I JOHN A. LITV AITIS.Department of Natural Resources, University of New Hampshire, Durham, NH 03824, USA

JUAN F. BELTRANEstacion Biologica de Donana, Consejo Superior de Investigaciones Cientificas, Apartado 1056, 41080 Sevilla, Spain

MIGUEL DELIBESEstacion Biologica de Doriana, Consejo Superior de Investigaciones Cientificas, Apartado 1056, 41080 Sevilla, Spain

.SACRAMENTO MORENOEstacion Biologica de Donana, Consejo Superior de Investigaciones Cientificas, Apartado 1056, 41080 Sevilla, Spain

RAFAEL VILLAFUERTEEstacion Biologica de Donana, Consejo Superior de Investigaciones Cientfficas, Apartado 1056, 41 080 Sevilla, Spain

Abstract: Worldwide. populations ofwild cats have been reduced and fragmented by exploitation and contemporary land uses. Although many ofthese populationsare now protected from legal exploitation. they continue to decline as human-related factors (e.g.. habitat degradation. poaching. and vehicle coIlisions) andstochastic events limit survival and reproduction. Local efforts to protect endangered populations of felids willlikely fail because of the area requirements of thesewide-ranging carnivores. Previous research has demonstrated the imponance of rnaintaining demographic connections (via habitat corridors) to ensure long-termviability ofthese populations. However. such management efforts may require decades to implement and small populations may perish before such effons are

completed.action. interim s!ep~, "nli Inng-r"nt1 Zr:c'c) ~,-. ,.c~~.c,.;"Z :!nli m"inr"it)it)g rh~~~ popl.!!8tiQI]~ Th:o ;!(!v;!t)r;!g~~ "nli 1imi!,,!ions of :;k':~, =, "i-'i-',v"".1, :!l!2exa.Tined ..':it.':information on bobcats ( L rufils) in the nonheastem United States and lberian Iynx (Lynx pardina) in southem Spain, Persistence of disjunct populations of felidsin human-dominated habitats willlikely be dependent on management efforts at several spatial and temporal sc ales.

Key words: corridors, felids, fragmentation, prey enhancement, scale, wild cats.

J. Wildl. Res. 1(3): 292-296, 1996

INTRODUCTION felids may perish before such effons are completed (e.g., Berger1990). Therefore, it is likely that future management effons willneed to be multi-scaled in space (local, landscape, regional, andinternational) and time (immediate action, interim steps, andlong-term goals) if they are to succeed. In this paper, weexamine the benefits and limitations associated with such anapproach to sustain felids in human-dominated habitats.

Populatilh'1s of wild cats have been substantially reducedthroughout the world, and many are currently threatened withextinction (reviews in Miller and Everett 1986). Habitat degra-dation and excessive hunting or trapping have been identifiedas the principal factors responsible für reductions in the abun-dance of these carnivores (e.g., Reza Khan 1986). Althoughmany populations offelids are now protected from legal exploi-tation, they continue to decline as other human-related factors(deforestation, poaching, and vehicle collisions) and stochasticeverns (e.g., disease ouibreük~) iulli.. :'UI v i v öl allo reproduclion(Seidensticker 1986, Ferreras et al. 1992). In response tothissituation, conservationists are hurriedly developing manage-ment programs to reverse these trends (e.g., Belden 1986,ICONA 1992, Beiet 1993). Local efforts to protect wild catsand their habitat are not sufficient because of the large areasrequirements ofthese carnivores. Previous research has demon-strated the importance of maintaining demographic connectionsamong disjunct populations offelids to ensure long-term viabi-lity (Litvaitis et al. 1991, Beier 1993). However, such effortsmay require decades to implement because of the obstaclescrcatcd by current land-ownership patterns (Maehr 1990) orpolilical borders (Litvaitis et al. 1991). Small populations of

DECLlNE OF FELIDS IN HUMAN-ALTEREDHABITATS

Although the forces that threalt:n PUPUIUlIuns 01 1elids arevaried, these forces may be placed into several categories thaioperate at different, bot not mutually exclusive scales (Fig. 1).Initial declines ofmany species ofwild cats were from overex-ploitation. High market values of pelts or body parts of ~~ecats [e.g., ocelots (Leopardus pardalis), and jaguars (Pa~iaonca), and tigers (P. tigris»), or a perceived competition fürgame and livestock between humans and felids [e.g., cougars(F. concolor) ted to extensive harvests. The effects of overex-ploitation on local densities were rapid, orten occurring in lessthan a decade. Over a longer period (several decades), defore-station, intensive agriculture and urban expansion producedincremental reductions in habitat quality and quantity. This

292

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FELID IN HUMAN-DOMINA TED LANDSCAPES Litvaitis et al. 293

Table 1. Summary of computer simulations used to examine the relative importance of initial population size. prey abundance. and immigrants onthe persistence of an isolated population of Canada Iynx (source: Litvaitis et al. 1991)..

4080408020202020

ModerateModerate

HighHigh

ModerateModerateModerateModerate

0.000.000.000.000.250.330.501.00

0.000.000.310.440.300.420.570.97

"Initial population restricted to yearlings and adults. bPrey abundance: moderate -< hare/ha, high -2-5 hare/ha. Annual survival with moderate prey: juvenile-0.05, yearling -0.62, adult -0.62 with high prey: juvenile -0.35. yearling -0.80. adult -0.80. Young/fernale with moderate prey: adult -1.1 withhigh prey -1.8. See Litvaitis et aJ. (1991) for coefficients of variation of these parameters.

the availability of prey consumed by bobcats. Competition withcoyotes may have had a substantial influence on bobcats innorthem New England where predator-prey systems are relati-velysimple (Litvaitis and !!arrison ! 989).

Populations of bobcats in New England have apparentlystabilized at reduced levels of abundance as harvest pressureshave diminished. Currently, populations in this region are di-sjunct and are threatened by increased fragmentation of rernnanthabitats (e.g., Vogelmann 1994), and other human-related mor-tality factors. Even in rural New England, the second mostfrequent mortality factor among a group of transmitter-equipped bobcats (20% of all mortalities) was collisions withmotor vehicles (Litvaitis et al. 1987).

Iberian IynxThe lberian lynx is considered taxonomically unique (Wer-

delin 1981, Honacki et alo 1982), and once ranged over a largeportion of the lberian peninsula (Graells 1897, as cited inICONA 1992). Historically, this species was hunted intensive-ly as agame species, or pursued as a potential predator of

Deforestation,Intensive Agriculture,

and Urbanization

+

PopulationFragmentatiorlOverexploitation

++

process created a matrix of low quality (sink) habitat thatsurrounds patches of suitable habitat that support small groupsof breeding individuals (source habitats). The regional expan-sion of such habitat degradaliun anu [ragmentation (ovcr manydecades) hag isolated remnant subpopulations from ODe anot-her.As demographic exchanges between these subpopulationscontinue to decline, surviving individuals may become inbredand vulnerable to stochastic extinctions (Fig. 1). Below, we willsummarize tw~ examples of how these forces have affectedfelid populations.

Bobcats in the northeastern United States

At the time of settlement of North America by Europeans,bobcats ranged throughout the contiguous Uni ted States (Yo-ung 1958). In New England (the northeast portion ofthe UnitedStates), bobcats were comm~_x7ept in the extreme northernareas where Canada lynx V)'nx) occurred (Silver 1974).During the early 1800s, widespread agriculture and bountyprograms reduced the abundance of bobcats (Litvaitis 1994).However, by the middle of the last century, large-scale aban-donment of agriculturallands and their subsequent reforestationresulted in expansion of bobcat populations throughout thisregion (Litvaitis 1993). As the second-growth forests maturedand became less productive für sm all and medium-size prey,bo'o". I_.:~_o ~~ -~~ .~ rI"'c1in" rap1.dl By th. t.

m..al PUPUlo1llU"" V~6"" ..~ ...~ ..~ y. 1S 1 e,urbanization also bad eliminated large tracts of habitat andbegan to fragment populations of many terrestrial vertebrates,including bobcats. Yet bobcats remained common in suitablehabitat. However, several unexpected events changed this situ-

ation.During the 1970s, the commercial value of bobcat pelts

increased draIUatically, and trappers and hunters concentratedtheir efforts on this species (Litvaitis 1987). Aseries of severewinters in the 1980s reduced annual recruitment and survival(Litvaitis et al. 1987), and shifted trapping/hunting mortality ofbobcats from partially additive to largely additive (K. Morse,Maine Dept. Inland Fisheries and Wildlife, perso~ommu-nication). Also during this period. colonizing po'tntfations ofcoyotes (Canis latrans) incfeased rapidly and may have reduced

InbreedingReduced density Sink / SourceHabitats

Fig. 1. Human-related forces and their effects on felid populations. Theseforces are expressed at different, but not mutually exclusive spatial and

temporal scales.

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Vol.I, No.3, Su~l996294

Journal ofWildlife Research

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Fig. 3. Demographic responses by felids 10 increased prey abundance.

Legislation/education

Legislation to eliminate trapping and hunting of decliningpopülations of felids Cllii be CI1C1~icd quickly. Such jegislationshould be flexible to local concerns (e.g.,livestock protection).When legislation is combined with an active campaign toeducate the public about the plight of wild cats (e.g., ProjectTiger), cat populations can respond rapidly. However, if com-mercial demands remain high, even international agreements toeliminate trade of endangered or threatened species (i.e., CI-TES) may not succeed. Education efforts, therefore, may needto be global and active for many years if attitudes toward felidsare to change.

livestock and game. By the early 1900s,lynx were restricted to

the southern half of Spain and' a small portion of Portugal.

Intensive agriculture, disruption ofnatural-disturbance regimes

(especially fire), and forest conversions to monocultures conti-

nued to reduce the habitat of lynx in Spain (Ales et al. 1991,

Moreno and Villafuerte 1994). Although recognition of the

downfall of this species resulted in legal protection in 1973, this

designation did not stop the decline of lynx.

Rodriguez and Delibes (1992) reported thai the breedin~

range of lynx in Spain is now restricted to about 11,000 km-,

and fragmented among 48 sites. Of these, 75% are <200 km2

and many support fewer than 50 breeding individuals. The total

population in Spain is approximately 1,100. Ferreras et al.

(1992) found thai human-related factors (incidental captures in

traps set für other species, collisions with motor vehicles, and

accidental drownings in wells) are still the main causes of

mortality among lynx, even in protected reserves. Myxomatosis

and arecent outbreak of viral hemorrhagic disease in Spain

(ViIlafuerte et al. 1994) have reduced the major prey of lynx,

European rabbits (Orycto/agus cunicu/us). AdditionaIly, gene-

ralist carnivores [e.g. red foxes (Vu/pes vu/pes)] have increased

"" h"bl .""'" ha "" h"""'

m " "'~" h" t ,,~"'nQ~O "~ (R n u n.

al 1985)"'U""u.."...u... uo u"' ,.. These factors may have reduced prey abundance and further

reduced lynx fertility and survival. FinaIly, the lack of demo-

graphic exchanges among disjunct populations of lynx may

have already resulted in a reduction in heterozygosity in these

populations (Beltran and Delibes 1993).

REVERSING THE DECLlNESAs these two examples illustrate, the forces affecting felid

populations operate at several spatial and temporal scales. We

suggest thai efforts to sustain orrestore populations ofwild cats

should also occur at several sc ales thai are not mutuaIly exclu-

sive (Fig. 2). ,

Legislationand Education

HabitatManipulation

HabitatCorridors

+~ + +Protection Rescue EffectsPrey

Enhancement

Habitat manipulation and rehabilitationThe abundance of prey consumed by felids has obvious

effects on several demographic parameters (Fig. 3). Spatial andtemporal variation in prey density of bobcats (Litvaitis et al.1986) and Canada 1ynx (analysis ofTable 2 ofWard and Krebs1985) explained 22-30% of the variation in horne range size.Survival and fenility of felids are sensitive to changes in preyabundance (e.g., Brand and Keith 1979). Therefore, this para-meter has obvious implications to increasing carrying capacityof felids that are restricted to limited habitats. Prey populationsof fe!ids m?y b~ very responsive to habitat ma.,ipulations. Forexample, Litvaitis et al. (1985) reported a close relationshipbetween understory density and the abundance of snowshoebare (Lepus americanus) that represented approximately 60%of the diet of bobcats in northem New England (Litvaitis et al.1986). Habitat of snowshoe bares can be increased and sustai-ned with even-aged forest management. Likewise, Moreno andVillafuene (1994) have demonstrated that the abundance ofEuropean rabbits consumed by lberian lynx can be increasedlocally by planting forage crops consumed by rabbits. Large-scale increases of this rabbit may be achieved by restoringnatural disturbance regimes, especially periodic flfes (Morenoand Villafuerte 1994).

The distribution of habitat management effons to enhance

'-'

)6 295

~h

~~~~f::

~~

Preyenhanc~ment

Fig. 4. Schematic representation of how habitat manipulations shouldbe placed in secure habitats (core regions of reserves or areas with fewroads) to limitthe eftects of human-related mortality (e.g., poaching andcollisions with motor vehicles). Polygons represent relative size of horne--ng -s .In ccmp ~. I ~o " +" pre v ~b' '" d ~"~~10 I C I " 01 ~ "'" 1 Q U" Q' "'w.

Fig. 5. The relative influence of conservation efforts to restore endange-red felid populations. Population viabiJity is greatest when these effortsare occurring at several spacial and temporal scales.

supplemented by immigrants on a regular basis.Although we have stressed the importance of corridors to

lang-term survival offelids, we must also emphasize that otherefforts (legal protection and enhanced prey populations) areimportant to maintaining population viability (Fig. 5). Theseefforts may be especially important during the period thatcorridors are not yet functional. In conclusion, we recommendthat conservationists involved in restoring endangered or thre-atened populations of wild cats work at several spatial andtemporal scales. Such an approach may be appropriate für awide variety of organisms (especially other camivores) that arethreatened with local or global extinction.

LITERATURE CITED

prey abundance should also be considered. These efforts maybe most influential when placed in remote areas where felidsare less likely to encounter humans. Ferreras et al. (1992)observed that Iberian lynx that resided at the edge of DorianaNational Park bad a higher mortality rate than individuals thatresided in the core of this reserve. Therefore, concentratingfelids in cores of reserves or in roadless areas willlikely increasethe security of a population (Fig. 4), and have a greater effecton population restoration than simply distributing habitat ma-nagement efforts throughout alandscape.

Habitat corridors

Although ~e value of habitat corridors that link disjuncthabitats has been a controversial issue among conservationbiologists (Simberloff and Cox 1987), recent research has de-monstrated that such features may be essential für assuringperiodic emigration/immigration among small, scattered popu-lations (Beier 1993). The "rescue effect" that immigrants haveon small populations (Brown and Kodric-Brown 1977, Fomeyand Gilpin 1989) may be of greater ~ignifir:l"C~ tn s11rvival ofthese populations than maintaining heterzygosity (Lande 1988).

We acknowledge that developing an effective system ofhabitat corridors is the most difficult portion of a managementpro gram to restore ~nd sustain felid populations in human-alte-red landscapes. Can a restoration effort be effective withoutthese linkages? We do not believe so. Litvaitis et al. (1991) andBeier (1993) demonstrated how influential even an occasionalimmigrant (e.g., 1 every other year) can be to a small populationof wild cats. Table 1 summarizes the relative effect of immi-gration on an isolated Canada Iynx population in comparison toelevating carrying capacity, fertility, and survival (with enhan-ced prey populatioQs). Even a very small population (20 year-lings and adults) had a high probability of surviving if it was

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