U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2011–1190

Evaluating Trapping Techniques to Reduce 

Potential for Injury to Mexican Wolves
Photo Credit: U.S. Fish and Wildlife Service, Mexican Wolf Interagency Field Team
Evaluating Trapping Techniques to Reduce 

Potential for Injury to Mexican Wolves

By T.T. Turnbull, J.W. Cain, III, and G.W. Roemer

Open-File Report 2011–1190

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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Suggested citation:

Turnbull, T.T., Cain, J.W., III, and Roemer, G.W., 2011, Evaluating trapping techniques to reduce potential for injury 

to Mexican wolves: U.S. Geological Survey Open-File Report 2011-1190, 11 p.
iii

Acknowledgments

Funding was provided by the New Mexico Department of Game and Fish. Reviews by 

M. J. Kauffman and P.R. Krausman improved an earlier draft of this report. 
Contents

Acknowledgments........................................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Methods...........................................................................................................................................................2

Sources of Mortality and Trapping Incidents for Mexican Wolves .............................................2

Trap-Injured Wolves and Cattle Depredation ..................................................................................2

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

Results .............................................................................................................................................................3

Sources of Mortality and Trapping Incidents for Mexican Wolves .............................................3

Trap-injured Wolves and Cattle Depredation...................................................................................5

Literature Review..................................................................................................................................5

Foothold Traps .......................................................................................................................................5

Snares ....................................................................................................................................................7

Discussion.......................................................................................................................................................8

References Cited............................................................................................................................................9

Figures

1. Known sources of mortality for Mexican wolves (Canis lupus baileyi)

in Arizona and New Mexico, 1998–2010. ..................................................................................3

Tables

1. Known nonrecovery program-related (that is, private) trapping incidents 

for Mexican wolves (Canis lupus baileyi) in Arizona and New Mexico, 

1998-2010........................................................................................................................................4

2. Mean injury score for coyotes (Canis latrans) from studies evaluating 

capture injuries resulting from the use of foothold traps and nonlethal 

cable snares ..........................................................................................................................................6

3. Percentage of wolf (Canis lupus) injuries by severity class summarized 

from studies evaluating wolf injuries caused by various types of foothold 

traps. In general, the severity of the injury increases with the severity score..................6

4. Mean injury score for red fox (Vulpes vulpes), coyotes (Canis latrans), and 

wolves (Canis lupus) from studies evaluating capture injuries resulting from 

the use of foothold traps and nonlethal cable snares............................................................6
Evaluating Trapping Techniques to Reduce Potential for 

Injury to Mexican Wolves

By Trey T. Turnbull,1 James W. Cain III,

2 Gary W. Roemer1

1

 Department of Fish, Wildlife, and Conservation Ecology, New Mexico State University, Las Cruces, NM 88003, USA

2

 U.S. Geological Survey, New Mexico Cooperative Fish and Wildlife Research Unit, Department of Fish, Wildlife, and Conservation Ecology, New Mexico 

State University, Las Cruces, NM 88003, USA

Abstract

Increased scrutiny of furbearer trapping has resulted 

in more regulation and even prohibition of common 

trapping methods in some States. Concerns regarding the 

potential negative impacts of regulated furbearer trapping on 

reintroduced Mexican gray wolves (Canis lupus baileyi) led 

now former Governor Bill Richardson to issue an executive 

order prohibiting trapping in the New Mexico portion of the 

Blue Range Wolf Recovery Area (BRWRA). This ban was 

to last for at least 6 months and required an evaluation of the 

risk posed to wolves by traps and snares legally permitted 

in New Mexico. We reviewed various threats to wolves in 

the BRWRA, including threats posed by regulated furbearer 

trapping. Seventy-eight Mexican wolf mortalities were 

documented during the reintroduction effort (1998-2010). 

More than 80 percent of documented mortalities were humancaused: illegal shooting (47.4 percent), vehicle collisions 

(15.4 percent), lethal removal by the U.S. Fish and Wildlife 

Service (USFWS) (14.1 percent), nonproject-related trapping 

(2.6 percent), project-related trapping (1.3 percent), and legal 

shooting by the public (1.3 percent). The remaining 

17.9 percent of mortalities were a result of natural causes. 

An additional 23 wolves were permanently removed from the 

wild by USFWS. Of 13 trapping incidents in New Mexico 

that involved trappers other than USFWS project personnel, 

7 incidents resulted in injuries to wolves, 2 wolves sustained 

injuries severe enough to result in leg amputations, and 

2 wolves died as a result of injuries sustained. Rubber-padded 

foothold traps and properly set snares would most likely 

reduce trap-related injuries to Mexican wolves; however, 

impacts caused by trapping are outnumbered by other, 

human-caused impacts.

Introduction

Trapping of furbearers for recreation or wildlife damage 

mitigation, while a long-standing tradition in the United States 

and other parts of the world, has received increased scrutiny 

by the public in recent years because commonly used 

trapping practices have been perceived as being inhumane 

(Onderka and others, 1990; Andelt and others, 1999). These 

concerns have led to increased regulation and even total 

prohibition of common trapping methods in some jurisdictions 

(Muth and others, 2006). Additionally, wildlife professionals 

often need to capture animals for study, and injured animals 

could bias results. As a result, a number of field projects have 

been conducted comparing various types of traps and methods 

in order to find solutions that minimize trauma to target and 

nontarget animals (Andelt and others, 1999; Frame and 

Meier, 2007). Similar concerns about animal welfare and 

public perception of trapping led to the development of the 

“Best Management Practices” (BMPs) for furbearer trapping 

in the United States by the Association of Fish and Wildlife 

Agencies (IAFWA, 1997). Given the potential for further 

restrictions being placed on trappers, such as potential bans on 

importation of furs collected by using certain methods (Proulx 

and others, 1994), testing of different devices to evaluate their 

impacts and identify means of mitigation for those impacts is 

likely to continue. 

The potential impacts of regulated furbearer trapping on 

reintroduced Mexican wolves (Canis lupus baileyi) in 

New Mexico has become a concern of some sectors of the 

public and, in part, prompted now former New Mexico 

Governor Bill Richardson to issue Executive Order 2010-029 

(Temporary Ban of Trapping in the Blue Range Wolf Recovery 

Area) on July 28, 2010. The Executive Order directed the 
2 Evaluating Trapping Techniques to Reduce Potential for Injury to Mexican Wolves

New Mexico Department of Game and Fish (NMDGF) to 

prohibit trapping in the New Mexico portion of the BRWRA 

for at least 6 months to allow a study to be conducted 

that would evaluate the risk posed to wolves by different 

types of traps and snares legally permitted in New Mexico. 

All previously legal methods to capture furbearers were 

prohibited except for residents trapping specifically to protect 

domesticated animals, or trapping of species not regulated by 

the NMDGF (for example, coyote [Canis latrans]). 

We reviewed scientific reports and other sources of 

information relevant to human-caused threats to wolves, 

including potential impacts from legally permitted traps and 

snares in the BRWRA to assist NMDGF in complying with 

EO 2010-029. Our specific objectives were to (1) review 

known sources of mortality and trapping incidents for 

Mexican wolves; (2) evaluate the potential risk of permanent 

injury or death to Mexican wolves resulting from the use of 

each trap or snare type currently allowed in New Mexico; and 

(3) identify trap and snare types, associated techniques, and 

potential modifications that may reduce risk of permanent 

injury or death to Mexican wolves by regulated furbearer 

trapping. Our review was primarily limited to trap types and 

snares legally permitted in New Mexico; more comprehensive 

reviews are found elsewhere (Iossa and others, 2007).

Methods

Sources of Mortality and Trapping Incidents for 

Mexican Wolves

We obtained information on sources of mortality and 

trapping incidents for Mexican wolves by request from the 

USFWS and by reviewing annual reports (USFWS, 2011a) 

and monthly updates on the Mexican Wolf Recovery Program 

(USFWS, 2011b). We reviewed information to determine the 

number of nonproject-trapping incidents (that is, unrelated to 

USFWS Mexican Wolf Recovery Program) involving Mexican 

wolves, injury status of trapped wolves, and current fate of 

wolves involved in these incidents. We attempted to obtain 

information on the trap types (and any modifications thereof) 

and anchoring mechanisms used, as well as species being 

targeted by nonproject trappers. We also requested information 

on the known causes of mortality for all wolves during the 

recovery program. 

Trap-Injured Wolves and Cattle Depredation

To determine if depredation of livestock increased 

following trap-related injuries, we reviewed information 

to determine the number of depredation incidents in which 

wolves were involved both prior to and after they were injured 

in nonproject trapping incidents. Based on the available 

information, we were unable to determine if multiple livestock 

injuries inflicted by wolves on the same day were distinct or if 

more than one cow was injured in the same incident; therefore, 

we treated each livestock injury as a separate incident.

Literature Review

We used Google Scholar, Journal Storage (JSTOR), 

and Web of Science to search the scientific literature (both 

peer-reviewed literature and unpublished reports) for studies 

that compared trap-related injuries and examined trap-injury 

mitigation. We used the following search terms: trap injury, 

foothold trap injury, leghold trap injury, foothold trap trauma, 

leghold trap trauma, wolf trap injury, furbearer trap injury, 

coyote trap injury, and bobcat (Lynx rufus) trap injury. We 

entered search terms without quotations, so exact word order 

was not required of search results, and searches were the 

broadest offered by each site (that is, not narrowed down by 

searching only keywords or only abstracts). Articles were 

deemed appropriate for review if they focused on trap-injury 

mitigation and/or best practices associated with trapping wolflike canids (for example, members of the genus Canis) or trap 

sizes were consistent with those used on canids (for example, 

bobcat studies). We further restricted the results of initial 

literature searches to only those trap types allowed by law in 

New Mexico and to regulated furbearer species and coyote 

because the size of traps commonly used by trappers targeting 

these species may present a risk of injury for Mexican wolves 

(NMDGF, 2011). We did not include lethal, Conibear-style 

traps in this review. In addition to content review, we reviewed 

the literature cited sections to find other relevant literature. 

We used tools available through Google Scholar, JSTOR, and 

Web of Science to locate articles citing those we had already 

obtained. This process was repeated on each new source, 

eventually reaching a point when no new, relevant material 

was discovered.

We also requested information on the average injury 

scores and sample sizes for each trap type recommended 

for use in the “Best Management Practices for Trapping in 

the United States” for wolves, coyote, and bobcat published 

by the Association of Fish and Wildlife Agencies (AFWA, 

2003, 2006a,b,c). The BMPs resulted from extensive studies, 

with relatively large sample sizes, evaluating animal welfare, 

efficiency, selectivity, practicality, and safety of a large number 

of trap types. Trauma scales used in the BMPs followed 

guidelines presented in the International Organization for 

Standardization (ISO, 1999). Trap types with an average 

cumulative injury score of greater than or equal to 55 on one 

scale, or greater than or equal to 70 percent of a sample with 

“no injuries or mild-moderate trauma” met the BMP animal 

welfare criteria (AFWA, 2006a). Because of the scope of this 

report, we requested data pertaining only to animal welfare. 
Results 3

Results

Sources of Mortality and Trapping Incidents for 

Mexican Wolves

Between 1998 and 2010, the USFWS documented 

78 mortalities of Mexican wolves (USFWS, 2010). 

Thirty-seven wolves were illegally shot, 12 were hit by 

vehicles, 11 were lethally removed by the USFWS, 2 died 

from trap-related injuries resulting from traps set by 

nonproject trappers, 1 was legally shot by the public, 1 died 

from trap-related injury during the course of USFWS research 

operations, and 14 died of natural causes (fig. 1). During this 

same period, 23 wolves were permanently removed from the 

wild by the USFWS. Thus, over a 12-year period, 101 wolves 

in total were removed from the wild; only 50 wolves were 

estimated to be alive in the wild in 2010 (J. Oakleaf, USFWS, 

written commun.).

Fourteen individual wolves were captured in foothold 

traps set by trappers other than USFWS project personnel 

15 times during the course of the reintroduction effort 

(table 1); female wolf 562 was captured twice. Thirteen 

of these incidents occurred in New Mexico, and 7 wolves 

incurred injuries as a result; 5 were apparently uninjured; and 

the injury status is unknown but suspected for 1 (table 1). 

Two wolves died as a result of injuries sustained, 2 sustained 

injuries severe enough to result in leg amputations, and 1 wolf 

had toes amputated and the pad removed from the right foot 

(table 1). The 2 wolves that had legs amputated were either 

alive as of April 2011 (M871) or were alive until January 2009 

but current fate is unknown (m1039) (USFWS, unpub. data). 

The 3 remaining wolves injured in traps had varying fates: 

1 wolf lived more than 2 years after the trapping incident, 

but its current fate is unknown; 1 was killed by illegal 

shooting; and another remained alive until at least April 2011 

(table 1). Fifty-seven percent of the wolves that were injured 

during trapping incidents pulled traps loose, including one 

mortality (m1041) and two with severe injuries (wolf m1039, 

Figure 1. Known sources of mortality for Mexican wolves (Canis lupus baileyi) (n = 78) in Arizona and New Mexico, 1998–2010.

47.4% Illegal shooting

14.1% Lethal removal by 

U.S. Fish and Wildlife Service 

1.3% Legal shooting by public

15.4% Vehicle collision

1.3% U.S. Fish and 

Wildlife Service project 

trapping incident

2.6% Nonproject 

related trapping 

incidents

17.9% Natural mortality
4 Evaluating Trapping Techniques to Reduce Potential for Injury to Mexican Wolves

Table 1. Known nonrecovery program related (that is, private) trapping incidents for Mexican wolves (Canis lupus baileyi) in Arizona and 

New Mexico, 1998-2010a

.

[Ariz, Arizona; BRWRA, Blue Range Wolf Recovery Area; IFT, Interagency Field Team; N.M., New Mexico; USFWS, U.S. Fish and Wildlife Service]

Date Animalb Location Reported injury Notes/fatec

Mar. 18, 2002 Male578 Outside BRWRA – N.M. None apparent Trap set for coyote; wolf removed by trapper; relocated by project 

personnel into the BRWRA/lethally removed by USFWS for 

livestock depredation in 2006.

Winter 2002-03 Female562 BRWRA – N.M. None apparent Wolf released by trapper/Known alive until June 2008; current 

fate unknown.

Winter 2002-03 Male 583 BRWRA – N.M. None apparent Wolf self released/found dead in May 2008; cause unknown.

Nov 20, 2003 Female858 Outside BRWRA –Ariz. None apparent Trap set for coyote; wolf relocated by project personnel into the 

BRWRA/alive as of March 2011. 

Nov. 22, 2003 Male859 Outside BRWRA – Ariz. None apparent Trap set for coyote; wolf relocated by project personnel into the 

BRWRA/lethally removed by USFWS for livestock 

depredation in 2006.

Oct. 15, 2005 Female562 BRWRA – N.M. Yes IFT observed animal with trap on its foot; captured via 

helicopter 2 days later to remove trap and treat (amputated toes 

and remove pad of right foot) the injured foot/suspected alive 

until June 2008; current fate unknown

Mar.26, 2006 male 1008 Outside BRWRA – N.M. None apparent Trap set for coyote; wolf removed from trap by project personnel/

killed by illegal shooting in August 2008

Oct. 18, 2006 Female923 BRWRA – N.M. Yes IFT received reports of a wolf with a trap on its foot; F923 was 

observed the same day in the same area limping (no trap on 

foot)/alive as of April 2011. 

Winter 2006-07 male1041 BRWRA – N.M. Yes Wolf m1041 observed with a trap on its foot in the winter 

2006-2007/died; upon necropsy (at death in May 2007) a 

lesion was noted to the right front foot suggestive of a steel trap 

type wound. Law enforcement confirms the death was due to 

trap-related complications. Trap injury occurred in N.M., and 

death occurred in Ariz.

Jan. 1, 2007 uncollared Outside BRWRA – N.M. Unknown Wolf pulled loose with trap. (May be M1107; M1107 first captured 

by project personnel in November 2007 and was missing two 

middle toes, consistent with a small trap capture. M1107 is not 

included in this compilation because of unknown status of injury 

and possible double count with this uncollared wolf). 

Jan. 19, 2008 Female1112 BRWRA –N.M. Yes Wolf first captured during helicopter survey and had old (healed) 

injury to front foot consistent with a nonproject 

trapping incident/killed by illegal shooting in April 2008.

Feb. 10, 2008 male1039 Outside BRWRA – N.M. Yes Trap set for coyote; wolf pulled loose with trap; captured via 

helicopter on Feb. 17, 2008, leg was amputated by project 

veterinarian/known alive until January 2009; fate unknown as 

of February 2009.

Nov. 16, 2008 Male922 BRWRA – N.M. Yes Found dead;animal died from injuries associated with 

nonproject trap. 

Jan. 23, 2009 Male871 BRWRA – N.M. Yes Captured during helicopter survey to replace radio collar; a 

portion of the front foot was missing, consistent with a 

nonproject trapping incident; leg was amputated by project 

veterinarian/alive as of April 2011. 

Feb. 18, 2009 Female1106 BRWRA – N.M. None apparent Wolf removed by trapper; released by project personnel/found 

dead in N.M. in November 2010; died of intestinal blockage.

a

Data obtained by request from USFWS.

b

Female = adult female, Male = adult male, male = subadult male.

c

Information obtained by request from USFWS, from annual reports (USFWS, 2011a), and from monthly project updates. (USFWS, 2011b).
Results 5

leg amputated by project veterinarians; wolf F562 toes and 

pad removed from right foot; table 1). All nonproject trapping 

incidents in which wolves were uninjured in New Mexico 

(n = 5) and Arizona (n = 2) involved traps that remained 

anchored; animals were released either by the trapper or 

USFWS personnel or were self-released (table 1). Fates of 

the five uninjured wolves involved in trapping incidents in 

New Mexico include survival greater than or equal to 1 year 

after the trapping incident and current fate unknown (n = 1), 

illegal shooting (n = 1), lethal removal by USFWS (n = 1), 

mortality more than 4 years after the trapping incident from 

unknown cause (n = 1) and in the final case, mortality caused 

by intestinal blockage (n = 1, table 1). 

For most trapping incidents we were unable to obtain 

specific information on the type of traps (for example, 

rubber-padded, offset jaw, laminated and offset), anchoring 

mechanisms, or species targeted by nonproject trappers whose 

traps captured Mexican wolves. It seems, however, that all 

of the trapping incidents involved the use of foothold traps; 

we could not find any information suggesting that snares 

were involved in any trapping incident. At least three of 

the nonproject trapping incidents in New Mexico and two 

in Arizona involved traps specifically set for coyotes. It is 

unknown if the traps involved in the other 10 incidents in New 

Mexico were set for coyotes or regulated furbearers; however, 

two of the trapping incidents resulting in injuries occurred 

outside the regulated furbearer trapping season, (that is, 

November 1–March 31) indicating that these traps were either 

set for coyote or illegally set out of season.

Trap-injured Wolves and Cattle Depredation

Four wolves (F562, F923, m1039, M871; table 1) that 

survived trap-related injuries were involved in depredation 

incidents resulting in injury or death of 19 head of livestock. 

Six incidents occurred before individual wolves were injured 

in traps, and 13 occurred after. There was no significant 

difference in the frequency of livestock depredation 

incidents by trap-injured wolves before or after being 

trapped (χ1

2

 = 2.579, P = 0.108). Most (n = 14) of the 

depredation incidents (4 before trapping and 10 after 

trapping) were attributed to wolf M871, which had its leg 

amputated as a result of a trapping incident. After being 

re-released into the wild, wolf M871 was involved in 

10 depredation incidents from August through September 

2009; no depredation incidents have been attributed to 

M871 since the end of September 2009.

Literature Review

We reviewed 28 sources on trap-injury studies; most 

were from either the Wildlife Society Bulletin (n =16) or 

the Journal of Wildlife Management (n = 8). Two sources 

were unpublished progress reports from ongoing research 

on BMPs for wolf trapping from AFWA, and one was a 

completed AFWA paper listing BMPs for trapping coyotes in 

western North America. The last report (Houben and others, 

1993) included was from the proceedings of the Great Plains 

Wildlife Damage Control Workshop, at the University of 

Nebraska-Lincoln. In addition, we obtained average injury 

scores and sample sizes for each trap type recommended for 

use in the BMPs for coyote and bobcat through consultation 

with the authors (B. White, AFWA, written pers. commun.).

Of the 28 sources, six included information on injuries 

sustained by gray wolves captured in several types of traps. 

Nearly half of the articles (n = 13) reported testing of various 

types of traps and snares on coyotes in addition to the data 

on injury scores obtained from AFWA on traps approved in 

BMP for coyote. This testing was apparently due to the ready 

availability and relatively unprotected status of coyotes as 

well as the existence of government-supported animal damage 

control efforts, which were used as sources of data in several 

studies (for example, Hubert and others, 1997; Darrow and 

others, 2009). Without the inclusion of data on trap-related 

injuries to coyotes, there would have been little data from 

which to draw inferences. Other carnivore species involved 

in trap and snare evaluations included bobcats, lynx (Lynx 

canadensis), puma (Puma concolor), red fox (Vulpes vulpes), 

gray fox (Urocyon cinereoargenteus), arctic fox (Vulpes 

lagopus), and raccoon (Procyon lotor). Lastly, one article 

was a summary comparing the results of trapping injury 

studies conducted on several species, most of which were also 

included in this report (Andelt and others, 1999). 

The 24 sources describing original field research on 

trap-related trauma used a variety of indices for evaluating 

the severity of injuries. The ISO procedures intended to 

standardize severity scores for capture-induced trauma did not 

exist until 1999 (Darrow and others, 2009), and three basic 

systems, and modifications thereof, were used in most of the 

studies. Olsen and others (1986) developed a scale that was 

used in four studies, all conducted on coyotes (table 2). A 

system devised by Van Ballenberghe (1984), and used in three 

studies involving wolves, assigned trapped animals to one of 

four severity categories (table 3). Lastly, six sources and the 

BMP studies (AFWA, 2006a) incorporated a system based 

on the 1999 ISO standards; these studies involved wolves, 

coyotes, bobcat, and red fox (table 4 and references therein). 

The ISO-based system is described in detail by Darrow and 

others (2009). Eleven of these 24 sources either did not use 

these systems or did not represent their data completely 

enough to be used in quantitative comparison. 

Foothold Traps

The most frequently tested type of trap was the smoothjaw, nonlaminated steel foothold trap. Studies which evaluated 

other devices either included these common steel traps for 

comparison or incorporated results of other reports which did. 

These devices are probably the most popular among North 

American trappers, particularly for capturing wolf-like canids 
6 Evaluating Trapping Techniques to Reduce Potential for Injury to Mexican Wolves

Table 4. Mean injury scorea for red fox (Vulpes vulpes), coyotes (Canis latrans), and wolves (Canis lupus) from studiesb evaluating 

capture injuries resulting from the use of foothold traps and nonlethal cable snares.

Species

Foot 

snare n

Neck 

snare n

Laminated, 

offset with stake n

Laminated, 

offset with drag n

Offset 

with drag n

Offset 

with stake n

Padded 

with stake n

Red fox 21.7 271 13.4 221

Coyote 41.7 882,3 12.1 403 92.2 1274 29.0 654

Gray wolf 23.0 55 51.0 106 53.4 356 47.1 246

a

Injury scores were assigned on the basis of the 1999 International Organization for Standardization (ISO) procedures. Scores are cumulative. Note that in 

the case of Phillips and others (1996), ISO procedures had not yet been published; however, the system used in that report is sufficiently comparable to include 

herein. The scores associated with each category of injury are described below, as in Darrow and others (2009): 5= “Edematous swelling, hemorrhage,or 

cutaneous abrasion,” 10= “Cutaneous laceration, minor periosteal abrasion or minor (below carpus or tarsus) subcutaneous soft-tissue maceration erosion,” 

25= “Severance of minor tendon or ligament,” 30= “Major (above carpus or tarsus) subcutaneous soft-tissue maceration erosion, major periosteal abrasion, or 

permanent tooth fracture exposing pulp cavity,” 50= “Simple fracture at or below the carpus or tarsus,” 100= “ Severance of major tendon or ligament or death.” 

b

Incorporates data from 1Muñoz-Igualada and others (2008), 2Darrow and others (2009), 3Shivik and others (2000), 4Phillips and others (1996), 5

White (2010),6White (2009).

Table 2. Mean injury scorea for coyotes (Canis latrans) from studiesb evaluating capture injuries resulting from the use of foothold 

traps and nonlethal cable snares. 

Conventional steel-jaw1,2,3 Laminated and offset1 Rubber-padded2,3,4 Cable foot snare3,4 Nonlethal neck snare4

Mean n Mean n Mean n Mean n Mean n

80.9 74 63 29 31.0 114 35.0 27 0.8 13

a

Numerical leg injury scores are additive for each trapped individual, but injuries which were part of higher-scoring injuries (that is, tendon damage which 

was associated with a joint luxation, or cutaneous laceration caused by a compound fracture) were not double-counted. Point values are defined by Olsen and 

others (1986) below. Severity of the injury increases with the severity index; that is, a larger index denotes a more severe injury. “Apparently normal=0, 

Edematous swelling and hemorrhage=5, Cutaneous laceration < 2cm=5, Cutaneous laceration > 2cm=10, Tendon and ligament laceration=20, 

Joint subluxation=30, Joint luxation=50, Compression fraction above or below carpus or tarsus=30, Simple fracture at or below carpus or tarsus=50, 

Compound fracture at or below carpus or tarsus=75, Simple fracture above carpus or tarsus=100, Compound fracture above carpus or tarsus=200, 

Amputation=400” 

b

Incorporates data from 1Hubert and others (1997), 2Olsen and others (1986), 3Onderka and others (1990), 4Shivik and others (2005) 

Table 3. Percentage of wolf (Canis lupus) injuries by severity class summarized from studiesa evaluating wolf injuries caused by 

various types of foothold traps. In general, the severity of the injury increases with the severity score.

Injury severity 

classb

Conventional 

smooth-jaw1 Offset smooth-jaw1 Toothed, offset1 Toothed, no offset1 Rubber-padded2

All unpadded 

trapsc,2,3

Class I 17 18 3 10 72 15

Class II 50 48 97 62 15 53

Class III 27 30 16 8 25

Class IV 7 5 12 1 8

n 269 116 40 129 96 663

a

Incorporates data from 1Kuehn and others (1986), 2Frame and Meier (2007), 3Van Ballenberghe (1984).

b

Each captured animal was assigned to one of four injury categories as described by Van Ballenberghe (1984): Class I= “slight foot and/or leg edema with 

no lacerations and no evidence of broken bones or dislocated joints,” Class II= “moderate edema with a skin laceration 2.5 cm or less long, bones and joints as 

in class I,” Class III= “injuries-skin laceration greater than 2.5 cm long with visible damage to underlying tissues, tendons intact, bone breakage limited to one 

phalanx or metacarpal,” Class IV= “various combinations of deep, wide lacerations, severed tendons, broken metacarpals, broken radius and ulna bones, and 

joint dislocations of the leg.”

c

This category, incorporating all traps except the rubber-padded model used by Frame and Meier (2007), is included because Van Ballenberghe (1984) made 

109 captures of wolves using three models of smooth-jawed and toothed offset steel traps but did not have sufficiently large sample sizes with all devices to 

make a comparison, so no differentiation was made among these models. A foot snare was also tested, but sample size was insufficient for inclusion in the 

original work.
Results 7

(Olsen and others, 1986; Phillips and others, 1996; Andelt and 

others, 1999). These traps consistently resulted in more severe 

injuries to wolves (Van Ballenberghe, 1984; Kuehn and others, 

1986; Sahr and Knowlton, 2000; Frame and Meier, 2007), 

coyotes (Onderka and others, 1990; Phillips and others, 1996; 

Hubert and others, 1997; AFWA, unpub. data), and other 

carnivores (Olsen and others, 1988; Kreeger and others, 1990; 

Earle and others, 2003) (tables 2, 3, and 4). Injuries that were 

more commonly sustained by animals captured in these traps 

were fractures, major cutaneous lacerations, joint luxation, 

tendon damage (Kuehn and others, 1986; Kreeger and others, 

1990; Andelt and others, 1999; Sahr and Knowlton, 2000), 

and possibly limb freezing that was due to the restriction of 

circulation caused by the pinching of the limb (Onderka and 

others, 1990). Some of the BMP-approved, steel-jaw traps 

tested on bobcats, however, caused less severe injuries and 

were comparable to other trap types (AFWA, unpub. data).

Steel foothold traps with varying degree of offset did not 

typically result in lower injury scores than nonoffset, smoothjaw traps (tables 2, 3, and 4), except one model also featuring 

laminated jaws (Houben and others, 1993), which resulted in 

less severe injuries to coyotes and in BMP-approved offset 

traps tested on bobcats and coyote (AFWA, unpub. data).

Steel, laminated traps were tested only on coyotes 

(table 2 and 4) and in the BMPs for coyote and bobcat 

(AFWA, 2006a,b,c). In the three published studies, these traps 

resulted in somewhat lower injury scores than did the standard 

and offset steel-jaw traps, but injury scores were still higher 

relative to other devices. In one evaluation (Houben and 

others, 1993) a trap modified by both laminating and offsetting 

the jaws resulted in lower injury scores for coyote than other 

more conventional foothold models. Steel, laminated traps 

without an offset were not recommended for use by AFWA in 

their BMP for coyote, but one such trap did meet BMP criteria 

for bobcat (AFWA 2006a,b,c; AFWA, unpub. data).

Traps with offset, toothed jaws were tested on wolves 

in two studies (Van Ballenberghe, 1984; Kuehn and others, 

1986); these resulted in markedly reduced injuries compared 

to smooth-jawed traps, with no “moderate” or “severe” 

injuries reported for this trap type in one study (Kuehn and 

others, 1986) (table 3). These results were similar to those for 

rubber-jawed traps. 

Among the rigid-jawed, foothold traps evaluated, 

rubber-padded traps consistently proved to be the most 

effective at mitigating injuries to all species of carnivores 

(tables 2, 3, and 4). Many (n =12) of the studies tested rubberpadded traps against other devices. Of these, 8 were tested on 

coyotes, 1 on gray wolves, 2 on bobcats, 2 on red foxes, 1 on 

gray foxes, 1 on raccoons, and 1 on lynx (tables 2, 3, and 4). 

In nearly all studies, there was a lower frequency of severe 

injury to captured animals compared with unpadded foothold 

traps; the single exception was the consistently minor injuries 

caused by the toothed trap tested by Kuehn and others (1986). 

Data from BMP were consistent with other studies for coyote, 

with rubber-padded traps having lower severity scores than 

other types of jaw traps (AFWA, unpub. data). One exception 

was the BMP study conducted on bobcat in which mean 

severity scores for rubber-padded traps overlapped with 

other trap types, particularly laminated and offset traps 

(AFWA, unpub. data). 

Snares

Several models of cable foot snares, as well as lethal 

and nonlethal cable neck snares were evaluated, primarily 

on coyotes. Foot snares were tested in nine published studies 

and in the BMP studies on bobcat and coyote. Six of these 

involved coyotes; the other five were conducted on puma, 

lynx, bobcat, red foxes, and wolves. There was considerable 

variation in the severity of injuries sustained from the use of 

different foot snare models when they were tested on coyotes. 

Onderka and others (1990) tested two types of foot snares, 

one of which produced injuries similar to that of an unpadded 

foothold trap, with the other model causing injuries similar 

to a padded foothold trap. Other authors found that various 

snares resulted in severity scores ranging from somewhat 

lower to slightly higher than those attributed to rubberpadded foothold traps (Shivik and others, 2000; Darrow 

and others, 2009). Studies evaluating foot snares with 

other species resulted in varying severity scores. Wolves 

(Van Ballenberghe, 1984), red foxes (Muñoz-Igualada and 

others, 2008), and pumas (Logan and others, 1999) generally 

had low to extremely low frequencies of severe injury 

(tables 2 and 4). Severity scores from BMP studies on coyote 

and bobcat were lower than or comparable to severity scores 

from rubber-padded traps (AFWA, unpub. data). Lynx, 

however, frequently sustained serious injuries including radius 

and ulna fractures when caught in a foot snare (Mowat and 

others, 1994). The authors noted, however, that the cable 

restraint never resulted in limb freezing as did the padded 

foothold trap tested, and that such snares might still be a better 

option during extremely cold weather, especially if the snare is 

securely anchored (improperly anchored snares were thought 

to be the cause of many of the severe injuries sustained by 

lynx) (tables 2 and 4). 

Four studies were conducted by using nonlethal cable 

neck snares: two on coyotes and two on red fox (table 4). 

Low to extremely low frequencies of serious injuries were 

recorded by using these devices (Shivik and others, 2000; 

Shivik and others, 2005; Muñoz-Igualada and others, 2008; 

Muñoz-Igualada and others, 2010). Three models of lethal 

neck snare, each with a breakaway device intended to release 

deer (mule deer [Odocoileus hemionus] and white-tailed 

deer [Odocoileus virginianus]) and livestock, were tested 

on coyotes (Phillips, 1996). Although these devices proved 

to be highly efficient (that is, near 90 percent of possible 

captures) at catching and quickly killing coyotes, they did not 

consistently release deer. Fifty-one of 91 deer were unable to 

break free; 47 died in the snares (Phillips, 1996).
8 Evaluating Trapping Techniques to Reduce Potential for Injury to Mexican Wolves

Discussion

The potential impacts of regulated furbearer trapping on 

reintroduced Mexican wolves in New Mexico has become a 

concern of some sectors of the public and, in part, prompted 

now former Governor Bill Richardson to issue Executive 

Order 2010-029, temporarily banning regulated furbearer 

trapping on the BRWRA. Among the reasons cited in the order 

in support of the ban were the 1976 listing of the subspecies 

under the Endangered Species Act, the small size of the 

reintroduced population (reintroduced as 10j non-essential 

experimental population), and injuries sustained by Mexican 

wolves because of trapping activities. It was also noted in the 

order that such injuries could potentially increase predation 

on livestock because of the inability of injured wolves to 

effectively hunt native prey. 

The current population, estimated at 50 wolves 

(USFWS, unpub. data) is still well short of the original 

U.S. Fish and Wildlife Service’s 2005 recovery goal of 

100 free-ranging individuals. To date, 78 wolf mortalities 

have been documented and an additional 23 animals have 

been permanently removed from the wild by USFWS. 

Approximately 82 percent of the documented mortalities were 

caused by humans with only 2.6 percent of all mortalities 

being caused by nonproject trappers (fig. 1). 

We were unable to obtain specific information on the 

type of traps or anchoring mechanisms involved in most 

of the documented trapping incidents of Mexican wolves. 

However, the majority of injuries, including the most severe 

ones, occurred during trapping incidents in which the traps 

were pulled loose, indicating that the method of anchoring 

was insufficient to hold a wolf until it could be released by 

a trapper or USFWS personnel. Conversely, most of the 

uninjured wolves were caught in traps in which the anchoring 

mechanism remained secure. General recommendations by 

AFWA for trappers suggest that the anchoring system should 

be sufficient to “hold the largest furbearer that might be 

captured” (AFWA, 2006a). Anchoring systems sufficient to 

hold coyotes or regulated furbearers may not be strong enough 

to hold Mexican wolves, potentially leading to more severe 

injuries to wolves if the trap is pulled loose.

The species targeted by trappers whose traps were 

involved in these incidents were not available for most cases; 

however, five trapping incidents (three in New Mexico and 

two in Arizona) involved traps that were set for coyotes. 

In addition, two of the trapping incidents in New Mexico 

occurred outside the regulated furbearer trapping season, 

indicating that these two traps were either set for coyote or 

illegally set out of season. As noted previously, residents 

trapping specifically to protect domestic animals, or trapping 

of coyotes were not affected by the trapping ban instituted 

by the Governor’s executive order; therefore, the incidents 

involving traps set for coyotes would not have been prevented 

by the trapping ban in the BRWRA. 

We found little evidence that trap-related injuries resulted 

in increased cattle depredation. Our results may have been 

influenced either by the low number of injured wolves that 

were included in our analysis or the fact that most depredation 

incidents involved a single wolf. There are little data from 

other studies to support the contention that injured wolves are 

more likely to depredate livestock (Fritts and others, 1992; 

Fritts and others, 2003). 

There were some definite differences in the level of risk 

presented to Mexican wolves by trapping devices legal for use 

in New Mexico. Unpadded, smooth-jawed steel traps, even if 

laminated or offset, generally presented the highest potential 

for injury to all species targeted in the studies. Wolves were 

no exception, with high percentages of those caught in these 

traps sustaining injuries including fractures, major cutaneous 

lacerations, and tendon damage (Sahr and Knowlton, 2000; 

Frame and Meier, 2007); however, the study by Houben and 

others (1993) suggested that traps that were both laminated 

and offset resulted in less severe injuries than smooth-jawed 

steel traps, laminated steel traps, or offset steel traps.

One trap that nearly eliminated serious injury to wolves, 

albeit in only one study, was a toothed, offset foothold model 

(Kuehn and others, 1986). Additionally, no studies were 

found that evaluated the potential for harm to other species 

caused by toothed-jaw traps. Toothed traps are prohibited 

under current (2011-2012) New Mexico trapping regulations 

(NMDGF 2011), and because these traps are illegal for 

recreational trapping in many other jurisdictions, few models 

are commercially available. A few companies nevertheless 

offer such traps in sizes specifically intended for use on large 

carnivores, including wolves.

Rubber-padded foothold traps generally resulted in 

less severe injury to all species captured than other types of 

foothold traps (Olsen and others, 1988; Andelt and others, 

1999; Frame and Meier, 2007). The authors of most of these 

studies were satisfied with the performance of these traps and 

recommended them as a sound option for both trappers and 

researchers, except possibly during extremely cold conditions 

when a cable foot snare may be safer because there is reduced 

potential for freezing limbs (Mowat and others, 1994). 

BMP data for bobcat, however, indicated that some models 

of padded-jaw traps resulted in severity scores that were 

comparable to traps that were offset and laminated or were 

offset with wide cast jaws; padded-jaw traps recommended 

in BMPs for coyote resulted in lower severity scores than all 

other jaw traps (AFWA, unpub. data). Based on the results of 

these studies and the focus of assessing trap-related injury to 

wolves, it is clear that rubber-padded foothold traps generally 

produced the lowest severity scores for wolf-like canids.

Because of well-founded concerns about the capture 

efficiency and even the injury mitigation capabilities of early 

rubber-padded traps, distrust of these traps still exists among 

trappers (Linscombe and Wright, 1988; Linhart and Dasch, 

1992). Currently manufactured models have gone through 

several modifications as a result of trapper dissatisfaction, 

and more recent studies have shown them to be as effective 

as unpadded models at catching and holding furbearers 

(Phillips and Mullis, 1996; Earle and others, 2003). Several 
References Cited 9

models of padded-jaw traps are among those recommended 

by AFWA for trapping of coyote and bobcat (AFWA, 2003; 

AFWA, 2006a,b,c).

The various cable foot snares evaluated, although 

somewhat inconsistent in performance, generally resulted 

in lower severity scores than did unpadded, non-toothed 

foothold traps. Devices in some studies equaled or exceeded 

the performance of rubber-padded traps in terms of trauma 

mitigation (Logan and others, 1999; Shivik and others, 2005; 

Muñoz-Igualada and others, 2005; Muñoz-Igualada and 

others, 2008; AFWA, unpub. data). Other studies, however, 

indicated that certain foothold snares could result in injuries 

comparable to unpadded steel traps if the snares were not 

properly anchored (Onderka and others, 1990; Mowat and 

others, 1994). 

The nonlethal cable neck snares used in four studies 

were found to be fairly safe devices for capturing red foxes 

and coyotes with a low potential for harm to nontarget 

species (Shivik and others, 2000; Shivik and others, 2005; 

Muñoz-Igualada and others, 2008; Muñoz-Igualada and 

others, 2010). No animals were permanently harmed by 

these devices, with the exceptions of one coyote killed by a 

malfunctioning device and a small percentage of canids that 

damaged teeth on the cable. These snares may be a viable 

option for use in areas where there is potential for wolf 

capture; however, we did not find any studies that 

specifically used nonlethal cable neck snares on wolves. 

The single study that examined lethal neck snares 

equipped with breakaway devices intended to release 

nontarget species larger than coyotes resulted in deaths of 

47 out of 91 deer (mule deer and white-tailed deer) because 

they were unable to generate enough force to escape 

(Phillips, 1996). Mexican wolves, especially pups, overlap 

in size with coyotes and are generally smaller than the deer 

killed in these snares.

Although some of the articles did describe in detail the 

trap size, chains, swivels, stakes, and drags employed, notably 

lacking were comparisons of these modifications and how 

they influenced the severity of injuries; some of the variability 

in severity scores documented could be due to differences in 

trap modifications other than jaw type. Two studies (White, 

2009; White, 2010) did test identical traps on wolves with 

either stakes or drags for anchoring (table 4), but no difference 

was found between anchoring systems; field research for this 

project is ongoing. Further evaluation of factors other than jaw 

type for minimizing trap-related injuries may be warranted.

Certain types of traps and snares clearly stood out 

as being more likely to reduce injury to both target and 

nontarget terrestrial mammals, including large canids. With 

the exception of some padded-jaw traps tested in BMP for 

bobcat, rubber-padded models consistently resulted in greatly 

reduced trauma scores for all species for which they were 

evaluated. Toothed, offset steel-jawed traps (currently legally 

restricted), resulted in severity scores classified as light-tomoderate for wolves and were comparable to rubber-padded 

foothold traps. Almost without exception, smooth-jawed steel 

traps, even if offset or laminated, were associated with more 

severe injuries than other devices used to capture wolves and 

other carnivores. Smooth-jawed steel traps that were both 

laminated and offset, however, resulted in fewer injuries and 

lower severity scores than unmodified smooth-jawed traps, 

offset smooth-jawed traps, or laminated traps, although injury 

scores were not reduced to the extent that they were with most 

rubber-padded traps. 

Of the varied human impacts, trapping-related injury 

and mortality to Mexican wolves is relatively minimal. 

Nevertheless, modifications to traps can be implemented to 

reduce impacts even further. Human-induced mortality has 

most likely impeded the recovery of the Mexican wolf, and 

those parties concerned with reestablishing the species could 

take a close look at those human-caused impacts of greatest 

conservation concern.

References Cited

Andelt, W.F., Phillips, R.L, Schmidt, R.H., and Gill, R.B., 

1999, Trapping furbearers: an overview of the biological 

and social issues surrounding a public policy controversy: 

Wildlife Society Bulletin, v. 27, p. 53-64.

Association of Fish and Wildlife Agencies (AFWA), 2003, 

Best management practices for trapping coyotes in the 

Eastern United States: Washington, D.C., Association of 

Fish and Wildlife Agencies, 13 p.

Association of Fish and Wildlife Agencies (AFWA), 2006a, 

Best management practices for trapping in the United 

States: introduction: Washington, D.C., Association of Fish 

and Wildlife Agencies, 13 p.

Association of Fish and Wildlife Agencies (AFWA), 2006b, 

Best management practices for trapping coyotes in the 

Western United States: Washington, D.C., Association of 

Fish and Wildlife Agencies, 12 p.

Association of Fish and Wildlife Agencies (AFWA), 2006c, 

Best management practices for trapping bobcats in the 

United States: Washington, D.C., Association of Fish and 

Wildlife Agencies, 14 p.

Darrow, P.A., Skirpstunas, R.T., Carlson, S.W., and Shivik, 

J.A., 2009, Comparison of injuries to coyote from 3 types 

of cable foot-restraints: Journal of Wildlife Management, 

v. 73, p. 1441-1444.

Earle, R.D., Lunning, D.M., Tuovila, V.R., and Shivik, J.A., 

2003, Evaluating injury mitigation and performance of #3 

Victor Soft Catch (R) traps to restrain bobcats: Wildlife 

Society Bulletin, v. 31, p. 617-629.

Frame, P.F., and Meier, T.J., 2007, Field-assessed injury to 

wolves captured in rubber-padded traps: Journal of 

Wildlife Management, v. 71, p. 2074-2076.
10 Evaluating Trapping Techniques to Reduce Potential for Injury to Mexican Wolves

Fritts, S.H., Paul, W.J., Mech, L.D., and Scott, D.P., 1992, 

Trends and management of wolf-livestock conflicts in 

Minnesota: U.S. Fish and Wildlife Service Resource 

Publication 181, 27 p.

Fritts, S.H., Stephenson, R.O., Hayes, R.D., and Boitani, 

Luigi., 2003, Wolves and humans, in Mech, D.L., and 

Boitani, Luigi., eds., Wolves: behavior, ecology and 

conservation: Chicago, Ill., University of Chicago Press, 

p. 289-316. 

Houben, J.M., Holland, Merrilee., Jack, S.W., and Boyle, C.R., 

1993, An evaluation of laminated offset jawed traps for 

reducing injuries to coyotes: Great Plains Wildlife Damage 

Control Workshop Proceedings, 147-153.

Hubert, G. F., Hungerford, L.L., and Bluett, R.D., 1997, 

Injuries to coyotes captured in modified foothold traps: 

Wildlife Society Bulletin, v. 25, p. 858-863.

International Organization for Standardization (ISO), 1999, 

Animal (mammal) traps, part 5, Methods for testing 

restraining traps: Geneva, Switzerland, International 

Organization for Standardization , International Standard 

ISO/DIS 10990-5.

International Association of Fish and Wildlife Agencies 

(IAFWA), 1997, Improving animal welfare in U.S. trapping 

programs: process recommendations and summaries of 

existing data: Washington, D.C., International Association 

of Fish and Wildlife Agencies (currently Association of 

Fish and Wildlife Agencies).

Iossa, Graziella., Soulsbury, C.D., and Harris, Stephen., 2007, 

Mammal trapping: a review of animal welfare standards 

of killing and restraining traps: Animal Welfare, v.16, 

p. 335-352.

Kreeger, T.J., White, P.J., Seal, U.S., and Tester, J.R., 1990, 

Pathological responses of red foxes to foothold traps: 

Journal of Wildlife Management, v. 54, p. 147-160.

Kuehn, D.W., Fuller, T.K., Mech, L.D., Paul, W.J., 

Fritts, S.H., and Berg, W.E., 1986, Trap-related injuries 

to gray wolves in Minnesota: Journal of Wildlife 

Management, v. 50, p. 90-91.

Linhart, S.B., and Dasch, G.J., 1992, Improved performance 

of padded jaw traps for capturing coyotes: Wildlife Society 

Bulletin , v. 20, p. 63-66.

Linscombe, R.G., and Wright, V.L., 1988, Efficiency of 

padded foothold traps for capturing terrestrial furbearers: 

Wildlife Society Bulletin, v. 16, p. 307-309.

Logan, K.A., Sweanor, L.L., Smith, J.F., and Hornocker, M.G., 

1999, Capturing pumas with foot-hold snares: Wildlife 

Society Bulletin, v. 27, p. 201-208.

Mowat, Garth., Slough, B.G., and Rivard, René., 1994, 

A comparison of three live capturing devices for lynx: 

capture efficiency and injuries: Wildlife Society Bulletin, 

v. 22, p. 644-650.

Muñoz-Igualada, Jaime., Shivik, J.A., Dominguez, F.G., 

Gonzalez, L.M., Moreno, A.A., Olalla, M.F., and Garcia, 

C.A., 2010, Traditional and new cable restraint systems 

to capture fox in central Spain: Journal of Wildlife 

Management, v. 74, p. 181-187.

Muñoz-Igualada, Jaime., Shivik, J.A., Dominguez, F.G., Lara, 

José., and Gonzalez, L.M., 2008, Evaluation of cage-traps 

and cable restraint devices to capture red foxes in Spain: 

Journal of Wildlife Management, v. 72, p. 830-836.

Muth, R.M., Zwick, R.R., Mather, M.E., Organ, J.F., Daigle, 

J.J., and Jonker, S.A., 2006, Unnecessary source of pain 

and suffering or necessary management tool: attitudes of 

conservation professionals toward outlawing leghold traps: 

Wildlife Society Bulletin, v. 34, p. 706-715.

New Mexico Department of Game and Fish (NMDGF), 2011, 

Big game and trapper rules and information: Santa Fe, 

N.M., New Mexico Department of Game and Fish, 63 p.

Olsen, G.H., Linhart, S.B., Holmes, R.A., Dasch, G.J., and 

Male, C.B., 1986, Injuries to coyotes caught in padded and 

unpadded steel foothold traps: Wildlife Society Bulletin, 

v. 14, p. 219-223.

Olsen, G.H., Linscombe, R.G., Wright, V.L., and Holmes, 

R.A., 1988, Reducing injuries to terrestrial furbearers by 

using padded foothold traps: Wildlife Society Bulletin, 

v. 16, p.303-307.

Onderka, D.K., Skinner, D.L., and Todd, A.W., 1990, 

Injuries to coyotes and other species caused by 4 models 

of footholding devices: Wildlife Society Bulletin, v. 18, 

p. 175-182.

Phillips, R.L., 1996, Evaluation of 3 types of snares for 

capturing coyotes: Wildlife Society Bulletin, v. 24, 

p. 107-110.

Phillips, R.L., Gruver, K.S., and Williams, E.S., 1996, Leg 

injuries to coyotes captured in three types of foothold traps: 

Wildlife Society Bulletin, v. 24, p. 260-263.

Phillips, R.L., and Mullis, Curt., 1996, Expanded field testing 

of the No 3 Victor Soft Catch(R) trap: Wildlife Society 

Bulletin, v. 24, p.128-131.

Proulx, Gilbert, Pawlina, I.M., Onderka, D.K., Badry, M.J., 

Seidel, Ken, 1994, Field evaluation of the number 1 1⁄2 

steel-jawed leghold and the Sauvageau 2001-8 traps to 

humanely capture arctic fox: Wildlife Society Bulletin, 

v. 22, p. 179-183.
References Cited 11

Sahr, D.P., and Knowlton, F.F., 2000, Evaluation of 

tranquilizer trap devices (TTDs) for foothold traps used 

to capture gray wolves: Wildlife Society Bulletin, 

v. 28, p. 597-605.

Shivik, J.A., Gruver, K.S., and DiLiberto, T.J., 2000, 

Preliminary evaluation of new cable restraints to capture 

coyotes: Wildlife Society Bulletin, v. 28, p. 606-613.

Shivik, J.A., Martin, D.J., Pipas, M.J., Turnan, John, and 

DiLiberto, T.J., 2005, Initial comparison: jaws, cables, and 

cage-traps to capture coyotes: Wildlife Society Bulletin, 

v. 33, p. 1375-1383.

U.S. Fish and Wildlife Service (USFWS), 2010, Mexican wolf 

population statistics: Accessed March 12, 2011 at http://

www.fws.gov/southwest/es/mexicanwolf/MWPS.shtml.

U.S. Fish and Wildlife Service (USFWS), 2011a, Annual 

reports on the Mexican Wolf Recovery Program: accessed 

April 14, 2011 at http://www.fws.gov/southwest/es/

mexicanwolf/documents.shtml.

U.S. Fish and Wildlife Service (USFWS), 2011b, Blue Range 

Wolf Reintroduction Area (BRWRA) monthly project 

updates: accessed April 14, 2011 at http://www.fws.gov/

southwest/es/mexicanwolf/BRWRP_notes.cfm.

Van Ballenberghe, Victor, 1984, Injuries to wolves sustained 

during live-capture: Journal of Wildlife Management, v. 48, 

p. 1425-1429.

White, Bryant, 2009, Testing restraining traps for the 

development of best management practices for trapping 

gray wolf in the United States: Washington, D.C., 

Association of Fish and Wildlife Agencies, 9 p.

White, Bryant, 2010, Testing restraining traps for the 

development of best management practices for trapping 

gray wolf in the United States: Washington, D.C., 

Association of Fish and Wildlife Agencies, 10 p.

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