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 – 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 

48 States and in Mexico, except 

that in Minnesota they were listed 

as threatened.** Alaska wolf 

populations number 6,000 to 7,000 

and are not considered endangered 

or threatened. 

The wolf ’s comeback nationwide 

is due to its listing under the 

Endangered Species Act, resulting 

in increased scientific research 

and protection from unregulated 

killing, along with reintroduction 

and management programs and 

education efforts that increased 

public understanding of wolf biology 

and behavior. Wolf recovery has 

been so successful that the U.S. Fish 

and Wildlife Service has removed 

the gray wolf in the western Great 

Lakes area from the threatened 

and endangered species list. Today 

about 3,020 wolves live in the wild 

in Minnesota, 30 on Lake Superior’s 

Isle Royale, about 434 in Michigan’s 

Upper Peninsula, and at least 465 in 

Wisconsin.

In the northern Rocky Mountains, 

the U.S. Fish and Wildlife Service 

reintroduced gray wolves into 

Yellowstone National Park and U.S. 

Forest Service lands in central Idaho 

in 1995 and 1996. The reintroduction 

was successful, and the recovery 

goals for this population have been 

exceeded. By December 2006 there 

were about 1,100 wolves in the 

Yellowstone area and Idaho; in total, 

at least 1,240 live in the northern 

Rocky Mountains of Montana, 

Idaho, and Wyoming. Wolf recovery 

has been so successful that the 

Service has proposed removal of 

the gray wolf in the northern Rocky 

Mountains from the threatened and 

endangered species list. 

The Mexican gray wolf, a subspecies, 

Canis lupus baileyi, has also been 

reintroduced into Arizona and New 

Mexico. Native to the Southwest, 

the wolves existed only in zoos until 

1998, when 13 of the animals were 

released in Arizona. By the end of 

2006, there were about 60 wolves in 

the wild in Arizona and New Mexico 

with another 300 in zoos and other 

facilities. Since 2002, wolf packs have 

produced pups in the wild. The goal 

is to establish a self-sustaining wild 

population of at least 100 wolves in 

their historical range.

Gray wolf populations fluctuate 

with food availability, strife within 

packs, and disease. In some areas 

wolf populations may change due to 

accidental or intentional killing by 

people. 

There is some concern that wolf 

recovery may pose a threat to human 

safety. However, wolf attacks on 

humans are extremely rare in North 

America, even in Canada and Alaska 

where there are consistently large 

wolf populations. Most documented 

attacks have been in areas where 

wolves habituated to people when 

they were fed by people or attracted 

to garbage. 

Special features of the Endangered 

Species Act have been used in parts 

of the wolf range to allow the removal 

of wolves that prey on livestock. 

There are programs to compensate 

for the loss of livestock and pets in 

most of the recovery areas. 

Photo by Tracy Brooks-Mission

The Yellowstone and Idaho wolves 

and the Mexican wolves in the 

southwestern United States 

are designated as non-essential, 

experimental populations under 

the Endangered Species Act. This 

designation allows more management 

flexibility while contributing to 

recovery. 

Wolf recovery efforts have restored 

a top predator to its ecosystem and 

improved our understanding of the 

complex interactions among species 

in their natural environments.

For more information:

http://ecos.fws.gov/speciesProfile/

SpeciesReport.do?spcode=A00D

*Endangered means a species is considered 

in danger of extinction throughout all or a 

significant portion of its range. 

** Threatened means a species is likely 

to become endangered in the foreseeable 

future. 

U.S. Fish & Wildlife Service

1-800-344-WILD

http://www.fws.gov

January 2007