About Canis lupus familiaris Linnaeus, 1758
The wolf is the largest living member of the canid family (Canidae). It can be distinguished from coyotes and jackals by a broader snout, shorter ears, a shorter torso, and a longer tail. It has a slender, powerfully built body with a large, deeply descending rib cage, a sloping back, and a heavily muscled neck. A wolf's legs are moderately longer than those of other canids, which lets the wolf move swiftly and travel through deep winter snow across most of its range, though some wolf populations have shorter-legged ecomorphs. The wolf's ears are relatively small and triangular. Its head is large and heavy, with a wide forehead, strong jaws, and a long, blunt muzzle. The wolf's skull measures 230–280 mm (9.1–11.0 in) in length and 130–150 mm (5.1–5.9 in) in width. The wolf's teeth are heavy and large, making them better suited to crushing bone than the teeth of other canids, though they are not as specialized as hyena teeth. Its molars have a flat chewing surface, but not as flat as a coyote's, since coyotes have a diet containing more vegetable matter. Female wolves typically have narrower muzzles and foreheads, thinner necks, slightly shorter legs, and less massive shoulders than male wolves. Adult wolves measure 105–160 cm (41–63 in) in total length and 80–85 cm (31–33 in) in shoulder height. Their tails are 29–50 cm (11–20 in) long, their ears are 90–110 mm (3.5–4.3 in) tall, and their hind feet measure 220–250 mm (8.7–9.8 in). The size and weight of modern wolves increases proportionally with latitude, following Bergmann's rule. The average body mass of a wolf is 40 kg (88 lb); the smallest recorded specimen weighed 12 kg (26 lb), and the largest weighed 79.4 kg (175 lb). On average, European wolves weigh 38.5 kg (85 lb), North American wolves weigh 36 kg (79 lb), and Indian and Arabian wolves weigh 25 kg (55 lb). Females in any wolf population typically weigh 2.3–4.5 kg (5–10 lb) less than males. Wolves weighing over 54 kg (119 lb) are uncommon, though exceptionally large individuals have been recorded in Alaska and Canada. In central Russia, exceptionally large males can reach a weight of 69–79 kg (152–174 lb).
Wolves occur across Eurasia and North America. However, deliberate human persecution—driven by livestock predation concerns and fear of attacks on humans—has reduced the wolf's current range to about one-third of its historic range. The wolf is now locally extinct (extirpated) from much of its former range in Western Europe, the United States, and Mexico, and completely extirpated from the British Isles and Japan. In modern times, wolves are found mostly in wilderness and remote areas. Their habitat spans from sea level up to 3,000 m (9,800 ft). Wolves live in forests, inland wetlands, shrublands, grasslands including Arctic tundra, pastures, deserts, and rocky mountain peaks. Wolf habitat use depends on prey abundance, snow conditions, livestock density, road density, human presence, and topography. When adjusted for body mass, the home range of grey wolves is 275–362.9 hectares per kg, which is comparable to the body mass-adjusted home ranges of cheetahs (310.1 hectares/kg) and African wild dogs (242.1 hectares/kg), and much larger than those of spotted hyenas (8.3 hectares/kg) and lions (5.5 hectares/kg).
Wolves are monogamous, and mated pairs usually stay together for life. If one member of a pair dies, the other will find a new mate quickly. In the wild, inbreeding does not occur when outbreeding is possible. Wolves reach maturity at two years of age, and become sexually mature at three years of age. The age of first breeding for wolves depends largely on environmental factors: when food is plentiful, or when wolf populations are heavily managed, wolves can raise pups at younger ages to better take advantage of abundant resources. Females are capable of producing litters every year, with an average of one litter per year. Oestrus and rut begin in the second half of winter and last for two weeks. Dens are usually built for pups during the summer. When constructing dens, females use natural shelters such as rock fissures, cliffs overhanging riverbanks, and holes thickly covered by vegetation. Sometimes, wolves take over burrows dug by smaller animals like foxes, badgers, or marmots, and these appropriated dens are often widened and partially remade. On rare occasions, female wolves dig their own burrows, which are usually small and short, with one to three openings. Dens are usually built no more than 500 m (1,600 ft) from a water source, and typically face south to get more sunlight for warmth and faster snow melt. Resting spots, play areas for pups, and food remains are commonly found around wolf dens. The smell of urine and rotting food from the den area often attracts scavenging birds such as magpies and ravens. Though wolves mostly avoid areas visible to humans, they have been recorded nesting near homes, paved roads, and railways. During pregnancy, female wolves stay in a den located away from the peripheral zone of their territories, where violent encounters with other wolf packs are less likely. The gestation period lasts 62–75 days, and pups are usually born in spring, or early summer in very cold regions such as the tundra. Young females give birth to four to five pups, while older females give birth to six to eight pups, and can have up to 14. Pup mortality rates are 60–80%. Newborn wolf pups look similar to German Shepherd Dog pups. They are born blind and deaf, and are covered in short, soft greyish-brown fur. They weigh 300–500 g (11–18 oz) at birth, and begin to see nine to 12 days after birth. Their milk canines erupt after one month. Pups first leave the den three weeks after birth. At one and a half months of age, they are agile enough to flee from danger. Mother wolves do not leave the den for the first few weeks, relying on the father to provide food for them and their young. Pups start eating solid food at three to four weeks old. They grow quickly during their first four months of life: in this period, a pup's weight can increase by nearly 30 times. Wolf pups begin play-fighting at three weeks old; unlike young coyotes and foxes, their bites are gentle and controlled. Actual fights to establish social hierarchy usually happen at five to eight weeks of age. This differs from young coyotes and foxes, which may begin fighting even before they develop play behaviour. By autumn, pups are mature enough to accompany adult wolves on hunts for large prey.
