Wolf

The wolf (Canis lupus), also known as the gray/grey wolf, is a canine native to the wilderness and remote areas of Eurasia and North America. It is the largest extant member of its family, with males averaging 40 kg (88 lb) and females 35.5–37.7 kg (78–83 lb). It is also distinguished from other Canis species by its less pointed features, particularly on the ears and muzzle. Its winter fur is long and bushy and predominantly a mottled gray colour, although nearly pure white, red and brown to black also occur. Mammal Species of the World (3rd ed., 2005), a standard reference work in zoology, recognizes 38 subspecies of C. lupus.

The wolf is the most specialized member of the genus Canis for cooperative big game hunting, as demonstrated by its physical adaptations to tackling large prey, its more social nature, and its highly advanced expressive behaviour. It is nonetheless closely related enough to smaller Canis species, such as the coyote and golden jackal, to produce fertile hybrids with them. It is the only species of Canis to have a range encompassing both Eurasia and North America. It travels in nuclear families consisting of a mated pair accompanied by their adult offspring. The wolf is mainly a carnivore and feeds primarily on large wild hooved animals, though it also eats smaller animals, livestock, carrion, and garbage.

The global wolf population is estimated to be 300,000. It has a long history of association with humans, having been despised and hunted in most pastoral communities because of its attacks on livestock, while conversely being respected in some agrarian and hunter-gatherer societies. Although the fear of wolves is pervasive in many human societies, the majority of recorded attacks on people have been attributed to animals suffering from rabies. Non-rabid wolves have attacked and killed people, mainly children, but this is rare because wolves are relatively few, live away from people, and have developed a fear of humans due to their experiences with hunters and shepherds.

Distribution and habitat

Wolf in mountainous habitat in Himachal Pradesh's Spiti Valley, India

Main article: Wolf distribution

Originally, wolves occurred across Eurasia above 12˚N and North America above 15˚N. However, deliberate human persecution has reduced the wolf's range to about one-third of what it once was because of livestock predation and fear of attacks on humans. The wolf is now extirpated (locally extinct) in much of Western Europe, Mexico, and much of the United States. In modern times, the wolf occurs mostly in wilderness and remote areas, particularly in Canada, Alaska and the northern United States, Europe, and Asia from about 75°N to 12°N.[2] The wolf can be found between sea level and 3,000 metres (9,800 ft). It lives in forests, inland wetlands, shrublands, grasslands (including arctic tundra), pastures, deserts, and rocky peaks on mountains.[2] Habitat use by wolves is strongly correlated with the abundance of prey, snow conditions, absence or low livestock densities, road densities, human presence and topography.[62] In cold climates, the wolf can reduce the flow of blood near its skin to conserve body heat. The warmth of the footpads is regulated independently from the rest of the body, and is maintained at just above tissue-freezing point where the pads come in contact with ice and snow.[64]

Diet

Wolf carrying caribou hindquarter, Denali National Park, Alaska

Like all land mammals that are pack hunters, the wolf predominantly feeds on herbivorous mammals that have a body mass similar to that of the combined mass of the pack members.[65][66] The wolf specializes in preying on the vulnerable individuals of large prey,[62] with a pack being capable of bringing down a 500 kg (1,100 lb) moose.[67] Wolves can digest their meal in a few hours and can feed several times in one day, making quick use of large quantities of meat.[68] A well-fed wolf stores fat under the skin, around the heart, intestines, kidneys, and bone marrow, particularly during the autumn and winter.[69]

Across their range, wolves predominantly feed on wild hoofed mammals that can be divided into large size 240–650 kg (530–1,430 lb) and medium size 23–130 kg (51–287 lb). The variation in diet between wolves living on different continents is based on the different varieties of hoofed mammals and of smaller and domestic prey that are available. In North America, the wolf's diet is dominated by wild large hoofed mammals and medium-sized mammals. In Asia and Europe, their diet is dominated by wild medium-sized hoofed mammals and domestic species. The wolf depends on wild species, and if these are not readily available, as in Asia, the wolf is more reliant on domestic species.[70] Across Eurasia, wolves prey mostly on moose, red deer, roe deer and wild boar.[71] In North America, important prey rangewide are elk, moose, caribou, white-tailed deer and mule deer.[72]

Nonetheless, wolves are not fussy eaters. Smaller sized animals that may supplement diet include rodents, hares, insectivores and smaller carnivores. They frequently eat waterfowl and their eggs. When such foods are insufficient, they prey on lizards, snakes, frogs, and large insects as available.[73] Wolves will eat grasshoppers when these are plentiful, with one scat found in Idaho containing the remnants of 181 of these insects.[74] Wolves in northern Minnesota prey on northern pike in freshwater streams.[75] The diet of coastal wolves in Alaska includes 20% salmon,[76] while coastal wolves in British Columbia includes 25% marine sources, and those on the nearby islands 75%.[77]

In Europe, wolves eat apples, pears, figs, melons, berries and cherries. In North America, wolves eat blueberries and raspberries. Wolves also eat grass, which may provide some vitamins.[78] They are known to eat the berries of mountain ash, lily of the valley, bilberries, cowberry, nightshade, grain crops, and the shoots of reeds.[73]

In times of scarcity, wolves will readily eat carrion.[73] In Eurasian areas with dense human activity, many wolf populations are forced to subsist largely on livestock and garbage.[71] The prey animals of North American wolves have largely continued to occupy suitable habitats with low human density, and these cases are under dire circumstances.[79] Cannibalism is not uncommon in wolves during harsh winters, when packs often attack weak or injured wolves, and may eat the bodies of dead pack members.

The wolf is a social animal.^[48] Their populations consist of packs and lone wolves, with most lone wolves being temporarily alone while they disperse from packs to form their own or join another pack.^[99] The wolf's basic social unit consists of a mated pair accompanied by their adult offspring.^[48] The average pack size in North America is 8 wolves and in Europe 5–6 wolves.^[42] The average pack across Eurasia consists of a family of 5–11 wolves (2 adults, 3–6 juveniles, and 1–3 yearlings),^[48] or sometimes 2 or 3 such families,^[62] with examples of exceptionally large packs consisting of up to 42 wolves being known.^[100] In ideal conditions, the mated pair produces pups every year, with such offspring typically staying in the pack for 10–54 months before dispersing.^[101] Triggers for dispersal include the onset of sexual maturity and competition within the pack for food.^[102] The distance travelled by dispersing wolves varies widely; some stay in the vicinity of the parental group, while other individuals may travel great distances of upwards of 206 km (128 mi), 390 km (240 mi), and 670 km (420 mi) from their natal packs.^[103] A new pack is usually founded by an unrelated dispersing male and female, travelling together in search of an area devoid of other hostile packs.^[104] Cortisol levels in wolves rise significantly when a pack member dies, indicating the presence of stress.^[105] Wolf packs rarely adopt other wolves into their fold, and typically kill them. In the rare cases where other wolves are adopted, the adoptee is almost invariably an immature animal of 1–3 years old, and unlikely to compete for breeding rights with the mated pair. In some cases, a lone wolf is adopted into a pack to replace a deceased breeder.^[100] During times of prey abundance caused by calving or immigration, different wolf packs may temporarily join together.^[48]

Wolves are highly territorial and generally establish territories far larger than they require to survive, which assures a steady supply of prey. Territory size depends largely on the amount of prey available and the age of the pack's pups, tending to increase in size in areas with low prey populations,^[106] or when the pups reach the age of six months when they have the same nutritional needs as adults.^[107] Wolf packs travel constantly in search of prey, covering roughly 9% of their territory per day, on average 25 km/d (16 mi/d). The core of their territory is on average 35 km² (14 sq mi), in which they spend 50% of their time.^[106] Prey density tends to be much higher on the territory's periphery, although wolves tend to avoid hunting on the fringes of their range except in desperation to avoid fatal confrontations with neighboring packs.^[108] The smallest territory on record was held by a pack of six wolves in northeastern Minnesota, which occupied an estimated 33 km² (13 sq mi), while the largest was held by an Alaskan pack of ten wolves encompassing 6,272 km² (2,422 sq mi).^[107] Wolf packs are typically settled, and usually only leave their accustomed ranges during severe food shortages.^[48]