PDF《Gray Wolf (Canis lupus)》

January

1998 U.

S. Fish & Wildlife Service Gray Wolf (Canis lupus) Photo by John & Karen Hollingsworth/USFWS Second only to humans in adapting to climate extremes, gray wolves once ranged from coast to coast and from Alaska to Mexico in North America. They were absent from the East and the Southeast, which were occupied by red wolves (Canis rufus), and from the large deserts in the southwestern States. By the early 20th century, government-sponsored predator control programs and declines in prey brought gray wolves to near extinction in the lower

48 States. Wolf groups, or packs, typically include a breeding pair (the alpha pair), their offspring, and other non-breeding adults. Wolves are capable of mating by age two or three and sometimes form a lifelong bond. Wolves can live

13 years and reproduce past

10 years of age. On the average five pups are born in early spring and are cared for by the entire pack. For the first six weeks, pups are reared in dens. Dens are often used year after year, but wolves may also dig new dens or use some other type of shelter, such as a cave. Pups depend on their mother's milk for the first month, then are gradually weaned and fed regurgitated meat brought by pack members. By seven to eight months of age, when they are almost fully grown, the pups begin traveling with the adults. After a year or two, wolves may leave and try to find a mate and form a pack. Lone, dispersing wolves have traveled as far as

600 miles in search of a new home. Wolf packs live within territories, which they defend from other wolves. Their territories range in size from

50 square miles to more than 1,000 square miles, depending on the available prey and seasonal prey movements. Wolves travel over large areas to hunt, as far as

30 miles in a day. Although they usually trot along at

5 miles per hour, wolves can run as fast as

40 miles per hour for short distances. Studies at Yellowstone National Park indicate that wolves support a wide variety of other animals. Ravens, foxes, wolverines, coyotes, bald eagles, and even bears feed on the carcasses of animals killed by wolves. Antelope are swift, elk are alert, and mountain goats are adept at climbing steep cliffs, in part because of the long-term effects of wolf predation. Wolves also help maintain the balance between these ungulates (hoofed animals) and their food supply, making room for plant-eaters such as beavers and small rodents. Wolves use their distinctive howl to communicate. Biologists have identified a few of the reasons that wolves howl. First, they like to howl. They also howl to reinforce social bonds within the pack, to announce the beginning or end of a hunt, sound an alarm, locate members of the pack, and warn other wolves to stay out of their territory. Wolves howl more frequently in the evening and early morning, especially during winter breeding and pup-rearing. Settlers moving westward depleted most populations of bison, deer, elk, and moose C animals that were important prey for wolves. Wolves then increasingly turned to sheep and cattle as a replacement for their natural prey. To protect livestock, ranchers and government agencies began an eradication campaign. Bounty programs initiated in the 19th century continued as late as 1965, offering $20 to $50 per wolf. Wolves were trapped, shot, dug from their dens, and hunted with dogs. Poisoned animal carcasses were left out for wolves, a practice that also killed eagles, ravens, foxes, bears, and other animals that fed on the tainted carrion. By the time wolves were protected by the Endangered Species Act of 1973, only a few hundred remained in extreme northeastern Minnesota and a small number on Isle Royale, Michigan. Gray wolves were listed as endangered* in the contiguous