2488 Federal Register / Vol. 80, No. 11 / Friday, January 16, 2015 / Rules and Regulations 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

[Docket No. FWS–HQ–ES–2013–0073; 

FXES11130900000–156–FF09E42000] 

RIN 1018–AY00 

Endangered and Threatened Wildlife 

and Plants; Endangered Status for the 

Mexican Wolf 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Final rule. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), determine 

endangered status under the 

Endangered Species Act of 1973, as 

amended, for the Mexican wolf (Canis 

lupus baileyi). The effect of this 

regulation will be to revise the List of 

Endangered and Threatened Wildlife by 

making a separate entry for the Mexican 

wolf. We are separating our 

determination on the listing of the 

Mexican wolf as endangered from the 

determination on our proposal regarding 

the delisting of the gray wolf in the 

United States and Mexico. This rule 

finalizes our determination for the 

Mexican wolf. 

DATES: This rule becomes effective 

February 17, 2015. 

ADDRESSES: This final rule is available 

on the internet at http://

www.regulations.gov and http://

www.fws.gov/southwest/es/

mexicanwolf/. Comments and materials 

we received, as well as some of the 

supporting documentation we used in 

preparing this rule, are available for 

public inspection at http://

www.regulations.gov. All of the 

comments, materials, and 

documentation that we considered in 

this rulemaking are available by 

appointment, during normal business 

hours at: Mexican Wolf Recovery 

Program, U.S. Fish and Wildlife Service, 

New Mexico Ecological Services Field 

Office, 2105 Osuna Road NE., 

Albuquerque, NM 87113; by telephone 

505–761–4704; or by facsimile 505– 

346–2542. 

FOR FURTHER INFORMATION CONTACT: 

Sherry Barrett, Mexican Wolf Recovery 

Coordinator, U.S. Fish and Wildlife 

Service, New Mexico Ecological 

Services Field Office, 2105 Osuna Road, 

NE., Albuquerque, NM 87113; by 

telephone 505–761–4704; or by 

facsimile 505–346–2542. If you use a 

telecommunications device for the deaf 

(TDD), call the Federal Information 

Relay Service (FIRS) at 800–877–8339. 

Further contact information can be 

found on the Mexican Wolf Recovery 

Program’s Web site at http://

www.fws.gov/southwest/es/

mexicanwolf/. 

SUPPLEMENTARY INFORMATION: 

Executive Summary 

Why we need to publish a rule. Under 

the Endangered Species Act (Act), a 

subspecies warrants protection if it is 

endangered or threatened throughout all 

or a significant portion of its range. 

Listing a subspecies as endangered or 

threatened can only be completed by 

issuing a rule. We proposed to delist the 

gray wolf and maintain protections for 

the Mexican wolf by listing it as an 

endangered subspecies on June 13, 2013 

(78 FR 35664). At this time, we are 

finalizing the proposal to list the 

Mexican wolf as an endangered 

subspecies. Elsewhere in this Federal 

Register, we are finalizing revisions to 

the regulations for the nonessential 

experimental population of the Mexican 

wolf. 

We note that the United States District 

Court for the District of Columbia 

recently vacated the final rule at 76 FR 

81666 (December 28, 2011) that 

removed protections of the Act from the 

gray wolf in the western Great Lakes. 

Humane Society v. Jewell, 2014 U.S. 

Dist. Lexis 175846 (D.D.C. December 19, 

2014). The court’s action was based, in 

part, on its conclusion that the Act does 

not allow the Service to use its authority 

to identify distinct population segments 

(DPSs) as ‘‘species’’ to remove the 

protections for part of a listed species. 

We have determined that the decision in 

Humane Society does not change our 

conclusions in this final rule. First, the 

district court’s interpretation of the Act 

is in error, and is in any case not 

binding on particular matters not at 

issue in that case. Second, the action 

here is distinguishable from that in 

Humane Society. Here, the Service is 

not designating a DPS, but is taking an 

action with respect to a subspecies of a 

listed entity. In addition, the Service is 

not reducing protections for the 

Mexican wolf or delisting it, but instead 

is confirming that it is an endangered 

species. 

This rule will finalize the listing of the 

Mexican wolf as an endangered 

subspecies. 

The basis for our action. Under the 

Act, a subspecies is determined to be 

endangered or threatened because of 

any of the following factors: (A) The 

present or threatened destruction, 

modification, or curtailment of its 

habitat or range; (B) overutilization for 

commercial, recreational, scientific, or 

educational purposes; (C) disease or 

predation; (D) the inadequacy of 

existing regulatory mechanisms; and (E) 

other natural or manmade factors 

affecting its continued existence. We 

have determined the Mexican wolf 

meets the definition of an endangered 

subspecies primarily because of illegal 

killing, inbreeding, loss of 

heterozygosity, loss of adaptive 

potential, small population size, and the 

cumulative effects of the 

aforementioned threats. Absent 

protection by the Act, regulatory 

protection would not be adequate to 

ensure the survival of the Mexican wolf. 

Peer review and public comment. 

Through the National Center for 

Ecological Analysis and Synthesis we 

sought comments from independent 

specialists to ensure that our 

designation is based on scientifically 

sound data, assumptions, and analyses. 

These peer reviewers were invited to 

comment on our listing proposal. We 

also considered all comments and 

information received during the public 

comment period. 

Background 

Previous Federal Actions for Mexican 

Wolves 

Gray wolves were originally listed as 

subspecies or as regional populations of 

subspecies in the contiguous United 

States and Mexico. We listed the 

Mexican gray wolf subspecies, Canus 

lupus baileyi, as endangered on April 

28, 1976 (41 FR 17736), in the 

southwestern United States and Mexico. 

In 1978, we published a rule (43 FR 

9607, March 9, 1978) classifying the 

gray wolf as an endangered population 

at the species level (Canis lupus) 

throughout the contiguous United States 

and Mexico, except for the Minnesota 

gray wolf population, which was 

classified as threatened. At that time, we 

considered the gray wolves in 

Minnesota to be a listable entity under 

the Act, and we considered the gray 

wolves in Mexico and the 48 contiguous 

United States other than Minnesota to 

be another listable entity (43 FR 9607 

and 9610, respectively, March 9, 1978). 

The separate subspecies listings thus 

were subsumed into the listings for the 

gray wolf in Minnesota and the gray 

wolf in the rest of the contiguous United 

States and Mexico. 

The 1978 listing of the gray wolf was 

undertaken to address changes in our 

understanding of gray wolf taxonomy, 

and recognize the fact that individual 

wolves sometimes disperse across 

subspecific boundaries, resulting in 

intergradation of neighboring 

populations. The 1978 rule also 

stipulated that ‘‘biological subspecies 


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would continue to be maintained and 

dealt with as separate entities’’ (43 FR 

9609), and offered ‘‘the firmest 

assurance that [the Service] will 

continue to recognize valid biological 

subspecies for purposes of its research 

and conservation programs’’ (43 FR 

9610, March 9, 1978). 

Accordingly, we implemented three 

gray wolf recovery programs in the 

following regions of the country: the 

Western Great Lakes (Minnesota, 

Michigan, and Wisconsin, administered 

by the Service’s Great Lakes, Big Rivers 

Region), the Northern Rocky Mountains 

(Idaho, Montana, and Wyoming, 

administered by the Service’s 

Mountain–Prairie Region and Pacific 

Region), and the Southwest (Arizona, 

New Mexico, Texas, Oklahoma, Mexico, 

administered by the Service’s Southwest 

Region). Recovery plans were developed 

in each of these areas (the northern 

Rocky Mountains in 1980, revised in 

1987; the Great Lakes in 1978, revised 

in 1992; and the Southwest in 1982) to 

establish and prioritize recovery criteria 

and actions appropriate to the unique 

local circumstances of the gray wolf. A 

separate recovery effort for gray wolves 

formerly listed as Canis lupus 

monstrabilis was not undertaken 

because this subspecies was subsumed 

with the Mexican wolf, C. l. baileyi, and 

thus addressed as part of the recovery 

plan for the Southwest. 

In the Southwest, on August 11, 2009, 

we received a petition dated the same 

day from the Center for Biological 

Diversity requesting that we list the 

Mexican wolf as an endangered 

subspecies or distinct population 

segment (DPS) and designate critical 

habitat under the Act. On August 12, 

2009, we received a petition dated 

August 10, 2009, from WildEarth 

Guardians and The Rewilding Institute 

requesting that we list the Mexican wolf 

as an endangered subspecies and 

designate critical habitat under the Act. 

On October 9, 2012, we published a 12- 

month finding in the Federal Register 

stating that, because all individuals that 

constitute the petitioned entity already 

receive the protections of the Act, the 

petitioned action was not warranted at 

that time (77 FR 61375). 

On February 29, 2012, we concluded 

a 5-year review of the Canis lupus listed 

entity, recommending that the entity 

currently described on the List of 

Endangered and Threatened Wildlife 

should be revised to reflect the 

distribution and status of C. lupus 

populations in the contiguous United 

States and Mexico by removing all areas 

currently included in the Code of 

Federal Regulations (CFR) range except 

where there is a valid species, 

subspecies, or DPS that is threatened or 

endangered. 

On June 13, 2013 (78 FR 35664), we 

published a proposed rule to delist the 

gray wolf and maintain protections for 

the Mexican wolf by listing it as an 

endangered subspecies. Upon 

publication of the proposed rule, we 

opened the public comment period on 

the proposal. On September 5 and 

October 2, 2013, we announced public 

hearings on the proposed rule (78 FR 

54614 and 78 FR 60813). The September 

5 document also extended the public 

comment period for the proposed rule to 

October 28, 2013. Following delays 

caused by the Federal Government lapse 

in appropriations, the Service 

announced rescheduled dates for three 

of the public hearings, scheduled a fifth 

public hearing, and extended the public 

comment period for the proposed rule to 

December 17, 2013 (78 FR 64192, 

October 28, 2013). On February 10, 2014 

(79 FR 7627), we reopened the public 

comment period on the proposal in 

conjunction with the submission of the 

peer review report. The comment period 

closed on March 27, 2014. 

Subspecies Information 

Taxonomy 

The Mexican wolf subspecies, Canis 

lupus baileyi, was originally described 

by Nelson and Goldman in 1929 as 

Canis nubilus baileyi, with a 

distribution of ‘‘Southern and western 

Arizona, southern New Mexico, and the 

Sierra Madre and adjoining tableland of 

Mexico as far south, at least, as southern 

Durango (Nelson and Goldman 1929, 

pp. 165–166).’’ Goldman (1944, pp. 

389–636) provided the first 

comprehensive treatment of North 

American wolves, in which he renamed 

C. n. baileyi as a subspecies of lupus 

(i.e., C. l. baileyi) and shifted the 

subspecies’ range farther south in 

Arizona. His gray wolf classification 

scheme was subsequently followed by 

Hall and Kelson (1959, pp. 847–851; 

Hall 1981, p. 932). Since that time, gray 

wolf taxonomy has undergone 

substantial revision, including a major 

taxonomic revision in which the 

number of recognized gray wolf 

subspecies in North America was 

reduced from 24 to 5, with the Mexican 

wolf, C. l. baileyi, being recognized as a 

subspecies ranging throughout most of 

Mexico to just north of the Gila River in 

southern Arizona and New Mexico 

(Nowak 1995, pp. 375–397). 

Three published studies of 

morphometric variation conclude that 

the Mexican wolf is a morphologically 

distinct and valid subspecies. Bogan 

and Mehlhop (1983) analyzed 253 gray 

wolf skulls from southwestern North 

America using principal component 

analysis and discriminant function 

analysis. They found that the Mexican 

wolf was one of the most distinct 

subspecies of southwestern gray wolf 

(Bogan and Mehlhop 1983, p. 17). 

Hoffmeister (1986) conducted principal 

component analysis of 28 skulls, also 

recognizing the Mexican wolf as a 

distinct southwestern subspecies (pp. 

466–468). Nowak (1995) analyzed 580 

skulls using discriminant function 

analysis. He concluded that the Mexican 

wolf was one of only five distinct North 

American gray wolf subspecies that 

should continue to be recognized 

(Nowak 1995, pp. 395–396). 

Genetic research provides additional 

validation of the recognition of the 

Mexican wolf as a subspecies. Studies 

have demonstrated that the Mexican 

wolf has unique genetic markers that 

distinguish the subspecies from other 

North American gray wolves. Garcia– 

Moreno et al. (1996, p. 384) utilized 

microsatellite analysis to determine 

whether two captive populations of 

Mexican wolves were pure C. l. baileyi 

and should be interbred with the 

captive certified lineage population that 

founded the captive breeding program. 

They confirmed that the two captive 

populations were pure Mexican wolves 

and that they and the certified lineage 

were closely related. Further, they 

found that, as a group, the three 

populations were the most distinct 

grouping of North American wolves, 

substantiating the distinction of the 

Mexican wolf as a subspecies. 

Hedrick et al. (1997, pp. 64–65) 

examined data for 20 microsatellite loci 

from samples of Mexican wolves, 

northern gray wolves, coyotes, and dogs. 

They concluded that the Mexican wolf 

was divergent and distinct from other 

sampled northern gray wolves, coyotes, 

and dogs. Leonard et al. (2005, p. 10) 

examined mitochondrial DNA sequence 

data from 34 wolves collected from 1856 

to 1916 from the historical ranges of 

Canis lupus baileyi and Canis lupus 

nubilus. They compared these data with 

sequence data collected from 96 wolves 

in North America and 303 wolves from 

Eurasia. They found that the historical 

wolves had twice the diversity of 

modern wolves, and that two-thirds of 

the haplotypes were unique. They also 

found that haplotypes associated with 

the Mexican wolf formed a unique 

southern clade distinct from that of 

other North American wolves. A clade 

is a taxonomic group that includes all 

individuals that have descended from a 

common ancestor. 

In another study, von Holdt et al. 

(2011, p. 7) analyzed single nucleotide 


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polymorphisms genotyping arrays and 

found Canis lupus baileyi to be the most 

genetically distinct group of New World 

gray wolves. Chambers et al. (2012, pp. 

34–37) reviewed the scientific literature 

related to classification of the Mexican 

wolf as a subspecies and concluded that 

this subspecies’ recognition remains 

well-supported. Most recently, Cronin et 

al. (2014, p. 9) analyzed single 

nucleotide polymorphism genotyping 

arrays and found single nucleotide 

polymorphisms differentiation of 

Mexican wolves from other North 

American wolves. However, Cronin et 

al. (2014, p. 9) challenge the subspecies 

concept for North American wolves, 

including the Mexican wolf, based on 

their interpretation of other authors 

work (most notably Leonard et al. 2005 

relative to mtDNA monophyly (see 

southern clade discussion above)). Maps 

of the Mexican wolf’s historical range 

are available in the scientific literature 

(Young and Goldman 1944, p. 414; Hall 

and Kelson, 1959, p. 849; Hall 1981, p. 

932; Bogan and Mehlhop 1983, p. 17; 

Nowak 1995, p. 395; Parsons 1996, p. 

106). The southernmost extent of 

Mexican wolf’s range in Mexico is 

consistently portrayed as ending near 

Oaxaca (Hall 1981, p. 932; Nowak 1995, 

p. 395). Depiction of the northern extent 

of the Mexican wolf’s pre-settlement 

range among the available descriptions 

varies depending on the authors’ 

taxonomic treatment of several 

subspecies that occurred in the 

Southwest and their related treatment of 

intergradation zones. Recent research 

based on historical specimens suggests 

the Mexican wolf ranged into southern 

Utah and southern Colorado across 

zones of intergradation where 

interbreeding with northern gray wolf 

subspecies may have occurred (Leonard 

et al. 2005, p. 11 and p. 15, insomuch 

as haplotype lu47 only had been 

documented to occur in Mexican wolves 

and was documented in a specimen in 

southern Colorado). 

Hall’s (1981, p. 932, based on Hall 

and Kelson 1959) map depicted a range 

for the Mexican wolf that included 

extreme southern Arizona and New 

Mexico, with Canis lupus mogollonensis 

occurring throughout most of Arizona, 

and C. l. monstrabilis, Canis l. youngi, 

C. l. nubilus, and C. l. mogollonensis 

interspersed in New Mexico. Bogan and 

Mehlhop (1983, p. 17) synonymized two 

previously recognized subspecies of 

gray wolf, C. l. mogollonensis and C. l. 

monstrabilis, with the Mexican wolf, 

concluding that the Mexican wolf’s 

range included the Mogollon Plateau, 

southern New Mexico, Arizona, Texas, 

and Mexico. This extended the Mexican 

wolf’s range northward to central 

Arizona and central New Mexico 

through the area that Goldman (1944) 

had identified as an intergrade zone 

with an abrupt transition from the 

Mexican wolf to C. l. mogollensis. Bogan 

and Mehlop’s analysis did not indicate 

a sharp transition zone between the 

Mexican wolf and C. l. mogollensis, 

rather the wide overlap between the two 

subspecies led them to synonymize the 

Mexican wolf and C. l. mogollensis. 

Hoffmeister (1986, p. 466) suggested 

that Canis lupus mogollonensis should 

be referred to as C. l. youngi, but 

maintained the Mexican wolf, C. l. 

baileyi, as a subspecies, stating that 

wolves north of the Mogollon Rim 

should be considered C. l. youngi. 

Nowak (1995, pp. 384–385) agreed with 

Hoffmeister’s synonymizing of C. l. 

mogollonensis with C. l. youngi, and 

further lumped these into C. l. nubilus, 

resulting in a purported northern 

historical range for Mexican wolf as just 

to the north of the Gila River in 

southern Arizona and New Mexico. 

Nowak (1995) and Bogan and Mehlhop 

(1983) differed in their interpretation of 

which subspecies to assign individuals 

that were intermediate between 

recognized taxa, thus leading to 

different depictions of historical range 

for the Mexican wolf. 

Subsequently, Parsons (1996, p. 104) 

included consideration of dispersal 

distance when developing a probable 

historical range for the purpose of 

reintroducing Mexican wolves in the 

wild pursuant to the Act, by adding a 

200-mi (322-km) northward extension to 

the most conservative depiction of the 

Mexican wolf historical range (i.e., Hall 

and Kelson 1959). This description of 

historical range was carried forward in 

the Final Environmental Impact 

Statement ‘‘Reintroduction of the 

Mexican Wolf within its Historic Range 

in the Southwestern United States’’ in 

the selection of the Blue Range Wolf 

Recovery Area as a reintroduction 

location for Mexican wolves (Service 

1996). 

Recent molecular genetic evidence 

from limited historical specimens 

supports morphometric evidence of an 

intergradation zone between Mexican 

wolf and northern gray wolves (Leonard 

et al. 2005, pp. 15–16). This research 

shows that, within the time period that 

the historical specimens were collected 

(1856–1916), a northern clade (i.e., 

group that originated from and includes 

all descendants from a common 

ancestor) haplotype was found as far 

south as Arizona, and individuals with 

southern clade haplotypes (associated 

with Mexican wolves) occurred as far 

north as Utah and Nebraska. Leonard et 

al. (2005, p. 10) interpret this 

geographic distribution of haplotypes as 

indicating gene flow was extensive 

across the subspecies’ limits during this 

historical period, and Chambers et al. 

(2012, p. 37) agree this may be a valid 

interpretation. 

Subspecies Description 

The Mexican wolf is the smallest 

extant gray wolf in North America. 

Adults weigh 23 to 41 kg (50 to 90 lb) 

with a length of 1.5 to 1.8 m (5 to 6 ft) 

and height at shoulder of 63 to 81 cm 

(25 to 32 in) (Brown 1988, p. 119). 

Mexican wolves are typically a patchy 

black, brown to cinnamon, and cream 

color, with primarily light underparts 

(Brown 1988, p. 118). Solid black or 

white coloration, as seen in other North 

American gray wolves, does not exist in 

Mexican wolves. Basic life history for 

Mexican wolves is similar to that of 

other gray wolves (Mech 1970, entire; 

Service 1982, p. 11; Service 2010, pp. 

32–41). 

Historical Distribution and Causes of 

Decline 

Prior to the late 1800s, the Mexican 

wolf inhabited the southwestern United 

States and Mexico. In Mexico, Mexican 

wolves ranged from the northern border 

of the country southward through the 

Sierra Madre Oriental and Occidental 

and the altiplano (high plains) to the 

Neovolcanic Axis (a volcanic belt that 

runs east-west across central-southern 

Mexico) (SEMARNAP 2000, p. 8), 

although wolf distribution may not have 

been continuous through this entire 

region (McBride 1980, pp. 2–7). The 

Mexican wolf is the only subspecies 

known to have inhabited Mexico. In the 

United States, Mexican wolves (and, in 

some areas, Canis lupus nubilus and the 

previously recognized subspecies C. l. 

monstrabilis, C. l. mogollonensis, and C. 

l. youngi) inhabited montane forests and 

woodlands in portions of New Mexico, 

Arizona, and Texas (Young and 

Goldman 1944, p. 471; Brown 1988, pp. 

22–23) (see Taxonomy). In southern 

Arizona, Mexican wolves inhabited the 

Santa Rita, Tumacacori, Atascosa– 

Pajarito, Patagonia, Chiricahua, 

Huachuca, Pinaleno, and Catalina 

Mountains, west to the Baboquivaris 

and east into New Mexico (Brown 1983, 

pp. 22–23). In central and northern 

Arizona, the Mexican wolf and other 

subspecies of gray wolf were 

interspersed (Brown 1983, pp. 23–24). 

The Mexican wolf and other subspecies 

were present throughout New Mexico, 

with the exception of low desert areas, 

documented as numerous or persisting 

in areas including the Mogollon, Elk, 

Tularosa, Diablo and Pinos Altos 


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Mountains, the Black Range, Datil, 

Gallinas, San Mateo, Mount Taylor, 

Animas, and Sacramento Mountains 

(Brown 1983, pp. 24–25). Gray wolf 

distribution (of other subspecies) 

continued eastward into the TransPecos region of Texas and northward up 

the Rocky Mountains and to the Grand 

Canyon (Young and Goldman 1944, pp. 

23, 50, 404–405), where intergradation 

between northern and southern wolf 

clades occurred (Leonard et al. 2005, 

pp. 11–15). 

Population estimates of gray wolves, 

and specifically Mexican wolves, prior 

to the late 1800s are not available for the 

southwestern United States or Mexico. 

Some trapping records and rough 

population estimates are available from 

the early 1900s, but do not provide a 

rigorous estimate of population size of 

Mexican wolves in the United States or 

Mexico. For New Mexico, a statewide 

carrying capacity (potential habitat) of 

about 1,500 gray wolves was 

hypothesized by Bednarz, with an 

estimate of 480 to 1,030 wolves present 

in 1915 (ibid, pp. 6, 12). Brown 

summarized historical distribution 

records for the wolf from McBride 

(1980, p. 2) and other sources, showing 

most records in the southwestern 

United States as being from the Blue 

Range and the Animas region of New 

Mexico (Brown 1983, p. 10). In Mexico, 

Young and Goldman (1944, p. 28) stated 

that from 1916 to 1918 the Mexican wolf 

was fairly numerous in Sonora, 

Chihuahua, and Coahuila, although 

McBride comments that Mexican 

wolves apparently did not inhabit the 

eastern and northern portions of 

Coahuila, even in areas with seemingly 

good habitat (1980, p. 2). 

The 1982 Mexican Wolf Recovery 

Plan cautioned: ‘‘It is important . . . not 

to accept unquestioningly the accounts 

of the 1800s and early 1900s that speak 

of huge numbers of wolves ravaging 

herds of livestock and game . . . . The 

total recorded take indicates a much 

sparser number of wolves in the treated 

areas than the complaints of damage 

state or signify, even when one 

remembers that these figures do not 

reflect the additional numbers of wolves 

taken by ranchers, bounty-seekers and 

other private individuals (Service 1982, 

p. 4).’’ 

Mexican wolf populations declined 

rapidly in the early and mid-1900s, due 

to government and private efforts across 

the United States to kill wolves and 

other predators. By 1925, poisoning, 

hunting, and trapping efforts drastically 

reduced Mexican wolf populations in 

all but a few remote areas of the 

southwestern United States, and control 

efforts shifted to wolves in the 

borderlands between the United States 

and Mexico (Brown 1983, p. 71). 

Bednarz (1988, p. 12) estimated that 

breeding populations of Mexican wolves 

were extirpated from the United States 

by 1942. The use of increasingly 

effective poisons and trapping 

techniques during the 1950s and 1960s 

eliminated remaining Mexican wolves 

north of the United States-Mexico 

border, although occasional reports of 

wolves crossing into the United States 

from Mexico persisted into the 1960s. 

Wolf distribution in northern Mexico 

contracted to encompass the Sierra 

Madre Occidental in Chihuahua, 

Sonora, and Durango, as well as a 

disjunct population in western Coahuila 

(from the Sierra del Carmen westward). 

Leopold (1959, p. 402) found conflicting 

reports on the status of the Coahuila 

population and stated that wolves were 

likely less abundant there than in the 

Sierra Madre Occidental. 

When the Mexican wolf was listed as 

endangered under the Act in 1976, no 

wild populations were known to remain 

in the United States or Mexico. McBride 

(1980, pp. 2–8) conducted a survey to 

determine the status and distribution of 

wolves in Mexico in 1977. He mapped 

3 general areas where wolves were 

recorded as still present in the Sierra 

Madre Occidental: (1) Northern 

Chihuahua and Sonora border (at least 

8 wolves); (2) western Durango (at least 

20 wolves in 2 areas); and (3) a small 

area in southern Zacatecas. Although 

occasional anecdotal reports have been 

made during the last three decades that 

a few wild wolves still inhabit forested 

areas in Mexico, no publicly available 

documented verification exists. Several 

Mexican wolf individuals captured in 

the wild in Mexico became the basis for 

the captive-breeding program that has 

enabled the reintroduction to the wild 

(see below, Current Distribution—In 

Captivity). 

Current Distribution in the United 

States 

On January 12, 1998, we published a 

final rule in the Federal Register to 

establish the Mexican Wolf 

Experimental Population Area 

(MWEPA) in central Arizona, New 

Mexico, and a small portion of 

northwestern Texas (63 FR 1752). In 

March of 1998 we released 11 Mexican 

wolves from the captive-breeding 

program to the wild. We have 

conducted additional initial releases or 

translocations of individuals and family 

groups into the Blue Range Wolf 

Recovery Area (BRWRA) within the 

MWEPA through 2014. At the end of 

2013, a single wild population of a 

minimum of 83 Mexican wolves 

(December 31, 2013, population count) 

inhabited the United States in central 

Arizona and New Mexico. Mexican 

wolves do not occupy the small portion 

of northwestern Texas included in the 

MWEPA. For more information 

regarding the MWEPA, please see 

Revision to the Regulations for the 

Nonessential Experimental Population 

of the Mexican Wolf, which published 

elsewhere in this Federal Register. 

Mexican wolves associated with the 

MWEPA also currently occupy the Fort 

Apache Indian Reservation of the White 

Mountain Apache Tribe, adjacent to the 

western boundary of the BRWRA. Since 

2000, an agreement between the Service 

and the White Mountain Apache Tribe 

permits the release, dispersal, and 

establishment of Mexican wolves onto 

the reservation, providing an additional 

2,500 mi2 (6,475 km2) of high-quality 

forested wolf habitat for the 

reintroduction (Service 2001, p. 4). The 

White Mountain Apache Tribe does not 

make information about the number and 

location of Mexican wolves on the 

reservation publicly available. 

Detailed information on the status of 

the experimental population and the 

reintroduction project can be found in 

the 2001 to 2013 annual reports, the 

2010 Mexican Wolf Conservation 

Assessment (Service 2010), and our 

online population statistics, available at 

http://www.fws.gov/southwest/es/

mexicanwolf/. 

Current Distribution in Mexico 

In October 2011, Mexico initiated the 

reestablishment of Mexican wolves to 

the wild (see Historical Distribution) 

with the release of five captive-bred 

Mexican wolves into the San Luis 

Mountains just south of the U.S.-Mexico 

border. Mexico has continued to release 

animals into the wild during the past 

few years. Through August 2014, 

Mexico released a total of 14 adult 

Mexican wolves, of which 11 died or are 

believed dead, and 1 was removed for 

veterinary care. Of the 11 Mexican 

wolves that died or are believed dead, 

6 were due to illegal killings (4 from 

poisoning and 2 were shot), 1 wolf was 

presumably killed by a mountain lion, 

3 causes of mortality are unknown 

(presumed illegal killings because 

collars were found, but not the 

carcasses), and 1 disappeared (neither 

collar nor carcass has been found). The 

remaining two adult Mexican wolves 

were documented with five pups in 

2014, marking the first successful 

reproductive event in Mexico. We 

expect the number of Mexican wolves in 

Mexico to fluctuate from zero to several 

packs in or around Sonora, Durango, 

and Chihuahua in the near future. 


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In Captivity 

Due to the extirpation of Mexican 

wolves in the United States and Mexico, 

the first step in the recovery of the 

subspecies was the development of a 

captive-breeding population to ensure 

the Mexican wolf did not go extinct. 

Between 1977 and 1980, a binational 

captive-breeding program between the 

United States and Mexico, referred to as 

the Mexican Wolf Species Survival Plan 

(SSP), was initiated with the capture of 

the last known Mexican wolves in the 

wild in Mexico and subsequent addition 

of wolves from captivity in Mexico and 

the United States. The individual 

unrelated seven wolves used to 

establish the captive-breeding program 

are considered the ‘‘founders’’ of the 

breeding population. These pure 

Mexican wolves represent three distinct 

lineages (family groups): McBride (also 

known as the Certified lineage; three 

individuals), Ghost Ranch (two 

individuals), and Aragon (two 

individuals). From the breeding of these 

7 Mexican wolves and generations of 

their offspring, the captive population 

has expanded to its current size of 248 

Mexican wolves in 55 facilities in the 

United States and Mexico (Siminski and 

Spevak 2014). 

The purpose of the SSP is to 

reestablish Mexican wolves in the wild 

through captive breeding, public 

education, and research. This captive 

population is the sole source of Mexican 

wolves available to reestablish the 

subspecies in the wild and is imperative 

to the success of the Mexican wolf 

reintroduction project and any 

additional efforts to reestablish the 

subspecies that may be pursued in the 

future in Mexico by the General del 

Vida Silvestre or by the Service in the 

United States. 

Captive Mexican wolves are routinely 

transferred among the zoos and other 

SSP holding facilities to facilitate 

genetic exchange (through breeding) and 

maintain the health and genetic 

diversity of the captive population. The 

SSP strives to house a minimum of 240 

wolves in captivity at all times to ensure 

the security of the subspecies in 

captivity, while still being able to 

produce surplus animals for 

reintroduction. 

In the United States, Mexican wolves 

from captive SSP facilities that are 

identified for potential release are first 

evaluated for release suitability and 

undergo an acclimation process. All 

Mexican wolves selected for release in 

the United States and Mexico are 

genetically redundant to the captive 

population, meaning their genes are 

already well represented in captivity. 

This minimizes any adverse effects on 

the genetic integrity of the remaining 

captive population in the event that 

Mexican wolves released to the wild do 

not survive. 

Habitat Description 

Historically, Mexican wolves were 

associated with montane woodlands 

characterized by sparsely to densely 

forested mountainous terrain consisting 

of evergreen oaks (Quercus spp.) or 

pinyon (Pinus edulus) and juniper 

(Juniperus spp.) to higher elevation pine 

(Pinus spp.), mixed-conifer forests, and 

adjacent grasslands at elevations of 

4,000 to 5,000 ft (1,219 to 1,524 m) 

where ungulate prey were numerous. 

Factors making these vegetation 

communities attractive to Mexican 

wolves likely included the abundance of 

ungulate prey, availability of water, and 

the presence of hiding cover and 

suitable den sites. Early investigators 

reported that Mexican wolves probably 

avoided desert scrub and semidesert 

grasslands that provided little cover, 

food, or water (Brown 1988, pp. 19–22). 

Prior to their extirpation in the wild, 

Mexican wolves were believed to have 

preyed upon white-tailed deer 

(Odocoileus virginianus), mule deer (O. 

hemionus), elk (Cervus elaphus), 

collared peccaries (javelina) (Tayassu 

tajacu), pronghorn (Antilocapra 

americana), bighorn sheep (Ovis 

canadensis), jackrabbits (Lepus spp.), 

cottontails (Sylvilagus spp.), and small 

rodents (Parsons and Nicholopoulos 

1995, pp. 141–142); white-tailed deer 

and mule deer were believed to be the 

primary sources of prey (Brown 1988, p. 

132; Bednarz 1988, p. 29). 

Today, Mexican wolves in Arizona 

and New Mexico inhabit evergreen 

pine–oak woodlands (i.e., Madrean 

woodlands), pinyon–juniper woodlands 

(i.e., Great Basin conifer forests), and 

mixed-conifer montane forests (i.e., 

Rocky Mountain, or petran, forests) that 

are inhabited by elk, mule deer, and 

white-tailed deer (Service 1996, pp. 3– 

5; AMOC and IFT 2005, p. TC–3). 

Mexican wolves in Arizona and New 

Mexico show a strong preference for elk 

compared to other ungulates (AMOC 

and IFT 2005, p. TC–14, Reed et al. 

2006, pp. 56, 61; Merkle et al. 2009, p. 

482). Other documented sources of prey 

include deer (O. virginianus and O. 

hemionus) and occasionally small 

mammals and birds (Reed et al. 2006, p. 

55). Mexican wolves are also known to 

prey and scavenge on livestock (Reed et 

al. 2006, p. 1129). 

Summary of Comments and 

Recommendations 

We requested written comments from 

the public on the proposed rule to 

remove the gray wolf from the List of 

Endangered and Threatened Wildlife 

and maintaining protections for the 

Mexican wolf by listing it as endangered 

during a 6-month comment period from 

June 13, 2013, to December 17, 2013. 

Between September 30, 2013, and 

December 3, 2013, the Service held a 

series of public hearings on the 

proposed rule: September 30, 2013, in 

Washington, District of Columbia; 

November 19, 2013, in Denver, 

Colorado; November 20, 2013, in 

Albuquerque, New Mexico; November 

22, 2013, in Sacramento, California; and 

December 3, 2013, in Pinetop, Arizona. 

We reopened the public comment 

period on February 10, 2014, in 

conjunction with announcing the 

availability of the independent scientific 

peer review report on the proposal. This 

comment period closed on March 27, 

2014. We also contacted appropriate 

Federal, Tribal, State, county, and local 

agencies, scientific organizations, and 

other interested parties and invited 

them to comment on the proposed rule 

during these comment periods. 

All substantive information 

specifically related to our proposal to 

list the Mexican wolf as an endangered 

subspecies provided during the 

comment periods, including the public 

hearings, has either been incorporated 

directly into this final determination or 

addressed below. Comments from peer 

reviewers and State agencies are 

grouped separately. In addition to the 

comments, some commenters submitted 

additional reports and references for our 

consideration, which were reviewed 

and incorporated into this final rule as 

appropriate. 

Peer Reviewer Comments 

The National Center for Ecological 

Analysis and Synthesis (NCEAS) was 

asked to perform an independent 

scientific review of the proposed rule to 

remove the gray wolf from the List of 

Endangered and Threatened Wildlife 

and maintain protections for the 

Mexican wolf by listing it as endangered 

(78 FR 35664, June 13, 2013). In 

accordance with our peer review policy 

published on July 1, 1994 (59 FR 

34270), NCEAS solicited expert 

opinions from seven knowledgeable 

individuals with scientific expertise that 

included familiarity with the species, 

the geographic region in which the 

species occurs, and conservation 

biology principles. NCEAS received 

responses from five of the seven peer 


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reviewers they contacted during the 

public comment period. 

Based on their panel discussion in 

January 2014, peer reviewers came to 

general consensus that the Mexican wolf 

is the most differentiated gray wolf in 

North America. Also, peer reviewers 

discussed and seemed to reach general 

concurrence that the historical range of 

the Mexican wolf was likely larger than 

described by the Service in the 

proposed rule based on the presence of 

genetic markers found in historical wolf 

specimens described by Leonard et al. 

2005, and they questioned how this 

information should be incorporated into 

decisions about its status. They 

expressed concern over the Service’s 

reliance on the Chambers et al. 2012, 

manuscript within the Service’s 

proposal to delist the gray wolf in the 

United States, which included the 

identification of, and discussion of the 

validity of, other gray wolf subspecies, 

but their concerns did not lead them to 

conclude that the Mexican wolf was not 

a valid entity to list under the Act. 

Rather, they focused on how the Service 

should ‘‘draw a line on a map’’ to 

indicate the historical range of the 

Mexican wolf and the appropriate 

geographic extent of the listed entity. 

We reviewed all comments received 

from the peer reviewers regarding the 

proposed listing of the Mexican wolf as 

an endangered subspecies. As 

previously noted, the peer reviewers 

generally concurred with our methods 

and conclusions that the Mexican wolf 

is ecologically and morphologically 

distinct. They also provided additional 

information, clarifications, and 

suggestions to improve this final rule. 

Peer reviewer comments are addressed 

in the following summary and 

incorporated into the final rule, as 

appropriate. 

(1) Comment: Peer reviewers stated 

that the Service did not use the best 

available information related to the 

exclusive reliance on the concordance 

method of identifying species/

subspecies utilized by Chambers et al. 

2012. The justification for the exclusive 

use of this approach is not well 

defended by the Service. 

Our response: As required by section 

4(b) of the Act, we used the best 

scientific and commercial data available 

in making this final determination for 

the Mexican wolf. We solicited peer 

review from knowledgeable individuals 

with scientific expertise that included 

familiarity with the species, the 

geographic region in which the species 

occurs, and conservation biology 

principles to ensure that our listing is 

based on scientifically sound data, 

assumptions, and analysis. 

Additionally, we requested comments 

or information from other concerned 

governmental agencies, Native 

American Tribes, the scientific 

community, industry, and any other 

interested parties concerning the 

proposed rule. The commenters’ 

concerns with the Service’s reliance on 

the Chambers et al. 2012, manuscript 

primarily focused on taxonomic issues 

associated with gray wolf populations 

other than the Mexican wolf. 

Taxonomic issues related to other gray 

wolf populations are not germane to this 

final rule to list the Mexican wolf as an 

endangered subspecies. Specific to the 

Mexican wolf, the peer reviewers 

concurred that the Mexican wolf is 

differentiated from other gray wolves by 

multiple morphological and genetic 

markers documented in the scientific 

literature. The Act is explicit that 

threatened or endangered subspecies are 

to be protected. 

(2) Comment: Peer reviewers noted 

that genetic markers indicate a larger 

historical range for Mexican wolf than 

described by the Service and should be 

taken into consideration when 

determining its status and the range 

within which recovery could occur. 

Our response: We have not attempted 

to define historical range for the 

Mexican wolf, but rather to describe 

available historical range information 

contained in the scientific literature, 

including the research by Leonard et al. 

2005 referenced by the peer reviewers. 

Listing the entire Mexican wolf 

subspecies means that all members of 

the taxon are afforded the protections of 

the Act regardless of where they are 

found; therefore, we do not demarcate a 

specific geographic area in which 

conservation and recovery efforts may 

take place. Rather, guidance about the 

abundance and distribution of the 

Mexican wolf necessary for delisting 

will be provided in a revised recovery 

plan containing recovery (delisting) 

criteria. Therefore, we recognize that 

current research such as Leonard et al. 

2005 suggests a larger historical 

geographic range for the Mexican wolf 

than described by prior accounts (Hall 

1981, p. 932; Bogan and Mehlhop 1983, 

p. 17; Nowak 1995, pp. 384–385). 

However, this information does not lead 

us to a different conclusion about the 

endangered status of the Mexican wolf, 

nor are any recovery options precluded 

by our discussion of historical range. 

Comments From States 

(3) Comment: One State agency 

expressed concern that the Service did 

not articulate reasons for choosing to list 

the Mexican wolf as a subspecies rather 

than a DPS, claiming that the Mexican 

wolf is legally eligible for a DPS listing 

under the Service’s policy, and, 

therefore, the choice to list it as a 

subspecies as opposed to a DPS is a 

discretionary act subject to review 

under the Administrative Procedure 

Act. 

Our response: Under section 3(16) of 

the Act, we may consider for listing any 

species, including subspecies, of fish, 

wildlife, or plants, or any DPS of 

vertebrate fish or wildlife that 

interbreeds when mature. As noted in 

our Policy Regarding the Recognition of 

Distinct Vertebrate Population Segments 

Under the Act (61 FR 4722, February 7, 

1996), Congress has instructed the 

Secretary to exercise authority to list 

DPS’s sparingly. Because a DPS is 

typically a subset of a species or 

subspecies, we first determine whether 

any negative impacts appear to be 

affecting the species or subspecies 

anywhere in its range, and whether any 

of these impacts rise to the level of 

threats such that the species or 

subspecies is endangered or threatened 

throughout its range. If we determine 

that a species or subspecies is 

endangered or threatened throughout its 

range, then we are not required to 

conduct a DPS analysis. In other words, 

we typically first assess whether or not 

an entity qualifies for listing as a species 

or subspecies before assessing whether 

it qualifies as a DPS. Because the 

Mexican wolf qualifies for listing as a 

subspecies throughout its range, we are 

not analyzing whether or not it warrants 

listing as a DPS. 

(4) Comment: Among other 

alternatives, the Service should also be 

considering listing two DPS’s of gray 

wolf or Mexican wolf (i.e., one in 

Arizona and New Mexico and the other 

in Mexico), the range of which is 

bisected by the International Border 

between the United States and Mexico. 

Our response: See response 

immediately above regarding listing a 

DPS of the Mexican wolf. 

(5) Comment: One State agency 

expressed concern that, if listed as a 

subspecies, the Mexican wolf will never 

be delisted in the United States. The 

commenter stated that a species or 

subspecies may be delisted only when 

it is no longer in danger of extinction 

throughout all or a significant portion of 

its range and that approximately 10 

percent of the Mexican wolf’s historical 

range occurs in the United States with 

the remainder in Mexico. Because the 

Mexican wolf in the United States will 

never constitute a significant portion of 

the subspecies’ range, delisting would 

require substantial wolf recovery in 

Mexico. 


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Our response: ‘‘Range’’ as referred to 

in the phrase ‘‘significant portion of its 

range’’ refers to the general geographical 

area within which the species can be 

found at the time the Service makes a 

status determination (79 FR 37578, July 

1, 2014). Prior to its extirpation in the 

1900’s, the Mexican wolf inhabited large 

portions of Mexico. Our colleagues in 

Mexico are continuing to investigate 

whether areas that functioned as wolf 

habitat historically are suitable for wolf 

reintroduction and recovery efforts 

today (Araiza et al. 2012, entire). 

Regardless, the Act does not stipulate 

that a species must inhabit all of its 

historical range in order to be recovered. 

Rather, threats to the species must be 

alleviated such that it is secure in its 

range at the time of status 

determination, such as delisting, listing, 

or reclassification. Therefore, listing the 

Mexican wolf as a subspecies does not 

preclude the ability to achieve recovery 

and delist the subspecies. A recovery 

strategy, including delisting criteria, 

will be developed in a revised recovery 

plan for the Mexican wolf. 

(6) Comment: One commenter 

expressed concern that if we have to 

wait for recovery to occur in Mexico 

before we can delist the Mexican wolf, 

States will be faced with unchecked 

population growth of Mexican wolves 

with no effective mechanism for 

controlling population growth, which 

will lead to the detriment of livestock 

and big game wildlife in the United 

States. 

Our response: See response above. 

The purpose of the Act is to recover 

species such that they are no longer in 

danger of extinction now or within the 

foreseeable future throughout all or a 

significant portion of their range, at 

which time they are delisted and 

management of the species is typically 

turned over to the State and tribal 

wildlife agencies. Further, in a separate 

rule in this Federal Register, we have 

published the Revision to the 

Nonessential Experimental Population 

of the Mexican Wolf, which contains 

take provisions for Mexican wolves by 

designated agencies and the public, 

demonstrating that the Service is 

cognizant of the need to include such 

(control) measures as a component of 

wolf reintroduction and recovery efforts. 

(7) Comment: One State agency noted 

that the Service’s proposed rule to list 

the Mexican wolf as an endangered 

subspecies referenced several important 

documents to which the public has not 

had access. 

Our response: All of the comments, 

materials, and documentation that we 

considered in this rulemaking were 

available by appointment, during 

normal business hours at: Mexican Wolf 

Recovery Program, U.S. Fish and 

Wildlife Service, New Mexico 

Ecological Services Field Office, 2105 

Osuna Road NE., Albuquerque, NM 

87113; by telephone 505–761–4704; or 

by facsimile 505–346–2542. 

(8) Comment: One State agency 

suggested that the Service should 

recognize Mexican wolf historical range 

as extending from central Mexico into 

Arizona and New Mexico south of 

Interstate Highway 40. 

Our response: We have utilized the 

best available science to describe 

historical range for the Mexican wolf in 

the Background section of this final 

rule. Maps of the Mexican wolf’s 

historical range are available in the 

scientific literature (Young and 

Goldman 1944, p. 414; Hall and Kelson, 

1959, p. 849; Hall 1981, p. 932; Bogan 

and Mehlhop 1983, p. 17; Nowak 1995, 

p. 395; Parsons 1996, p. 106). Depiction 

of the northern extent of the Mexican 

wolf’s historical range among the 

available descriptions varies depending 

on the authors’ taxonomic treatment of 

several subspecies that occurred in the 

Southwest and their related treatment of 

intergradation zones. In any case, there 

is evidence indicating that the Mexican 

wolf may have ranged north into 

southern Utah and southern Colorado 

within zones of intergradation where 

interbreeding with other gray wolf 

subspecies may have occurred (Leonard 

et al. 2005, p. 11 and p. 15). 

(9) Comment: The Service does not 

provide cooperators and stakeholders 

with sufficient time to comprehensively 

analyze the Service’s varied proposals 

on Mexican wolf listing. The Service 

expects stakeholders and cooperators, in 

a matter of months, to review and digest 

hundreds of pages of material, sort out 

the interconnected points concerning all 

the facets of the entirety, review the 

alternatives, formulate comments, and 

otherwise meaningfully participate in 

the review process. 

Our response: The Service recognizes 

that public involvement is an essential 

part of the rulemaking process, helping 

to inform both the agency and the 

affected public. That is why we 

requested written comments from the 

public on the proposed rule and 

contacted appropriate Federal, Tribal, 

State, county, and local agencies, 

scientific organizations, and other 

interested parties and invited them to 

comment on the proposed rule during 

the open comment period from June 13, 

2013, to December 17, 2013, and the 

reopened comment period from 

February 10, 2014, to March 27, 2014. 

We believe that the nearly 8-month 

open comment period was sufficient 

time for cooperators and stakeholders to 

comprehensively analyze the Service’s 

proposed rule and provide comment. 

Comments From Tribes 

(10) Comment: Any listing or delisting 

of the gray wolf or the Mexican wolf 

must recognize the Tribe’s rights and 

sovereignty in managing wildlife on 

Tribal lands. The proposed rule fails in 

this respect. 

Our response: The Service recognizes 

the Tribe’s rights and sovereignty in 

managing wildlife on Tribal lands (see 

Government to Government 

Relationships with Tribes section 

below). Under their sovereign authority 

Tribes have the option of allowing 

Mexican wolves to occupy Tribal trust 

land or to request their removal. Also, 

elsewhere in this Federal Register, we 

are finalizing revisions to the 

nonessential experimental population of 

the Mexican wolf, which will give 

Tribes the option to enter into voluntary 

agreements with the Service for the 

management of Mexican wolves on 

Tribal trust land. 

Public Comments 

(11) Comment: We received numerous 

requests from diverse interest groups 

and individuals asking that we 

subdivide our final determination on 

listing the Mexican wolf as endangered 

from the final determination on our 

proposal regarding the current listing for 

gray wolf in all or portions of 42 States 

and Mexico. 

Our response: We are separating our 

determination on the listing of the 

Mexican wolf as endangered from the 

determination on our proposal regarding 

removing the current listing for gray 

wolf from the List of Endangered and 

Threatened Wildlife. This rule finalizes 

our determination for the Mexican wolf. 

A subsequent decision will be made for 

the rest of the United States. 

(12) Comment: A problematic aspect 

of the rule is the fact that the Service 

does not designate the species as 

endangered over a specific geographic 

area, but instead designates the 

subspecies as endangered where found. 

Genetic analysis of historic Mexican 

wolves showed that the range of the 

Mexican wolf likely extended beyond 

the historic range initially inferred from 

limited record data. 

Our response: Unless we designate a 

Distinct Population Segment, which has 

a geographic component to the 

designation, a species or subspecies 

listing means that all members of the 

taxon are afforded the protections of the 

Act regardless of where they are found. 

We have described the historical range 


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of the Mexican wolf in the Background 

section of this rule. 

(13) Comment: Listing the Mexican 

wolf as endangered would negatively 

impact the private landowners and 

ranchers in the State of Arizona by 

imposing additional restrictions on 

those private lands, which is an 

economic and operational burden on the 

public. 

Our response: This final rule to list 

the Mexican wolf as an endangered 

subspecies will not change the protected 

status of the Mexican wolf as, to date, 

it has been listed as endangered within 

the broader gray wolf listing; rather, this 

final rule creates an independent listed 

entity for the Mexican wolf on the List 

of Endangered and Threatened Wildlife, 

separate from the gray wolf entity. As 

previously noted, we are finalizing 

revisions to the nonessential 

experimental population of the Mexican 

wolf elsewhere in this Federal Register, 

which relaxes some of the Act’s 

prohibitions for take of Mexican wolves 

in certain circumstances. With this final 

rule to list the Mexican wolf as an 

endangered subspecies, there are no 

additional restrictions to private 

landowners. 

(14) Comment: Has the Service 

examined the biological ramifications of 

the illegal killings? What analyses were 

used to estimate the level of impact of 

a 0 to 15 percent annual mortality 

attributed to illegal killing of wolves? 

The proposed listing stated 3 Mexican 

wolves died from disease, 3 from 

predation, 14 from vehicular collisions, 

4 from other reason, 9 for unknown 

reasons, and 46 from illegal killing. 

What was the fate of the 13 wolves 

unaccounted for in this document that 

died from 1998 to 2012? The Service 

should show mortality graphically; what 

is the ratio of illegal kills to population 

size? 

Our response: We recognize that 

illegal killing is the number one source 

of mortality to Mexican wolves in the 

wild; see Factor C. Disease and 

Predation, for our discussion and 

assessment of this mortality factor. 

Known wolf mortality is documented 

annually and is available on our Web 

site at http://www.fws.gov/southwest/es/ 

mexicanwolf/MWPS.cfm. 

(15) Comment: The Mexican wolf 

experimental population has been 

unsuccessful due to weak genetics that 

caused malformed jaws and other 

deformities, hybridization with dogs 

after releases into the wild, habituation 

to humans, dependence on human food 

including livestock regardless of 

abundant wild ungulate prey 

availability, and a variety of other fatal 

flaws. 

Our response: We describe known 

instances of hybridization in Factor E of 

this final rule. Based on the low number 

of occurrences of Mexican wolf-dog 

hybrids, we do not consider 

hybridization to be a threat to the 

Mexican wolf. We also discuss genetic 

concerns in Factor E, which, although 

not specific to physical deformities, we 

do determine inbreeding and loss of 

heterozygosity to be threats to the 

Mexican wolf. We have not documented 

Mexican wolf dependence on human 

food, including livestock; while 

Mexican wolves do occasionally prey on 

livestock, their primary prey in the 

Mexican Wolf Experimental Population 

Area is elk (see Background section). 

(16) Comment: The Service fails to 

present the expected outcomes of 

genetic depression (decreased fitness, 

negatively biased population growth 

rate, loss of adaptive potential) on the 

Mexican wolf. How does the Service 

quantify loss of adaptive potential? 

What does the Service propose to do to 

address their concerns over inbreeding? 

If the nonessential population is 

genetically depressed, why does the 

Service continue to release Mexican 

wolves that are inbred? Over what 

timeframe does the Service expect to be 

able to effect a change in the genetic 

depression of the Mexican gray 

population? 

Our response: Tracking of the genetic 

status of the captive and wild Mexican 

wolf populations is conducted by the 

Species Survival Plan, which tracks the 

mean kinship of wolves and other 

relevant metrics of the captive and wild 

population. We describe our concerns 

related to the genetic composition of the 

Mexican wolf population under Factor 

E. In a separate rule published in this 

Federal Register, Revision to the 

Nonessential Experimental Population 

of the Mexican Wolf, and our associated 

Environmental Impact Statement, we 

address our need to increase the number 

of initial releases we conduct in order 

to improve the genetic composition of 

the nonessential population. We expect 

to substantially improve the genetic 

status of the nonessential population 

within several Mexican wolf 

generations, or about 12 to 16 years. 

(17) Comment: Except in cases of 

absolute isolation, what we call 

subspecies are populations with 

variable rates of gene flow over time and 

space. It is time for the Service to 

abandon typological thinking, stop 

using subspecies for listings, and use 

the biologically robust concepts of 

populations with quantifiable rates of 

gene flow and phylogenetic 

independence. 

Our response: The Act is explicit that 

threatened or endangered subspecies are 

to be protected. Our Service regulations 

require us to rely on standard taxonomic 

distinctions and the biological expertise 

of the Department of the Interior and the 

scientific community concerning the 

relevant taxonomic group (50 CFR 

424.11). 

(18) Comment: According to the 

Service, the ‘‘nature of the available data 

does not permit the application of many 

traditional subspecies criteria’’, and 

many experts actually reject the notion 

of wolf subspecies due to the ease with 

which wolves move and interbreed. The 

Service further admits that the 

taxonomy for wolves is complicated and 

continuously evolving. These 

statements clearly show the lack of 

definitive information supporting the 

identification of gray wolf subspecies. 

Our response: We recognize that wolf 

taxonomy is complicated and 

continuously evolving. However, the 

controversy in the scientific community 

has focused on wolf populations other 

than the Mexican wolf (but see Cronin 

et al. 2014, p. 9), which are outside the 

purview of this final rule. The best 

available scientific literature, and our 

Service regulations that require us to 

rely on standard taxonomic distinctions, 

support the recognition of the Mexican 

wolf as a subspecies of gray wolf. 

(19) Comment: Review of the 

literature shows that the Mexican wolf 

does not warrant subspecies status. Data 

for 170,000 single nucleotide 

polymorphisms (Cronin et al. in 

preparation) and 48,000 single 

nucleotide polymorphisms (vonHoldt et 

al. 2011) shows that single nucleotide 

polymorphisms allele frequency 

differentiation of Mexican wolves and 

other North American wolves is 

relatively high. However, Mexican 

wolves lack mtDNA monophyly and 

share haplotypes with wolves in other 

areas (Leonard et al. 2005), and mtDNA 

haplotypes in Mexican wolves have low 

sequence divergence from other wolf 

haplotypes. This sequence divergence is 

particularly low because it is for the 

hypervariable control region. 

Our response: As required by section 

4(b) of the Act, we used the best 

scientific and commercial data available 

and continue to recognize the Mexican 

wolf (Canis lupus baileyi) as a distinct 

gray wolf subspecies. Taxonomic issues 

related to other gray wolf populations 

are not germane to this final rule to list 

the Mexican wolf as an endangered 

subspecies. Specific to the Mexican 

wolf, the peer reviewers concurred that 

the Mexican wolf is differentiated from 

other gray wolves by multiple 

morphological and genetic markers 


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documented in the scientific literature. 

Further, Leonard et al. (2005, p. 10) 

found that haplotypes associated with 

the Mexican wolf formed a unique 

southern clade distinct from that of 

other North American wolves. A clade 

is a taxonomic group that includes all 

individuals that have descended from a 

common ancestor. 

(20) Comment: A science-based 

recovery plan has the potential to 

reduce conflict over the long term by 

minimizing litigation, minimizing 

resources needed by the Service for 

defending its actions, and speeding the 

eventual delisting of the Mexican wolf. 

Because lack of an updated recovery 

plan seriously hampers efforts to 

recover the subspecies, we encourage 

the Service to resume the recovery 

planning process immediately. 

Our response: We intend to resume 

the recovery planning process to 

develop a revised recovery plan for the 

Mexican wolf after completion of this 

final rule. 

(21) Comment: Several commenters 

recommended management of the 

Mexican wolf be returned to the States. 

Delisting of the wolf would 

automatically trigger this return of State 

control. 

Our response: In our final rule, 

published elsewhere in this Federal 

Register, Revision to the Nonessential 

Experimental Population of the Mexican 

Wolf, we allow for States (or other 

agencies) to cooperate in the 

management of Mexican wolves as 

designated agencies. Due to our 

determination of endangered status for 

the Mexican wolf, we are not delisting 

the Mexican wolf at this time. When the 

Mexican wolf has been recovered and 

delisted, management control will be 

turned over to State and tribal agencies. 

(22) Comment: The States of Arizona 

and New Mexico have sufficient 

regulations and trained personnel and 

programs in place to protect Mexican 

wolves so that a Federal listing is 

unwarranted under the Act. 

Our response: We have no 

information to suggest that, absent the 

Act’s protections, illegal killing of 

Mexican wolves in the United States 

would cease. Rather, illegal killing of 

Mexican wolves could increase, as State 

penalties (assuming wolves were 

granted protected status by the States) 

would be less severe than current 

Federal penalties under the Act. Thus, 

existing State penalties in Arizona and 

New Mexico would not serve as an 

adequate deterrent to illegal take. Also, 

in 2011, the New Mexico Department of 

Game and Fish withdrew from the 

Mexican Wolf Recovery Program and 

has shown no intention of rejoining or 

further cooperating with the program. 

We address this issue under Factor D. 

Adequate Regulatory Mechanisms. 

(23) Comment: Several commenters 

stated that local citizens are fearful of 

Mexican wolves and noted the need to 

protect themselves when in areas 

occupied by wolves, psychological 

impacts on children, pet safety, and 

related topics. One commenter stated 

that he would face criminal charges if 

he defended himself against a wolf. 

These commenters stated that the 

Service has not adequately recognized 

or addressed these issues. 

Our response: There are no historical 

or recent cases of Mexican wolves 

attacking humans. If a Mexican wolf 

were to attack someone, the Act allows 

a person to take (including kill) a 

Mexican wolf in self-defense or in 

defense of another person. Elsewhere in 

this Federal Register, we have 

published a final Revision to the 

Nonessential Experimental Population 

of the Mexican Wolf, which provides 

conditional take provisions (in addition 

to take for self-defense) of Mexican 

wolves by the Service, designated 

agencies, and individuals under certain 

circumstances. 

(24) Comment: The Service states that 

the status of Mexican wolves in Mexico 

is unknown. Mexican wolves should be 

managed through a coordinated effort 

internationally according to sound 

biological principles and with 

consideration to all other State, 

national, and international laws that 

protect the health, safety, and welfare of 

humans. 

Our response: We are fully aware of 

the status of Mexican wolves in Mexico, 

as we are in continual communication 

with the Federal agencies in Mexico that 

are responsible for the reintroduction of 

the Mexican wolf. We have clarified 

language in this final rule regarding the 

status of wolves in Mexico; see Current 

Distribution in Mexico. While we may 

at times coordinate various Mexican 

wolf management activities with 

Federal agencies in Mexico (such as 

sharing equipment or transferring 

captive wolves between captive 

facilities), the reintroduction of Mexican 

wolves in the United States and Mexico 

are independent efforts. 

(25) Comment: The Service should 

consider the negative impacts to our elk, 

deer, bighorn sheep, and javelina 

populations from predation by possible 

reintroduced Mexican wolves. A 

decrease in these game animals will 

create a significant economic and 

recreational loss to our State. 

Our response: While the Act is 

explicit that our listing determinations 

must be made solely on the basis of the 

best scientific and commercial data 

available, in a separate action published 

elsewhere in this Federal Register we 

have considered the impacts to ungulate 

populations from the experimental 

population of Mexican wolves in our 

Environmental Impact Statement, 

Revision to the Nonessential 

Experimental Population of the Mexican 

Wolf, available on our Web site at 

http://www.fws.gov/southwest/es/

mexicanwolf/NEPA_713.cfm. 

Summary of Changes From the 

Proposed Rule 

In this final rule, we make one 

substantive change from the proposal. 

We are separating our determination on 

the listing of the Mexican wolf as 

endangered from the determination on 

our proposal regarding the delisting of 

the gray wolf in the United States and 

Mexico. This rule finalizes our 

determination for the Mexican wolf. A 

subsequent decision will be made for 

the gray wolf. 

Summary of Factors Affecting the 

Mexican Wolf 

Several threats analyses have been 

conducted for the Mexican wolf. In the 

initial proposal to list the Mexican wolf 

as endangered in 1975 and in the 

subsequent listing of the entire gray 

wolf species in the contiguous United 

States and Mexico in 1978, the Service 

found that threats from habitat loss 

(factor A), sport hunting (factor B), and 

inadequate regulatory protection from 

human targeted elimination (factor D) 

were responsible for the Mexican wolf’s 

decline and near extinction (40 FR 

17590, April 21, 1975; 43 FR 9607, 

March 9, 1978). In the 2003 

reclassification of the gray wolf into 

three distinct population segments, 

threats identified for the gray wolf in the 

Southwestern Distinct Population 

Segment (which included Mexico, 

Arizona, New Mexico, and portions of 

Utah, Colorado, Oklahoma, and Texas) 

included illegal killing and (negative) 

public attitudes (68 FR 15804, April 1, 

2003). The 2010 Mexican Wolf 

Conservation Assessment (Conservation 

Assessment) contains the most recent 

five-factor analysis for the Mexican wolf 

(Service 2010, p. 60). The purpose of the 

Conservation Assessment, which was a 

non-regulatory document, was to 

evaluate the status of the Mexican wolf 

reintroduction project within the 

broader context of the subspecies’ 

recovery. The Conservation Assessment 

found that the combined threats of 

illegal shooting, small population size, 

inbreeding, and inadequate regulatory 

protection were hindering the ability of 

the current population to reach the 


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population objective of at least 100 

wolves in the BRWRA (Service 2010, p. 

60). 

The threats we address in this fivefactor analysis and our conclusions 

about a given factor may differ from 

previous listing actions due to new 

information, or, in the case of the 

Conservation Assessment, the difference 

in perspective necessitated by the listing 

process compared to that of the 

Conservation Assessment, which was 

focused on recovery. For example, in 

this five-factor analysis we analyze 

currently occupied habitat, whereas the 

Conservation Assessment included 

discussion of unoccupied habitat that 

may be important in the future for 

recovery. In this five-factor analysis, we 

are assessing which factors pose a threat 

to the existing population of wolves in 

the BRWRA or would pose a threat to 

these wolves if the protections of the 

Act were not in place. 

Factor A. The Present or Threatened 

Destruction, Modification, or 

Curtailment of Its Habitat or Range 

As previously discussed, wolves are 

considered habitat generalists with 

fairly broad ecological capabilities and 

flexibility in using different prey and 

vegetation communities (Peterson and 

Ciucci 2003, pp. 104–111). Gray wolves 

hunt in packs, primarily pursuing 

medium to large hooved mammals. Wolf 

density is positively correlated to the 

amount of ungulate biomass available 

and the vulnerability of ungulates to 

predation (Fuller et al. 2003, pp. 170– 

175). These characterizations apply to 

the Mexican wolf and form our basis for 

defining suitable habitat. 

We consider suitable habitat for the 

Mexican wolf as forested, montane 

terrain containing adequate wild 

ungulate populations (elk, white-tailed 

deer, and mule deer) to support a wolf 

population. Suitable habitat has 

minimal roads and human 

development, as human access to areas 

inhabited by wolves can result in wolf 

mortality. Specifically, roads can serve 

as a potential source of wolf mortality 

due to vehicular collision and because 

they provide humans with access to 

areas inhabited by wolves, which can 

facilitate illegal killing of wolves. 

Although the road itself could be 

considered a form of habitat 

modification, the primary threat to 

wolves related to roads stems from the 

activities enabled by the presence of 

roads (i.e., vehicular collision and 

illegal killing) rather than a direct effect 

of the road on the wolf such as a 

boundary to dispersal. We address 

illegal killing under factor C. Disease or 

Predation, and vehicular collision under 

factor E. Other. 

For the Mexican wolf, we define 

habitat destruction, modification, or 

curtailment as a decrease or 

modification in the extent or quality of 

forested, montane terrain in currently 

occupied habitat, or a decrease in 

ungulate populations in currently 

occupied habitat, such that wolves 

would not persist in that area. In order 

to assess whether habitat destruction, 

modification, or curtailment is a threat 

to Mexican wolves, we consider 

information related to land status (as a 

characteristic of quality related to 

minimal human development) and the 

effects of catastrophic wildfire on 

Mexican wolves and ungulates. Our 

definitions of suitable habitat and of 

habitat destruction, modification, and 

curtailment are the same for the United 

States and Mexico. Implications of 

climate change are addressed under 

factor E. Other. 

United States—Mexican wolves 

currently inhabit only the BRWRA as 

identified in the January 12, 1998, final 

rule to designate an experimental 

population (63 FR 1752), as well as the 

adjacent Fort Apache Indian 

Reservation as allowed by an agreement 

between the White Mountain Apache 

Tribe and the Service. As noted above, 

we finalize revisions to our regulations 

for the experimental population of the 

Mexican wolf, which published 

elsewhere in this Federal Register. With 

this MWEPA revision, Mexican wolves 

will be allowed to inhabit the entire 

MWEPA, with the exception of any 

tribal areas where their removal is 

requested. In the revised MWEPA, there 

are 32,244 mi2 (83,512 km2) of suitable 

Mexican wolf habitat (Service 2014, p. 

25). Of this suitable habitat, 63 percent 

occurs on federally owned land; of that, 

the U.S. Forest Service accounts for 91 

percent, the Bureau of Land 

Management, 7 percent, and other 

Federal land ownership comprises the 

final 2 percent. 

We consider Federal land in the 

revised MWEPA to be an important 

characteristic of the quality of the 

reintroduction area. Federal lands such 

as National Forests are considered to 

have the most appropriate conditions 

for Mexican wolf reintroduction and 

recovery efforts because they typically 

have significantly lesser degrees of 

human development and habitat 

degradation than other land-ownership 

types (Fritts and Carbyn 1995, p. 26). 

We do not have any information or 

foresee any change in the size, status, 

ownership, or management of the 

National Forests in the revised MWEPA 

in the future. If Mexican wolves were 

not protected by the Act, we cannot 

foresee any changes to the status of 

these National Forests such that 

suitability for Mexican wolves would 

significantly diminish. 

Current and reasonably foreseeable 

management practices in all of the 

Apache, Gila, and Sitgreaves National 

Forests; the Payson, Pleasant Valley, 

and Tonto Basin Ranger Districts of the 

Tonto National Forest; and the 

Magdalena Ranger District of the Cibola 

National Forest are expected to support 

ungulate populations at levels that will 

sustain a growing Mexican wolf 

population in the revised MWEPA. Prey 

populations throughout all of Arizona 

and New Mexico continue to be 

monitored by the State wildlife agencies 

within Game Management Units, the 

boundaries of which are defined in each 

State’s hunting regulations. We do not 

predict any significant change to 

ungulate populations that inhabit the 

National Forests such that habitat 

suitability for Mexican wolves would 

diminish. 

On the other hand, wildfire is a type 

of habitat modification that could affect 

the Mexican wolf population in two 

primary ways—by killing of wolves 

directly or by causing changes in the 

abundance and distribution of 

ungulates. Two recent large wildfires, 

the Wallow Fire and the WhitewaterBaldy Complex Fire, have burned 

within close proximity to denning wolf 

packs. Due to their very large size and 

rapid spread, both of these fires are 

considered catastrophic wildfires. 

On May 29, 2011, the Wallow Fire 

began in Arizona and spread to over 

538,000 ac (217,721 ha) in Arizona 

(Apache, Navajo, Graham, and Greenlee 

Counties; San Carlos Apache Indian 

Reservation, Fort Apache Indian 

Reservation) and New Mexico (Catron 

County) by the end of June. The Wallow 

Fire was human-caused and is the 

largest fire in Arizona’s recorded history 

to date. The Wallow Fire burned 

through approximately 11 percent of the 

BRWRA. Three known or presumed 

wolf pack denning locations (Rim pack, 

Bluestem pack, Hawks Nest pack) were 

within the fire’s boundaries (Service 

2011). Although we had initial concern 

that denning pups (which are not as 

mobile as adults or may depend on 

adults to move them from the den) may 

not survive the fire due to their 

proximity to the rapidly spreading fire, 

we did not document any wolf 

mortalities as a result of the fire. 

Telemetry information indicated all 

radio-collared animals survived, and 

pups from two of the packs whose den 

areas burned survived through the 

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year population survey. While denning 

behavior was observed in the third pack, 

the presence of pups had not been 

confirmed prior to the fire, and no pups 

were documented with this pack at the 

year’s end (Service 2011). 

In addition to possible direct negative 

effects of the Wallow Fire (i.e., mortality 

of wolves, which we did not document), 

we also considered whether the fire was 

likely to result in negative short- or 

long-term effects to ungulate 

populations. The Wallow Fire Rapid 

Assessment Team’s postfire assessment 

hypothesized that elk and deer 

abundance will respond favorably as 

vegetation recovers, with ungulate 

abundance exceeding prefire conditions 

within 5 years due to decreased 

competition of forage and browse with 

fire-killed conifers (Dorum 2011, p. 3). 

Based on this information, we recognize 

and will continue to monitor the 

potential for this fire to result in 

beneficial (increased prey) effects for 

Mexican wolves over the next few years. 

On May 16, 2012, the WhitewaterBaldy Complex Fire was ignited by 

lightning strikes in New Mexico. It 

burned at least 297,845 ac (120,534 ha), 

including an additional (to the Wallow 

Fire) 7 percent of the BRWRA. The 

Whitewater-Baldy Complex Fire was 

contained 2 mi (3 km) from a denning 

wolf pack to the north (Dark Canyon 

pack) and 5 mi (8 km) from a denning 

wolf pack to the east (Middle Fork 

pack). We have not documented any 

adverse effects, including mortality, 

from the fire to these packs. We 

similarly hypothesize, as with the 

Wallow Fire, that elk and deer 

abundance will respond favorably as 

vegetation recovers in the burned area, 

with ungulate abundance exceeding prefire conditions within several years. 

Given that we have not observed any 

wolf mortality associated with the 

Wallow and Whitewater-Baldy Complex 

fires, these specific fires have not 

significantly affected the Mexican wolf 

population. Moreover, although these 

fires demonstrate the possibility that a 

catastrophic wildfire within the 

reintroduction area could result in 

mortality of less mobile, denning pups, 

we recognize that adult wolves are 

highly mobile animals and can move 

out of even a catastrophic fire’s path. 

While mortality of pups would slow the 

growth of the population over a year or 

two, the adult, breeding animals drive 

the ability of the population to persist. 

We do not consider even these 

catastrophic fires to be a significant 

mortality risk to adult wolves given 

their mobility and, therefore, do not 

consider wildfire to be a significant 

threat to the Mexican wolf. Further, we 

predict that these fires will result in 

changes in vegetation communities and 

prey densities that will be favorable to 

wolves within a few years. We have no 

information to indicate there would be 

changes to the effects of fire on Mexican 

wolves if they were not protected by the 

Act. 

Mexico—The Mexican wolf appears to 

have been extirpated from the wild in 

Mexico for more than 30 years. 

Recently, researchers and officials in 

Mexico identified priority sites for 

reintroduction of Mexican wolves in the 

States of Sonora, Durango, Zacatecas, 

Chihuahua, Coahuila, Nuevo Leon, and 

Tamaulipas based on vegetation type, 

records of historical wolf occurrence, 

and risk factors affecting wolf mortality 

associated with proximity to human 

development and roads (Araiza et al. 

2012, pp. 630–637). In October 2011, 

Mexico initiated a reintroduction 

program with the release of five captivebred Mexican wolves into the San Luis 

Mountains just south of the United 

States-Mexico border. Through August 

2014, Mexico released a total of 14 adult 

Mexican wolves, of which 11 died or are 

believed dead, and 1 was removed for 

veterinary care. The remaining two 

adult Mexican wolves were documented 

with five pups in 2014, marking the first 

successful reproductive event in 

Mexico. We expect the number of 

Mexican wolves in Mexico to fluctuate 

from zero to several wolves or packs of 

wolves during 2015 and into the future 

in or around Sonora and Chihuahua or 

other Mexican States as wolves are 

released to the wild from captivity by 

Mexico and subsequently may survive, 

breed, die of natural causes, or be 

illegally killed. 

We recognize that Mexican wolves are 

being reintroduced in Mexico to areas 

identified as priority sites based on 

recent research (Araiza et al. 2012). 

However, we also note that Araiza et 

al.’s habitat assessment does not include 

assessment of prey availability within 

the six identified areas, which is a 

critical indicator of habitat suitability. 

Some information on prey availability is 

currently being collected and 

synthesized by Mexico for specific 

locations, but is not publicly available at 

this time. We also note that, due to the 

majority of land in Mexico being held in 

private ownership, large patches of 

secure public land are unavailable in 

Mexico to support reintroduction, 

which has been an important 

characteristic of reintroduction sites in 

the United States. We will continue to 

observe the status of the wolf 

reintroduction effort in Mexico. At this 

time, because our focus in this analysis 

is on currently occupied range, the 

absence of a Mexican wolf population in 

Mexico precludes analysis of habitat 

threats there. 

Summary of Factor A 

We have no information indicating 

that present or threatened habitat 

destruction, modification, or 

curtailment is significantly affecting the 

Mexican wolf or is likely to do so in the 

future. Zones 1 and 2 of the revised 

MWEPA provide an adequately sized 

area containing high-quality forested 

montane terrain with adequate ungulate 

populations (deer and elk) to support 

Mexican wolves in the experimental 

population. We do not foresee any 

changes in the status of the area 

(primarily U.S. Forest Service land). 

Further, we do not consider wildfire to 

be resulting in habitat destruction, 

modification, or curtailment that is 

threatening the Mexican wolf, although 

we recognize that future catastrophic 

wildfires have the potential to slow the 

growth of the population if pup 

mortality occurs in several packs. 

We have not conducted an analysis of 

threats under factor A in Mexico due to 

the lack of a Mexican wolf population 

there for more than 30 years. Based on 

the mortality of reintroduced Mexican 

wolves in Mexico from 2011 to 2013, we 

do not expect a population to be 

established there for at least several 

years. 

Factor B. Overutilization for 

Commercial, Recreational, Scientific, or 

Educational Purposes 

Since the inception of the Mexican 

wolf reintroduction project in 1998, we 

have not authorized legal killing or 

removal of wolves from the wild for 

commercial, recreational (i.e., hunting), 

scientific, or educational purposes. We 

are not aware of any instances of illegal 

killing of Mexican wolves for their pelts 

in the Southwest, or of illegal trafficking 

in Mexican wolf pelts or parts. Mexican 

wolf pelts and parts from wolves that 

die in captivity or in the wild may be 

used for educational or scientific 

purposes, such as taxidermy mounts for 

display, when permission is granted 

from the Service; most wolf parts are 

sent to a curatorial facility at the 

University of New Mexico to be 

preserved, catalogued, and stored. A 

recreational season for wolf hunting is 

not currently authorized in the 

Southwest. 

We have authorized, through a section 

10(a)(1)(A) research-and-recovery 

permit under 50 CFR 17.32, as well as 

in accordance with the Mexican wolf 

experimental population rule and 

section 10(j) management rule under 50 

CFR 17.84(k), agency personnel to take 


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any Mexican wolf in the experimental 

population, as well as to conduct 

activities related directly to the recovery 

of reintroduced experimental 

populations of Mexican wolf within 

Arizona and New Mexico. While 

removal of individual Mexican wolves 

(including lethal take) has occurred by 

the Service as a result of these measures, 

these actions are conducted within the 

purpose of our recovery program to 

contribute to the conservation of the 

Mexican gray wolf. 

Several Mexican wolf research 

projects occur in the BRWRA or 

adjacent tribal lands by independent 

researchers or project personnel, but 

these studies have utilized radiotelemetry, scat analysis, and other 

noninvasive methods that do not entail 

direct handling of, or impact to, wolves 

(e.g., Cariappa et al. 2008, Breck et al. 

2011, Rinkevich 2012). Nonlethal 

research for the purpose of conservation 

is also conducted on Mexican wolves in 

the SSP captive-breeding program; 

projects include research on 

reproduction, artificial insemination, 

and gamete collection and preservation 

(see Service Mexican Wolf Recovery 

Program annual reports online at 

www.fws.gov/southwest/es/

mexicanwolf/ for descriptions of past 

and current research projects). Research 

on disease and conditioned taste 

aversion is also being conducted in the 

SSP captive-breeding program. In all 

cases, any take authorized by the 

Service for scientific, educational, and 

conservation purposes must benefit the 

Mexican wolf and promote its recovery. 

Since reintroductions began in 1998 

and have continued through December 

31, 2013, we are aware of 25 incidents 

in which Mexican wolves were captured 

in nongovernmental (private) traps, at 

least 7 have been severely injured, and 

at least 3 have died as a result of injuries 

or activities associated with being 

captured in a leg-hold trap. While these 

seven injuries may have a significant 

effect on the individual Mexican wolf 

and may affect that particular animal’s 

pack, they are relatively rare 

occurrences. We conclude that the 3 

mortalities through 2013 have not 

affected the Mexican wolf’s population 

growth because this accounts for only 3 

mortalities in 15 years, and at the end 

of 2013, the minimum population size 

was 83 Mexican wolves. 

Absent the protection of the Act, 

Mexican wolves could be protected 

from overutilization in the United States 

by State regulations and programs in 

Arizona and New Mexico and Federal 

law in Mexico. The Arizona Revised 

Statutes Title 17 gives the Arizona Game 

and Fish Commission (Commission) the 

authority to regulate take of wildlife in 

the State of Arizona. ‘‘Take’’ (to pursue, 

shoot, hunt, trap, kill, capture, snare, or 

net) of wildlife in Arizona on lands 

under the authority of the Arizona Game 

and Fish Commission is prohibited, 

unless a provision (e.g., Commission 

Order, special rule, permit) is made to 

allow take. Arizona Game and Fish 

Commission Rules, Article 4, outlines 

additional restrictions that would 

provide further protections from 

overutilization including regulating and 

outlining prohibitions on possession 

and transport of illegally taken wildlife, 

and regulating and placing restrictions 

on scientific collection/handling of 

wildlife. Because Commission Order 14 

(Other Birds and Mammals) does not 

open a hunting season on wolves, all 

take of Mexican wolf in Arizona is 

prohibited (except via special permit, as 

for science and management purposes; 

permits that in-turn require the 

permittee to secure all required Federal 

permits). A hunting season could be 

opened if the agency documented a 

harvestable surplus or identified a need 

for population reduction in a specific 

area. The Arizona Game and Fish 

Department, the administrative, 

management, and enforcement arm of 

the Commission, is charged with 

carrying out the Commission’s programs 

and enforcing its regulations. 

Pursuant to the Wildlife Conservation 

Act of New Mexico, it is unlawful to 

take, possess, transport, export, process, 

sell, or offer for sale or ship any State 

or Federal endangered species or 

subspecies (17–2–41 New Mexico 

Statutes Annotated [NMSA]), thus, as a 

State-listed endangered subspecies, the 

Mexican wolf would be protected from 

take related to overutilization. 

Similarly, in Mexico, the General 

Wildlife Law (‘‘Ley General de Vida 

Silvestre’’, 2000, as amended) provides 

regulation against take of species or 

subspecies identified by the Norma 

Oficial Mexicana NOM–059– 

SEMARNAT–2010, ‘‘Proteccio ́n 

ambiental–Especies nativas de Me ́xico 

de flora y fauna silvestres.’’ These 

regulatory provisions are further 

discussed under factor D. The 

Inadequacy of Existing Regulatory 

Mechanisms. 

Summary of Factor B 

Based on available information, 

overutilization for commercial, 

recreational, scientific, or educational 

purposes does not occur or is 

exceedingly rare in the United States. In 

addition, we have no examples of these 

forms of take occurring in Mexico since 

the Mexican reintroduction program 

began in 2011. Arizona, New Mexico, 

and Mexico have regulatory provisions 

under which Mexican wolves could be 

protected against overutilization if the 

subspecies were not protected by the 

Act. Due to the nonexistent or very low 

level of overutilization occurring, and 

the ability of the States and Mexico to 

regulate overutilization, we do not 

consider overutilization to be affecting 

the Mexican wolf now or in the future. 

Factor C. Disease or Predation 

A number of viral, fungal, and 

bacterial diseases and endo- and 

ectoparasites have been documented in 

gray wolf populations (Kreeger 2003, 

pp. 202–214). However, little research 

has been done specific to disease in 

Mexican wolves, and little 

documentation exists of disease 

prevalence in wild wolves in the 

BRWRA population. We obtain the 

majority of our information on 

documented mortalities (from all 

sources, including disease) in the 

BRWRA from animals wearing radio 

collars. We may, therefore, 

underestimate the number of mortalities 

resulting from disease (e.g., due to the 

number of uncollared wolves). 

Typically, infectious diseases (such as 

viruses and bacteria) are transmitted 

through direct contact (e.g., feces, urine, 

or saliva) with an infected animal, by 

aerosol routes, or by physical contact 

with inanimate objects (fomites). 

Parasites are infective through water, 

food sources, or direct contact. Wolves 

are able to tolerate a number of 

parasites, such as tapeworms or ticks, 

although occasionally such organisms 

can cause significant disease, or even be 

lethal (Kreeger 2003, p. 202). 

Mexican wolves are routinely 

vaccinated for rabies virus, distemper 

virus, parvovirus, parainfluenza virus, 

and adenovirus before release to the 

wild from captive facilities. In addition, 

common dewormers and external 

parasite treatments are administered. 

Wolves captured in the wild are 

vaccinated for the same diseases and 

administered dewormers and external 

parasite treatments. Kreeger (2003, pp. 

208–211) describes the transmission 

route and effect of these diseases on 

gray wolves and can be referenced for 

general information. Recent rules for the 

Western Great Lakes and Northern 

Rocky Mountain gray wolf populations 

contain information from studies of 

disease occurrences in those geographic 

regions, and can also serve as a 

reference for a more comprehensive 

discussion of these (and other) diseases 

than that provided below (72 FR 6051, 

February 8, 2007; 73 FR 10513, February 

27, 2008). 


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Rabies, caused by a rhabdovirus, is an 

infectious disease of the central nervous 

system typically transmitted by the bite 

of an infected animal. Rabies can spread 

between infected wolves in a population 

(e.g., among and between packs), or 

between populations, resulting in severe 

population declines. Rabies is 

untreatable and leads to death. A rabies 

outbreak in and near the BRWRA began 

in 2006 in eastern Arizona and 

continued through 2009, with positive 

rabies diagnoses (fox variant) in both 

foxes and bobcats. No Mexican wolves 

in the BRWRA were diagnosed with 

rabies during this outbreak (Arizona 

Department of Health Services 2012; 

New Mexico Department of Health 

2011) or throughout the history of the 

reintroduction. 

Canine distemper, caused by a 

paramyxovirus, is an infectious disease 

typically transmitted by aerosol routes 

or direct contact with urine, feces, and 

nasal exudates. Death from distemper is 

usually caused by neurological 

complications (e.g., paralysis, seizures), 

or pneumonia. Distemper can cause 

high fatality rates, though survivors are 

occasionally documented in canine 

populations. Distemper virus may have 

been a contributing factor to high levels 

of pup mortality in Yellowstone 

National Park during several summers 

(Smith and Almberg 2007, p. 18). 

Although wolf populations are known 

to be exposed to the virus in the wild, 

mortality from distemper in wild 

Mexican wolves is uncommon. 

However, we expect Mexican wolf pups, 

in general, would be most susceptible to 

death from distemper virus at a time 

period prior to when they are captured, 

collared, and vaccinated. Therefore, our 

collared sample of pups may not be 

accurately documenting this source of 

mortality. 

Distemper has been documented in 

one wild litter of Mexican wolves in the 

BRWRA. Two sibling Mexican wolf 

pups brought to a captive-wolfmanagement facility in 2000 from the 

wild were diagnosed with distemper 

(indicating they were exposed to the 

disease in the wild) and died in 

captivity (AMOC and IFT 2005, p. TC– 

12). (Note: these captive deaths are not 

included in the BRWRA mortality 

statistics.) These are the only known 

mortalities due to distemper 

documented in relation to the current 

experimental population (AMOC and 

IFT 2005, p. TC–12). 

Canine parvovirus is an infectious 

disease caused by a parvoviridae virus 

that results in severe gastrointestinal 

and myocardial (heart disease) 

symptoms. Parvovirus is persistent in 

the environment and can be spread by 

direct contact or viral particles in the 

environment. Symptoms of an infected 

adult animal may include severe 

vomiting and diarrhea, resulting in 

death due to dehydration or electrolyte 

imbalance. Pups may die from 

myocardial (heart) disease if infected 

with canine parvovirus while in utero or 

soon after birth from cardiac 

arrhythmias. Although canine 

parvovirus has been documented in 

wild wolf populations, documented 

mortalities due to parvovirus are few; 

researchers hypothesize that parvovirus 

is a survivable disease, although less so 

in pups. Parvovirus is thought to have 

slowed various stages of colonization 

and dispersal of wolves in the greater 

Minnesota population (Mech et al. 2008, 

pp. 832–834). 

Parvovirus has been documented in 

one wild litter of wolves in the BRWRA. 

Three sibling Mexican wolf pups were 

documented having, and then dying 

from, parvovirus in 1999: One pup died 

in an acclimation release pen in the 

BRWRA, indicating it had been exposed 

to the disease in the wild (AMOC and 

IFT 2005, p. TC–12). The other two 

pups, which also may have been 

exposed to the disease in the wild, were 

transferred to, and died at, a prerelease 

captive facility and are considered 

captive mortalities. Mortality from 

canine parvovirus has otherwise not 

been documented in the BRWRA 

population. However, we expect pups, 

in general, to be most susceptible to 

death from parvovirus prior to when 

they are captured, collared, and 

vaccinated. Therefore, our collared 

sample of pups may not be accurately 

documenting this source of mortality. 

Three of 100 total documented 

Mexican wolf deaths in the BRWRA 

population between 1998 and 2013 have 

been attributed to disease: 1 to canine 

parvovirus, 1 to chronic bacterial 

pleuritis (bacterial infection around the 

lungs), and 1 to bacterial pneumonia. 

The pleuritis and pneumonia cases, 

though bacterial diseases, are likely both 

secondary to other unknown natural 

factors, rather than contagious, 

infectious diseases. Potential pup 

mortality caused by infectious disease 

may be poorly documented in the freeranging population because these pups 

are too young to radio collar and thus 

difficult to detect or monitor. In 

addition, collared animals are 

vaccinated, which reduces the potential 

for mortality to occur among collared 

wolves. 

We do not have evidence that disease 

was a significant factor in the decline of 

Mexican wolves prior to its protection 

by the Act in the 1970’s. However, we 

recognize that, in a general sense, 

disease has the potential to affect the 

size and growth rate of a wolf 

population and could have a negative 

impact on the experimental population 

if the active vaccination program were 

not in place. We also recognize that 

some diseases are more likely to spread 

as wolf-to-wolf contact increases 

(Kreeger 2003, pp. 202–214), thus the 

potential for disease outbreaks to occur 

may increase as the current population 

expands in numbers or density, 

although the effect on the population 

may be lower because a larger wolf 

population would be more likely to 

sustain the epidemic. Absent the 

protection of the Act, the potential for 

disease to affect the Mexican wolf 

population would primarily depend on 

whether State wildlife agencies or other 

parties provided a similar level of 

vaccination to the population as that 

which we currently provide. 

In addition to disease, we must also 

assess whether predation is affecting the 

Mexican wolf now or in the future 

under factor C. In our assessment of 

predation, we focus on wild predators 

as well as illegal killing of Mexican 

wolves. 

Wild predators do not regularly prey 

on wolves (Ballard et al. 2003, pp. 259– 

271). Although large prey may 

occasionally kill wolves during selfdefense (Mech and Peterson 2003, p. 

134), this occurrence is rare and not 

considered predation on the wolf. 

Between 1998 and December 31, 2013, 

three documented Mexican wolf 

mortalities are attributed to predators 

(wolf, mountain lion, and unknown) 

(Service 2013, Mexican Wolf Blue Range 

Reintroduction Population Statistics). 

This may be an underestimate (e.g., due 

to the number of uncollared wolves), 

but we still consider the overall 

incidence to be low based on the 

occurrences we have documented. 

Monitoring of Northern Rocky Mountain 

wolf populations demonstrates that 

wolf-to-wolf conflicts may be the biggest 

source of predation among gray wolves, 

but this typically occurs from territorial 

conflicts and has not occurred at a level 

sufficient to affect the viability of these 

populations (73 FR 10513; February 27, 

2008). As the Mexican wolf population 

begins to saturate available habitat, wolf 

mortalities resulting from territorial 

conflicts may become more prevalent 

but this type of mortality is not 

currently a concern. We do not foresee 

any change in the occurrence of wild 

predation on Mexican wolves if the 

subspecies was not protected by the Act 

and, therefore, do not consider 

predation from wild predators to be 

affecting the Mexican wolf. 


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Illegal mortalities have been the 

biggest source of Mexican wolf 

mortalities since the reintroduction 

began in 1998 (Service 2013: Mexican 

Wolf Blue Range Reintroduction Project 

Statistics). Out of 100 wild wolf 

mortalities documented between 1998 

and 2013, 55 deaths are attributed to 

illegal killing (55 percent of total 

mortalities). Documented illegal 

shootings have ranged from zero to 

seven per year between 1998 and 

December 2013, with one or more 

occurring every year with the exception 

of 1999. Illegal shooting has varied from 

no impact to the population (e.g., in 

1999 when no illegal shootings were 

documented) to resulting in the known 

mortality of about 15 percent of the 

population in a given year (e.g., in 

2001). Documented causes of illegal 

shooting in other gray wolf populations 

have included intentional killing and 

mistaken identity as a coyote or dog 

(Fuller et al. 2003, p. 181). We do not 

know the reason for each instance of 

illegal shooting of a Mexican wolf. 

We recognize that some wolf 

populations can maintain themselves 

despite sustained human-caused 

mortality rates of 17 to 48 percent 

(Fuller et al. 2003 [+/– 8 percent], pp. 

184–185; Adams et al. 2008 [29 

percent], p. 22; Creel and Rotella 2010 

[22 percent], p. 5; Sparkman et al. 2011 

[25 percent], p. 5; Gude et al. 2011 [48 

percent], pp. 113–116; Vucetich and 

Carroll In Review [17 percent]) and that 

human-caused mortality sometimes 

replaces much of the wolf mortality in 

a population that would have occurred 

naturally (e.g., due to intraspecific strife 

from territorial conflicts occurring in 

populations that have saturated 

available habitat) (Fuller et al. 2003, p. 

186). Regardless, for the Mexican wolf 

experimental population, we think it is 

likely that the majority of illegal 

shootings function as additive mortality 

(that is, these mortalities are in addition 

to other mortalities that occur, rather 

than compensatory mortality where the 

deaths from illegal shooting would 

substitute for deaths that would occur 

naturally) (Murray et al. 2010, pp. 2515, 

2522). Illegal mortalities have a negative 

effect on the size and growth rate of the 

experimental population at its current 

small size, but the effect of these 

mortalities on the population has likely 

been masked to some degree by the 

number of captive Mexican wolves 

released into the wild over the course of 

the reintroduction effort. Additionally, 

we are unable to document all Mexican 

wolf mortalities (i.e., uncollared wolves) 

and, therefore, may be underestimating 

the number of mortalities caused by 

illegal shooting. 

We expect that, absent the protection 

of the Act, killing of Mexican wolves 

would continue at current levels or, 

more likely, increase significantly 

because Federal penalties would not be 

in place to serve as a deterrent. Mexican 

wolves could be protected from take by 

State regulations in Arizona and New 

Mexico and Federal regulations in 

Mexico, but State penalties are less 

severe than Federal penalties (see a 

description and discussion of this under 

factor D), and Federal protection in 

Mexico does not infer protection for 

Mexican wolves in the United States. 

Based on the continuous occurrence of 

illegal shooting taking place while the 

Mexican wolf is protected by the Act 

and the likelihood of increased 

occurrences of wolf shooting absent the 

protection of the Act, we consider 

illegal killing of Mexican wolves to be 

significant to the population. We further 

consider the threat of illegal shooting to 

Mexican wolves in ‘‘Combination of 

Factors/Focus on Cumulative Effects,’’ 

which discusses this and other threats 

within the context of the small, 

geographically restricted and isolated 

experimental population. 

In Mexico, illegal killing of Mexican 

wolves released to the wild in between 

2011 and 2013 has already been 

documented. Through August 2014, 

Mexico released a total of 14 adult 

Mexican wolves, of which 11 died or are 

believed dead, and 1 was removed for 

veterinary care. Of the 11 Mexican 

wolves that died or are believed dead, 

6 were due to illegal killings (4 from 

poisoning and 2 were shot), 1 wolf was 

presumably killed by a mountain lion, 

3 causes of mortality are unknown 

(presumed illegal killings because 

collars were found, but not the 

carcasses), and 1 disappeared (neither 

collar nor carcass has been found). The 

illegal killing of at least six Mexican 

wolves has significantly hindered 

Mexico’s initial efforts to establish a 

population; continued monitoring of the 

wolves Mexico releases in the future 

will be necessary to document whether 

these initial events were by chance or 

are indicative of a significant, ongoing 

threat to Mexican wolves in Mexico. 

Summary of Factor C 

Based on the low incidence of disease 

and mortality from wild predators, we 

do not consider these factors to be 

significantly affecting the Mexican wolf 

nor do we expect them to in the future. 

Illegal shooting has been a continuous 

source of mortality to the experimental 

population in the United States since its 

inception, and we expect that if 

Mexican wolves were not protected by 

the Act the number of shootings would 

increase substantially in the United 

States. Therefore, we consider illegal 

shooting to be significantly affecting 

Mexican wolves in the United States. In 

Mexico, four wolves released in 2011 

were illegally poisoned within months 

of their release to the wild, significantly 

hindering their reintroduction efforts. 

Illegal poisoning may affect the future 

Mexican wolf population in Mexico 

significantly if such events continue. 

Factor D. The Inadequacy of Existing 

Regulatory Mechanisms 

The Act requires us to examine the 

adequacy of existing regulatory 

mechanisms with respect to those 

existing and foreseeable threats, 

discussed under the other factors that 

may affect the Mexican wolf. In this 

five-factor analysis, we consider illegal 

shooting (factor C), inbreeding (factor E), 

and small population size (factor E) to 

be significantly affecting Mexican 

wolves. We address regulatory 

mechanisms related to illegal shooting, 

as no regulatory mechanisms are 

available to address inbreeding or small 

population size beyond the overarching 

protection of the Act. 

As discussed in factor C, illegal 

killing (or ‘‘take,’’ as it is referred to in 

the Act) of Mexican wolves currently 

occurs at significant levels in both the 

United States and Mexico. In the United 

States, illegal shooting of Mexican 

wolves has been a continuous source of 

mortality over the course of the 

reintroduction project. In Mexico, illegal 

killing has resulted in a setback to the 

reestablishment of a population of 

Mexican wolves in the State of Sonora 

and the Western Sierra Madre; we are 

unsure of whether this threat will 

continue. 

The Act provides broad protection of 

listed subspecies to prohibit and 

penalize illegal take but has not been 

sufficient to deter all illegal killing of 

Mexican wolves in the United States. 

Section 9 of the Act (Prohibited acts) 

prohibits the take of any federally-listed 

species, subspecies, or DPS. Section 11 

(Penalties and enforcement) provides 

civil penalties up to $25,000, and 

criminal penalties up to $50,000 and/or 

not more than 1 year in jail for knowing 

violations of section 9. Experimental 

populations are treated as if they are 

listed as threatened, which limits 

criminal penalties to up to $25,000 and 

imprisonment for not more than 6 

months. 

All cases of suspected illegal take of 

Mexican wolves in the United States are 

investigated by the Service’s Office of 

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the-ground personnel involved in 

preventing illegal take of a Mexican 

wolf and apprehending those who 

commit illegal take include Service 

Special Agents, Arizona Game and Fish 

Department (AGFD) Game Wardens, 

New Mexico Department of Fish and 

Game Conservation Officers, U.S. Forest 

Service special agents and Law 

Enforcement Officers (LEOs), San Carlos 

Apache Tribe LEOs, and White 

Mountain Apache Tribe LEOs. Specific 

actions to reduce illegal take include 

targeted patrols during high-traffic 

periods (hunting seasons and holidays); 

the ability to restrict human activities 

within a 1-mi (1.6-km) radius of release 

pens, active dens, and rendezvous sites; 

proactive removal of road kills to reduce 

the potential of wolves scavenging, 

which may result in vehicular collision 

or illegal take of a Mexican wolf; and 

monetary rewards for information that 

leads to a conviction for unlawful take 

of the subspecies. Of the 55 wolf 

mortalities classified as illegal 

mortalities between 1998 and 2013, only 

4 individuals have been convicted and 

1 individual has paid a civil penalty. 

If Mexican wolves were not protected 

by the Act, they would be protected by 

State regulations in Arizona and New 

Mexico, and by Federal law in Mexico. 

In Arizona, the Mexican wolf is 

managed as Wildlife of Special Concern 

(Arizona Game and Fish Commission 

Rules, Article 4, R12–4–401) and is 

identified as a Species of Greatest 

Conservation Need (Tier 1a, 

endangered) (Species of Greatest 

Conservation Need 2006, pending). 

Species with these designations are 

managed under the AGFD’s Nongame 

and Endangered Wildlife Management 

program, which seeks to protect, restore, 

preserve, and maintain such species. 

These provisions, i.e., the Species of 

Greatest Conservation Need list and the 

Wildlife of Special Concern list, are 

nonregulatory. However, Arizona 

Revised Statute Title 17 establishes 

AGFD with authority to regulate take of 

wildlife in the State of Arizona. ‘‘Take’’ 

(to pursue, shoot, hunt, trap, kill, 

capture, snare, or net) of wildlife in 

Arizona on lands under the authority of 

the Arizona Game and Fish Commission 

is prohibited, unless a provision (e.g., 

Commission Order, special rule, permit) 

is made to allow take. Penalties for 

illegal take or possession of wildlife can 

include revocation of hunting license or 

civil penalties up to $8,000 depending 

on its classification as established 

through annual regulations. 

In New Mexico, the Mexican wolf is 

listed as endangered (Wildlife 

Conservation Act, pp. 17–2–37 through 

17–2–46 NMSA 1978). Pursuant to the 

Wildlife Conservation Act, it is 

unlawful to take, possess, transport, 

export, process, sell or offer for sale, or 

ship any State or Federal endangered 

species or subspecies (17–2–41 NMSA). 

Penalties for violating the provisions of 

17–2–41 may include fines of up to 

$1,000 or imprisonment. 

In Mexico, several legal provisions 

provide regulatory protection for the 

Mexican wolf. The Mexican wolf is 

classified as ‘‘E’’ (‘‘probably extinct in 

the wild’’) by the Norma Oficial 

Mexicana NOM–059–SEMARNAT– 

2010, ‘‘Proteccio ́n ambiental–Especies 

nativas de Me ́xico de flora y fauna 

silvestres–Categorı ́as de riesgo y 

especificaciones para su inclusio ́n, 

exclusio ́n o cambio–Lista de especies en 

riesgo’’ (NOM–059–SEMARNAT–2010), 

which is a list of species and subspecies 

at risk. This regulation does not directly 

provide protection of the listed species 

or subspecies; rather it includes the 

criteria for downlisting, delisting, or 

including a species, subspecies, or 

population on the list. The General 

Wildlife Law (‘‘Ley General de Vida 

Silvestre,’’ 2000, as amended), however, 

has varying restrictions depending on 

risk status that apply only to species or 

subspecies that are listed in the NOM– 

059–SEMARNAT–2010. 

Mexico’s Federal Penal Law (‘‘Co ́digo 

Penal Federal’’ published originally in 

1931) Article 420 assigns a fine of 300 

to 3,000 days of current wage and up to 

9 years prison to those who threaten the 

viability of a species, subspecies, or 

population, transport a species at risk, 

or damage a specimen of a species at 

risk. Administrative fines are imposed 

by an administrative authority 

(PROFEPA, ‘‘Procuraduria Federal de 

Proteccion al Ambiente,’’ or the 

Attorney General for Environmental 

Protection) and are calculated on the 

basis of minimum wage in Mexico City 

($62.33 daily Mexican pesos). The fines 

established in the General Wildlife Law 

range from 1,246.60 to 311,650 Mexican 

pesos (approximately U.S. $98 to U.S. 

$24,400) for the four minor infractions, 

to a range of 3,116 to 3,116,500 Mexican 

pesos (approximately U.S. $244 to U.S. 

$244,400) for the other offenses, 

including the killing of a wolf. Penal 

fines are imposed by a judge and are 

calculated on the basis of the current 

daily wage of the offender including all 

their income. 

We have no information to suggest 

that, absent the Act’s protections, 

shooting of Mexican wolves in the 

United States would cease. Rather, we 

believe that shooting of Mexican wolves 

could increase, as State penalties 

(assuming wolves were granted 

protected status by the States) would be 

less severe than current Federal 

penalties under the Act. Thus, existing 

State penalties in Arizona and New 

Mexico would not serve as an adequate 

deterrent to illegal take. The illegal 

killing of at least four wolves in Mexico 

(see factor C) between 2011 and 2014 

suggests that Federal penalties in 

Mexico may not be an adequate 

deterrent to illegal take there, although 

Federal fines in Mexico are potentially 

higher than those available under the 

Act in the United States. The adequacy 

of these penalties to address 

overutilization (factor B) is not an issue, 

as instances of overutilization do not 

occur or are exceedingly rare and, 

therefore, do not significantly affect the 

Mexican wolf. 

Summary of Factor D 

Regulatory mechanisms to prohibit 

and penalize illegal killing exist under 

the Act, but illegal shooting of wild 

Mexican wolves in the United States 

persists. We conclude that, absent the 

protection of the Act, killing of wolves 

in the United States would increase, 

potentially drastically, because State 

penalties are less severe than current 

Federal penalties. In regards to 

regulatory protection for the Mexican 

wolf in Mexico, the recent poisoning of 

several reintroduced wolves suggests 

that illegal killing may be a challenge 

for that country’s reintroduction efforts 

as well. Thus, in the absence of the Act, 

existing regulatory mechanisms will not 

act as an effective deterrent to the illegal 

killing of Mexican wolves in the United 

States, and this inadequacy will 

significantly affect the Mexican wolf. 

Factor E. Other Natural or Manmade 

Factors Affecting Its Continued 

Existence 

We document sources of mortality in 

six categories as part of our ongoing 

monitoring of Mexican wolves in the 

experimental population: Illegal Killing, 

Vehicle Collision, Natural, Other, 

Unknown, and Awaiting Necropsy. In 

factor C, we assessed illegal shooting in 

the United States, disease, and 

predation (our mortality category 

‘‘Natural’’ includes disease and 

predation). In factor E, we assess the 

impacts to the Mexican wolf from the 

remaining sources of mortality—Vehicle 

Collision, Natural, Other, and 

Unknown. As stated in our discussions 

of disease, predation, and illegal 

shooting, we may not be documenting 

all mortalities to the population because 

mortality of uncollared wolves is not 

typically detected; similarly, we may 

underestimate the number of mortalities 

attributed to any one cause discussed 

below. We also assess intolerance of 


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wolves by humans, land-use conflicts, 

hybridization, inbreeding, climate 

change, and small population size. 

Our category of ‘‘Natural’’ causes of 

mortality includes a number of 

mortality sources, such as predation, 

starvation, interspecific strife, lightning 

strikes, and disease. Because we have 

documented three or fewer natural 

mortalities per year since 1998, we do 

not consider natural mortalities to be 

occurring at a level, individually or 

collectively, that significantly affects the 

Mexican wolf (and see factor C for 

additional discussion of disease and 

predation) (Service 2013: Mexican Wolf 

Blue Range Reintroduction Project 

Statistics). Therefore, we do not further 

discuss these ‘‘Natural’’ causes of 

mortality. Similarly, mortalities caused 

by ‘‘Other’’ sources of mortality, which 

also includes several sources of 

mortality (capture-related mortalities, 

public-trap mortality, legal public 

shooting, etc.) and ‘‘Unknown’’ causes 

are occurring at very low levels (5 of 100 

mortalities, and 8 of 100 mortalities, 

respectively) and are not occurring at a 

level that significantly affects the 

Mexican wolf. 

Vehicular collision has accounted for 

14 percent of Mexican wolf mortalities 

from 1998 to December 31, 2013 (14 out 

of 100 total documented Mexican wolf 

deaths) (Service 2013: Mexican Wolf 

Blue Range Reintroduction Project 

Statistics). Thirteen out of 14 Mexican 

wolf mortalities attributed to vehicular 

collision throughout the course of the 

reintroduction (through December 31, 

2013) occurred along paved U.S. or 

State highways; one wolf died on a 

Forest Service dirt road as a result of 

vehicle collision. The number of 

vehicular-related mortalities, which has 

ranged from zero to two per year, with 

the exception of a high of four 

vehicular-related wolf deaths in 2003, 

has not shown a trend (increasing or 

decreasing) over time. Given the 

occurrence of these mortalities on 

highways, it is likely that these 

collisions were accidental events that 

occurred from vehicles traveling at 

relatively high speeds. We are cognizant 

that different types of roads present 

different levels of threats to Mexican 

wolves—paved roads with higher speed 

limits present more risk of wolf 

mortality due to vehicular collision than 

unpaved roads with lower speed limit. 

Roads, both paved and unpaved, in 

currently occupied Mexican wolf range 

in the Gila and Apache National Forests 

primarily exist to support forest 

management, livestock grazing, 

recreational access, resource protection, 

and transport of forest products on the 

National Forests (Service 1996, pp. 3– 

13). National Forests contain various 

road types (paved, unpaved, opened, 

closed, etc.) and trails (motorized, 

nonmotorized), but are generally 

considered to be driven at relatively low 

speeds and have relatively low traffic 

volume. Non-Forest Service roads (e.g., 

highways and other paved roads) are 

limited in currently occupied range, and 

include portions of U.S Highways 191 

and 180, and State Highways 260, 152, 

90, 78, 32, and 12. U.S. highway 60 runs 

immediately to the north of this area. 

It has been recommended that areas 

targeted for wolf recovery have low road 

density of not more than 1 linear mile 

of road per square mile of area (1.6 

linear km of road per 2.56 square 

kilometers; Thiel 1985, pp. 406–407), 

particularly during colonization of an 

area (Fritts et al. 2003, p. 301). Road 

density in the BRWRA was estimated at 

0.8 mi road per mi2 (1.28 km road per 

km2) prior to the reintroduction 

(Johnson et al. 1992, p. 48). The U.S. 

Forest Service Southwest Region 

recently calculated road densities for 

the Gila and Apache-Sitgreaves National 

Forests during analysis of alternatives to 

designate a system of roads, trails, and 

areas designated for motor vehicle use 

in compliance with the Travel 

Management Rule. They did not assess 

road use in terms of a baseline of traffic 

volume or projections of traffic volume 

for the future. Both the Gila and 

Apache-Sitgreaves National Forests 

continue to have an appropriately low 

density of roads for the Mexican wolf 

reintroduction effort, with no plans to 

increase road density in either Forest— 

road density in the Apache portion of 

the Apache-Sitgreaves National Forest is 

estimated at 0.94 mi road per mi2 for all 

roads (1.5 km road per km2) (open, 

closed, decommissioned) and motorized 

trails, or 0.43 mi road per mi2 (0.69 km 

road per km2) for open roads and 

motorized trails (USDA 2010a, p. 102); 

road density in the Gila National Forest 

is estimated at 1.02 mi per mi2 (1.64 km 

per km2) for open and closed (but not 

decommissioned) roads and motorized 

trails (an overall average of 0.99 mi per 

mi2 (1.59 km per km2) (USDA 2010b, p. 

149). Therefore, these Forests provided 

Mexican wolf habitat with appropriately 

low road density for establishment 

(colonization) of the experimental 

population. 

The revised MWEPA includes the 

addition of the Sitgreaves National 

Forest, Magdalena Ranger District of the 

Cibola National Forest, and Tonto, 

Payson, and Pleasant Valley Ranger 

Districts of the Tonto National Forest to 

the Gila and Apache National Forests as 

Zone 1, the area in which we will 

primarily conduct initial releases; these 

Forests have appropriately low road 

densities compared with non-Forest 

Service land to support these 

management activities (Service 2014, Ch 

3, p. 2). In Zone 2, which comprises a 

wider matrix of habitat quality than 

Zone 1, including areas of substantially 

higher road density of paved, highspeed roads, we recognize that wolf 

morality due to vehicular collision may 

increase. However, we do not have any 

data to determine the degree to which 

this may occur or whether it will 

significantly affect the Mexican wolf. 

In summary, Mexican wolf mortalities 

from vehicular collision show a strong 

pattern of occurrence on high-speed 

paved State or U.S. Highways rather 

than on Forest Service roads, and are 

currently occurring at relatively low 

levels (two or fewer mortalities per year, 

with the exception of 1 year in which 

four mortalities were attributed to 

vehicular collision). We consider it 

possible that wolf mortalities due to 

vehicular collision may increase in the 

future as Mexican wolves will be 

allowed to disperse beyond the Gila and 

Apache National Forests into areas with 

higher road density within the MWEPA. 

We will continue to document wolf 

mortality due to vehicular collision to 

determine whether this becomes 

significant. In absence of Federal 

protection, we would not expect that 

incidence rate of wolf-vehicular 

collision to change, due to the 

accidental nature of these incidents. 

Therefore, with or without the 

protections of the Act, we conclude that 

vehicular collisions, considered in 

isolation of other sources of mortality, 

are not significantly affecting the 

Mexican wolf. We further consider the 

significance of these mortalities in 

Combination of Factors/Focus on 

Cumulative Effects. 

Intolerance by Humans—Human 

attitudes have long been recognized as 

a significant factor in the success of gray 

wolf recovery efforts to the degree that 

it has been suggested that recovery may 

depend more on human tolerance than 

habitat restoration (see Boitani 2003, p. 

339, Fritts et al. 2003; Mech 1995). In 

the Southwest, extremes of public 

opinion vary between those who 

strongly support or oppose the recovery 

effort. Support may stem from such 

feelings as an appreciation of the 

Mexican wolf as an important part of 

nature and an interest in endangered 

species restoration, while opposition 

may stem from negative social or 

economic consequences of wolf 

reintroduction, general fear and dislike 

of wolves, or Federal land-use conflicts. 

Public polling data in Arizona and 

New Mexico shows that most 


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respondents have positive feelings about 

wolves and support the reintroduction 

of the Mexican wolf to public land 

(Research and Polling 2008a, p. 6, 

Research and Polling 2008b, p. 6). These 

polls targeted people statewide in 

locations outside of the reintroduction 

area, and thus provide an indication of 

regional support. 

In any case, there is no direct 

evidence to indicate that intolerance by 

humans of Mexican wolves will result 

in increased illegal killings. Without 

additional information, we are unable to 

confirm whether, or the degree to 

which, disregard for or opposition to the 

reintroduction project is a causative 

factor in illegal killings. Similarly, in 

Mexico, we do not know whether the 

illegal poisoning of four reintroduced 

Mexican wolves was purposeful and 

stemmed from opposition to the 

reintroduction or rather was targeted 

more generally at (other) predators. We 

recognize that humans can be very 

effective at extirpating wolf populations 

if human-caused mortality rates 

continue at high levels over time, as 

demonstrated by the complete 

elimination of Mexican wolves across 

the Southwest and Mexico prior to the 

protection of the Act. At this time, 

however, we do not have enough 

information to determine whether, or 

the degree to which, intolerance by 

humans may pose a threat to the 

Mexican wolf. 

Land-Use Conflicts—Historically, 

land-use conflict between Mexican 

wolves and livestock producers was a 

primary cause of the wolf’s 

endangerment due to human killing of 

wolves that depredated livestock. At the 

outset of the reintroduction effort, the 

amount of permitted grazing in the 

recovery area was identified as a 

possible source of public conflict for the 

project due to the potential for wolves 

to depredate on livestock (Service 1996, 

p. 4–4). Since the reintroduction project 

began in 1998, 73 Mexican wolves have 

been removed from the wild due to 

livestock depredation, reaching a high 

of 16 and 19 removals in 2006 and 2007, 

respectively (Service 2013 Mexican 

Wolf Blue Range Project Statistics). 

Since 2007, the Service, other State, 

Federal, and tribal agencies, private 

parties, and livestock producers have 

increased proactive efforts (e.g., hazing, 

fencing, range riders) to minimize 

depredations, resulting in fewer 

removals from 2008 to 2013 than in the 

first 10 years of the program. Since 

2007, we removed one Mexican wolf in 

2012 and two Mexican wolves in 2013 

from the experimental population due 

to confirmed livestock depredation 

(Service 2013 Mexican Wolf Blue Range 

Project Statistics). While recognizing 

that management removals must be part 

of an overall management scheme that 

promotes the growth of the 

experimental population, the Service is 

committed to actively managing 

depredating Mexican wolves to improve 

human tolerance. 

Furthermore, the Service, in 

cooperation with the National Fish and 

Wildlife Foundation, established the 

Mexican Wolf/Livestock Interdiction 

Trust Fund (Trust Fund), which was 

founded on September 23, 2009. The 

objective of the Trust Fund is to 

generate long-term funding for 

prolonged financial support to livestock 

operators with the framework of 

cooperative conservation and recovery 

of Mexican wolf populations in the 

Southwest. Funding is provided for 

initiatives that address management, 

monitoring, and proactive conservation 

needs for Mexican wolves related to 

livestock protection, measures to avoid 

and minimize depredation, habitat 

protection, species protection, scientific 

research, conflict resolution, 

compensation for damage, education, 

and outreach activities. The Trust Fund 

is overseen by the Mexican Wolf/

Livestock Coexistence Council, an 11- 

member group of ranchers, Tribes, 

county coalitions, and environmental 

groups that may identify, recommend, 

and approve conservation activities, 

identify recipients, and approve the 

amount of the direct disbursement of 

Trust Funds to qualified recipients. It is 

the current policy of the Coexistence 

Council to pay 100 percent of the 

market value of confirmed depredated 

livestock and 50 percent market value 

for probable kills. 

Based on these efforts, we conclude 

that land-use conflicts are not 

significantly affecting the Mexican wolf. 

As noted above, since 2007 we removed 

three Mexican wolves from the 

experimental population due to 

confirmed livestock depredation 

(Service 2013 Mexican Wolf Blue Range 

Project Statistics). Also, when we 

remove Mexican wolves due to 

confirmed livestock depredation, many 

of the wolves are released back into a 

different part of the experimental 

population area where they are less 

likely to cause livestock depredations. 

We are able to manage problem Mexican 

wolves in a manner that does not 

significantly affect the experimental 

population. In the absence of protection 

by the Act, land-use conflicts would 

still occur in areas where Mexican 

wolves and livestock coexist. However, 

because the Mexican wolf is protected 

by State law in Arizona and New 

Mexico, we expect that livestock 

producers and State agencies would 

continue to employ effective practices of 

hazing or other active management 

measures to reduce the likelihood of 

occurrence of depredation incidents. 

Therefore, we conclude that land-use 

conflicts are unlikely to significantly 

affect the Mexican wolf if it was not 

protected by the Act. 

Hybridization—Hybridization 

between wolves and other canids can 

pose a significant challenge to recovery 

programs (e.g., the red wolf recovery 

program) (Service 2007, pp. 10–11) 

because species in the Canis genus can 

interbreed and produce viable offspring. 

In the Mexican wolf experimental 

population, hybridization is a rare 

event. Three confirmed hybridization 

events between Mexican wolves and 

dogs have been documented since the 

reintroduction project began in 1998. In 

the first two cases, hybrid litters were 

humanely euthanized (Service 2002, p. 

17, Service 2005:16.). In the third case, 

four of five pups were humanely 

euthanized; the fifth pup, previously 

observed by project personnel but not 

captured, has not been located and its 

status is unknown (BRWRA Monthly 

Project Updates, June 24, 2011, http://

www.fws.gov/southwest/es/

mexicanwolf/CEBRWRA.cfm). No 

hybridization between Mexican wolves 

and coyotes has been confirmed through 

our genetic monitoring of coyotes, 

wolves, and dogs that are captured in 

the wild as part of regular management 

activities of canids in the wild. 

Our response to hybridization events 

has negated potential impacts to the 

BRWRA population from these events 

(e.g., effects to the genetic integrity of 

the population). Moreover, the 

likelihood of hybrid animals surviving, 

or having detectable impacts on wolf 

population genetics or viability, is low 

due to aspects of wolf sociality and 

fertility cycles (Mengel 1971, p. 334; 

Vila and Wayne 1999, pp. 195–199). 

We do not foresee any change in the 

likelihood of hybridization events 

occurring, or the potential effect of 

hybridization events, if the Mexican 

wolf was not protected by the Act; that 

is, hybridization events and effects 

would continue to be rare. Therefore, 

we conclude that hybridization is not 

significantly affecting the Mexican wolf 

population now nor is it likely to do so 

in the future. 

Inbreeding, Loss of Heterozygosity, 

and Loss of Adaptive Potential— 

Mexican wolves have pronounced 

genetic challenges resulting from an 

ongoing and severe genetic bottleneck 

(that is, a reduction in a population’s 

size to a small number for at least one 

generation) caused by its near 


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extirpation in the wild and the small 

number of founders upon which the 

captive population was established. 

These challenges include inbreeding 

(mating of close relatives), loss of 

heterozygosity (a decrease in the 

proportion of individuals in a 

population that have two different 

alleles for a specific gene), and loss of 

adaptive potential, three distinct but 

interrelated phenomena. 

When a population enters a genetic 

bottleneck, the strength of genetic drift 

(random changes in gene frequencies in 

a population) is increased and the 

effectiveness of natural selection is 

decreased. As a result, formerly 

uncommon alleles may drift to higher 

frequencies and become fixed (the only 

variant that exists), even if they have 

deleterious (negative) effects on the 

individuals that carry them. Conversely, 

beneficial alleles may become less 

common and even be lost entirely from 

the population. In general, rare alleles 

are lost quickly from populations 

experiencing bottlenecks. 

Heterozygosity is lost much more 

slowly, but the losses may continue 

until long after the population has 

grown to large size (Nei et al. 1975, 

entire). The extent of allele and 

heterozygosity loss is determined by the 

depth (the degree of population 

contraction) and duration of a 

bottleneck. Heterozygosity is important 

because it provides adaptive potential 

and can mask (prevent the negative 

effects of) deleterious alleles. 

Inbreeding can occur in any 

population, but is most likely to occur 

in small populations due to limited 

choice of mates. The potential for 

inbreeding to negatively affect the 

captive and reintroduced Mexican wolf 

populations has been a topic of concern 

for over a decade (Parsons 1996, pp. 

113–114; Hedrick et al. 1997, pp. 65– 

68). Inbreeding affects traits that reduce 

population viability, such as 

reproduction (Kalinowski et al. 1999, 

pp. 1371–1377; Asa et al. 2007, pp. 326– 

333; Fredrickson et al. 2007, pp. 2365– 

2371), survival (Allendorf and Ryman 

2002, pp. 50–85), and disease resistance 

(Hedrick et al. 2003, pp. 909–913). 

Inbreeding is significant because it 

reduces heterozygosity and increases 

homozygosity (having two of the same 

alleles) throughout the genome. 

Inbreeding depression is thought to be 

primarily a result of the full expression 

of deleterious alleles that have become 

homozygous as a result of inbreeding 

(Charlesworth and Willis 2009, entire). 

In other words, rare deleterious alleles, 

or gene variants that have deleterious 

effects such as deformities, are more 

likely to be inherited and expressed in 

an offspring of two related individuals 

than of unrelated individuals (that is, 

the offspring may be homozygous). 

Theory suggests that, although lethal 

alleles (those that result in the death of 

individuals with two copies) may be 

purged or reduced in frequency in small 

populations (Hedrick 1994, pp. 363– 

372), many other mildly and moderately 

deleterious alleles are likely to become 

fixed in the population (homozygous in 

all individuals) with little or no 

reduction in the overall genetic load 

(amount of lethal alleles) (Whitlock et 

al. 2000, pp. 452–457). In addition, 

there is little empirical evidence in the 

scientific literature that purging reduces 

the genetic load in small populations. 

As previously described, Mexican 

wolves experienced a rapid population 

decline during the 1900s, as predator 

eradication programs sought to 

eliminate wolves from the landscape. 

Subsequently, a captive-breeding 

program was initiated. The McBride 

lineage was founded with three wolves 

in 1980. The Ghost Ranch and Aragon 

lineages were each founded by single 

pairs in 1961 and around 1976, 

respectively. These lineages were 

managed separately until the mid-1990s, 

by which time all three lineages had 

become strongly inbred. Inbreeding 

coefficients (f) (a measure of how 

closely related two individuals are) for 

McBride pups born in the mid-1990s 

averaged about 0.23—similar to 

inbreeding levels for offspring from 

outbred full sibling or parent–offspring 

pairs (f = 0.25). Inbreeding coefficients 

for Aragon and Ghost Ranch lineage 

pups born in the mid-1990s were 

higher, averaging 0.33 for Aragon pups 

and 0.64 for Ghost Ranch pups (Hedrick 

et al. 1997, pp. 47–69). 

Of the three lineages, only the 

McBride lineage was originally managed 

as a captive-breeding program to aid in 

the conservation of Mexican wolves. 

However, out of concern for the low 

number of founders and rapid 

inbreeding accumulation in the McBride 

lineage, the decision was made to merge 

the Aragon and Ghost Ranch lineages 

into the McBride lineage after genetic 

testing confirmed that this approach 

could improve the gene diversity of the 

captive population (Garcia-Moreno et al. 

1996, pp. 376–389). Consequently, 

pairings (for mating) between McBride 

wolves and Aragon wolves and between 

McBride and Ghost Ranch wolves began 

in 1995 with the first generation (F1) of 

these pups born in 1997. Although the 

parents of these first generation wolves 

were strongly inbred, the offspring were 

expected to be free of inbreeding and 

free of the inbreeding depression. Fortyseven F1 wolves were produced from 

1997 to 2002. Upon reaching maturity, 

the F1 wolves were paired among 

themselves, backcrossed with pure 

McBride wolves, and paired with the 

descendants of F1 wolves called ‘‘crosslineage’’ wolves to maintain gene 

diversity and reduce inbreeding in the 

captive population. 

Although there was slight statistical 

evidence of inbreeding depression 

among captive wolves of the McBride 

and Ghost Ranch lineages, the outbred 

F1 wolves proved to have far greater 

reproductive fitness than contemporary 

McBride and Ghost Ranch wolves 

(which were strongly inbred) as well as 

minimally inbred wolves from early in 

the McBride and Ghost Ranch 

pedigrees. Pairings between F1 wolves 

were 89 percent more likely to produce 

at least one live pup, and mean litter 

sizes for F1 × F1 pairs were more than 

twice as large as contemporary McBride 

pairings (7.5 vs 3.6 pups per litter; 

Fredrickson et al. 2007, pp. 2365–2371). 

The large increases in reproductive 

fitness among F1 wolves suggested that 

the McBride and Ghost Ranch lineages 

were suffering from a large fixed genetic 

load of deleterious alleles. In other 

words, McBride and Ghost Ranch 

wolves had accumulated identical 

copies of gene variants that had negative 

effects on their health or reproductive 

success at many locations (loci) 

throughout their genome. In addition, 

pups born to cross-lineage dams (mother 

wolves) had up to 21 percent higher 

survival rates to 180 days than 

contemporary McBride lineage pups 

(Fredrickson et al. 2007, pp. 2365– 

2371). 

Although the F1 wolves had high 

reproductive fitness, strong inbreeding 

depression among cross-lineage wolves 

in captivity has been documented. 

Inbreeding levels of both dams and sires 

(mother and father wolves, respectively) 

were found to negatively affect the 

probability that a pair would produce at 

least one live pup. For example, the 

estimated probabilities of a pair 

producing at least one live pup dropped 

from 0.96 for F1 × F1 pairs (with no 

inbreeding in the dam and sire) to 0.40 

for pairs with a mean inbreeding 

coefficient of 0.15 (Fredrickson et al. 

2007, pp. 2365–2371). Consistent with 

the finding that inbreeding levels of 

sires affected the probability of 

producing at least one live pup, Asa et 

al. (2007, pp. 326–333) found that two 

measures of semen quality, sperm cell 

morphology and motility of sperm cells, 

declined significantly as inbreeding 

levels increased. Among pairs that 

produced at least one live pup, 

increases of 0.1 in the inbreeding 

coefficients of both the dam and pups 


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was estimated to reduce litter size by 2.8 

pups. Inbreeding levels of the pups were 

found to have about twice the 

detrimental effect as inbreeding in the 

dam, suggesting that inbreeding 

accumulation in pups was causing pups 

to die prior to being born (Fredrickson 

et al. 2007, pp. 2365–2371). 

As of July 2014, the captive 

population of Mexican wolves consisted 

of 258 wolves, of which 33 are 

reproductively compromised or have 

very high inbreeding coefficients, 

leaving 225 wolves as the managed 

population (Siminski and Spevak 2014). 

The age structure of the population, 

however, is heavily skewed, with 

wolves 7 years old and older comprising 

about 62 percent of the population— 

meaning that most of the population is 

composed of old wolves who will die 

within a few years. This age structure, 

which has resulted from the high 

reproductive output of the F1 wolves 

and their descendants in captivity, the 

combination of few releases of captiveborn wolves to the wild in recent years, 

removal of wolves from the wild 

population to captivity, and limited pen 

space for pairings, means that additional 

gene diversity will be lost as the captive 

population continues to age (R. 

Fredrickson, pers. comm., 2014). 

The SSP strives to minimize and slow 

the loss of gene diversity of the captive 

population but (due to the limited 

number of founders) cannot increase it. 

As of 2014, the gene diversity of the 

captive program was 83.36 percent of 

the founding population, which falls 

below the average mammal SSP (93 

percent) and below the recognized SSP 

standard to maintain 90 percent of the 

founding population diversity. Below 90 

percent, the SSP states that 

reproduction may be compromised by 

low birth weight, smaller litter sizes, 

and related issues. 

Representation of the Aragon and 

Ghost Range lineages in 2014 was 17.94 

percent and 20.07 percent, respectively 

(Siminski and Spevak 2014, p. 8). More 

specifically, the representation of the 

seven founders is very unequal in the 

captive population, ranging from about 

30 percent for the McBride founding 

female to 4 percent for the Ghost Ranch 

founding male. Unequal founder 

contributions lead to faster inbreeding 

accumulation and loss of founder 

alleles. The captive population is 

estimated to retain only 3.00 founder 

genome equivalents, suggesting that 

more than half of the alleles (gene 

variants) from the seven founders have 

been lost from the population. 

With the current gene diversity of 

83.36 percent and current space 

limitations of 300 captive Mexican 

wolves, retaining 75 percent gene 

diversity for only 41 years from present 

is possible with the current generation 

length of 5.8 years in the captive 

population, population growth rate of l 

= 1.065, effective population size (Ne) of 

26.96, and a ratio of effective to census 

size (Ne / N; that is, the number of 

breeding animals as a percentage of the 

overall population size) of 0.1266 

(Siminski and Spevak 2014, p. 7). The 

genetically effective population size is 

defined as the size of an ideal 

population that would result in the rate 

of inbreeding accumulation or 

heterozygosity loss as the population 

being considered. The effective sizes of 

populations are almost always smaller 

than census sizes of populations. A rule 

of thumb for conservation of small 

populations holds Ne should be 

maintained above 50 to prevent 

substantial inbreeding accumulation, 

and that small populations should be 

grown quickly to much larger sizes (Ne 

≥ 500) to maintain evolutionary 

potential (Franklin 1980, entire). The 

low ratio of effective to census 

population sizes in the captive 

population reflects the limitations on 

breeding (due to a lack of cage space) 

over the last several years, while the low 

effective population size is another 

indicator of the potential for inbreeding 

and loss of heterozygosity. 

The gene diversity of the 

experimental population of Mexican 

wolves can only be as good as the 

diversity of the captive population from 

which it is established. Based on 

information available in July 11, 2014, 

the genetic diversity of the wild 

population was 74.52 percent of the 

founding population (Siminski and 

Spevak 2014, pp. 9), with 5.36 percent 

and 14.56 percent representation of 

Aragon and Ghost Range lineages, 

respectively. At the end of 2013, the 

minimum population in the Mexican 

wolf experimental population was 83 

Mexican wolves, but the experimental 

population is a poor representative of 

the genetic variation remaining in the 

captive population. Founder 

representation in the experimental 

population is more strongly skewed 

than in the captive population. Mean 

inbreeding levels are 65 percent greater, 

and founder genome equivalents are 35 

percent lower than in the captive 

population. In addition, the estimated 

relatedness of the Mexican wolf 

experimental population is on average 

65 percent greater than that in the 

captive population (population mean 

kinship: 0.2548 versus 0.1664; Siminski 

& Spevak 2014, p. 9). Without 

substantial management action to 

improve the genetic composition of the 

population, inbreeding will accumulate 

and heterozygosity and alleles will be 

lost much faster than in the captive 

population. 

There is evidence of strong inbreeding 

depression in the Mexican wolf 

experimental population. Fredrickson et 

al. (2007, pp. 2365–2371) estimated that 

the mean observed litter size (4.8 pups 

for pairs producing pups with no 

inbreeding) was reduced on average by 

0.8 pups for each 0.1 increase in the 

inbreeding coefficient of the pups. For 

pairs producing pups with inbreeding 

coefficients of 0.20, the mean litter size 

was estimated to be 3.2 pups. Computer 

simulations of the experimental 

population incorporating the Mexican 

wolf pedigree suggest that this level of 

inbreeding depression may substantially 

reduce the viability of the experimental 

population (Carroll et al. 2014, p. 82). 

The recent history of Mexican wolves 

can be characterized as a severe genetic 

bottleneck that began no later than the 

founding of the Ghost Ranch lineage in 

1960. The founding of the three lineages 

along with their initial isolation likely 

resulted in the loss of most rare alleles 

and perhaps even some moderately 

common alleles. Heterozygosity loss 

was accelerated as a result of rapid 

inbreeding accumulation. The merging 

of the captive lineages likely slowed the 

loss of alleles and heterozygosity, but 

did not end it. The consequences to 

Mexican wolves of the current genetic 

bottleneck will be future populations 

that have reduced fitness (for example, 

smaller litter sizes, lower pup survival) 

due to inbreeding accumulation and the 

full expression of deleterious alleles. 

The loss of alleles will limit the ability 

of future Mexican wolf populations to 

adapt to environmental challenges. 

Based on data from the SSP 

documenting loss of genetic variation, 

research documenting viability-related 

inbreeding effects in Mexican wolves, 

and our awareness that the wild 

population is at risk of inbreeding due 

to its small size, we conclude that 

inbreeding, and loss of heterozygosity, 

and loss of adaptive potential are 

significantly affecting Mexican wolves 

and are likely to continue to do so in the 

future. If the Mexican wolf was not 

protected by the Act, these risks would 

remain, and may increase if States or 

other parties did not actively promote 

genetic diversity in the experimental 

population by releasing wolves with 

appropriate genetic ancestry to the 

population. 

Small Population Size—Rarity may 

affect the viability (likelihood of 

extinction or persistence over a given 

time period) of a subspecies depending 


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on the subspecies’ biological 

characteristics and threats acting upon 

it. We consider several types of 

information to determine whether small 

population size is affecting the Mexican 

wolf, including historical conditions, 

consideration of stochastic (or, chance) 

events, theoretical recommendations of 

population viability, and applied 

population-viability models specific to 

Mexican wolves. We discuss three types 

of stochastic events—demographic, 

environmental, and catastrophic—as the 

fourth type of stochastic event— 

genetic—is addressed under the 

subheading of Inbreeding. We further 

discuss the significance of small 

population size in Combination of 

Factors/Focus on Cumulative Effects, 

below. 

Historical abundance and distribution 

serve as a qualitative reference point 

against which to assess the size of the 

current population. Prior to European 

colonization of North America, Mexican 

wolves were geographically widespread 

throughout numerous populations 

across the southwestern United States 

and Mexico. Although we do not have 

definitive estimates of historical 

abundance, we can deduce from gray 

wolf population estimates (Leonard et 

al. 2005, p. 15), trapping records, and 

anecdotal information that Mexican 

wolves numbered in the thousands 

across its range in the United States and 

Mexico. We, therefore, recognize that 

the current size and geographic 

distribution of the Mexican wolf 

represents a substantial contraction 

from its historical (pre-1900s) 

abundance and distribution. 

Scientific theory and practice 

generally agree that a subspecies 

represented by a small population faces 

a higher risk of extinction (or a lower 

probability of population persistence) 

than a subspecies that is widely and 

abundantly distributed (Goodman 1987, 

pp. 11–31; Pimm et al. 1988, p. 757). 

One of the primary causes of this 

susceptibility to extinction is the 

sensitivity of small populations to 

random demographic events (Shaffer 

1987, pp. 69–86, Caughley 1994, p. 217). 

In small populations, even those that are 

growing, random changes in average 

birth or survival rates could cause a 

population decline that would result in 

extinction. This phenomenon is referred 

to as demographic stochasticity. As a 

population grows larger and individual 

events tend to average out, the 

population becomes less susceptible to 

extinction from demographic 

stochasticity and is more likely to 

persist. 

Two Mexican wolf populationviability analyses were initiated 

subsequent to the development of the 

1982 Mexican Wolf Recovery Plan but 

prior to the reintroduction of Mexican 

wolves into the experimental 

population in 1998 (Seal 1990 entire, 

IUCN 1996 entire, Service 2010, p. 66), 

although neither was completed. 

Population-viability modeling will be 

conducted as part of the development of 

draft recovery criteria; these results will 

be available to the public when the draft 

recovery plan is published. In the 

meantime, Carroll et al. (2014, p. 81) 

conducted a population viability model 

for Mexican wolves and found that the 

risk of extinction varied by both 

population size and the number of 

effective migrants per generation. The 

risk of extinction for population sizes 

below 200 was affected by the number 

of migrants, such that populations of 

100 had a greater than 5 percent 

extinction risk, even with 3 effective 

migrants per generation, while 

populations of 125 were more secure 

with 2.5 to 3.0 effective migrants per 

generation, and populations of 150 were 

secure with greater than 0.5 effective 

migrants per generation (Carroll et al. 

2014, p. 81). Given our understanding of 

the high extinction risk of the current 

size of the experimental population and 

our awareness that this rarity is not the 

typical abundance and distribution 

pattern for Mexican wolves, we consider 

the small population size of the 

Mexican wolf. 

At the end of 2013, the minimum 

population size was 83 Mexican wolves, 

meaning the experimental population is, 

by demographic measures, considered 

small and has a low probability of 

persistence (Shaffer 1987, p. 73; Boyce 

1992, p. 487; Mills 2007, p. 101; Service 

2010, pp. 63–68). Absent the protection 

of the Act, the extinction risks 

associated with small population size 

would remain, and may increase if 

Arizona or New Mexico does not 

actively support the experimental 

population through appropriate 

management measures. The 

vulnerability of a small population to 

extinction can also be driven by the 

population’s vulnerability to decline or 

extinction due to stochastic 

environmental or catastrophic events 

(Goodman 1987, pp. 11–31; Pimm et al. 

1988, p. 757). While we consider these 

types of events to be critically important 

considerations in our recovery efforts 

for the subspecies, we have not 

identified any single environmental 

event (i.e., disease, climate change 

(below)) or catastrophic event (wildfire) 

to be significantly affecting Mexican 

wolf based on our current information 

and management practices (e.g., 

vaccinations, monitoring). However, we 

reconsider the concept of vulnerability 

to these events below, in Combination 

of Factors/Focus on Cumulative Effects. 

Climate Change—Our analyses under 

the Act include consideration of 

ongoing and projected changes in 

climate. The terms ‘‘climate’’ and 

‘‘climate change’’ are defined by the 

Intergovernmental Panel on Climate 

Change (IPCC). ‘‘Climate’’ refers to the 

mean and variability of different types 

of weather conditions over time, with 30 

years being a typical period for such 

measurements, although shorter or 

longer periods also may be used (IPCC 

2013, p. 1450). The term ‘‘climate 

change’’ thus refers to a change in the 

mean or variability of one or more 

measures of climate (e.g., temperature or 

precipitation) that persists for an 

extended period, typically decades or 

longer, whether the change is due to 

natural variability, human activity, or 

both (IPCC 2013, p. 1450). Various types 

of changes in climate can have direct or 

indirect effects on the Mexican wolf. 

These effects may be positive, neutral, 

or negative, and they may change over 

time, such as the effects of interactions 

of climate with other variables (e.g., 

habitat fragmentation). In our analysis, 

we use our expert judgment to weigh 

relevant information, including 

uncertainty, in our consideration of 

various aspects of climate change. 

Research to investigate the possible 

impacts of climate change specifically 

on the Mexican wolf has not been 

conducted. Therefore, we base our 

analysis on pertinent information from 

the scientific literature related to 

Mexican wolf habitat and prey. 

Throughout their circumpolar 

distribution, gray wolves persist in a 

variety of ecosystems with temperatures 

ranging from ¥70 to 120 degrees 

Fahrenheit (¥56 to 48 degrees Celsius) 

with wide-ranging prey type and 

availability (Mech and Boitani 2003, p. 

xv). Mexican wolves historically 

inhabited, and still inhabit, a range of 

southwestern ecotypes subsisting on 

large ungulate prey as well as small 

mammals Mexican wolves did not 

historically, (nor currently), inhabit 

extreme desert areas or semi-desert 

grasslands except potentially during 

dispersal movements (Service 2010, p. 

39). Due to their plasticity and lack of 

reliance on microhabitat, we generally 

do not consider Mexican wolves to be 

highly vulnerable or sensitive to climate 

change (Dawson et al. 2011, p. 53). 

However, we recognize that climate 

change is already having detectable 

impacts on the ecosystems of the 

Southwest, and future changes could 

affect Mexican wolves or their prey. For 


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example, warmer temperatures, more 

frequent and severe drought, and 

reductions in snowpack, streamflows 

and water availability are projected 

across the southwestern US (Garfin et al. 

2014, pp. 464–466). To the degree that 

warmer temperatures and increased 

aridity or decreased water availability 

(Dai 2011, p. 58) or any of these other 

conditions, limit prey abundance, we 

would also expect decreased Mexican 

wolf densities. Information suggests that 

ungulate prey populations in more xeric 

ecoregions in the Southwest may be 

impacted more negatively than those in 

wetter areas due to decreased forage 

quality and availability (deVoss and 

McKinney 2012, p. 19). However, 

Mexican wolves are associated with 

mid-to high-elevation montane forests 

and adjacent grasslands rather than 

areas with more xeric conditions. 

Reduced water in the system, due to 

reduced summer base flow in streams, 

and the earlier onset of summer lowflow conditions, may reduce or localize 

big game populations in the summer 

months; such changes have the potential 

to adversely affect the wolf within the 

next 50 to 100 years through reductions 

or distributional shifts in wild ungulate 

populations. Information also suggests 

that mule deer may be more susceptible 

to climate change impacts that alter 

vegetation patterns than elk (deVoss and 

McKinney 2012, pp. 16–19), but elk are 

currently a much more important source 

of prey for Mexican wolves than mule 

deer. 

Both Mexican wolves and their 

primary prey (elk) may exhibit 

reasonable adaptive capacity (Dawson et 

al. 2011, p. 53), such that they could 

shift habitats in response to changing 

climatic conditions or potentially 

persist in place. Elk, which make up 

approximately 77 to 80 percent of the 

Mexican wolf’s diet in the experimental 

population, are known to be habitat 

generalists due to their association with 

wide variation in environmental 

conditions (Kuck 1999, p. 1). Both 

positive and negative impacts to elk 

from climate change have been 

hypothesized in the literature, although 

no specific regional research has been 

conducted (deVoss and McKinney 2012, 

p. 18). For example, if climate change 

results in decreased winter snow pack 

in the Colorado Plateau Region (which 

includes central Arizona and New 

Mexico), elk populations could expand 

in number due to milder winters and 

increased forage availability (National 

Wildlife Federation 2013, p. 14). 

Conversely, if migratory elk herds stop 

migrating in response to milder winters, 

increased elk densities in some areas 

could lead to higher levels of disease 

transmission between elk, which may 

increase mortality (ibid). With these 

types of positive and negative 

considerations in mind, several sources 

tentatively suggest that overall elk may 

respond favorably in range and 

population size to climate change 

(National Wildlife Federation 2013, p. 

14, deVoss and McKinney 2012, p. 19). 

In Mexico, elk are not present as a 

source of prey for Mexican wolves. 

Therefore, the effects of climate change 

on deer populations could be important 

for the establishment and maintenance 

of a wolf population there. Seasonal 

decreases in precipitation and resulting 

changes in vegetation quality and 

availability could lead to the same type 

of impacts to ungulates as hypothesized 

in the United States, such as range 

contraction or decreasing populations. 

However, as with Factors A–D and 

because our focus in this analysis is on 

currently occupied range, the absence of 

a Mexican wolf population in Mexico 

precludes analysis of climate change 

there. 

Therefore, based on the relatively low 

vulnerability and sensitivity of the 

Mexican wolf to changes in climate, and 

the potential for elk to respond 

favorably to climate change in this 

region, we conclude that climate change 

is not substantially affecting the 

Mexican wolf at the current time nor do 

we expect it to do so in the future. 

Summary of Factor E 

Inbreeding, loss of adaptive potential, 

loss of heterozygosity, and small 

population size are significantly 

affecting the Mexican wolf. Inbreeding 

and loss of heterozygosity have the 

potential to affect viability-related 

fitness traits in Mexican wolves and, 

therefore, to affect the persistence of the 

subspecies in the wild in the near term; 

loss of genetic variation (adaptive 

potential) significantly affects the 

likelihood of persistence of the Mexican 

wolf over longer timeframes. Absent the 

protection of the Act, inbreeding, loss of 

heterozygosity, and loss of adaptive 

potential would persist and possibly 

increase depending on whether the 

States or other parties undertook active 

promotion of the maintenance of gene 

diversity. 

The small size of the Mexican wolf 

experimental population results in a 

high risk of extinction due to the 

susceptibility of the population to 

stochastic demographic events. The 

minimum estimated population of 83 

Mexican wolves at the end of 2013 is 

not a sufficient size to ensure 

persistence into the future. Absent the 

protection of the Act, small population 

size would continue to significantly 

affect the Mexican wolf, or may increase 

if States or other parties did not actively 

support the experimental population 

through appropriate management 

measures. Intolerance by humans, landuse conflicts, hybridization, and climate 

change are not significantly affecting the 

Mexican wolf, nor are they expected to 

do so in the future. Vehicular collision 

is not significantly affecting the 

Mexican wolf; however, we expect that 

this source of mortality may increase in 

the future due to wolf dispersal and 

occupancy in areas of higher road 

density than currently occupied habitat. 

We do not have data to estimate how 

significant this may become. 

Combination of Factors/Focus on 

Cumulative Effects 

In the preceding review of the five 

factors, we found that the Mexican wolf 

is most significantly affected by illegal 

killing, inbreeding, loss of 

heterozygosity, loss of adaptive 

potential, and small population size. In 

absence of the Act’s protections, these 

issues would continue to affect the 

Mexican wolf, and would likely 

increase in frequency or severity. We 

also identify several potential sources of 

mortality or risk (disease, vehicular 

collision, wildfire, hybridization, etc.) 

that we do not currently consider to be 

significantly affecting the Mexican wolf 

due to their low occurrence, minimal 

impact on the population, or lack of 

information. However, we recognize 

that multiple sources of mortality or risk 

acting in combination have greater 

potential to affect the Mexican wolf than 

each factor alone. Thus, we consider 

how factors that, by themselves may not 

have a significant effect on the Mexican 

wolf, may affect the subspecies when 

considered in combination. 

The small population size of the 

Mexican wolf exacerbates the potential 

for all other factors to 

disproportionately affect the Mexican 

wolf. The combined effects of 

demographic, genetic, environmental, 

and catastrophic events to a small 

population can create an extinction 

vortex—an unrecoverable population 

decline—that results in extinction. 

Small population size directly and 

significantly increases the likelihood of 

inbreeding depression, which has been 

documented to decrease individual 

fitness, hinder population growth, and 

decrease the population’s probability of 

persistence. Small population size also 

increases the likelihood that concurrent 

mortalities from multiple causes that 

individually may not be resulting in a 

population decline (e.g., vehicular 

collisions, natural sources of mortality) 


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could collectively do so, depending on 

the population’s productivity, especially 

when additive to an already significant 

source of mortality, such as illegal 

shooting. Effects from disease, 

catastrophe, environmental conditions, 

or loss of heterozygosity that normally 

could be sustained by a larger, more 

resilient population have the potential 

to rapidly affect the size, growth rate, 

and genetic integrity of the small 

experimental population when they act 

in combination. Therefore we consider 

the combination of factors C, D, and E 

to be significantly affecting the Mexican 

wolf. 

Summary of Five-Factor Analysis 

We do not find habitat destruction, 

curtailment, or modification to be 

significantly affecting the Mexican wolf 

now, nor do we find that these factors 

are likely to do so in the future 

regardless of whether the subspecies is 

protected by the Act. The size and 

federally protected status of the 

National Forests in Arizona and New 

Mexico are adequate and appropriate for 

the reintroduction project. These 

National Forests provide secure habitat 

with an adequate prey base and habitat 

characteristics to support the current 

wolf population. The Wallow Fire and 

the Whitewater-Baldy Complex Fire, 

while catastrophic, were not sources of 

habitat modification, destruction, or 

curtailment that affected the Mexican 

wolf because there were no documented 

wolf mortalities during the fires, and 

prey populations are expected to 

increase in response to post-fire positive 

effects on vegetation. 

We do not find overutilization for 

commercial, recreational, scientific, or 

educational purposes to be significantly 

affecting the Mexican wolf because we 

have no evidence to indicate that legal 

killing or removal of wolves from the 

wild for commercial, recreational (i.e., 

hunting), scientific, or educational 

purposes is occurring. The killing of 

wolves for their pelts is not known to 

occur, and Mexican wolf researchrelated mortalities are minimal or 

nonexistent. Incidents of injuries and 

mortalities from trapping (for other 

animals) have been low. In absence of 

Federal protection, State regulations in 

Arizona and New Mexico, and Federal 

regulations in Mexico, could provide 

regulations to protect Mexican wolves 

from overutilization. Overutilization of 

Mexican wolves would not likely 

increase if they were not listed under 

the Act due to the protected status they 

would be afforded by the States and 

Mexico. 

Based on known disease occurrences 

in the current population and the active 

vaccination program, we do not 

consider disease to be significantly 

affecting the Mexican wolf. Absent the 

protection of the Act, a similar 

vaccination program would need to be 

implemented by the States or other 

parties, or the potential for disease to 

significantly affect the Mexican wolf 

could increase. 

Predation (by nonhuman predators) is 

not significantly affecting the Mexican 

wolf. No wild predator regularly preys 

on wolves, and only a small number of 

predator-related wolf mortalities have 

been documented in the current 

Mexican wolf experimental population. 

We do not consider predation likely to 

significantly affect the Mexican wolf in 

the future or if the subspecies was not 

protected by the Act. 

Illegal shooting is identified as 

significantly affecting the Mexican wolf 

and is a significant threat. Adequate 

regulatory protections are not available 

to protect Mexican wolves from illegal 

shooting without the protection of the 

Act. We would expect shooting of 

Mexican wolves to increase if they were 

not federally protected, as State 

penalties (assuming Mexican wolves 

were maintained as State-protected) are 

less than Federal penalties. 

Inbreeding, loss of heterozygosity, 

loss of adaptive potential, and small 

population size are significantly 

affecting the Mexican wolf. We 

recognize the importance of the captive 

management program and the active 

reintroduction project and recovery 

program in addressing these issues. 

Absent the protection of the Act, their 

effects on Mexican wolf would 

continue, or possibly increase 

depending on the degree of active 

management provided by the States or 

other parties. 

Vehicular collisions, intolerance by 

humans, land-use conflicts, 

hybridization, and climate change are 

not significantly affecting the Mexican 

wolf, nor are they expected to do so in 

the near future or if the Mexican wolf 

was not protected by the Act. 

Climate change is not significantly 

affecting the Mexican wolf nor would it 

do so in the absence of the Act’s 

protections. The effects of climate 

change may become more pronounced 

in the future, but as is the case with all 

stressors that we assess, even if we 

conclude that a species or subspecies is 

currently affected or is likely to be 

affected in a negative way by one or 

more climate-related impacts, it does 

not necessarily follow that these effects 

are significant to the species or 

subspecies. The habitat generalist 

characteristics of the wolf and their 

primary prey, elk, lead us to conclude 

that climate change will not 

significantly affect the Mexican wolf in 

the future. 

The cumulative effects of factors that 

increase mortality and decrease genetic 

diversity are significantly affecting the 

Mexican wolf, particularly within the 

context of its small population size (a 

characteristic that significantly 

decreases the probability of a 

population’s persistence). The 

cumulative effects of these threats are 

significantly affecting the Mexican wolf 

at the current time and likely will 

continue to do so in the future. Absent 

the protection of the Act, the cumulative 

effects of these threats may increase due 

to the potential for more killing of 

Mexican wolves, increased risk of 

inbreeding, and other sources of 

mortality, all exacerbated by the 

Mexican wolf’s small population size. 

Determination 

Section 4 of the Act (16 U.S.C. 1533), 

and its implementing regulations at 50 

CFR part 424, set forth the procedures 

for adding species to the Federal Lists 

of Endangered and Threatened Wildlife 

and Plants. Under section 4(a)(1) of the 

Act, we may list a species, subspecies, 

or DPS based on (A) The present or 

threatened destruction, modification, or 

curtailment of its habitat or range; (B) 

Overutilization for commercial, 

recreational, scientific, or educational 

purposes; (C) Disease or predation; (D) 

The inadequacy of existing regulatory 

mechanisms; or (E) Other natural or 

manmade factors affecting its continued 

existence. Listing actions may be 

warranted based on any of the above 

threat factors, singly or in combination. 

We have carefully assessed the best 

scientific and commercial data available 

regarding the past, present, and future 

threats to the Mexican wolf and have 

determined that the subspecies warrants 

listing as endangered throughout its 

range. As required by the Act, we 

considered the five potential threat 

factors to assess whether the Mexican 

wolf is endangered or threatened 

throughout its range. Based on our 

analysis, we find that the Mexican wolf 

is in danger of extinction throughout all 

of its range due to small population size, 

illegal killing, inbreeding, loss of 

heterozygosity and adaptive potential, 

and the cumulative effect of all threats. 

Also, existing regulatory mechanisms 

are not adequate to ensure the survival 

of the Mexican wolf. 

Our finding that the Mexican wolf is 

in danger of extinction throughout all of 

its range is consistent with our 

administrative approach to determining 

which subspecies are on the brink of 

extinction and, therefore, warrant listing 


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as endangered. Prior to the early 1900s, 

the Mexican wolf was distributed over 

a large geographic area that included 

portions of the Southwest and much of 

Mexico. The Mexican wolf was nearly 

eliminated in the wild by the mid1900’s due to predator eradication 

efforts, which led to its listing as an 

endangered subspecies in 1976 and 

again as part of the species-level gray 

wolf listing in 1978. Therefore, the 

Mexican wolf is a subspecies that was 

formerly widespread but was reduced to 

such critically low numbers and 

restricted range (i.e., eliminated in the 

wild) that it is at high risk of extinction 

due to threats that would not otherwise 

imperil it. 

At the time of its initial listing, no 

robust populations of Mexican wolves 

remained in the wild. The establishment 

and success of the captive-breeding 

program temporarily prevented 

immediate absolute extinction of the 

Mexican wolf and, by producing surplus 

animals, has enabled us to undertake 

the reestablishment of Mexican wolves 

in the wild by releasing captive animals 

into the experimental population. In the 

context of our current proposal to list 

the Mexican wolf as an endangered 

subspecies, we recognize that, even with 

these significant improvements in the 

Mexican wolf’s status, its current 

geographic distribution is a very small 

portion of its former range. Moreover, 

within this reduced and restricted 

range, the Mexican wolf faces 

significant threats that are intensified by 

its small population size. The Mexican 

wolf is highly susceptible to inbreeding, 

loss of heterozygosity, and loss of 

adaptive potential due to the bottleneck 

created during its extreme population 

decline prior to protection by the Act, 

the limited number of and relatedness of 

the founders of the captive population, 

and the loss of some genetic material 

from the founders. The effects of 

inbreeding have been documented in 

Mexican wolves and require active, 

ongoing management to minimize. 

Mexican wolf mortality from illegal 

killing, as well as all other sources of 

mortality or removal from the wild 

experimental population, is occurring 

within the context of a small 

population. Smaller populations have 

low probabilities of persistence 

compared to larger, more geographically 

widespread populations. Absent the 

protection of the Act, illegal killing 

would likely increase dramatically, 

further reducing the population’s size 

and increasing its vulnerability to 

genetic and demographic factors, 

putting the Mexican wolf at imminent 

risk of extinction. These factors are 

occurring throughout the Mexican 

wolf’s range in the wild, resulting in our 

determination that the subspecies 

warrants listing as endangered 

throughout its range. 

After a thorough review of all 

available information and an evaluation 

of the five factors specified in section 

4(a)(1) of the Act, as well as 

consideration of the definitions of 

‘‘threatened species’’ and ‘‘endangered 

species’’ contained in the Act and the 

reasons for delisting as specified in 50 

CFR 424.11(d), we revise the List of 

Endangered and Threatened Wildlife 

(50 CFR 17.11) by listing the Mexican 

wolf subspecies (Canis lupus baileyi) as 

endangered. The Mexican wolf is in 

danger of extinction throughout all of its 

range and thus warrants the protections 

of the Act. Listing the entire Mexican 

wolf subspecies means that all members 

of the taxon are afforded the protections 

of the Act regardless of where they are 

found. 

The Act defines an endangered 

species as any species that is ‘‘in danger 

of extinction throughout all or a 

significant portion of its range’’ and a 

threatened species as any species ‘‘that 

is likely to become endangered 

throughout all or a significant portion of 

its range within the foreseeable future.’’ 

We find that the Mexican wolf is in 

danger of extinction throughout all of its 

range due to illegal killing, inbreeding, 

loss of heterozygosity, loss of adaptive 

potential, small population size, and the 

cumulative effects of factors C, D, and 

E. Historically, the Mexican wolf was 

distributed across portions of the 

southwestern United States and 

northern and central Mexico. The 

subspecies may have also ranged north 

into southern Utah and southern 

Colorado within zones of intergradation 

where interbreeding with other gray 

wolf subspecies may have occurred 

(Leonard et al. 2005, pp. 15–16). The 

Mexican wolf was near extinction prior 

to protection by the Act in the 1970’s, 

such that the captive-breeding program 

was founded with only seven wolves. 

Although our recovery efforts for the 

Mexican wolf, which are still under 

way, have led to the reestablishment of 

a wild population in the United States, 

the single, small population of Mexican 

wolves would face an imminent risk of 

extinction from the cumulative effects of 

small population size, inbreeding, and 

illegal shooting, without the protection 

of the Act. Absent protection by the Act, 

regulatory protection, especially against 

illegal killing, would not be adequate to 

ensure the survival of the Mexican wolf. 

Therefore, on the basis of the best 

available scientific and commercial 

information, we list the Mexican wolf as 

endangered in accordance with sections 

3(6) and 4(a)(1) of the Act. We find that 

a threatened subspecies status is not 

appropriate for the Mexican wolf 

because of the contracted range, because 

the threats are occurring rangewide and 

are not localized, and because the 

threats are ongoing and expected to 

continue into the future. 

Under the Act and our implementing 

regulations, a subspecies may warrant 

listing if it is endangered or threatened 

throughout all or a significant portion of 

its range. The threats to the survival of 

the Mexican wolf occur throughout its 

range and are not restricted to any 

particular significant portion of that 

range. Accordingly, our assessment and 

proposed determination applies to the 

Mexican wolf throughout its entire 

range. 

Effects of the Rule 

This final rule lists the Mexican wolf 

as an endangered subspecies. As a 

matter of procedure, in a separate but 

concurrent rulemaking published in this 

Federal Register, we also finalize the 

revision to the regulations for the 

nonessential experimental population of 

the Mexican wolf to ensure appropriate 

association of the experimental 

population with this Mexican wolf 

subspecies listing. 

Required Determinations 

National Environmental Policy Act 

We determined that an environmental 

assessment or an environmental impact 

statement, as defined under the 

authority of the National Environmental 

Policy Act of 1969, need not be 

prepared in connection with regulations 

adopted pursuant to section 4(a) of the 

Act. We published a notice outlining 

our reasons for this determination in the 

Federal Register on October 25, 1983 

(48 FR 49244). 

Paperwork Reduction Act of 1995 

Office of Management and Budget 

(OMB) regulations at 5 CFR part 1320, 

which implement provisions of the 

Paperwork Reduction Act (44 U.S.C. 

3501 et seq.), require that Federal 

agencies obtain approval from OMB 

before collecting information from the 

public. This rule does not contain any 

new collections of information that 

require approval by OMB under the 

Paperwork Reduction Act. This rule will 

not impose recordkeeping or reporting 

requirements on state or local 

governments, individuals, businesses, or 

organizations. An agency may not 

conduct or sponsor, and a person is not 

required to respond to, a collection of 

information unless it displays a 

currently valid OMB control number. 


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Government-to-Government 

Relationship With Tribes 

In accordance with the President’s 

memorandum of April 29, 1994, 

Government-to-Government Relations 

with Native American Tribal 

Governments (59 FR 22951), E.O. 13175, 

and the Department of the Interior’s 

manual at 512 DM 2, we readily 

acknowledge our responsibility to 

communicate meaningfully with 

recognized Federal Tribes on a 

government-to-government basis. In 

accordance with Secretarial Order 3206 

of June 5, 1997 (American Indian Tribal 

Rights, Federal-Tribal Trust 

Responsibilities, and the Endangered 

Species Act), we readily acknowledge 

our responsibilities to work directly 

with Tribes in developing programs for 

healthy ecosystems, to acknowledge that 

tribal lands are not subject to the same 

controls as Federal public lands, to 

remain sensitive to Indian culture, and 

to make information available to Tribes. 

We have coordinated with affected 

Tribes through correspondence and 

meetings in order to both (1) provide 

them with an understanding of the 

changes, and (2) to understand their 

concerns with those changes. We fully 

considered all of the comments on the 

proposed rule that were submitted by 

Tribes and Tribal members during the 

public comment period, and we 

addressed those concerns, new data, 

and new information where appropriate. 

References Cited 

A complete list of all references cited 

in this document is posted on http://

www.regulations.gov at Docket No. 

FWS–HQ–ES–2013–0073 and available 

upon request from the New Mexico 

Ecological Services Field Office, 

Albuquerque, NM (see FOR FURTHER

INFORMATION CONTACT). 

Data Quality Act 

In developing this rule we did not 

conduct or use a study, experiment, or 

survey requiring peer review under the 

Data Quality Act (Pub. L. 106–554). 

Authors 

The primary authors of this rule are 

the staff members of the Mexican Wolf 

Recovery Program (see FOR FURTHER

INFORMATION CONTACT). 

List of Subjects in 50 CFR Part 17 

Endangered and threatened species, 

Exports, Imports, Reporting and 

recordkeeping requirements, 

Transportation. 

Regulation Promulgation 

For the reasons set forth in the 

preamble, the Service amends 50 CFR 

part 17 as follows: 

PART 17—[AMENDED] 

■ 1. The authority citation for part 17 

continues to read as follows: 

Authority: 16 U.S.C. 1361–1407; 1531– 

1544; and 4201–4245, unless otherwise 

noted. 

■ 2. Amend § 17.11(h) in the List of 

Endangered and Threatened Wildlife 

under Mammals by: 

■ a. Revising the entry for ‘‘Wolf, gray 

(Canis lupus)’’; and 

■ b. Adding two entries for ‘‘Wolf, 

Mexican (Canis lupus baileyi)’’ in 

alphabetic order. 

The revision and additions read as 

follows: 

§ 17.11 Endangered and threatened 

wildlife. 

* * * * * 

(h) * * * 

Species 

Historic range Vertebrate population where endangered 

or threatened Status When listed Critical habitat 

Special 

rules Common name Scientific name 

Mammals 

* * * * * * * 

Wolf, gray ................. Canis lupus ............. Holartic .................... U.S.A.: All of AL, AR, CA, CO, CT, DE, 

FL, GA, KS, KY, LA, MA, MD, ME, 

MO, MS, NC, NE, NH, NJ, NV, NY, 

OK, PA, RI, SC, TN, TX, VA, VT and 

WV; and portions of AZ, IA, IN, IL, ND, 

NM, OH, OR, SD, UT, and WA as follows: (1) Northern AZ (that portion 

north of the centerline of Interstate 

Highway 40); (2) Southern IA, (that 

portion south of the centerline of Highway 80); (3) Most of IN (that portion 

south of the centerline of Highway 80); 

(4) Most of IL (that portion south of the 

centerline of Highway 80); (5) Western 

ND (that portion south and west of the 

Missouri River upstream to Lake 

Sakakawea and west of the centerline 

of Highway 83 from Lake Sakakawea 

to the Canadian border); (6) Northern 

NM (that portion north of the centerline 

of Interstate Highway 40); (7) Most of 

OH (that portion south of the centerline 

of Highway 80 and east of the 

Maumee River at Toledo); (8) Western 

OR (that portion of OR west of the 

centerline of Highway 395 and Highway 78 north of Burns Junction and 

that portion of OR west of the centerline of Highway 95 south of Burns 

Junction); (9) Western SD (that portion 

south and west of the Missouri River); 

(10) Most of Utah (that portion of UT 

south and west of the centerline of 

E 1, 6, 13, 15, 35 NA NA 


rljohnson on DSK3VPTVN1PROD with RULES2
2512 Federal Register / Vol. 80, No. 11 / Friday, January 16, 2015 / Rules and Regulations 

Species 

Historic range Vertebrate population where endangered 

or threatened Status When listed Critical habitat 

Special 

rules Common name Scientific name 

Highway 84 and that portion of UT 

south of Highway 80 from Echo to the 

UT/WY Stateline); and (11) Western 

WA (that portion of WA west of the 

centerline of Highway 97 and Highway 

17 north of Mesa and that portion of 

WA west of the centerline of Highway 

395 south of Mesa). Mexico 

* * * * * * * 

Wolf, Mexican ........... Canis lupus baileyi Southwestern 

United States and 

Mexico.

Entire, except where included in an experimental population as set forth in 

17.84(k).

E .......................... NA NA 

Wolf, Mexican ........... Canis lupus baileyi Southwestern 

United States and 

Mexico.

U.S.A. (portions of AZ and NM)—see 

17.84(k).

XN .......................... NA 17.84(k) 

*******

* * * * * 

Dated: January 7, 2015. 

Stephen Guertin, 

Director, U.S. Fish and Wildlife Service. 

[FR Doc. 2015–00441 Filed 1–15–15; 8:45 am] 

BILLING CODE 4310–55–P 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

[Docket No. FWS–R2–ES–2013–0056; 

FXES11130900000–156–FF09E42000] 

RIN 1018–AY46 

Endangered and Threatened Wildlife 

and Plants; Revision to the 

Regulations for the Nonessential 

Experimental Population of the 

Mexican Wolf 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Final rule. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), revise the 

regulations for the nonessential 

experimental population of the Mexican 

wolf (Canis lupus baileyi) under section 

10(j) of the Endangered Species Act of 

1973, as amended. This action is being 

taken in coordination with our final rule 

in this Federal Register to list the 

Mexican wolf as an endangered 

subspecies. The regulatory revisions in 

this rule will improve the project to 

reintroduce a nonessential experimental 

population, thereby increasing potential 

for recovery of this species. 

DATES: This rule becomes effective 

February 17, 2015. 

ADDRESSES: This final rule, along with 

the public comments, environmental 

impact statement (EIS), and record of 

decision, are available on the Internet at 

http://www.regulations.gov, Docket No. 

FWS–R2–ES–2013–0056 or from the 

office listed in FOR FURTHER INFORMATION

CONTACT. 

FOR FURTHER INFORMATION CONTACT: 

Sherry Barrett, Mexican Wolf Recovery 

Coordinator, U.S. Fish and Wildlife 

Service, New Mexico Ecological 

Services Field Office, 2105 Osuna Road 

NE., Albuquerque, NM 87113; by 

telephone 505–761–4704; or by 

facsimile 505–346–2542. If you use a 

telecommunications device for the deaf 

(TDD), call the Federal Information 

Relay Service (FIRS) at 800–877–8339. 

Further contact information can be 

found on the Mexican Wolf Recovery 

Program’s Web site at http://

www.fws.gov/southwest/es/

mexicanwolf/. 

SUPPLEMENTARY INFORMATION: 

Executive Summary 

Why we need to publish a rule. We are 

revising the regulations under the 

Endangered Species Act of 1973 (16 

U.S.C. 1531 et seq.) (Act or ESA) that 

established the experimental population 

of the Mexican wolf (Canis lupus 

baileyi) to further its conservation by 

improving the effectiveness of the 

reintroduction project in managing the 

experimental population. We intend to 

do this by: (1) Modifying the geographic 

boundaries in which Mexican wolves 

are managed south of Interstate-40 in 

Arizona and New Mexico under section 

10(j) of the Act; (2) modifying the 

management regulations that govern the 

initial release, translocation, removal 

and take of Mexican wolves; and (3) 

issuing a permit under section 

10(a)(1)(A) of the Act for management of 

Mexican wolves both inside and outside 

of the Mexican Wolf Experimental 

Population Area (MWEPA). Revisions to 

the regulations, which were 

promulgated in 1998, and the section 

10(a)(1)(A) permit are needed because: 

(1) Under the current regulations we 

will not be able to achieve the necessary 

population growth, distribution, and 

recruitment that would contribute to the 

persistence of, and improve the genetic 

variation within, the experimental 

population; (2) there is a potential for 

Mexican wolves to disperse into 

southern Arizona and New Mexico from 

reintroduction areas in the States of 

Sonora and Chihuahua in northern 

Mexico; and (3) certain provisions lack 

clarity, are inadequate, or limit the 

efficacy and flexibility of our 

management of the experimental 

population of Mexican wolves. 

Also, this final rule is necessitated by 

a related action we are taking to classify 

the Mexican wolf as an endangered 

subspecies. The Mexican wolf has been 

listed under the Act in the Code of 

Federal Regulations (CFR) at 50 CFR 

17.11(h) as part of the gray wolf (Canis 

lupus) listing since 1978. Therefore, 

when we designated the Mexican wolf 

experimental population in 1998 (1998 

Final Rule; 63 FR 1752, January 12, 

1998), it corresponded to the gray wolf 

listing in even though it was specific to 

our Mexican wolf recovery effort. With 

this publication of the final rule to list 

the Mexican wolf as an endangered 

subspecies, we need to revise 50 CFR 

17.11(h) such that the experimental 

population will be associated with the 

Mexican wolf subspecies listing rather 

than with the gray wolf species. 


rljohnson on DSK3VPTVN1PROD with RULES2