U.S. Fish & Wildlife Service
Gray wolf
Canis lupus
Second only to humans in adapting
to climate extremes, gray wolves
in North America once ranged
from coast to coast and from
Alaska to Mexico. They were
absent from the East and the
Southeast, which were occupied by
red wolves (Canis rufus), and from
the extreme southwestern states.
However, government-sponsored
wolf control programs brought the
gray wolf to near extinction in the
lower 48 states by the early 20th
Century.
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 2 or 3,
sometimes mating for life. An
average of five pups are born in
early spring and are cared for by
the entire pack. Pups are reared in
dens for the first 6 weeks. 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 7 to 8 months old,
when almost fully grown, the pups
begin traveling with the adults.
After 1 or 2 years of age young
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 how much prey is available 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 m.p.h.,
wolves can run as fast as 40 m.p.h.
for short distances.
Studies at Yellowstone National
Park indicate that wolves support
a wide variety of other animals.
Ravens, foxes, wolverines,
vultures, 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 smaller plant-eaters such as
beavers and small rodents.
Wolves are noted for their howl,
which they use as a form of
communication. Wolves may howl
before and after a hunt, to sound
an alarm, or to locate other pack
members when separated. They
howl more frequently in the
evening and early morning,
especially during winter breeding
and spring pup-rearing. Howling is
also used by packs to warn other
wolves to stay out of their
territory.
Settlers moving westward
depleted most populations of bison,
deer, elk, and moose – animals that
were important prey for wolves.
Wolves then turned to sheep and
cattle which had replaced 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 initially
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.
The wolf’s comeback nationwide is
due to its listing under the
Endangered Species Act,which
resulted in increased scientific
research, protection from
unregulated killing, reintroduction
and management programs, and
education efforts that increased
public understanding of wolves.
Gray wolves are listed as
endangered in the contiguous 48
states, except in Minnesota where
they are listed as threatened.
Endangered means a species is
considered in danger of extinction
throughout all or a significant
portion of its range, and threatened
means a species is likely to become
endangered in the foreseeable
future. In Alaska wolf populations
number 6,000 to 8,000 and are not
considered endangered or
threatened.
Wolf recovery has been so
successful that in 2006 the U.S.
Fish and Wildlife Service proposed
to remove the gray wolves found 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 405 in
Michigan’s Upper Peninsula, 425 in
Wisconsin.
In the northern Rocky Mountains,
the U.S. Fish and Wildlife Service
reintroduced gray wolves into
Yellowstone and U.S. Forest
Service lands in central Idaho in
1995 and 1996. The reintroduction
was successful, and by December
2005 there were about 890 wolves
in the Yellowstone area and Idaho;
in total,about 1,020 live in the
northern Rocky Mountains of
Montana, Idaho, and Wyoming.
Wolves have also been
reintroduced in Arizona and New
Mexico. Mexican gray wolves are
native to the Southwest but
recently existed only in zoos until
1998, when 13 wolves were
released in Arizona. By the end of
2005, there were about 50 wolves
in in the wild in Arizona and New
Mexico with another 275 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 the species’
historical range.
Occasionally, wolves are also seen
in states adjacent to these
recovery areas.
Gray wolf populations fluctuate
with food availability, strife within
packs, and disease. In some areas
where they are not protected by
law, wolf populations may change
due to accidental and intentional
killing by people.
Many people oppose wolf recovery
because of concerns for 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 the
animals were hand-fed or attracted
to garbage.
Some ranchers and farmers fear
wolves because they prey on
livestock and pets. To address this
concern, special features of the
Endangered Species Act have been
used in parts of wolf range to allow
removal of wolf packs that prey on
livestock. There are programs to
compensate for the loss of
livestock and pets in most of the
recovery areas.
The Yellowstone and Idaho wolves
are designated as non-essential,
experimental populations under
the Endangered Species Act. This
allows more management flexibil-ity.
A similar program is used to
restore Mexican wolves in the
southwestern United States.
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.
Revised March 2006
