Canis Lupus (Gray Wolf) Information [Wikipedia]

Scientific Classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Subfamily: Caninae
Tribe: Canini
Genus: Canis
Species: C. lupus
Binomial name: Canis lupus

The gray wolf or grey wolf (Canis lupus), often known simply as the wolf, is the largest extant wild member of the Canidae family. Though once abundant over much of Eurasia, North Africa and North America, the gray wolf inhabits a reduced portion of its former range due to widespread destruction of its territory, human encroachment, and the resulting human-wolf encounters that sparked broad extirpation. Even so, the gray wolf is regarded as being of least concern for extinction by the International Union for Conservation of Nature, when the entire gray wolf population is considered as a whole. Today, wolves are protected in some areas, hunted for sport in others, or may be subject to population control or extermination as threats to livestock, people, and pets.

Gray wolves are social predators that live in nuclear families consisting of a mated pair which monopolises food and breeding rights, followed by their biological offspring and, occasionally, adopted subordinates. They primarily feed on ungulates, which they hunt by wearing them down in short chases. Gray wolves are typically apex predators throughout their range, with only humans and tigers posing significant threats to them.


DNA sequencing and genetic drift studies reaffirm that the gray wolf shares a common ancestry with the domestic dog. A number of other gray wolf subspecies have been identified, though the actual number of subspecies is still open to discussion.

In areas where human cultures and wolves both occur, wolves frequently feature in the folklore and mythology of those cultures, both positively and negatively.

The most likely ancestral candidate of the gray wolf is Canis lepophagus, a small, narrow skulled North American canid of the Miocene era, which may have also given rise to coyotes. Some larger, broader skulled C. lepophagus fossils found in northern Texas may represent the ancestral stock from which true wolves derive. The first true wolves began to appear at the end of the Blancan North American Stage and the onset of the early Irvingtonian. Among them was Canis priscolatrans, a small species closely resembling the red wolf, which colonised Eurasia by crossing the Bering land bridge. The new Eurasian C. priscolatrans population evolved into Canis etruscus, then Canis mosbachensis.[3]

This primitive wolf closely resembled the modern southern wolf populations of the Arabian Peninsula and South Asia, which were once distributed in Europe in the early Quaternary glaciation until about 500,000 years ago (see Subspecies).[4] C. mosbachensis evolved in the direction of Canis lupus, and recolonised North America in the late Rancholabrean era. There, a larger canid species called Canis dirus was already established, but it became extinct 8,000 years ago after the large prey it relied on was wiped out. Competition with the newly arrived gray wolves for the smaller and swifter prey that survived may have contributed to its decline. With the extinction of dire wolves, gray wolves became the only large and widespread canid species left.[3]

The North American recolonisation likely occurred in several waves, with the most distinctive populations occurring in the periphery of the range. These populations (C. l. arctos on the high arctic islands, C. l. lycaon in the eastern forests, C. l. baileyi in the far south and C. l. rufus at the continental corner opposite the point of invasion) may represent survivors of early migrations from Eurasia. C. l. baileyi, C. l. lycaon and C. l. rufus display some primitive traits and systematic affinity to one another. Fossil remains from the late Pleistocene of large bodied wolves similar to C. l. arctos and C. l. albus occur in coastal southern California, indicating that large North American gray wolf subspecies were once widespread, and may have been driven southward by glaciation, though wolves no longer reside there. Fossils of small bodied wolves similar to C. l. baileyi have been found in a range encompassing Kansas and southern California. This indicates a late Pleistocene population flux, in which large, Arctic forms of wolf moved farther south, with smaller, warmth adapted wolves expanding as the climate moderated.

The now extinct Japanese wolves were descended from large Siberian wolves which colonised the Korean Peninsula and Japan, prior to its separation from mainland Asia, 20,000 years ago during the Pleistocene. During the Holocene, the Tsugaru Strait widened and isolated Honshu from Hokkaidō, thus causing climactic changes leading to the extinction of most large bodied ungulates inhabiting the archipelago. Japanese wolves likely underwent a process of island dwarfism 7,000–13,000 years ago in response to these climatological and ecological pressures. C. l. hattai (formerly native to Hokkaidō) was significantly larger than it southern cousin C. l. hodophilax, as it inhabited higher elevations and had access to larger prey, as well as a continuing genetic interaction with dispersing wolves from Siberia.

Gray wolves are slender, powerfully built animals with large, deeply descending ribcages and sloping backs. Their abdomens are pulled in, and their necks heavily muscled. Their limbs are long and robust, with comparatively small paws.[29] The front paws have five toes each, while the back paws have four. The forelimbs are seemingly pressed into the chest, with the elbows pointed inward, and the feet outward.[24] Females tend to have narrower muzzles and foreheads, thinner necks, slightly shorter legs and less massive shoulders than males.[30] Wolves are very strong for their size, possessing sufficient strength to turn over a frozen horse or moose carcass.[31]

They are also capable of running at speeds of 56–64 km (34–38 miles) per hour, and can continue running for more than 20 minutes, though not necessarily at that speed.[32] In cold climates, wolves can reduce the flow of blood near their skin to conserve body heat. The warmth of the footpads is regulated independently of the rest of the body, and is maintained at just above tissue-freezing point where the pads came in contact with ice and snow.[33] The intestines of adult wolves measure 460–575 cm, the ratio to body length being 4.13–4.62.[34] The stomach can hold 7–9 kg (15–20 lb) of food[24] and up to 7.5 litres (8 U.S. qt) of water.[35] The liver is relatively large, weighing 0.7–1.9 kg (1.6–4.2 lb) in males and 0.68–0.82 kg (1.5–1.8 lb) in females.[24]

Wolves' heads are large and heavy, with wide foreheads, strong jaws and long, blunt muzzles. The ears are relatively small and triangular. Wolves usually carry their heads at the same level as their backs, raising their heads only when alert.[29] The sagittal and lambdoid crests are well developed, the former dividing just in front of the bregma into two ridges curving outward to form posterior border of postorbital processes. The interorbital region is moderately elevated and well defined, with distinct longitudinal concavity between raised and thickened postorbital processes.[36]

The teeth are heavy and large, being better suited to bone crushing than those of other extant canids, though not as specialised as those found in hyenas.[37][38] The canine teeth are robust and relatively short (26 mm).[24] The animal can develop a crushing pressure of perhaps 1,500 lbf/in2 compared to 750 lbf/in2 for a German shepherd. This force is sufficient to break open most bones,[39] as well as cut through half inch lassos with one snap.[40]

They generally resemble German shepherds or huskies in bodily configuration, but are distinguishable from them by their orbital angle of 40°–45° rather than 53°–60°,[24] and the greater size of their heads and teeth (see Domestication).[41] Compared to coyotes, wolves are larger and have broader snouts, shorter ears, and a proportionately smaller brain case[24] and lack sweat glands on their pawpads.[42] Compared to golden jackals, wolves are larger and heavier, and have proportionately longer legs, shorter torsos and longer tails.[43] The teeth are overall less trenchant than the jackal's, particularly in the upper molars, which have lower cusps, are broader, and are more terete.[44]

Gray wolves are the largest extant members of the Canidae, excepting certain large breeds of domestic dog.[24] Gray wolf weight and size can vary greatly worldwide, tending to increase proportionally with latitude as predicted by Bergmann's Rule.[45] Adult wolves are 105–160 cm (41–63 in) in length and 80–85 cm (32–34 in) in shoulder height.[46] The tail is ⅔ the length of the head and body,[47] measuring 29–50 cm (11–20 in) in length. The ears are 90–110 millimeters (3.5–4.3 in) in height, and the hind feet are 220–250 mm.[46] Wolf weight varies geographically; on average, European wolves may weigh 38.5 kilograms (85 lb), North American wolves 36 kilograms (79 lb), Indian and Arabian wolves 25 kilograms (55 lb)[48] and North African wolves 13 kilograms (29 lb).[49]

Females in any given wolf population typically weigh 5–10 lbs less than males.[50] Wolves weighing over 54 kg (120 lbs) are uncommon, though exceptionally large individuals have been recorded in Alaska, Canada,[50] and the former Soviet Union.[46][51] The heaviest recorded gray wolf in North America was killed on 70 Mile River in east-central Alaska on July 12, 1939 and weighed 79.4 kilograms (175 lb),[50] while the heaviest recorded wolf in Eurasia was killed after World War II in the Kobelyakski Area of the Poltavskij Region, Ukrainian SSR, and weighed 86 kilograms (190 lb).[51]

Gray wolves have very dense and fluffy winter fur, with short underfur and long, coarse guard hairs.[29] Most of the underfur and some of the guard hairs are shed in the spring and grow back in the autumn period.[48] The longest hairs occur on the back, particularly on the front quarters and neck. Especially long hairs are found on the shoulders, and almost form a crest on the upper part of the neck. The hairs on the cheeks are elongated and form tufts. The ears are covered in short hairs which strongly project from the fur. Short, elastic and closely adjacent hairs are present on the limbs from the elbows down to the calcaneal tendons.[52]

The winter fur is highly resistant to cold; wolves in northern climates can rest comfortably in open areas at −40° by placing their muzzles between the rear legs and covering their faces with their tail. Wolf fur provides better insulation than dog fur, and, as with wolverines, it does not collect ice when warm breath is condensed against it.[48] In warm climates, the fur is coarser and scarcer than in northern wolves.[29]

Female wolves tend to have smoother furred limbs than males, and generally develop the smoothest overall coats as they age. Older wolves generally have more white hairs in the tip of the tail, along the nose and on the forehead. The winter fur is retained longest in lactating females, though with some hair loss around their nipples.[30] Hair length on the middle of the back is 60–70 mm. Hair length of the guard hairs on the shoulders generally does not exceed 90 mm, but can reach 110–130 mm.[53]

Coat colour ranges from almost pure white through various shades of blond, cream, and ochre to grays, browns, and blacks.[54] Differences in coat colour between sexes are largely absent,[55] though females may have redder tones.[56] Fur colour does not seem to serve any camouflage purpose, with some scientists concluding that the blended colors have more to do with emphasizing certain gestures during interaction.[57] Black coloured wolves (which occur through wolf-dog hybridisation) rarely occur in Eurasia, where interactions with domestic dogs has been reduced over the past thousand years due to the depletion of wild wolf populations.[58] They are more common in North America; about half of the wolves in the reintroduced wolf population in Wyoming's Yellowstone National Park are black.[58] In southern Canada and Minnesota the black phase is more common than the white, though gray coloured wolves predominate.[54]

Their sense of smell is relatively weakly developed when compared to that of some hunting dog breeds, being able to detect carrion upwind no farther than 2–3 km. Because of this, they rarely capture hidden hares or birds, though they can easily follow fresh tracks.[59] Captive wolves are known to be able to detect what foods their handlers have eaten by smell.[60] Their auditory perception is very sharp, being able to hear up to a frequency of 26 kHz,[61] and is greater than that of foxes. Their hearing is sharp enough to register the fall of leaves in the autumn period.[59] The legend that wolves fear the sound of string instruments may have a basis in fact, as captive wolves in the Regent's Park Zoo were shown to exhibit signs of intense distress when hearing low minor chords.[62] Their eyesight is not as powerful as that of dogs, though their night vision is the most advanced of the Canidae.[59]

In popular literature, wolf packs are often portrayed as strictly hierarchical social structures with a breeding "alpha" pair which climbs the social ladder through fighting, followed by subordinate "beta" wolves and a low ranking "omega" which bears the brunt of the pack's aggression. This terminology is based heavily on the behaviour of captive wolf packs composed of unrelated animals, which will fight and compete against each other for status. Also, as dispersal is impossible in captive situations, fights become more frequent than in natural settings. In the wild, wolf packs are little more than nuclear families whose basic social unit consists of a mated pair, followed by its offspring.[63] Northern wolf packs tend not to be as compact or unified as those of African wild dogs and spotted hyenas,[64] though they are not as unstable as those of coyotes.[65] Southern wolves are more similar in social behaviour to coyotes and dingoes, living largely alone or in pairs.[66] The average pack consists of 5–11 animals; 1–2 adults, 3–6 juveniles and 1–3 yearlings,[67] though exceptionally large packs consisting of 42 wolves are known. Wolf packs rarely adopt other wolves into their fold, and typically kill them. In the rare cases where strange wolves are adopted, the adoptee is almost invariably a young animal of 1–3 years of age, while killed wolves are mostly fully grown.[68] The adoption of a new member can be a lengthy process, and can consist of weeks of exploratory, non-fatal attacks in order to establish whether or not the newcomer is trustworthy.[69] During times of ungulate abundance (migration, calving etc.), different wolf packs may temporarily join forces.[70] Wolves as young as five months and as old as five years have been recorded to leave their packs to start their own families, though the average age is 11–24 months. Triggers for dispersal include the onset of sexual maturity and competition within the pack for food and breeding.[71]

In areas with low wolf densities, wolves are generally monogamous.[72] Mated pairs usually remain together for life if one of the wolves does not die. Upon the death of one mated wolf, pairs are quickly re-established. Since males often predominate in any given wolf population, unpaired females are a rarity.[73] Polygamy does occur, but primarily in captive situations. Multiple litters are rarely successful, due to infanticide by the pack's females.[74] The age of first breeding in wolves depends largely on environmental factors; when food is abundant, or when wolf populations are heavily managed, wolves can rear pups at younger ages in order to exploit the newly available resources. Captive wolves have been known to breed as soon as they reach 9–10 months, while the youngest recorded breeding wolves in the wild were 2 years old. Females are capable of producing pups every year, with one litter annually being the average. Unlike coyotes, wolves never reach reproductive senescence before they die.[75] Incest rarely occurs, though inbreeding depression has been reported to be a problem for wolves in Saskatchewan[76] and Isle Royale.[77]

Estrus typically occurs in late winter, with older, multiparous females entering estrus 2–3 weeks earlier than younger females. Before the rut ensues, wolf packs will temporarily dissolve until the end of the mating season.[73] When receptive, females will avert the base of their tails to one side, exposing the vulva. During mating, the pair is locked into a copulatory tie which may last 5–36 minutes. Because estrus in wolves only lasts a month, the males do not abandon their mates to find other females to inseminate as dogs do. During pregnancy, female wolves will remain in a den located away from the peripheral zone of their territories, where violent encounters with other packs are more likely.[78] Old females usually whelp in the den of their previous litter, while younger females typically den near their birthplace. The gestation period lasts 62–75 days, with pups usually being born in the summer period.[79] The average litter consists of 5–6 pups. Litters of 14–17 occur 1% of the time.[80] Litter sizes tend to increase in areas where prey is abundant.[81] Wolves bear relatively large pups in small litters compared to other canid species.[82] Pups are born blind and deaf, and are covered in short soft grayish-brown fur. They weigh 300–500 grams at birth, and begin to see after 9–12 days. The milk canines erupt after one month. Pups first leave the den after 3 weeks. At 1.5 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 fathers to provide food for them and their young.[82][83] Unlike wolf mothers, the fathers do not regurgitate the pup's food, but carry them pieces from a kill. If the mother dies prior to the pups weaning period, they are suckled by the pack's other females.[84] Pups begin to eat solid food at the age of 3–4 weeks. Pups have a fast growth rate during their first four months of life: during this period, the pup's weight can increase nearly 30 times.[82][83]

The reproductive behaviour of introduced wolf packs in Yellowstone is unusual, as they often have multiple breeding females who mate with lone male wolves that encroach upon the pack territories during the mating season. These so called "Casanova wolves" are young males that, having failed to procure mates or territories after leaving their natal pack, mate with the daughters of already established breeding pairs from other packs. Unlike males from established packs, Casanova wolves do not form pair bonds with the females they mate with. Because of the great abundance of prey in Yellowstone, female wolves there can bear multiple litters in this fashion.[85]

Wolves use different places for their diurnal rest; places with cover are preferred during cold, damp and windy weather, while wolves in dry, calm and warm weather readily rest in the open. During the autumn-spring period, when wolves are more active, they willingly lie out in the open, whatever their location. Actual dens are usually constructed for pups during the summer period. When building dens, females make use of natural shelters such as fissures in rocks, cliffs overhanging riverbanks and holes thickly covered by vegetation. Sometimes, the den is the appropriated burrow of smaller animals such as foxes, badgers or marmots. An appropriated den is often widened and partly remade. On rare occasions, female wolves will dig burrows themselves, which are usually small and short with 1-3 openings.[86] Wolves do not line their denning places, a likely precaution against parasites.[87] The den is usually constructed not more than 500 metres away from a water source. Resting places, play areas for the pups and food remains are commonly found around wolf dens. The odour of urine and rotting food emanating from the denning area often attracts scavenging birds such as magpies and ravens. As there are few convenient places for burrows, wolf dens are usually occupied by animals of the same family. Though they mostly avoid areas within human sight, wolves have been known to nest near domiciles, paved roads and railways.[86]

Wolves are highly territorial animals, and generally establish territories far larger than they require to survive in order to assure a steady supply of prey. Territory size depends largely on the amount of prey available: in areas with an abundance of prey, the territories of resident wolf packs are smaller. Wolf packs travel constantly in search of prey, covering roughly 9% of their territory per day (average 25 km/d or 15 mi/d). The core of their territory is on average 35 km2 (14 sq mi), in which they spend 50% of their time.[88] Prey density tends to be much higher in the territory's surrounding areas. Despite this higher abundance of prey, wolves tend to avoid hunting in the fringes of their territory unless desperate, due to the possibility of fatal encounters with neighboring packs.[89] The size of their territory may increase when the pack's pups reach the age of 6 months, and thus have the same nutritional requirements as adults. The smallest territory on record was held by a pack of six wolves in northeastern Minnesota, which occupied an estimated 33 km2. The largest was held by an Alaskan pack of ten wolves encompassing a 6,272 km2 area. In some areas, wolves may shift territories during their prey's migration season.[90]

Wolves defend their territories from other packs through a combination of scent marking, direct attacks and howling (see Communication). Scent marking is used for territorial advertisement, and involves urination, defecation and ground scratching. Scent marks are generally left every 240 metres throughout the territory on regular travelways and junctions. Such markers can last for 2–3 weeks,[90] and are typically placed near rocks, boulders, trees or the skeletons of large animals.[91] When scent marking and howling fail to deter strange wolf packs from entering another's territory, violent interactions can ensue.[90] Territorial fights are among the principal causes of wolf mortality: one study on wolf mortality in Minnesota and the Denali National Park and Preserve concluded that 14–65% of wolf deaths were due to predation by other wolves.[92] In fact, 91% of wolf fatalities occur within 3.2 km (2.0 mi) of the borders between neighboring territories.[93] Because the consequences of trespassing can be fatal, such incursions are thought to be largely due to desperation or deliberate aggressiveness.[90]

Wolves primarily feed on medium to large sized ungulates (sometimes 10–15 times larger than themselves[26]), though they are not fussy eaters. Medium and small sized animals preyed on by wolves include marmots, hares, badgers, foxes, polecats, ground squirrels, mice, hamsters, voles and other rodents, as well as insectivores. They frequently eat waterfowl (particularly during their moulting period and winter, when their greasy and fatty meat helps wolves build up their fat reserves) and their eggs.[94][95] When such foods are insufficient, they will prey on lizards, snakes, frogs, rarely toads and large insects. In times of scarcity, wolves will readily eat carrion, visiting cattle burial grounds and slaughter houses.[94] Wolf packs in Astrakhan will hunt Caspian seals on the Caspian Sea coastline.[96] Some wolf packs in Alaska and Western Canada have been observed to feed on salmon.[97] Cannibalism is not uncommon in wolves; during harsh winters, packs often attack weak or injured wolves, and may eat the bodies of dead pack members.[98][99][100] However, they are not known to eat their young as coyotes sometimes do.[84] Humans are rarely, but occasionally preyed upon (see Attacks on humans).[101][102][103][104] Wolves will supplement their diet with fruit and vegetable matter; they willingly eat the berries of mountain ash, lily of the valley, bilberries, blueberries and cowberry. Other fruits include nightshade, apples and pears. They readily visit melon fields during the summer months.[98] Wolves can survive without food for long periods; two weeks without food will not weaken a wolf's muscle activity.[35]

In Eurasia, many wolf populations are forced to subsist largely on livestock and garbage in areas with dense human activity, though wild ungulates such as moose,[105] red deer, roe deer and wild boar are still important food sources in Russia and the more mountainous regions of Eastern Europe. Other prey species include reindeer, mouflon, wisent, saiga, ibex, chamois, wild goats, fallow deer and musk deer.[106] The prey animals of North American wolves have largely continued to occupy suitable habitats with low human density, and cases of wolves subsisting largely on garbage or livestock are exceptional. Animals commonly preyed on by North American wolves include moose, white-tailed deer, elk, mule deer, mountain sheep and caribou.[107] In North Africa, wolves feed on various cultivated crops and vegetables and domestic animals.[108]

Although wolf packs do cooperate strategically in bringing down prey, they do not do so as frequently or as effectively as lionesses do; unlike lions, wolves rarely remain with their pack for more than two years, thus they have less time to learn how to hunt cooperatively. Contrary to lion prides, food acquisition per wolf decreases with pack size.[109] Overall, single wolves or mated pairs typically have higher success rates in hunting than do large packs. Single wolves have occasionally been observed to kill large prey such as moose, bison and muskoxen unaided.[110] When hunting, wolves will attempt to conceal themselves as they approach their prey. With ungulate herds, they then either attempt to break up the herd, or isolate one or two animals from it.[111] If the targeted animal stands its ground, the wolves either ignore it, or try to intimidate it into running.[112] When chasing small prey, wolves will attempt to catch up with their prey as soon as possible. With larger animals, the chase is prolonged, in order to wear the selected prey out.[110] Wolves usually give up chases after 1–2 km (0.62-1.3 mi), though one wolf was recorded to chase a deer for 21 km (13 mi).[32] Sometimes, a single wolf will distract the herd with its presence, acting as a decoy, while its pack mates attack from behind.[113] Wolf packs may also set up ambush trails; Indian wolves have been observed to chase gazelle herds through ravines where other wolves lie in wait within holes dug prior to the hunt,[114] while Russian wolves will set up ambushes near water holes, sometimes using the same site repeatedly.[111] Both Russian and North American wolves have been observed to drive prey onto crusted ice, precipices, ravines, slopes and steep banks to slow them down.[115] Mature wolves usually avoid attacking large prey frontally, instead focusing on the rear and sides of the animal. They kill large prey by biting large chunks of flesh from the soft perineum area, causing massive blood loss. Such bites can cause wounds 10–15 cm in length, with three such bites to the perineum usually being sufficient to bring down a large deer in optimum health.[115] When attacking moose, they occasionally bleed it to death by biting its soft nose.[99] With medium-sized prey such as roe deer or sheep, northern wolves kill by biting the throat, severing nerve tracks and the carotid artery, thus causing the animal to die within a few seconds to a minute,[116] while the smaller southern wolves may grab the animal by the neck and stun it by jerking its head downward, hitting its nose on the ground.[9] When prey is vulnerable and abundant, wolves may occasionally surplus kill. Such instances are common in domestic animals, but rare in the wild. In the wild, surplus killing primarily occurs during late winter or spring, when snow is unusually deep (thus impeding the movements of prey)[117] or during the denning period, when wolves require a ready supply of meat when denbound.[118] Medium-sized prey are especially vulnerable to surplus killing, as the swift throat-biting method by which they are killed allows wolves to quickly kill one animal and move on to another.[116] Surplus killing may also occur when adult wolves are teaching their young to hunt.[119]

The breeding pair typically monopolizes food in order to continue producing pups. When food is scarce, this is done at the expense of other family members, especially non-pups.[95][120] This is in marked contrast to the feeding behaviours of dholes and African wild dogs, who give priority to their pups when feeding.[121] The breeding pair typically eats first, though as it is they who usually work the hardest in killing prey, they may rest after a long hunt and allow the rest of the family to eat unmolested. Once the breeding pair has finished eating, the rest of the family will tear off pieces of the carcass and transport them to secluded areas where they can eat in peace. Wolves typically commence feeding by consuming the larger internal organs of their prey, such as the heart, liver, lungs and stomach lining. The kidneys and spleen are eaten once they are exposed, followed by the muscles.[122]