Wolves are highly social and live in packs. The pack usually consists of a dominant breeding pair (an alpha male and alpha female), their offspring from the previous year, and new pups. Other breeding-age adults may be present. The pack hunts, feeds, travels, and rests together. It also shares pup-rearing responsibilities, including hunting and tending pups. Pack size is highly variable, but commonly averages four to11 animals.
Few wolves live more than five years in the wild, although individuals have been known to reach 15 years of age. Research in the northern Rocky Mountain states has shown that humans cause most wolf deaths in the region. Causes include lethal controls to resolve conflicts, illegal killings, legal harvest, and car and train collisions. However, in areas such Yellowstone National Park, where wolves are fully protected, most wolves die from natural causes, such territorial conflicts with wolves in neighboring packs, injuries while hunting prey, starvation, or disease.
Wolves usually mate in mid- to late February, and the pups are born about two months later. Most packs produce one litter annually, typically consisting of four to six pups. Wolves often develop dens in underground burrows, but also use abandoned beaver lodges, hollow trees, and shallow rock caves.
As pups grow older, they are taken from the den to a protected location known as a rendezvous site. One or more rendezvous sites are used over the summer until the pups are large enough to travel and hunt with the pack.
With their large size, powerful jaws, large teeth, speed, endurance, and habit of hunting in packs, wolves are keenly adapted to hunt large prey. In the central and northern Rocky Mountains of the U.S. and Canada, wolves often prey on elk, deer and moose. Despite their hunting abilities, the majority of wolf hunts are unsuccessful. Wolves are opportunistic hunters and tend to prey mainly on younger, older, and debilitated animals. This can leave prey herds with more healthy animals of prime age, thereby enhancing productivity.
Wolves also will scavenge carrion and eat smaller animals. They also kill and feed on domestic livestock, especially cattle and sheep.
A pack establishes a territory and defends it against neighboring packs. Territories usually average 140 to 400 square miles, and their size often varies from year to year. Territories are often smaller when prey is common and other packs live nearby.
Howling is a common behavior that helps pack members communicate and stay together. Howls are audible for up to five miles. The howls of wolves tend to be long and drawn out compared to the shorter yapping sounds made by coyotes. Wolves also growl and bark.
Most young wolves leave their birth packs when they are 2 or 3 years old, to search for a mate and to start a new pack of their own. Dispersing wolves usually move about 60 miles, but can travel more than 500 miles.
Wolves are highly adaptable and can live in a variety of habitats if sufficient prey is available. In the Northwestern states and Western Canada, wolves are most common in forested areas with relatively flat, open spaces such as river valleys and basins, where prey animals are easier to chase and catch. Wolf populations fare best in areas away from humans and their activities. These tend to be remote, relatively unpopulated areas with extensive public lands, few roads, and few or no livestock.
Wolves’ presence can benefit natural plant and animal communities by preventing the overpopulation of prey and helping to maintain the natural occurrence of certain plant and wildlife species. For example, research in Olympic National Park suggests that over-browsing by elk in the absence of wolves during the century caused substantial changes in riparian habitats, including severe declines in small and medium-sized cottonwood and bigleaf maple trees.
The availability of wolf-killed carcasses can help scavenging animals, such as bald eagles, bears, wolverines, foxes, mink, ravens, magpies, jays, crows, golden eagles, and vultures. This benefit is especially important during the winter, when other foods become scarce.