A Survey to Examine Vulture Predation on Calves in Tennessee

A Research Paper Presented for the Master of Science in

Agriculture and Natural Resources Degree The University of Tennessee at Martin

Jeremy Spires August 2014

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Copyright © 2014 by Jeremy Spires All rights reserved.

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Acknowledgements

I would like to thank Dr. Philip Smartt and Dr. Barb Darroch of the University of

Tennessee at Martin for their guidance and assistance on this project. I would like to

thank Dr. Robert Burn, statewide agriculture and natural resource program leader for the

University of Tennessee Extension office, for allowing the University of Tennessee

Extension staff to participate in this survey. I would like to thank Dr. Ben West, Western

Region Director for the University of Tennessee Extension office, for suggesting the

topic of this research.

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Abstract Agricultural professionals across the southeastern United States have noted an

apparent increase in calf mortality associated with vulture predation. Between 1997 and

2002 depredation reports from eighteen states showed black vulture depredation of cattle.

Virginia, Florida, Texas, South Carolina, and Tennessee accounted for 84% of the

reported predation incidents. The objectives of this project were to estimate the amount

of calf mortality in Tennessee caused by vulture predation and to determine if this

predation is widespread or isolated. Additionally, this research project addressed the

issue of livestock species other than cattle being impacted by vulture predation. To meet

these objectives, a survey of agricultural extension agents from each county was

conducted. Of the 56 Tennessee counties responding to this survey, 89% reported calf

predation by vultures. Additionally, 52% of these counties reported vulture predation of

livestock species other than cattle. This survey has no way to verify that all reports of

vulture predation to livestock are actually predation by vulture species. The data

presented in this report are based only on reports of predation to agricultural extension

agents. Without witnessing the predation or performing a necropsy it is difficult to

determine the exact cause of death. Even so, this survey has shown that predation by

vultures is something that should be considered by Tennessee cattle producers and

something that requires additional research.

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Table of Contents

Chapter 1 Introduction and General Information ................................................................ 1

Chapter 2 Literature Review .............................................................................................. 2

Vulture Biology and Range ........................................................................................ 2

Cattle Industry in Tennessee ....................................................................................... 2

Predation of Livestock by Vultures ............................................................................ 3

Prevention Methods .................................................................................................... 4

Research Needs ........................................................................................................... 5

Objectives ................................................................................................................... 5

Chapter 3 Materials and Methods ...................................................................................... 7

Survey Procedures ...................................................................................................... 7

Study Population ......................................................................................................... 7

Data Collection ........................................................................................................... 7

Data Analysis .............................................................................................................. 8

Chapter 4 Results and Discussion ...................................................................................... 9

Chapter 5 Conclusions and Recommendations ................................................................ 14

List of References ............................................................................................................. 15

Appendix A ....................................................................................................................... 17

Appendix B ....................................................................................................................... 20

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List of Tables

Table 1. Species of vulture responsible for calf mortality as reported by agricultural extension agents in Tennessee .................................................................................... 9

Table 2. Percent of calf mortality in the county attributed to vulture predation as reported by agricultural extension agents ................................................................................ 11

Table 3. Method used to attribute calf mortality to vulture predation .............................. 11

Table 4. Timing of vulture presence at farms experiencing vulture predation in Tennessee as reported by agricultural extension agents ............................................................. 12

Table 5. Mortality of other livestock species attributed to vulture predation as reported by Tennessee agricultural extension agents ................................................................... 13

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List of Figures

Figure 1. Geographic distribution of survey responses ...................................................... 9

Figure 2. Livestock deaths other than cattle attributed to vulture predation as reported by Tennessee agricultural extension agents .............................................................. 13

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Chapter 1

Introduction and General Information

Agricultural professionals across the southeastern United States have noted an

apparent increase in calf mortality associated with vulture predation. The black vulture

(Coragyps atratus) in particular is thought to have a significant impact on livestock

mortality because this species will subdue, capture and eat live prey in addition to feeding

on carrion (Avery and Cumming 2004). Between 1997 and 2002, depredation reports

from eighteen states showed black vulture depredation of cattle. Virginia, Florida,

Texas, South Carolina, and Tennessee accounted for 84% of the reported depredation

incidents. These predations have increased an average of 18% annually (Humphrey et al.

2004). Complaints of vulture damage in Virginia have steadily increased from 2

complaints in 1990 to 207 complaints in 1995 (Lowney 1999). While these depredation

events usually involve young animals, damage to cows during or immediately after

giving birth has been severe enough in some instances to require the injured animals to be

euthanized (Avery and Cumming 2004).

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Chapter 2

Literature Review

Vulture Biology and Range

Black Vultures have a wingspan up to 1.4 m. Adults and juveniles are

morphologically similar with a dark gray head, short tail feathers, and a black body with

a white patch at the end of each wing. Black vulture range in the United States includes

all of the southeastern states north to portions of New Jersey and west to portions of

Texas (National Audubon Society). Turkey Vultures (Catharates aura) have a wingspan

up to 1.8 m. Adults have a small reddish head with a black body. Juveniles have a gray

head. Turkey Vultures reside year-round in the southeastern United States north to

Maryland and west to portions of Texas. Summer range of migratory turkey vultures

includes all of the continental United States north to southern Canada (National Audubon

Society). While black vultures and turkey vultures generally feed on carrion, black

vultures tend to feed more on large (>20 kg) carrion than turkey vultures (Coleman and

Fraser 1987). Additionally, black vultures will prey on sick, weak or young birds and

mammals (National Audubon Society). Black vultures do not depend on olfactory senses

to locate food, instead relying on sight or the presence of turkey vultures, which locate

carrion by olfaction (Buckley 1996).

Cattle Industry in Tennessee

Tennessee ranks fifteenth in beef cow number (USDA 2013) and in the top four

states in cow-calf operations (Parkman 2005). As of 2004, the 2.17 million cattle in

Tennessee were valued at $1.6 billion (Parkman 205). In 2012, the cattle and calves sold

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in Tennessee were valued at $7.3 million (USDA 2013). The cattle industry via the sale

of cattle and calves represents 18.7% of the state’s total agricultural income, making the

cattle industry the greatest source of agricultural income in Tennessee. Cow-calf

operations make up 90% of the beef cattle operation in Tennessee (Parkman 2005). Of

the calves lost to predators in Tennessee in 2010, coyotes accounted for 62.5% followed

by domestic dogs (16.0%) and vultures (8.8%) with unknown predators accounting for

11.5 % of calf mortality (USDA 2011).

Predation of Livestock by Vultures

Avery and Cumming (2004) conducted research in central Florida that showed

that both black vultures and turkey vultures were present in large numbers in fields where

active calving was occurring. While both species of vultures were observed feeding on

afterbirth, only black vultures were observed at depredation events. The vultures were

observed pecking out the calf’s eyes then attacking soft areas such as the rectum, nose

and genitals. Similar research conducted by Humphrey et al. (2004) on a central Florida

ranch showed that while the ratio of turkey vultures to black vultures was 3:1, the black

vultures were the only species observed preying on newborn livestock. The turkey

vultures utilized pastures with cows and calves but focused primarily on the afterbirth

and manure from young calves. Predation of calves by vultures is not limited to the

United States. Amador-Alcala et al. (2013) found that multiple calf deaths were

attributed to black vultures in southeast Mexico.

In addition to predation of calves, vultures have been reported to prey on other

livestock. Between 1994 and 1995, twelve counties in Virginia reported vulture

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predation on livestock other than cattle including farm-raised deer (Lowney 1999).

Breen (2011) found that up to 3.7% of sheep ewes were fed on by turkey vultures during

the lambing season with approximately half of farmers surveyed considering vultures a

major threat to sheep in the Falkland Islands. Bellati and von Thungen (1990) found that

predation by black and turkey vultures occurs when a lamb has been temporarily or

permanently abandoned by the ewe, usually in an unhealthy condition.

Prevention Methods

Historically, preventative methods were not used to reduce vulture predation on

livestock. Instead vultures in areas experiencing predation were trapped in baited wire

cages and dispatched (Wade et al. 1984). Since federal protections of vulture species

were enacted in 1918, agricultural professionals and agricultural producers have been

forced to develop non-lethal means of dealing with vulture predation. These methods

include roost dispersal, effigies, and proper disposal of livestock carcasses. Trapping and

relocation has proven to be ineffective at decreasing vulture numbers at specific sites

(Davis 1998).

Avery et al. (2006) found that dispersal of the main roost site has no effect on

vulture use of livestock facilities. It was not until dispersal activities included alternative

roost sites that roost dispersal had any effect on vulture use of livestock facilities.

Dispersal methods fall into two categories: environmental modifications including

pruning or removing vegetation and the use of frightening devices including

pyrotechnics, distress calls, and visual frightening devices (Booth 1994). Seamons

(2004) found that using a taxidermy mount of a vulture reduced the number of turkey

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vultures at roost sites but did not eliminate the use of the roost site. Proper disposal of

livestock carcasses has been shown to reduce vulture use of agricultural properties

(Avery et al. 2006, Beranger and Walters 2007).

Research Needs

Bruggers et al. (2002) listed “Conduct research into understanding the problems

and developing methods to reduce the negative impact of black vultures and turkey

vultures on livestock production and property” as one of the thirteen highest priority

research issues derived from 103 research needs identified by United States Department

of Agriculture (USDA) Wildlife Services (WS) program staff. Avery and Cumming

(2004) suggested that additional research is needed to determine why some livestock

operations incur vulture damage while other ranches are not affected. This could be due

to onsite or offsite conditions at the ranch including locations of vulture roosts,

housekeeping issues such as the removal of dead livestock, using calving barns or other

conditions. Humphrey et al. (2004) suggested that additional research is needed to

determine the significance of black vultures as predators of livestock.

Objectives

This research project was developed to determine the impacts vulture predation

have on calf mortality in Tennessee. Agricultural professionals have noted an apparent

increase in calf mortality associated with vulture predation. The objectives of this project

were to estimate the amount of calf mortality in Tennessee caused by vulture predation

and to determine if this predation is widespread or isolated. This research project also

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addressed the issue of livestock species other than cattle being impacted by vulture

predation.

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Chapter 3

Materials and Methods

Survey Procedures

A seven question survey was created to address the objectives of this study

(Appendix A). Survey questions were developed to determine the prevalence of vulture

predation on calf mortality in Tennessee as identified by University of Tennessee

Agricultural Extension Agents. The survey contained qualitative and quantitative

questions regarding the prevalence of vulture predation in each county in Tennessee.

Qualtrics.com was used to administer the survey.

The first page of the survey was an informed consent document that provided

information on the survey objectives and the voluntary nature of the survey. Prior to

administering, the survey for this project was approved by the University of Tennessee at

Martin Institutional Review Board (14-344-E05-4005/Spir,Wil; Appendix B).

Study Population

An e-mail list of University of Tennessee Agricultural Extension Agents for each

of the 95 counties in Tennessee was used for the survey. The survey was distributed by

the University of Tennessee Extension office in Knoxville, Tennessee.

Data Collection

Qualtrics.com was used to administer the survey. The data were downloaded

from the website as an Excel spreadsheet. The survey was e-mailed to all participants on

July 9, 2014 requesting participation and explaining that participation was voluntary.

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The survey was closed July 18, 2014 with a total of 56 respondents for a participation

rate of 58%.

Data Analysis

Microsoft Excel® was used to analyze the survey results. A chi-square test was

used to determine if region of Tennessee was related to vulture predation or the percent

of calf mortality attributed to vulture predation.

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Chapter 4

Results and Discussion

Survey responses were received from 56 of the 95 counties in Tennessee for a

survey coverage rate of 58% of the state (Figure 1). Fifty counties (89.2% of the

respondents) indicated that the county had experienced calf mortality attributed to

vultures. The presence or absence of vulture predation was not related to Tennessee

region (Chi Square P value = 0.49).

Of those counties indicating calf mortality attributed to vultures, 60% (30

respondents) indicated that calf mortality was attributed to black vulture whereas 2% (1

respondent) indicated that calf mortality was attributed to turkey vultures (Table 1).

Fourteen respondents (28) indicated that calf mortality was attributed to both black and

turkey vultures.

Figure 1. Geographical distribution of survey responses

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Table 1. Species of vulture responsible for calf mortality as reported by agricultural extension agents in Tennessee

Species of Vulture Number of Respondents Percent of Respondents

(%) Black Vulture 30 60

Turkey Vulture 1 2

Both 14 28

Unknown 5 10

Not Applicable 6 -

While these results contradict those of Humphrey et al. (2004) who found only

black vultures preyed on livestock, it is possible that turkey vultures were observed

feeding on calves killed by black vultures, or other predators and were mistaken for the

species responsible for the predation.

The estimated percent of calf mortality in each county attributed to vultures is

shown in Table 2. In most counties, respondents estimated that 1 to 10% of calf mortality

was due to vulture predation. A P-value of 0.35 for a Chi Square test indicated that the

percent of calf mortality due to vulture predation was not significantly related to the

regions of Tennessee.

As part of the survey, University of Tennessee Agricultural Extension Agents

were asked about what methods were used to determine that calf mortality was attributed

to vulture predation (Table 3). All respondents stated that more than one method was

used to attribute calf mortality to vulture predation except for respondents answering

“Not Applicable”.

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Table 2. Percent of calf mortality in the county attributed to vulture predation as reported by agricultural extension agents Percent of Mortality Attributed to Vulture Predation

Number of Respondents Percent of

Respondents (%)

1-10% 36 72

11-20% 10 20

21-30% 1 2

No Response 3 6

Not Applicable 6 -

Table 3. Method used to attribute calf mortality to vulture predation Method of Attributing Calf Mortality to Vulture Predation

Number of Respondents* Percent of Respondents

(%)

Necropsy 1 2

Other Livestock with Injuries Attributed to Vultures

21 42

Vulture Roost Nearby 33 66

Dirt/Sand/Grit in the Hooves 19 38

Other 30 60

Not Applicable 6 -

*Respondents could select more than one answer

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Survey respondents were asked about the presence of vultures at the farms

experiencing vulture predation. Of those counties indicating calf mortality attributed to

vultures, 20% (10 respondents) indicated vultures were present only during calving, 42%

(21 respondents) indicated vultures were present year round, and 38% (19 respondents)

stated that vulture presence varied between farms (Table 4).

Finally, the University of Tennessee Agricultural Extension Agents who were

surveyed were asked about predation of other livestock species attributed to vultures in

each county. Of the livestock species in the list of choices, goats and sheep were selected

by 48% and 38% or respondents respectively (Table 5). Of those counties indicating calf

mortality attributed to vultures, 12 respondents did not answer this question, 12 counties

indicated that no other livestock species were subject to vulture predation, 5 counties

indicated one additional livestock species deaths were attributed to vulture predation, and

the remaining 21 counties indicated deaths of more than one additional livestock species

that were attributed to vulture predation (Figure 2).

Table 4. Timing of vulture presence at farms experiencing vulture predation in Tennessee as reported by agricultural extension agents Timing of Vultures Presence at Farms Experiencing Predation

Number of Respondents Percent of Respondents

(%)

Only When Calving 10 20

Year Round 21 42

Varies Between Farms 19 38

Not Applicable 6 -

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Table 5. Mortality of other livestock species attributed to vulture predation as reported by Tennessee agricultural extension agents

Species Number of Respondents* Percent of Respondents

(%) Sheep 19 38

Goats 24 48

Horses 3 6

Fowl 3 6

Other 2 4

Not Answered 12 -

Not Applicable 18 -

* Respondents could select more than one answer

Figure 2. Livestock deaths other than cattle attributed to vulture predation as reported by Tennessee agricultural extension agents

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Chapter 5

Conclusions and Recommendations

While only 56 respondents, each representing one county, responded to the

survey, the geographical distribution of the responses covered the state. If we assume

that the 56 survey responses received are representative of the entire state of Tennessee

then the majority of counties within Tennessee are impacted by vulture predation of not

only calves but other livestock species as well. Additionally there was no significant

difference amoung regions of Tennessee in regards to the presence of vulture predation

on calves or the estimated percent of mortality of calves attributed to vulture predation.

This survey had no way to verify that all reports of vulture predation to livestock are

actually predation by vulture species. The data presented in this report are based only on

reports of predation to agricultural extension agents. Without witnessing the predation or

performing a necropsy it is difficult to determine the exact cause of death.

While the percent of mortality attributed to vulture predation was relatively low,

this should be monitored over time. Additional research is needed to determine why some

vulture predation occurs at some livestock operations while other livestock operations are

not affected, specifically if location such as distance to vulture roosts or housekeeping

issues such as use of calving barns or disposal of dead livestock have any impact on the

occurrence of vulture predation or vulture predation rates.

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List of References

Amador-Alcala, S., Naranjo, E., and Jimenez-Ferrer, G. (2013) Wildlife predation on livestock and poultry: Implications for predator conservation in the rainforest of south-Eeast Mexico. Oryx 47;2: 243-250. Avery, M.L. and Cumming, J.L. (2004) Livestock depredations by black vultures and golden eagles. USDA National Wildlife Research Center - Staff Publications. Paper 76. Avery, M.L., Humphrey, J.S., Tillman, E.A., and Milleson, M.P. (2006) Responses of black vultures to roost dispersal in Radford, Virginia. Proceedings of the Twenty-Second Vertebrate Pest Conference. 239-243. Bellati, J. and von Thungen J. (1990) Lamb predation in Patagonian ranches. Proceedings of the Fourteenth Vertebrate Pest Conference 1990. Paper 6. Beranger, J. and Walters, M. (2007) How to raise heritage turkeys on pasture. Chapter 8: Protecting heritage turkeys from predators. 73-78. Published by American Livestock Breeds Conservancy. Booth, T.H. (1994) Bird dispersal techniques. The Handbook: Prevention and Control of Wildlife Damage. Paper 58. Breen, B.M. (2011) Sheep farmers and turkey vultures (Cathartes aura) in the Falkland Islands: from conflict to coexistence [MSc thesis]. University of Minnesota. Bruggers, R.L., Owens, R., and Hoffman, T. (2002) Wildlife damage management research needs: perceptions of scientists, wildlife managers, and stakeholders of the USDA/Wildlife Services Program. USDA National Wildlife Research Center - Staff Publications. Paper 468. Buckley, N.J. (1996) Food finding and the influence of information, local enhancement, and communal roosting on foraging success of North American vultures. The Auk 113; 2: 473-488. Coleman, J.S. and Fraser, J.D. (1987) Food habitats of black vultures in Pennsylvania and Maryland. The Journal of Wildlife Management 51; 4: 733-739. Davis, E.R. (1998) Strategies for alleviating vulture damage in industrial plants. Proceedings of the Eighteenth Vertebrate Pest Conference. Paper 40. Humphrey, J.S., Tillman, E.A., and Avery, M.L. (2004) Vulture-cattle interactions at a central Florida ranch. USDA National Wildlife Research Center - Staff Publications. Paper 344.

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Lowney, M.S. (1999) Damage by black and turkey vultures in Virginia, 1990-1996. Wildlife Society Bulletin 27; 3: 715-719. Parkman, P. (2005). Crop profile for beef cattle in Tennessee. http://www.ipmcenters.org/cropprofiles/docs/TNbeef.pdf. National Audubon Society, Inc. birds.audubon.org. Accessed on August 4, 2014. Seamons, T.W. (2004) Response of roosting turkey vultures to a vulture effigy. USDA National Wildlife Research Center - Staff Publications. Paper 385. USDA (2011) Cattle death loss. National Agricultural Statistics Board. Released May 12, 2011. USDA (2013) National Agricultural Statistics Service. http://www.nass.usda.gov/Quick_Stats/Ag_Overview/stateOverview.php?state=TENNESSEE. Accessed on August 6, 2014. Wade, D.A., Hawthorn, D.W., Nunley, G.L., and Caroline, M. (1984) History and status of predator control in Texas. Proceedings of the Eleventh Vertebrate Pest Conference. Paper 42.

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Appendix A

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Survey Questions

1. What county or counties do you work in?

2. Has that county experienced calf mortality that has been attributed to vultures? A. Yes B. No

3. If so, which species of vulture?

A. Black Vultures (Coragyps atratus) B. Turkey Vultures (Cathartes aura) C. Both D. Unknown E. Not Applicable

4. What percent of calf mortality in the county has been attributed to vultures (Can be an

estimate)? A. None B. 1-10% C. 11-20% D. 21-30% E. 31-40% F. 41-50% G. 51-60% H. 61-70% I. 71-80% J. 81-90% K. 91-100

5. How was the determination made that vultures were the cause of the calf mortality (check

all that apply)? A. Necropsy B. Other cows or livestock with injuries attributed to vultures C. Vulture roost nearby D. Dirt/sand/grit in the hooves indicating the calf was not still born and no

indications of predation by other species E. Other F. Not Applicable

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6. Is the presence of vultures at the farms experiencing vulture predation consistent year round or is vulture presence is tied to calving?

A. Vultures issues only occur when calving B. Vultures present year round C. Varies between farms D. Not Applicable

7. Have any other livestock deaths been attributed to vultures in the county and if so which

species (check all that apply)? A. Sheep B. Goats C. Horses D. Fowl E. Other F. Not Applicable

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Appendix B