Mexican Gray Wolf

Canis lupus baileyi

Description

The Mexican gray wolf, Canis lupus baileyi, is an endangered subspecies of gray wolf that was extirpated from the southwestern United States by 1970. The gray wolf species (C. lupus) is native to most of North America north of Mexico City. An exception is in the southeastern United States, which was occupied by the red wolf species (C. rufus).

In physical appearance the gray wolf, Canis lupus, resembles a large domestic dog, such as the Alaskan malamute. It is larger than the endangered red wolf. Adult males average about 95 lb (43 kg), and can weigh as much as 175 lb (80 kg). Females are smaller, averaging about 80 lb (36 kg), but can get as large as 125 lb (57 kg). The gray wolf's markings vary with both habitat and season; it is usually gray with black speckles and a yellowish underbelly and stockings. Entirely black or white wolves occur in northern Canada and Alaska.

Behavior

The gray wolf is strongly social and territorial. It typically hunts a territory in a pack consisting of several or as many as 20 members, depending on the abundance of prey species. A pack can range as far as 100 mi (160 km) in search of prey. When on the hunt, wolves shelter for sleep in rocky crevices or in thick underbrush; in open country they may dig protective holes.

Life within a wolf pack is highly regulated. A strict social hierarchy, with distinct dominance and subordinance, governs each animal's behavior. Hunting, breeding, and pup rearing require a high degree of group cooperation, but males compete vigorously for rank within each pack. Each pack is led by a pair of co-dominant wolves, the alpha-male and alpha-female. Leadership in hunting, feeding, and reproduction is assumed by the alpha pair, which mates for life. Usually the alpha pair is the only pair in the pack to mate and reproduce. Subordinate wolves are harassed and discouraged from mating by the dominant pair. Subordinate males who challenge the alpha-male are often driven out of the pack. This ejected male or "lone wolf" might encounter a solitary young female and start a new pack in an uncontested area. Sometimes, competition within a pack or a lack of prey causes a pack to split into smaller packs.

The gray wolf is a fierce carnivore. It is the primary predator on large, hoofed mammals, such as moose, elk, or deer. Wolves can bring down these large animals because the disciplined pack is able to coordinate and sustain its attack, often wearing down the prey animal. Wolves can run for hours at a time, sometimes at speeds of 20-25 mph (32-40 kph).

Yet wolves do not kill indiscriminately. When stalking a herd of moose or elk, they identify weaker members of the herd-usually young, aged, or sick animals-separate one of them from the herd, then encircle and kill it. If a pursued animal fights back with any spirit, the pack will often abandon its attack and seek a more acquiescent prey. Hunting packs have been observed to make more than a dozen forays at different herds before finally making a kill.

When another species of prey—deer, for example—is more plentiful in the territory than moose or elk, a wolf pack will generally kill a higher proportion of deer, leaving much of the carcass uneaten, allowing other animals to feed on the carcass.

Hunting behaviors such as these are considered by some biologists to be beneficial to prey populations, since the weeding out of weak animals maintains herd vigor and controls explosive population growth.

When larger prey is unavailable, gray wolves will feed on smaller animals, such as beavers, rodents, domestic animals, or even carrion. Overall, the size of the wolf population of any area is tied closely to the availability of prey. Wolves would not completely eliminate a caribou herd into extinction, as some have suggested, but would switch to other prey species, split up the pack, or otherwise limit the number of animals in the territory.

The breeding season of the wolf is from January to March. After a gestation period of about 60 days, the alpha-female bears a litter that averages seven pups. The female prepares a den for whelping and suckles the pups, which are born blind and helpless. The pups' eyes open after about a week. After about ten weeks, the mother returns to hunt with the pack, leaving her playful pups with another, usually younger, female.

During the summer, after pups are weaned and while they are still too young to join the hunting pack, they remain at a series of "rendezvous sites." The mother returns regularly to regurgitate food for them. A number of these sites are used by the pack until the fall when the pups are mature enough to travel with the adults. Young wolves become fully mature in two to three years and learn to hunt from both parents. Wolves can live as long as ten years in the wild and slightly longer in captivity.

Some naturalists cite the wolf's cooperative group behavior and its territoriality as evidence that it is the ancestor of the domestic dog. The dog shares similar behaviors, and there has certainly been scattered interbreeding between wolves and dogs in the past. The wolf, however, is not suited for domestication because when brought into captivity it treats humans as packmates and will fight them for social rank and dominance. It is suspected that this is the reason wolves raised by humans will sometimes attack their owners unprovoked.

Habitat

The gray wolf occupies areas that supported populations of hoofed mammals (ungulates), its major food source.

Distribution

The Mexican gray wolf historically occurred over much of New Mexico, Arizona, Texas, and northern Mexico, mostly in or near forested, mountainous terrain.

The subspecies is now considered extirpated from its historic range in the south western United States because no wild wolf has been confirmed since 1970. Occasional sightings of "wolves" continue to be reported from U.S. locations, but none have been confirmed. Ongoing field research has not confirmed that wolves remain in Mexico.

Threats

Mexican wolves were eradicated before their natural history had been systematically studied. The decline of this subspecies is believed to coincide with the reasons for the decline of all North American wolves, primarily hunting and systematic eradication by humans. Numbering in the thousands before European settlement, the "lobo" declined rapidly when its reputation as a livestock killer led to concerted eradication efforts. Other factors contributing to its decline were commercial and recreational hunting and trapping, killing of wolves by game managers on the theory that more game animals would be available for hunters, habitat alteration, and human safety concerns, although no documentation exists of Mexican wolf attacks on humans.

Conservation and Recovery

The Mexican Wolf Recovery Plan was adopted by the Directors of the Service and the Mexican Direccion General de la Fauna Silvestre in 1982. Its objective is to conserve and ensure survival of the sub-species by maintaining a captive breeding program and reestablishing a viable, self-sustaining population of at least 100 Mexican wolves in a 5,000-sq mi (129,500-sq km) area within the subspecies' historic range. The plan guides recovery efforts for the sub-species, laying out a series of recommended actions. The recovery plan is currently being revised.

A captive breeding program was initiated with the capture of five wild Mexican wolves between 1977 and 1980, from Durango and Chihuahua, Mexico. Three of these animals (two males and a female that was pregnant when captured) produced off-spring, founding the "certified" captive lineage. Two additional captive populations were determined in July 1995 to be pure Mexican wolves— each has two founders. The captive population included 148 animals as of January 1997—119 are held at 25 facilities in the United States and 29 at five facilities in Mexico.

In 1998 the U.S. Fish and Wildlife Service (FWS) decided to reintroduce the Mexican gray wolf into the Blue Range Wolf Recovery Area, a designatd area within the subspecies' probable historic range. This reintroduction will be the first step toward recovery of the Mexican wolf in the wild. The Blue Range Wolf Recovery Area consists of the entire Apache and Gila National Forests in east-central Arizona and west-central New Mexico. If the FWS later finds it to be both necessary for recovery and feasible, it will reintroduce wolves into the White Sands Wolf Recovery Area, which also lies within the subspecies' probable historic range. This area consists of all land within the boundary of the White Sands Missile Range in south-central New Mexico together with designated land immediately to the west of the missile range.

Captive Mexican wolves are selected for release based on genetics, reproductive performance, behavioral compatibility, response to the adaptation process, and other factors. Selected wolves have been moved to the FWS's captive wolf management facility on the Sevilleta National Wildlife Refuge in central New Mexico where they have been paired based on genetic and behavioral compatibility and measures are being taken to adapt them to life in the wild. As wolves are moved to release pens, more will be moved to the Sevilleta facility. Additional wolves for reintroduction may be obtained from selected cooperating facilities that provide an appropriate captive environment.

Initially, wolves will be reintroduced by a "soft release" approach designed to reduce the likelihood of quick dispersal away from the release areas. This involves holding the animals in pens at the release site for several weeks in order to acclimate them and to increase their affinity for the area.

In the Blue Range Wolf Recovery Area, approximately 14 family groups have been released over a period of five years, with the goal of reaching a population of 100 wild wolves. Approximately five family groups of captive raised Mexican wolves will be released over a period of three years into the White Sands Wolf Recovery Area, if this back-up area is used, with the goal of reaching a population of 20 wolves.

Contact

Mexican Gray Wolf Recovery Program
U.S. Fish and Wildlife Service
P.O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6920
Fax: (505) 248-6922

Reference

U.S. Fish and Wildlife Service. 12 January 1998. "Establishment of a Nonessential Experimental Population of the Mexican Gray Wolf in Arizona and New Mexico." Federal Register 63 (7): 1752-1772