The Gray Wolf (Canis lupus), also known as the timber wolf, or simply the wolf, is a large canine native to Eurasia and North America. It is the largest wild canid and is considered the ancestor of all modern domestic dogs.
It is the only species of Canis to have a range encompassing both the Old and New Worlds, and originated in Eurasia during the Pleistocene, colonizing North America on at least three separate occasions during the Rancholabrean. Mammal Species of the World (3rd ed., 2005), a standard reference work in zoology, recognizes 38 subspecies of C. lupus.
The gray wolf is social animal, traveling in nuclear families consisting of a mated pair, accompanied by the pair's adult offspring. The wolf is typically an apex predator throughout its range, with only humans and tigers posing a serious threat to it. It feeds primarily on large ungulates such as deer, wild boar and bison, though it also eats smaller animals such as rodents, rabbits and fish. They will also eat livestock, carrion, and garbage. A 7 year-old wolf is considered to be relatively old, and the maximum lifespan of a grey wolf is about 16 years.
Wolves are considered to be vital to ecosystem health. When wolves were eradicated in Yellowstone National Park in 1926, the populations of deer and elk rose and overpopulation started to become a major problem since there were no wolves to control their numbers and overgrazing started to cause soil erosion since there were less plants to keep the soil together. When ecologists became worried about the absence of wolves, they reintroduced them on January 12, 1995. Since then, wolves have been maintaining and repairing the ecological damage that their absence has left behind.
The wolf is the largest extant member of the Canidae family, and is further distinguished from coyotes and jackals by a broader snout, shorter ears, a shorter torso and a longer tail. It is slender and powerfully built, with a large, deeply descending rib cage, a sloping back, and a heavily muscled neck. The wolf's legs are moderately longer than those of other canids, which enables the animal to move swiftly, and to overcome the deep snow that covers most of its geographical range in winter. The ears are relatively small and triangular. The wolf's head is large and heavy, with a wide forehead, strong jaws and a long, blunt muzzle. The skull is 9–11 in in length and 5–6 in in width. The teeth are heavy and large, making them better suited to crushing bone than those of other canids. They are not as specialized as those found in hyenas though. Its molars have a flat chewing surface, but not to the same extent as the coyote, whose diet contains more vegetable matter. Females tend to be smaller, have narrower muzzles and foreheads, thinner necks, slightly shorter legs, and less massive shoulders than males.
The size and weight of the modern wolf increases proportionally with latitude in accord with Bergmann's rule. The mean body mass of the wolf is 88 lb, the smallest specimen recorded at 26 lb and the largest at 175 lb. On average, European wolves weigh 85 lb, North American wolves 79 lb, and Indian and Arabian wolves 55 lb. Females in any given wolf population typically weigh 5–10 lb less than males. Wolves weighing over 119 lb are uncommon, though exceptionally large individuals have been recorded in Alaska and Canada. In middle Russia, exceptionally large males are given a maximum weight of 152–174 lb. The largest known type of grey wolf is the Mckenzie valley wolf also called the Alaskan grey wolf.
Wolves typically dominate other canid species in areas where they both occur. In North America, incidents of wolves killing coyotes are common, particularly in winter, when coyotes feed on wolf kills. Wolves may attack coyote den sites, digging out and killing their pups, though rarely eating them. There are no records of coyotes killing wolves, though coyotes may chase wolves if they outnumber them.
Wolves also compete with larger predators like bears and pumas. Wolves generally tend to avoid bears for the most part, but both animals will kill each others' young if the opportunity arises