The gray wolf or grey wolf (Canis lupus) is a canid native to the wilderness and remote areas of North America, Eurasia, and North Africa. It is the largest member of its family, with males averaging 43–45 kg (95–99 lb), and females 36–38.5 kg (79–85 lb). It is similar in general appearance and proportions to a German shepherd,[4] or sled dog, but has a larger head, narrower chest, longer legs, straighter tail, and bigger paws. Its winter fur is long and bushy, and predominantly a mottled gray in colour, although nearly pure white, red, or brown to black also occur.[4]
Within the genus Canis, the gray wolf represents a more specialised and progressive form than its smaller cousins (the coyote and golden jackal), as demonstrated by its morphological adaptations to hunting large prey, its more gregarious nature, and its highly advanced expressive behavior. It is a social animal, travelling in nuclear families consisting of a mated pair, accompanied by the pair's adult offspring. The gray 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, though it also eats smaller animals, livestock, carrion, and garbage.
The gray wolf is one of the world's most well known and well researched animals, with probably more books written about it than any other wildlife species.[15] It has a long history of association with humans, having been despised and hunted in most agricultural communities due to its attacks on livestock, while conversely being respected by some Native American tribes. It is the sole ancestor of the dog, which was first domesticated in the Middle East. Although the fear of wolves is prevalent 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 unusual, as wolves are relatively few, live away from people, and have been taught to fear humans by hunters and shepherds. Hunting and trapping has reduced the species' range to about one third of its original range, though its still relatively widespread range and stable population means that the species is not threatened at a global level, and is therefore classified by the IUCN as Least Concern.
The gray wolf is a slender, powerfully built animal with a large, deeply descending ribcage and a sloping back. Its abdomen is pulled in, and its neck heavily muscled. Its limbs are long and robust, with comparatively small paws. 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, thus allowing both fore and hind limbs on the same side to swing in the same line. The wolf's legs are moderately longer than those of other canids. This enables the animal to move swiftly, and allows it to overcome the deep snow that covers most of its geographical range. Females tend to have narrower muzzles and foreheads, thinner necks, slightly shorter legs and less massive shoulders than males.[59] Compared to its smaller cousins (the coyote and golden jackal), the gray wolf is larger and heavier, with a broader snout, shorter ears, a shorter torso and longer tail.
The gray wolf's head is large and heavy, with a wide forehead, strong jaws and a long, blunt muzzle. The ears are relatively small and triangular. The teeth are heavy and large, being better suited to crushing bone than those of other extant canids, though not as specialised as those found in hyenas. The canine teeth are robust and relatively short (26 mm). The wolf can exert 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. 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 of the rest of the body, and is maintained at just above tissue-freezing point where the pads come in contact with ice and snow.
The gray wolf usually carries its head at the same level as the back, raising it only when alert. It usually travels at a loping pace, placing its paws one directly in front of the other. This gait can be maintained for hours at a rate of 8–9 km/h,[65] and allows the wolf to cover great distances. On bare paths, a wolf can quickly achieve speeds of 50–60 km/h. The gray wolf has a running gait of 55 to 70 km/h, can leap 5 metres horizontally in a single bound, and can maintain rapid pursuit for at least 20 minutes.[66] A running wolf holds its head slightly low and cocked to one side, directing one ear forward and the other back. This posture allows the wolf to continually make use of its exceptional hearing.
The gray wolf is the largest extant member of the Canidae, excepting certain large breeds of domestic dog. Gray wolf weight and size can vary greatly worldwide, tending to increase proportionally with latitude as predicted by Bergmann's Rule, with the large wolves of Alaska and Canada sometimes weighing 3–6 times more than their Middle Eastern and South Asian cousins. On average, adult wolves measure 105–160 cm (41–63 in) in length and 80–85 cm (32–34 in) in shoulder height.] The tail is ⅔ the length of the head and body, measuring 29–50 cm (11–20 in) in length. The ears are 90–110 millimetres (3.5–4.3 in) in height, and the hind feet are 220–250 mm. The skull averages 9–11 inches in length, and 5–6 inches wide. Wolf weight varies geographically; on average, European wolves may weigh 38.5 kilograms (85 lb), North American wolves 36 kilograms (79 lb) and Indian and Arabian wolves 25 kilograms (55 lb). Females in any given wolf population typically weigh 5–10 lbs less than males.[73]
Wolves weighing over 54 kg (120 lbs) are uncommon, though exceptionally large individuals have been recorded in Alaska, Canada, and the former Soviet Union. 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), while the heaviest recorded wolf in Eurasia was killed after World War II in Kobeliaky, Poltavskij Region, Ukrainian SSR, and weighed 86 kilograms (190 lb).
The gray wolf has very dense and fluffy winter fur, with short underfur and long, coarse guard hairs. Most of the underfur and some of the guard hairs are shed in the spring and grow back in the autumn period. 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. 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 does not collect ice when warm breath is condensed against it. In warm climates, the fur is coarser and scarcer than in northern wolves. 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.[59] 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.
Coat colour ranges from almost pure white through various shades of blond, cream, and ochre to grays, browns, and blacks. Variation in fur color tends to increase in higher latitudes. Differences in coat colour between sexes are largely absent, though females may have redder tones.[80] Fur color doesn't seem to serve any camouflage purpose, with some experts concluding that the blended colors have more to do with emphasizing certain gestures during interaction. Black coloured wolves (which occur through wolf-dog hybridisation) rarely occur in Eurasia, where interactions with domestic dogs have been reduced over the past thousand years due to the depletion of wild wolf populations. Black specimens are more common in North America, with about half the wolves in Yellowstone National Park being black.
The gray wolf's 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, it rarely manages to capture hidden hares or birds, though it can easily follow fresh tracks. Its auditory perception is sharper than that of the fox, being able to hear up to a frequency of 26 kHz, which is sufficient to register the fall of leaves in the autumn period. The urban legend that wolves fear the sound of string instruments may have a basis in fact, as captive wolves have been shown to exhibit signs of intense distress when hearing low minor chords. Its night vision exceeds that of other Canids.
Although some wolves are solitary, most are highly gregarious animals. The basic social unit of a wolf pack is the mated pair, accompanied by the pair's adult offspring. In ideal conditions, the mated pair produces pups every year, with such offspring typically staying in the pack for 10–54 months before dispersing. The average pack consists of a family of 5–11 animals (1–2 adults, 3–6 juveniles and 1–3 yearlings), or sometimes two or three such families, with exceptionally large packs consisting of 42 wolves being known. Triggers for dispersal include the onset of sexual maturity and competition within the pack for food. The distance travelled by dispersing wolves varies widely - some stayed in the vicinity of the parental group, while other individuals have been recorded travelling great distances of 390 km, 206 km, and 670 km from their natal packs. A new pack is usually founded by an unrelated male and female, travelling together in search of an area devoid of other hostile packs. 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 (1–3 years of age) 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.[88] During times of ungulate abundance (migration, calving etc.), different wolf packs may temporarily join forces.
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 and the age of the pack's pups, tending to increase in size in areas with low prey populations or when the pups reach the age of 6 months, thus having the same nutritional needs as adults. 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. Prey density tends to be much higher in the territory's surrounding areas, though wolves tend to avoid hunting in the fringes of their territory unless desperate, due to the possibility of fatal encounters with neighboring packs.[95] 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 a 6,272 km2 (2,422 sq mi) area.[94] Wolf packs are typically settled, and usually only leave their accustomed ranges during severe food shortages.
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, and are typically placed near rocks, boulders, trees or the skeletons of large animals. When scent marking and howling fail to deter strange wolf packs from entering another's territory, violent interactions can ensue.[94] 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.
Although the wolf's intelligence has not been quantified, scattered reports and laboratory studies do give indications on the species' ability to remember, associate events, and learn. During the extermination of the American bison on the Great Plains, wolves learned to follow the sounds of gunshots, and would wait until the hunters had skinned and abandoned the bison carcasses before feeding on them. In northern Montana, where wolves were heavily persecuted by aerial hunters, wolves learned to avoid open areas whenever they heard aircraft. Conversely, biologists using aircraft to study wolves have managed to condition wolves not to fear their approach, even when flying low. When hunting, wolves tend to target the easiest options available to them: in areas populated by both moose and smaller deer species, the latter are taken in much higher proportion. The wolf's powers of memory were described by George Mivart, who reported that a tame wolf was able to recognise its master after a three-year absence. Non-rabid wolves are able to distinguish between armed and unarmed people, and typically avoid investigating people who display self-confident demeanors typical of being armed. Adult wolves have been known to skillfully select hidden approaches when entering their dens, using bushes, wind-fallen trees, stumps, and other natural structures to conceal their approach. Wolves with prior experience to traps may learn how to avoid or even harmlessly trigger them: in his hunt for the Currumpaw wolf, naturalist Ernest Thompson Seton noted that his initial attempts at capturing it were unsuccessful, as the wolf would dig up and spring the traps, or ignore them altogether.
Though wolves are trainable, they lack the same degree of tractability seen in dogs. They are generally not as responsive as dogs are to coercive techniques involving fear, aversive stimuli and force. Generally, far more work is required to obtain the same degree of reliability seen in most dogs. Even then, once a certain behavior has been repeated several times, wolves may get bored and ignore subsequent commands. Wolves are more responsive toward positive conditioning and rewards, though simple praise is not sufficient as in most dogs. Unlike dogs, wolves tend to respond more to hand signals than voice. Most attempts to train wolves as working dogs have met with failure. German biologist Erik Zimen attempted to train his captive wolves as sled dogs, and although his wolves eventually accepted the harness and the need to pull the sled in a straight line, they were ultimately unreliable, as they fought for personal space, would ignore commands once tired, and were distracted by other wildlife. However, John James Audubon recorded an instance of a wolf being trained to hunt deer in Kentucky, and Henry Wharton Shoemaker published a similar account of settlers in western and central Pennsylvania using wolves as hunting dogs.[137] Buffon wrote in his Natural History of tamed wolves in Persia being trained to perform dances and tricks.