The wolf is a carnivorous mammal of the genus Canis in the dog family. 
Once distributed over most of the Northern Hemisphere, 
wolves are now confined to the wilder parts of a reduced range. 
Three wolf species (the gray wolf, red wolf, and coyote) are generally recognized, 
although there is much local variation within them.

Other living members of the genus Canis are the jackal and the dog. 
All Canis species can interbreed, producing fertile offspring; 
the Eskimos have interbred wolves and dogs to produce hardy animals for pulling sleds.
 The maned wolf, Chrysocyon brachyurus,  
found in wooded areas of central South America, is not a true wolf,
 although it is a canine (member of the dog family).
 It has extremely long, stiltlike legs and an erectile mane on the neck.
 Strand wolf is a name for the brown hyena (not a canine) of Africa.
 The aardwolf is also a member of the hyena family.

The most widespread is the gray wolf, C. lupus, of circumpolar distribution;
 it is also known as the timber wolf in North America. 
Extinct in W Europe except in a few isolated pockets, 
it is still found in SE Europe, Russia, and much of Asia. 
In the New World it is found in wilderness forests and tundra from 

Greenland and the shores and islands of the Arctic Ocean to the extreme N United States. 
There is a healthy population in Alaska, but it has endangered-species status 
in the 48 contiguous United States (except for Minnesota, where it has a “threatened” status). 
Thus protected, it is now steadily increasing its range,
 especially in the Great Lakes region in Minnesota, Wisconsin, and Michigan.
 Despite the opposition of area ranchers, small populations of
 Canadian wolves were reintroduced into Yellowstone National Park in 1995,
 in the hope of restoring balance to the Yellowstone ecosystem. 
Canadian wolves were also introduced in central Idaho in 1995 and 1996,

 and natural reproduction has since steadily increased the numbers of both populations. 
Wolves in these areas could be reclassified from endangered 
to threatened status if conservation successes continue. 
A comparable wolf recovery program for the NE United States 
was under consideration by federal officials in the late 1990s.
The gray wolf is similar in appearance to a German shepherd dog, with a thick,
 shaggy coat, erect ears, and a bushy tail. 
Its fur is usually gray mixed with black and brown but may be nearly black or, 

in the Arctic, nearly white. 
An average-sized adult male is about 3 ft (90 cm) high at the shoulder and 4 ft (120 cm) long,
 excluding the tail, and weighs about 100 lb (45 kg); some individuals weigh twice as much.
Active mostly at night, gray wolves prey on birds and small 
mammals and on weak members of larger species, such as deer; 
they also eat vegetable matter and some carrion.
 They can run at speeds of up to 35 mi (56 km) per hour and can clear 16 ft (4.9 m) in a single bound. While hunting they can maintain a speed of about 20 mi (32 km) per hr for many hours,
 eventually wearing down even the swiftest prey. 
They roam over large areas and may migrate in response to migrations by or

 numerical fluctuations in their prey species.
Gray wolves hunt singly and in family groups, 
called packs, which typically include about five individuals. 
Under severe conditions, especially in winter, several families may join together,
 forming a pack of up to 30 individuals, rarely more. 
During the mating season a wolf pair establish a den, usually in a cave or underground burrow, 
in which they raise the young; both parents bring home food. 
A pair is believed to remain mated for life.

Because of farmers' fears of raids on livestock,
 which wolves usually take only when wild prey is unavailable,
 gray wolves have been hunted ruthlessly, 
resulting in their extermination in all but the most sparsely populated areas. 
North American gray wolves have not been known to attack humans without provocation,
 although Siberian gray wolves have on occasion attacked riders of horses or horse-drawn vehicles. There are many stories of human children being raised by gray wolves,
 particularly in India, but none has been authenticated.

The red wolf, C. rufus, is a smaller species that varies in color from reddish gray to nearly black.
 It has been nearly eradicated from most of its range in the forest
 and brush country of the S central United States and is listed as endangered. 
However, captive breeding programs are slowly increasing its numbers, 
and some have been reintroduced to the wild. 
The red wolf is similar in behavior to, and may be a hybrid of, the prairie wolf, 
C. latrans, better known as the coyote. 
Smallest of the wolves, coyotes are still widespread in W North America.