U.S. Fish & Wildlife Service
Gray wolf Canis lupus
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, pups
begin traveling with the adults.
After they are 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 five 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 other 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, or 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
Photo by John & Karen Hollingsworth/USFWS
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 7,700 to 11,200
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. Today about 2,921
wolves live in the wild in Minnesota,
19 on Lake Superior’s Isle Royale,
about 557 in Michigan’s Upper
Peninsula, and at least 690 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 2009 there were about
1,359 wolves in the Yellowstone area
and Idaho; in total, at least 1,599 live
in the northern Rocky Mountains of
Montana, Idaho, and Wyoming.
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
2009, there were 42 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.
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
March 2011
Photo by Tracy Brooks-Mission
