of State and Territory-Level FerretRegulations 2009 Available online httpwwwferretorgpdfsgeneral2009-StateByStatepdf (accessedon 8 September 2017)

30 King CM Immigrant Killers Introduced Predators and the Conservation of Birds in New Zealand OxfordUniversity Press Oxford UK 1984

31 Moore TG Whisson DA Potential risks associated with the legalization of exotic predators such as theferret (Mustela putorius furo) in California In Proceedings of the 18th Vertebrate Pest Conference Costa MesaCalifornia 2ndash5 March 1998 Baker RO Crabb AC Eds University of California Davis Davis CA USA1998 Volume 62 pp 96ndash99

32 Jurek RM Ryan P 1996ndash97 Nationwide Ferret Survey of State Wildlife Agencies Habitat Conservation andPlanning Branch Species Conservation and Recovery Program Report California Department of Fish andGame Sacramento CA USA 1999 pp 1ndash69

33 Lenth BE Knight RL Brennan ME The effects of dogs on wildlife communities Nat Areas J 2008 28218ndash227 [CrossRef]

34 Frincham JE Response rates and responsiveness for surveys standards and the journal Am J Pharm Educ2008 72 1ndash3

35 Ponto J Understanding and evaluating survey research J Adv Pract Oncol 2015 6 168ndash171 [PubMed]36 Ayhan HO Memory recall errors in retrospective surveys A reverse record check study Qual Quant 2004

38 475ndash493 [CrossRef]37 Cornish J Response problems in surveysmdashImproving the response and minimising the load In Proceedings

of the UNSD Regional Seminar on lsquoGood Practices in the Organization and Management of Statistical Systemsrsquofor ASEAN countries Yangon Myanmar 11ndash13 December 2002 UNSD New York NY USA 2014 Availableonline httpsunstatsunorgunsdmethodsstatorgWorkshopsYangonSession4_Surveys_Cornish_Paperpdf (accessed on 8 September 2017)

38 Huss RJ No Pets Allowed Housing Issues and Companion Animals Animal Law Review at Lewis amp Clark LawSchool Portland OR USA 2005 Volume 11 pp 69ndash121

39 New York City Housing Authority (NYCHA) Available online httpwww1nycgovassetsnychadownloadspdfPet_GM_Policy_Overview_2010_04_d2pdf (accessed on 8 September 2017)

40 Umbach KW Ferrets A Selective Overview of Issues and Options California Research Bureau California StateLibrary Sacramento CA USA 1997 Volume 4 pp 1ndash9 Available online httpswwwlibrarycagovCRB97notesv4n3pdf (accessed on 8 September 2017)

41 California Department of Fish and Wildlife (CDFW) Available online httpswwwwildlifecagovliving-with-wildliferestricted-pet-species (accessed on 8 September 2017)

42 Boni SE Anthropomorphism How it affects the humanndashCanine bond J Appl Comp Anim Behav 2008 216ndash21

43 Peterson B The Atlantic Available online httpswwwtheatlanticcommagazinearchive201612the-case-against-cats505838 (accessed on 8 September 2017)

44 Kellert SR American attitudes toward and knowledge of animals An update Int J Stud Anim Probl1980 1 87ndash119

45 American Board of Veterinary Practitioners Available online httpabvpcomveterinary-certificationrecognized-veterinary-specialties (accessed on 8 September 2017)

46 California Code of Regulations Title 14 Section 641671 Importation transportation and possession oflive restricted animals California Natural Resources Agency Department of Fish and Wildlife SacramentoCA USA

47 Nemec J GRIT Available online httpwwwgritcomanimalswater-buffalo-herds-growing-in-the-united-states (accessed on 8 September 2017)

48 Anderson S The New York Times Magazine Available online httpwwwnytimescom20121014magazinebuffalo-mozzarella-craig-raminihtmlmcubz=0 (accessed on 8 September 2017)

49 Palmer C Animals in Context Columbia Press New York NY USA 2010

Animals 2017 7 78 18 of 18

50 Valeacutery L Fritz H Lefeuvre JC Simberloff D In search of a real definition of the biological invasionphenomenon itself Biol Invasions 2008 10 1345ndash1351 [CrossRef]

51 Valeacutery L Fritz H Lefeuvre JC Simberloff D Invasive Species Can Also be Native Trends Ecol Evol2009 24 585 [CrossRef] [PubMed]

52 Davis MA Invasion Biology In Encyclopaedia of Biological Invasions Simberloff D Rejmanek M EdsUniversity of California Press BerkeleyLos Angeles CA USA 2011 Volume 3 pp 364ndash369

53 The Definitions Subcommittee of the Invasive Species Advisory Committee (ISAC) Invasive Species DefinitionClarification and Guidance White Paper The National Invasive Species Council (NISC) Washington DC USA2006 pp 1ndash11

copy 2017 by the authors Licensee MDPI Basel Switzerland This article is an open accessarticle distributed under the terms and conditions of the Creative Commons Attribution(CC BY) license (httpcreativecommonsorglicensesby40)