The gray wolf (Canis lupus), also called the timber wolf (along with many other local names), is one of the most widely distributed of all mammals—some say second only to humans. They have adapted to climates as different as deserts, the Arctic tundra, and forests.

However, as humans took over wolf habitat, they often exterminated the animals. By the beginning of the 20th century, settlers had rendered wolves practically extinct in the continental United States, in part because of the assumption that wolves were responsible for the loss of livestock, but also because of the general notion that wildlife was detrimental to progress and that large carnivores were considered cruel.

By 1973, the gray wolf was placed on the Endangered Species List in the United States. Although wolf populations have yet to recover, there is a movement—led by livestock owners (who fear that wolves will eat their livestock) and hunters (who want to kill or avoid competing with wolves)—to lift Endangered Species Act protections in several states.

Indeed, as humans simultaneously took over wolf habitat, filled the habitat with livestock, and depleted the staples of the wolf's traditional diet (deer, elk, caribou, and bison), the wolf turned to sheep and cattle to supplement its diet. The wolf eats a varied diet: When in packs, wolves will successfully bring down larger mammals such as bison, elk, deer, musk oxen, and moose. (They tend to focus on ill, old, or weak members of a herd.)

Conversely, a solitary wolf will hunt smaller animals such as beavers and rabbits. A wolf may travel as far as 30 miles in a single, 24-hour period (often at night) to find prey. The carcasses left behind serve an important ecosystem function, as they provide fodder for such scavengers as wolverines, vultures, foxes, and sometimes bears.

A pack generally comprises 5 to 9 wolves, led by a dominant ("alpha") pair of a male and a female. Although pack size may swell to over 20 individuals, the mechanisms that govern pack size are poorly understood. Researchers believe that factors such as food availability, habitat, season, mortality, and weather may play a part in influencing pack size and social dynamics.

You can determine the social hierarchy of the pack by watching: It's the alpha pair who eat first and who successfully reproduce. Wolves also act out their hierarchy via body language and submissive behavior. Dominant members of the pack can often be seen with their ears and tails up; subordinate pack members show their submissiveness by lowering their ears and tails, sometimes by rolling on their backs to expose their bellies to dominant members. Regardless of social rank, when any wolf returns to the pack after an absence, the other pack members greet him or her with muzzle licking and mouthing.

Wolf packs tend to occupy a defined territory, which may be anywhere from 50 to 1,000 square miles. The territory size may be dictated by the movement and abundance of prey. A pack will defend its territory against other wolves if necessary.

Wolves mate any time between January and April. The litter, usually born in a den or small cave, will consist of 5 to 9 pups, who are both deaf and blind at birth. The pups nurse for 8 to 10 weeks, and then are fed regurgitated food by all pack members. The pups generally stay with the pack for about two years, after which they may roam on their own until they find a mate and territory.

Wolves communicate using scent marking, physical signals and howls. Although biologists are not yet certain of the function of howling, they postulate that howls may serve as alarms, as declarations that a hunt is over, as warnings to ward off another pack, or as devices to find pack members who have strayed. Clues to the function of howling may come from daily and seasonal variation in the frequency of howls. For example, biologists have noted that wolves howl more often early in the morning and at evening. Breeding and rearing seasons seem to inspire more howls than other seasons.

The gray wolf is as variable in color as it is in habitat. Although often gray, wolves' thick fur ranges from black to white, although some boast red and brown coats. Male wolves, who are larger than females on average, stand at more than 30 inches tall and weigh as much as 175 pounds. They are the largest of the wild canids, although some people confuse them on sight with their smaller relative, the coyote.

Traditionally feared by humans, wolves actually shy away from human contact. According to the U.S. Fish and Wildlife Service, no attack on a human by a healthy, wild wolf has ever been confirmed in North America. There have been cases of aggression recorded, but a wild, healthy wolf who is not habituated to humans (that is, who has not been taught to see humans as a source of food) and who is not provoked poses very little risk to humans.

 

 

Sources

Feldhamer, G.A., B. C. Thompson and J.A. Chapman (eds.) 2003. Wild Mammals of North America, 2nd edition. The Johns Hopkins University Press: Baltimore, MD, USA.

Smithsonian National Museum of Natural History: Canis lupus

 

Updated Feb. 1, 2007