Canis lupus
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Status: Endangered, ESA (Arizona, part of Colorado, New Mexico, Oklahoma, Texas, part of Utah); Threatened, ESA (California, part of Colorado, Connecticut, Iowa, Idaho, Illinois, Indiana, Kansas, Massachusetts, Maine, Michigan, Minnesota, Missouri, Montana, North Dakota, Nebraska, New Hampshire, New Jersey, Nevada, New York, Ohio, Oregon, Pennsylvania, Rhode Island, South Dakota, part of Utah, Vermont, Washington, Wisconsin, Wyoming)
Range: Canada, USA

Wolf, gray

Canis lupus

Description and biology

The North American gray wolf, also known as the timber wolf, is the largest member of the canidae (dog) family. An average adult measures 5 to 6 feet (1.5 to 1.8 meters) from nose to tail, and stands 26 to 32 inches (66 to 81 centimeters) at its shoulder. It can weigh between 70 and 110 pounds (32 and 50 kilograms). Females are slightly smaller than males. The wolf’s coat is usually tan or a grizzled gray and black. Some wolves are all black or all white.
The gray wolf is well-adapted for hunting. It has long legs and keen senses of hearing and smell. The wolf is a carnivore,or meat-eater. It feeds on a variety of mammals from large hoofed animals such as elk and deer to smaller animals such as beavers and rabbits. It will also eat small rodents like mice. Wolves generally kill animals that are young, old, diseased, or deformed—those that are easy to capture. However, if the opportunity arises, the wolf will kill a healthy adult animal.
Wolves live in packs or family groups typically composed of a set of parents, their offspring, and other nonbreeding adults. The social structure within a pack is complex. The dominant male and female are both called alphas, but they may not mate with each other. The alpha female, who has the dominant role in the pack, will sometimes mate with a superior male (or superior males) in the pack. The hierarchy (pronounced HIGH-a-rar-key) or ranking of dominant and subordinate animals within a pack help it function as a unit.
The packs generally hunt within a specific territory. Territories may be as large as 50 square miles (130 square kilometers) or even extend to 1,000 square miles (2,590 square kilometers), depending on available food. Wolves communicate with fellow pack-mates and other wolf packs through facial and body postures, scent markings (urine and feces), and vocalizations, which include barks, whimpers, growls, and howls.
Gray wolves begin mating when they are two to three years old. A female digs a den or uses an existing shelter or structure in which to rear her pups for the first six weeks of their lives. In early spring, she gives birth to an average litter of six pups. The pups depend completely on their mother’s milk for the first month, then they are gradually weaned off the mother’s milk. By seven to eight months of age, when they are almost fully grown, the young wolves begin hunting with the adults. Often after one or two years of age, a young wolf will leave and try to form its own pack.

Habitat and current distribution

In North America, the gray wolf is found in wilderness forests and tundra areas of northern Canada and the United States (gray wolves are also found in small pockets in Europe, Asia, and the Middle East). A subspecies of the gray wolf, the Mexican gray wolf, once inhabited Mexico and the southwestern United States.
In the United States, the gray wolf is found primarily in Alaska (listed as neither endangered nor threatened) and Minnesota (listed as threatened). Where it is found in other parts of the United States—Idaho, Michigan, Montana, Wisconsin, Wyoming, and possibly Washington—it was, until 2003, listed as endangered, but is currently listed as threatened.
Approximately 50,000 wolves remain in Canada and 7,500 to 10,500 in the United States (5,000 to 8,000 of which are in Alaska). Some 150,000 remain elsewhere in the world.

History and conservation measures

Gray wolves once lived everywhere north of about 20° latitude, a parallel that runs through Mexico City and southern India. They occupied an array of climates and ecosystems (ecological communities consisting of living things and their environment), from dry deserts to deciduous (tree or plants that shed) forests to frozen tundra. On the North American continent, they ranged from coast to coast and from Canada to Mexico.
As settlers moved west across America in the nineteenth century, they killed off most of the populations of bison, deer, elk, and moose—animals that were important prey for wolves. With little natural prey left, wolves then turned to sheep and cattle. To protect livestock, ranchers and government agencies began a decades-long campaign to eliminate the animals. Wolves were trapped, shot, and hunted with dogs. Animal carcasses (dead bodies) salted with strychnine (pronounced STRICK-nine; a poison) were left out for wolves to eat. Unfortunately, this practice killed eagles, ravens, foxes, bears, and other animals that also fed on the poisoned carcasses. By the late 1920s, no wolves were left in Yellowstone National Park.
At present, gray wolves occupy just 6 percent of their former range in the contiguous United States (connected 48 states). In 1995 and 1996, the U.S. government relocated about 65 gray wolves from Canada to Yellowstone National Park and central Idaho. The wolves adjusted quickly. Within two years, they had reshaped the Yellowstone ecosystem, improving the overall balance of species in the park. The wolves killed many of the park’s coyotes, which allowed the rodent population to increase. This, in turn, allowed animals that feed on rodents to increase in number. Other animals, such as grizzly bears, benefitted by feeding on the remains of elk killed by wolves.
From the beginning, however, ranchers and farm groups have opposed wolf reintroduction efforts, asserting that wolves are a threat to livestock in the area. To ease the concerns of ranchers, the U.S. government downgraded the wolves’ status in Yellowstone and Idaho from “endangered” to “threatened.” This change gave ranchers the legal right to shoot wolves attacking their livestock.
This compromise was still not enough for some livestock groups. They sued to stop the reintroduction efforts. Certain environmental groups, including the Audubon Society, also filed a suit against the government to stop the reintroduction. They wanted to keep full “endangered” status for the two or three wolves already living in central Idaho.
In December 1997, a federal judge ruled that the government had violated parts of the Endangered Species Act when it reintroduced wolves to Yellowstone. The judge did stay (delay) his decision, allowing federal agencies and other environmental groups time to file an appeal. A federal appeals court reversed the decision, and the gray wolves remained at Yellowstone. If the judge’s decision is upheld, all of the gray wolves in Yellowstone (a population of about 160) would have had to be killed.
In a very controversial move in 2003, the U.S. Fish and Wildlife Service announced that gray wolves had been reclassified from endangered to threatened in midwestern, northeastern, and southeastern states, leaving them in endangered status only in the Southwest. The federal agency said it had done this because it had fulfilled its job. It estimates there are 664 wolves in 44 packs in western Montana, Idaho, and in and around Yellowstone National Park. The goal of having more than 30 breeding pairs in those states had been met for three years in a row, which was the target set when wolves were given federal protection. The gray wolf population in the western Great Lakes has also reached its recovery goal; there are more than 2,445 wolves in Minnesota, 323 in Wisconsin, and 278 in Michigan. Conservationists criticized the Fish and Wildlife Service for removing wolves from endangered status in those states in the Northeast and Southeast that have no population of wolves. Without the protection received with endangered status, there is little possibility that wolves could ever be reintroduced into the northeast or elsewhere. The northeastern conservationists in particular protested that reclassification of states where the gray wolf does not currently exist means that the species will be limited to the isolated areas it now inhabits and will never fully recover to roam its former ranges.

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