Two species of wolves occur in North America, gray wolves (Canis lupus) and red wolves (Canis rufus). The common names are misleading since individuals of both species vary in color from grizzled gray to rusty brown to black. Some gray wolves are even white. The largest subspecies of the gray wolf are found in Alaska and the Northwest Territories of Canada. Adult male gray wolves typically weigh 80 to 120 pounds (36.3 to 54.4 kg), and adult females 70 to 90 pounds (31.8 to 40.8 kg). Although males rarely exceed 120 pounds (54.4 kg), and females 100 pounds (45.4 kg), some individuals may weigh much more. Gray wolves vary in length from about 4.5 to 6.5 feet (1.4 to 2 m) from nose to tip of tail and stand 26 to 36 inches (66 to 91.4 cm) high at the shoulders (Mech 1970).
Red wolves are intermediate in size between gray wolves and coyotes. Typical red wolves weigh 45 to 65 pounds (20.4 to 29.5 kg). Total length ranges from about 4.4 to 5.4 feet (1.3 to 1.6 m) (Paradiso and Nowak 1972).
Figure 1. Adult gray wolf, Canis lupus.
General Biology, Reproduction, and Behavior
Gray wolves are highly social, often living in packs of two to eight or more individuals. A pack consists of an adult breeding pair, young of the year, and offspring one or more years old from previous litters that remain with the pack. The pack structure of gray wolves increases the efficiency of wolves in killing large prey. Red wolves may be less social than gray wolves, although red wolves appear to maintain a group social structure throughout the year.
Each wolf pack has a home range or territory that it defends against intruding wolves. Packs maintain their territories by scent marking and howling. On the tundra, packs of gray wolves may have home ranges approaching 1,200 square miles (3,108 km2). In forested areas, ranges are much smaller, encompassing 40 to 120 square miles (104 to 311 km2). Some wolves leave their pack and territory and become lone wolves, drifting around until they find a mate and a vacant area in which to start their own pack, or wandering over large areas without settling. Extreme movements, of 180 to 551 miles (290 to 886 km), have been reported. These movements were probably of dispersing wolves. The home ranges of red wolves are generally smaller than those of gray wolves. Red wolf home ranges averaged 27.3 square miles (71 km2) in southern Texas (Shaw 1975).
Wild gray wolves usually are sexually mature at 22 months of age. Breeding usually takes place from early February through March, although it has been reported as early as January and as late as April. Pups are born 60 to 63 days after conception, usually during April or May. Most litters contain 4 to 7 young.
Courtship is an intimate part of social life in the pack. Mating usually occurs only between the dominant (alpha) male and female of the pack. Thus, only 1 litter will be produced by a pack during a breeding season. All pack members aid in rearing the pups.
Dominance is established within days after gray wolf pups are born. As pups mature, they may disperse or maintain close social contact with parents and other relatives and remain members of the pack.
Little is known about reproduction in red wolves, but it appears to be similar to that of gray wolves. Red wolves may breed from late December to early March. Usually 6 to 8 pups are produced.
Mech (1970) reported that gray wolves prey mainly on large animals including white-tailed deer, mule deer, moose, caribou, elk, Dall sheep, bighorn sheep, and beaver. Small mammals and carrion make up the balance of their diet. During the 1800s, gray wolves on the Great Plains preyed mostly on bison. As bison were eliminated and livestock husbandry established, wolves commonly killed livestock.
Red wolves in southern Texas fed primarily on small animals such as nutria, rabbits, muskrats, and cotton rats (Shaw 1975). Carrion, wild hogs, calves, and other small domestic animals were also common food items.
During the 1800s, gray wolves ranged over the North American continent as far south as central Mexico. They did not inhabit the southeastern states, extreme western California, or far western Mexico (Young and Goldman 1944). In the late 1800s and early 1900s, wolves were eliminated from most regions of the contiguous United States by control programs that incorporated shooting, trapping, and poisoning. Today, an estimated 55,000 gray wolves exist in Canada and 5,900 to 7,200 in Alaska. In the contiguous United States, the distribution of the gray wolf has been reduced to approximately 3% of its original range.
Minnesota has the largest population of wolves in the lower 48 states, estimated at 1,550 to 1,750. A population of wolves exists on Isle Royale in Lake Superior, but the population is at an all-time low of 12 animals. In recent years, wolves have recolonized Wisconsin, the Upper Peninsula of Michigan, northwestern Montana, central and northern Idaho, and northern Washington. A few isolated gray wolves may also exist in remote areas of Mexico.
Current efforts to re-establish gray wolves are being conducted in northwestern Montana, central Idaho, the Greater Yellowstone area, and northern Washington (USFWS 1987). Recovery through natural recolonization is likely in northwestern Montana, central Idaho, and northern Washington. Due to Greater Yellowstone’s geographic isolation from areas with established wolf populations, recovery there would likely require the reintroduction of wolves into Yellowstone National Park.
Red wolves originally occurred from central Texas to Florida and north to the Carolinas, Kentucky, southern Illinois, and southern Missouri (Young and Goldman 1944). Years of predator control and habitat conversion had, by 1970, reduced the range of the red wolf to coastal areas of southeastern Texas and possibly southwestern Louisiana. When red wolf populations became low, interbreeding with coyotes became a serious problem. In the mid-1970s, biologists captured the last few red wolves for captive breeding before the species was lost to hybridization. The red wolf was considered extinct in the wild until 1987, when reintroductions began.
Red wolf recovery attempts have been made on Bulls Island near Charleston, South Carolina, and on Alligator River National Wildlife Refuge in eastern North Carolina (Phillips and Parker 1988). The Great Smoky Mountains National Park in western North Carolina and eastern Tennessee is also being considered as a red wolf reintroduction area. The goal of the red wolf recovery plan is to return red wolves to non-endangered status by “re-establishment of self-sustaining wild populations in at least 2 locations within the species’ historic range” (Abraham et al. 1980:14).
Gray wolves occupy boreal forests and forest/agricultural edge communities in Minnesota, northern Wisconsin, and northern Michigan. In northwest Montana, northern Idaho, and northern Washington, wolves inhabit forested areas. In Canada and Alaska, wolves inhabit forested regions and alpine and arctic tundra. In Mexico, gray wolves are limited to remote forested areas in the Sierra Madre Occidental Mountains.
The last areas inhabited by red wolves were coastal prairie and coastal marshes of southeastern Texas and possibly southwestern Louisiana. These habitats differ markedly from the diverse forested habitats found over most of the historic range of red wolves.
William J. Paul. District Supervisor. USDA-APHIS-Wildlife Services. Grand Rapids, Michigan 55744
Philip S. Gipson. Unit Leader. Kansas Cooperative Fish and Wildlife. Research Unit. Division of Biology. Kansas State University. Manhattan, Kansas 66506-3501