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Mexican Gray Wolf
(Canis lupus baileyi)

Three males and five females—all siblings. The wolves, born in April 2008, arrived at Brookfield Zoo in November 2010 from the Endangered Wolf Center in Eureka, Missouri.

Until 1998, when reintroduction efforts began, Mexican gray wolves were considered extinct in the wild. (There once were approximately 4,000 wolves in their historic range.) In May 1976, the species was listed on the Endangered Species List by the U.S. Fish & Wildlife Service (USFWS).

Mexican gray wolves are part of a captive breeding program that is managed with the U.S. Fish & Wildlife Service by the Association of Zoos and Aquariums (AZA) under its Species Survival Plan (SSP) and the Mexican Technical Advisory Subcommittee for the Conservation of Mexican Wolves. Currently, there are 283 Mexican gray wolves in 52 institutions across the United States. The 2011 census recorded a minimum count of 57 individuals in the wild in New Mexico and Arizona, and in October 2011 five wolves were released for the first time in the Northern Mexican state of Sonora.

The reintroduction of Mexican gray wolves to the wild is a cooperative, multi-agency partnership between U.S. Fish & Wildlife Service and the Arizona Game and Fish Department, New Mexico Department of Game and Fish, White Mountain Apache Tribe, USDA Forest Service, and USDA Animal and Plant Health Inspection Service - Wildlife Services, as well as private organizations.

The species is also listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), an international treaty with more than 144 member countries. Species listed on Appendix I cannot be traded commercially. Killing a Mexican gray wolf is a violation of the federal Endangered Species Act and can invoke criminal penalties of up to $25,000 and/or six months in jail or a civil penalty of up to $25,000.

Natural Habitat
Historically, Mexican gray wolves’ habitat in the wild ranged from central and northern Mexico to western Texas, southern New Mexico, and central Arizona. Today, the species has been reintroduced to the Apache National Forest in southeastern Arizona and the adjacent Gila National Forest in western New Mexico, and as mentioned above, for the first time in the northern Mexican state of Sonora. They live in mountain forests, grasslands, and shrublands. (They are not low desert dwellers.)

Mexican gray wolves are the smallest subspecies of North American gray wolves. (Some other subspecies of gray wolves are commonly called timber wolves, Arctic wolves, tundra wolves, and Great
Plains wolves.) Commonly referred to as “los lobos,” Mexican gray wolves can be tawny, gray, and/or buff with various darker markings. Wolves vary in color, depending on their region. Their face and underparts have whitish to cream markings. The back of their neck and the back and top half of their tail have a blanket of black streaked with shades of brown.

Their fur is long and thick, with two layers of coat. Their undercoat is thick, trapping air and providing insulation. Their visible top-coat is long and protects their undercoat from getting wet. They shed excessively in early spring. Wolves in the southern portions of their range have a thinner, shorter coat than wolves of northern regions. Their ears are erect and rounded. They have a short, thick muzzle and a large nose pad. They have long legs with large, strong feet, enabling them to travel long distances, grip the terrain in all weather conditions, bury food caches, and dig burrows.

Mexican gray wolves have 42 very strong teeth and powerful jaws that they use to hold their prey, cut tendons, and crush bones. A full-grown Mexican gray wolf is between 25 and 32 inches tall (shoulder height) and weighs between 60 and 80 pounds. (Males are larger than females.)

Social Behavior
Wolves have a very complex social structure. A pack usually consists of an alpha male and female (the breeding pair), yearlings from the previous year’s litter, and new pups. In the wild, most packs are made up of the breeding pair and their young of the last two years. As the parents, the breeding pair is dominant over all other pack members because the other members are their offspring. Young wolves usually leave the pack to start their own pack before they reach sexual maturity. There is no consistent dominance hierarchy among the young, so the social structure of most wild wolf packs is based on a dominant breeding pair and their subordinate offspring. In some packs, there may be other adult members that could be called the beta wolves.

Wolves are territorial and risk the chance of being killed if they trespass in another pack’s territory. The alpha pair marks its territory using raised-leg urination. The subordinates squat to urinate. Pack sizes average from two to 10 animals but can range to up to 20. They use a variety of vocalizations—howls, yips, squeals, growls, and barks—for communication, with the howl being the best known. They may howl upon awaking, to bring the pack together, before and after a kill, and for other reasons, including enjoyment. Facial expressions and body postures play an important role in communication. These behaviors include showing dominance and submission, courtship, threats, pouncing, and play, as well as greeting ceremonies with lots of licking.

Breeding Behavior
Usually only an alpha male and female produce one litter of pups a year. Males and females reach reproductive maturity at about 2 years old. During courtship, a female may approach a male and place her forepaws, neck, or head across his shoulders or greet him in a subordinate posture, then back up toward him with her tail raised as she moves in a feathery dance step. Breeding occurs from February through March. Following a gestation of about two months, four to six pups are born. The pair actively discourages mating between other pack members. However, in some cases multiple litters may be born in a pack due to the mating of a subordinate female. Although wolves often have long-lasting attachments to their mates, if one wolf dies, the widowed mate may breed with another wolf. A female seeks out a den from an already existing hole, hollow log, or cleft between rocks, usually preferring elevated areas near water. She then adds to it by digging a birthing tunnel with room enough for her to lie down. Once the pups are born, the alpha male is very protective of the den and often acts as a decoy, leading predators away from the site. Wolves have social bonding and care-giving behaviors that are second only to those of humans and primates.

Natural History of Young
Pups are born blind and deaf. Their coat is dark, making it almost impossible to see them in the den. At two weeks old, their eyes open. At three weeks, they begin to appear outside the den. They are weaned between six and eight weeks. They begin to eat solid, regurgitated food from the adults of the pack. Pups whine, nudge, nibble, or lick the face and corners of an adult’s mouth to encourage it to regurgitate. The pups start their learning process by exploring, pouncing on blowing leaves, and play-fighting.

Hunting and Feeding Strategies
Wolves use sight, sound, and smell to hunt. The outer perimeter of their retinas is extremely sensitive to movement, which is a great advantage for hunting at night. They have an incredible sense of smell, which they use to trail a deer and other game up to several miles away. After the lead animals start the chase, they concentrate their efforts on the most vulnerable prey—animals that are the youngest, oldest, or weakest in a herd. They stalk and move as close to the prey as possible, with the wind in their favor so that a prey animal does not smell them. They chase from behind, grabbing onto their prey’s rump, while a few wolves may go for the nose. They can run 25 to 40 miles per hour. They are successful in capturing prey in about one in 10 chases.

In spring, they consume a fawn or an elk calf in one meal, getting calcium from the bones, protein from the hooves, and fat and other nutrients from bone marrow. In fall, they eat beavers, which are a good source of fat that helps them gain weight for the winter months. They prey mostly on elk, deer, and rabbits during winter and summer.

Life Span
In the wild, they live from five to nine years. In a zoo or similar facility, they live an average of 13 to 14 years.

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