Wolf Wölfe Tiere Animals Natur SelMcKenzie Selzer-McKenzie

Wolf
Author Selzer-McKenzie
The grey wolf or gray wolf (Canis lupus), also known as the timber wolf or simply wolf, is the largest wild member of the Canidae family. It is an ice age survivor originating during the Late Pleistocene around 300,000 years ago.[3] DNA sequencing and genetic drift studies reaffirm that the gray wolf shares a common ancestry with the domestic dog (Canis lupus familiaris). Although certain aspects of this conclusion have been questioned, including recently[4], the main body of evidence confirms it. A number of other gray wolf subspecies have been identified, though the actual number of subspecies is still open to discussion. Gray wolves are typically apex predators in the ecosystems they occupy. Though not as adaptable as more generalist canid species[4], wolves have thrived in temperate forests, deserts, mountains, tundra, taiga, grasslands, and even urban areas.[5]

Though once abundant over much of Eurasia and North America, the gray wolf inhabits a very small portion of its former range because of widespread destruction of its territory, human encroachment of its habitat, and the resulting human-wolf encounters that sparked broad extirpation. Even so, the gray wolf is regarded as being of least concern for extinction according to 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 extermination as perceived threats to livestock and pets.

In areas where human cultures and wolves are sympatric, wolves frequently feature in the folklore and mythology of those cultures, both positively and negatively.
Gray wolf weight and size can vary greatly worldwide, tending to increase proportionally with latitude as predicted by Bergmann's Rule. In general, height varies from 0.6 to .95 meters and (26–38 inches) at the shoulder. Wolf weight varies geographically; on average, European wolves may weigh 85 lbs, North American wolves 80 lbs, and Indian and Arabian wolves 55 lbs.[6] Though rarely encountered, extreme specimens of more than 77 kg (170 lb.) have been recorded in Alaska, Canada[7], and the former Soviet Union.[8] The heaviest recorded gray wolf in the New World was killed on 70 Mile River in east-central Alaska on July 12, 1939 and weighed 79 kg (175 lb.)[6], while the heaviest recorded wolf in the Old World was killed after World War II in the Kobelyakski Area of the Poltavskij Region in the Ukrainian SSR, and weighed 86 kg (189 lb.).[9] Grey wolves are sexually dimorphic, with females in any given wolf population typically weighing 20% less than males.[10] Females also have narrower muzzles and foreheads; slightly shorter, smoother furred legs; and less massive shoulders.[6] Gray wolves can measure anywhere from 1.3 to 2 meters (4.5–6.5 feet) from nose to the tip of the tail, which itself accounts for approximately one quarter of overall body length.[11]
Gray Wolf skeleton.

Gray wolves are built for stamina, possessing features ideal for long-distance travel. Their narrow chests and powerful backs and legs facilitate efficient locomotion. They are capable of covering several miles trotting at about a pace of 10 km/h (6 mph), and have been known to reach speeds approaching 65 km/h (40 mph) during a chase.[12] One female gray wolf was recorded to have made 7 metre bounds when chasing prey.[9]

Gray wolf paws are able to tread easily on a wide variety of terrains, especially snow. There is a slight webbing between each toe, which allows them to move over snow more easily than comparatively hampered prey. Gray wolves are digitigrade, which, with the relative largeness of their feet, helps them to distribute their weight well on snowy surfaces. The front paws are larger than the hind paws, and have a fifth digit, the dewclaw, that is absent on hind paws.[13] Bristled hairs and blunt claws enhance grip on slippery surfaces, and special blood vessels keep paw pads from freezing.[14] Scent glands located between a wolf's toes leave trace chemical markers behind, helping the wolf to effectively navigate over large expanses while concurrently keeping others informed of its whereabouts.[14] Unlike dogs and western coyotes, gray wolves have a lower density of sweat glands on their paws. This trait is also present in Eastern Canadian Coyotes which have been shown to have recent wolf ancestry.[15] Wolves in Israel are unique due to the middle two toes of their paws being fused, a trait originally thought to be unique to the African Wild Dog
Wolves have bulky coats consisting of two layers. The first layer is made up of tough guard hairs that repel water and dirt. The second is a dense, water-resistant undercoat that insulates. The undercoat is shed in the form of large tufts of fur in late spring or early summer (with yearly variations). A wolf will often rub against objects such as rocks and branches to encourage the loose fur to fall out. The undercoat is usually gray regardless of the outer coat's appearance. Wolves have distinct winter and summer pelages that alternate in spring and autumn. Females tend to keep their winter coats further into the spring than males.

Fur coloration varies greatly, running from gray to gray-brown, all the way through the canine spectrum of white, red, brown, and black. These colors tend to mix in many populations to form predominantly blended individuals, though it is not uncommon for an individual or an entire population to be entirely one color (usually all black or all white). With the exception of Italy, in which black wolves can constitute 20-25% of the entire population, melanistic wolves rarely occur outside the North American continent.[17] According to genetic examinations, the black coat colour is based on a mutation that first arose among domestic dogs and later migrated into the wolf-population via interbreeding.[18] A multicolor coat characteristically lacks any clear pattern other than it tends to be lighter on the animal's underside. Fur color sometimes corresponds with a given wolf population's environment; for example, all-white wolves are much more common in areas with perennial snow cover. Aging wolves acquire a grayish tint in their coats. It is often thought that the coloration of the wolf's pelage serves as a functional form of camouflage. This may not be entirely correct, as some scientists have concluded that the blended colors have more to do with emphasizing certain gestures during interaction.[6]

At birth, wolf pups tend to have darker fur and blue irises that will change to a yellow-gold or orange color when the pups are between 8 and 16 weeks old.[19]
Adolescent wolf with golden-yellow eyes.

Wolves' long, powerful muzzles help distinguish them from other canids, particularly coyotes and Golden Jackals, which have more narrow, pointed muzzles. In wolves, the anterior incisure of the nasal bones does not have a medial protrusion, unlike jackals. The cingulum on the external edge of the first upper molar is only slightly expressed, while it is broad and distinctly marked in jackals.[20]

Wolves differ from domestic dogs in a more varied nature. Anatomically, wolves have smaller orbital angles than dogs (>53 degrees for dogs compared with <45>

Wolves and most larger dogs share identical dentition. The maxilla has six incisors, two canines, eight premolars, and four molars. The mandible has six incisors, two canines, eight premolars, and six molars.[22] The fourth upper premolars and first lower molars constitute the carnassial teeth, which are essential tools for shearing flesh. The long canine teeth are also important, in that they hold and subdue the prey. Capable of delivering up to 10,000 kPa (1450 lbf/in²) of pressure, a wolf's teeth are its main weapons as well as its primary tools.[6] This is roughly twice the pressure that a domestic dog of similar size can deliver.[23] The dentition of grey wolves is better suited to bone crushing than those of other modern canids, though it is not as specialised as that found in hyenas.[24]

Wolf saliva has been shown to reduce bacterial infection in wounds and accelerate tissue regeneration
Generally, mating occurs between January and April — the higher the latitude, the later it occurs.[26] A pack usually produces a single litter unless the breeding male mates with one or more subordinate females. During the mating season, breeding wolves become very affectionate with one another in anticipation of the female's ovulation cycle. The pack tension rises as each mature wolf feels urged to mate. During this time, the breeding pair may be forced to prevent other wolves from mating with one another.[27] Incest rarely occurs, though Inbreeding depression has been reported to be a problem for wolves in Saskatchewan[28] and Isle Royale.[29] When the breeding female goes into estrus (which occurs once per year and lasts 5–14 days),[30] she and her mate will spend an extended time in seclusion. Pheromones in the female's urine and the swelling of her vulva make known to the male that the female is in heat. The female is unreceptive for the first few days of estrus, during which time she sheds the lining of her uterus; but when she begins ovulating again, the two wolves mate.

The gestation period lasts between 60 and 63 days. The pups, which weigh 0.5 kg (1 lb) at birth, are born blind, deaf, and completely dependent on their mother.[26][31] The average litter size is 5-6 pups, though there are two Soviet records of litters consisting of 17 pups.[9] The pups reside in the den and stay there for two months. The den is usually on high ground near an open water source, and has an open chamber at the end of an underground or hillside tunnel that can be up to a few meters long.[14] During this time, the pups will become more independent, and will eventually begin to explore the area immediately outside the den before gradually roaming up to a mile away from it at around 5 weeks of age. Wolf growth rate is slower than that of coyotes and dholes.[32] They begin eating regurgitated foods after 2 weeks of feeding on milk, which in wolves has less fat and more protein and arginine than dog milk.[10] By this time, their milk teeth have emerged — and are fully weaned by 10 weeks. During the first weeks of development, the mother usually stays with her litter alone, but eventually most members of the pack will contribute to the rearing of the pups in some way.[26] After two months, the restless pups will be moved to a rendezvous site, where they can stay safely while most of the adults go out to hunt. One or two adults stay behind to ensure the safety of the pups. After a few more weeks, the pups are permitted to join the adults if they are able, and will receive priority on anything killed, their low ranks notwithstanding. Letting the pups fight for eating privileges results in a secondary ranking being formed among them, and allows them to practice the dominance/submission rituals that will be essential to their future survival in pack life.[26] During hunts, the pups remain ardent observers until they reach about 8 months of age, by which time they are large enough to participate actively.

Wolves typically reach sexual maturity after two or three years, at which point many of them will be compelled to leave their birth packs and seek out mates and territories of their own.[26][33] Wolves that reach maturity generally live 6 to 10 years in the wild, although in captivity they can live to twice that age.[34] High mortality rates give them a low overall life expectancy. Pups die when food is scarce; they can also fall prey to predators such as bears, tigers, or other wolves. The most significant causes of mortality for grown wolves are hunting and poaching, car accidents, and wounds inflicted while hunting prey. Although adult wolves may occasionally be killed by other predators, rival wolf packs are often their most dangerous non-human enemy.
Diseases recorded to be carried by wolves include brucella, deerfly fever, leptospirosis, foot-and-mouth disease, and anthrax. Wolves are major hosts for rabies in Russia, Iran, Afghanistan, Iraq, and India.[35] Though wolves are not reservoirs for the disease, they can catch it from other species. Wolves develop an exceptionally severe aggressive state when rabid and can bite numerous people in a single attack. Before a vaccine was developed, bites were almost always fatal. Today, wolf bites can be treated, but the severity of rabid wolf attacks can sometimes result in outright death, or a bite near the head will make the disease act too fast for the treatment to take effect. Rabid attacks tend to cluster in winter and spring. With the reduction of rabies in Europe and North America, few rabid wolf attacks have been recorded, though some still occur annually in the Middle East.[36] Wolves also carry the Canine coronavirus, infections being most prelevant in winter months.[37]

Wolves in Russia have been recorded to carry over 50 different kinds of harmful parasites, including echinococcus, cysticercosis, and coenuri.[35] Wolves are also carriers of Trichinella spiralis. Between 1993-94, 148 wolf carcasses near Fairbanks, Alaska were examined for larvae, 54 (36%) of which were found to be infected. Prevalence of Trichinella spiralis in wolves is significantly related to age.[38] Wolves may carry Neospora caninum, which is of particular concern to farmers, as the disease can be spread to livestock; infected animals being three to thirteen times more likely to abort than those not infected.[39]

Despite their habit of carrying harmful diseases, large wolf populations are not heavily regulated by epizootic outbreaks as with other social canids. This is largely due to the habit of infected wolves vacating their packs, thus preventing mass contagion
Occasionally, single wolves are found in the wild, though packs are more common.[40][41] Lone wolves are typically old specimens driven from their pack or young adults in search of new territory.[42] Wolf packs in the northern hemisphere tend not to be as compact or unified as those of African Wild Dogs and Spotted Hyenas,[43] though they are not as unstable as those of coyotes.[44] Normally, the pack consists of a male, a female, and their offspring, essentially making the pack a nuclear family.[40][41] The size of the pack may change over time and is controlled by several factors, including habitat, personalities of individual wolves within a pack, and food supply. Packs can contain between 2 and 20 wolves, though 8 is a more typical size.[45] An unusually large pack consisting of 36 wolves was reported in 1967 in Alaska.[46] While most breeding pairs are monogamous, there are exceptions.[47] Wolves will usually remain with their parents until the age of two years. Young from the previous season will support their parents in nursing pups of a later year. Wolf cubs are very submissive to their parents, and remain so after reaching sexual maturity. On occasion in captivity, subordinate wolves may rise up and challenge the dominant pair; such revolts may result in daughters killing mothers and sons killing fathers.[48] This behavior has never been documented in the wild,[49] and it is hypothesized that it only happens in captivity because dispersal is impossible.[50] There are no documented cases of subordinate wolves challenging the leadership of their parents.[40][41][47] Instead of openly challenging the leadership of the pack leaders, most young wolves between the ages of 1-4 years leave their family in order to search for, or start, a pack of their own.[47] Wolves acting unusually, such as epileptic pups or thrashing adults crippled by a trap or a gunshot, are usually killed by other members of their own pack.[6] Asiatic and Middle Eastern wolves tend to be less inclined to socialising with any other member of their species outside their own nuclear family, passing their lives more frequently either in pairs or as social individuals, much like coyotes and dingoes.[51]

In literature, wolf packs are commonly portrayed as strongly hierarchic communities, with a dominant breeding "Alpha pair", a group of subordinate "Beta" individuals, and the scapegoat "Omega wolf" on the lowest end of the hierarchy. These descriptions are heavily based on research on captive wolves and cannot be extrapolated to wild wolf packs. In captivity, dispersal of mature individuals is impossible, resulting in frequent aggressive hierarchic encounters.[40][41] According to wolf biologist L. David Mech, "Calling a wolf an alpha is usually no more appropriate than referring to a human parent or a doe deer as an alpha. Any parent is dominant to its young offspring, so alpha adds no information."[47] The term may be valid under certain circumstances, such as when a pack adopts an unrelated dispersed wolf, when the breeding pair die, thus leaving the alpha position open, or when siblings disperse from a pack together. In these cases, the standard nuclear family model does not apply, which may cause wild wolves to behave more like they do in captivity.
Wolves are territorial animals. Studies have shown that the average size of a wolf pack's territory is close to 200 km2.[52] Wolf packs travel constantly in search of prey, covering roughly 9% of their territory per day (average 25 km/d). The core of their territory is on average 35 km2, in which they spend 50% of their time.[53] 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.[54] Established wolf packs rarely accept strangers into their territories, with one study on wolf mortality in Minnesota and the Denali National Park and Preserve concluding that 14–65% of wolf deaths were due to predation by other wolves.[55] In fact, 91% of wolf fatalities occur within 3.2 km of the borders between neighboring territories.[56] The majority of killed wolves are dominant animals, due to their greater assertiveness in confronting other packs.[57] In rare cases in which a stranger is accepted into the pack, the animal itself is almost invariably a young specimen of 1–3 years of age, while the majority of killed wolves are adults.[58]

Communication between these boundaries is achieved in part through scent marking and howling. Howling is the principle means of spacing in wolf populations. It communicates the location of a core territory as well as enforcing a territory-independent buffer zone around the roaming wolf pack. This territory-independent buffer zone is a means of avoiding encounters with neighboring packs near territory borders.[59] Lone wolves, in contrast, rarely respond to howls, instead taking an "under the radar" approach. Howling communicates a core territory over time, as a wolf packs spends much of their time there.
Dispersion

Offspring of the breeding pair tend to stay with the pack for some portion of their adulthood. These "subordinate" wolves play a number of important roles in the pack, including participating in hunts, enforcing discipline and raising pups[60]. This behavior is achieved, in part, by an active suppression of reproduction in subordinate wolves by the breeding pair. Thus, while they remain members of the pack, they are unable to reproduce, even if there are other subordinate unrelated wolves in the pack. In many wolves, the drive to reproduce leads them to leave the pack. Dispersals occur at all times during the year, and typically involve wolves that have reached sexual maturity prior to the previous breeding season.[42] Dispersed wolves search for new territory and companionship, a hazardous process that could lead to death.[61] Successful dispersions end when the wolf has found another single wolf of the opposite sex and bonds with it. Thus it takes two such dispersals from two separate packs for a new breeding pair to be formed, for dispersing wolves from the same maternal pack tend not to mate.[27] Once two dispersing wolves meet and begin traveling together, they immediately begin the process of seeking out territory, preferably in time for the next mating season.[26]

Scent marking
Wolves scent-roll to bring scents back to the pack.

Wolves, like other canines, use scent marking to lay claim to anything—from territory to fresh kills.[62] Breeding wolves scent mark the most often, with males doing so more than females. The most widely used scent marker is urine. Male and female breeding wolves urine-mark objects with a raised-leg stance (all other pack members squat) to enforce rank and territory. They also use marks to identify food caches and to claim kills on behalf of the pack. Defecation markers are used for the same purpose as urine marks, and serve as a more visual warning, as well.[62] Defecation markers are particularly useful for navigation, keeping the pack from traversing the same terrain too often and also allowing each wolf to be aware of the whereabouts of its pack members. Above all, though, scent marking is used to inform other wolves and packs that a certain territory is occupied, and that they should therefore tread cautiously.

Wolves have scent glands all over their bodies, including at the base of the tail, between toes, and in the eyes, genitalia, and skin.[62] Pheromones secreted by these glands identify each individual wolf. A dominant wolf will "rub" its body against subordinate wolves to mark such wolves as being members of a particular pack. Wolves may also "paw" dirt to release pheromones instead of urine marking.[63]

Dietary habits

Wolves feed primarily on medium to large sized ungulates, though they are opportunistic feeders, and will generally eat any meat that is available,[64] including non-ungulate species[65], carrion and garbage.[64] Cannibalism is not uncommon in wolves, and has been recorded to occur, in times of food scarcity,[66], when a pack member dies,[67] and during territorial disputes.[57] Some wolf packs in Alaska and Western Canada have been observed to feed on salmon.[68][69] Wolves will typically avoid a potential prey item which does not conform to what they experienced during their lives. Generally, the greater the discrepancy to what wolves are previously accustomed to, the greater their resistance to exploring it. This is only increased should the new prey act bold, assertive, and fearless. Nevertheless, even if there is no food shortage, wolves will explore alternative prey if they continually come into close contact with it and habituate themselves.[70]
An American Bison standing its ground, thereby increasing its chance for survival.

Wolf packs show little strategic cooperation in hunting unlike lions, though wolf pairs have been shown to strategize when attacking large prey.[64] Though commonly portrayed as targeting solely sick or infirm animals,[33] there is little evidence that they actively limit themselves to such targets. Rather, the evidence shows that wolves will simply target the easiest options available, which as well as sick and infirm animals, can also include young animals and pregnant females.[71] Wolves typically attempt to conceal themselves as they approach their prey.[9] Often, they will wait for the prey to graze, when it is distracted.[9] If the prey animal stands its ground or confronts the pack, the wolves will approach and threaten it. The wolves will eventually leave if their prey does not run, though the length of time can range from hours to days.[64] If their prey attempts to flee, the wolves will give chase. Wolves generally do not engage in long chases, and will usually stop a pursuit after a chase of 10-180 metres, though there has been one documented case of a wolf chasing a moose for 36 km.[9] Female wolves tend to be better at chasing prey than males, while the latter are more adept at wrestling large prey to the ground once it is caught. Packs composed largely of female wolves thrive on fleet footed prey such as elk, while packs specialising in bison tend to have a greater number of males.[72]

Upon catching large prey such as moose, wolves will typically kill by tearing at the haunches and perineum, causing massive bleeding and loss of coordination. A single bite can cause a wound up to 10-15 cm in length. A large deer in optimum health generally succumbs to three bites at the perineum area after a chase of 150 metres.[9] Sometimes, with medium sized prey such as dall sheep, wolves will bite the throat, severing the windpipe or jugular.[73] When attacking canid prey, such as dogs, coyotes or other wolves, wolves will kill by biting the back, neck or head.[57][74][75] With prey of equal or lesser weight to the wolf, such as lambs or small children, wolves will grab their quarry by the neck, chest, head or thigh and carry them off to a secluded spot.[9][76] Once the prey collapses, the wolves will tear open the abdominal cavity and commence feeding on the animal, sometimes while it is still alive.[9] On some occasions, wolves will not press an attack, and will wait for their prey to die from their wounds before feeding begins.[77] Wolves will occasionally attack pregnant ungulates to feed on the fetus(es), whilst leaving the mother uneaten.[78] Usually, it is the dominant pair that works the hardest in killing the pack's target.[64] Wolves have on occasion been observed to engage in acts of surplus killing. This phenomenon is common when wolves target livestock.[79] In the wild, this usually occurs in late winter or spring when deep snow impedes their prey's escape.[79][80]

Pack status is reinforced during feeding. The breeding pair usually eats first, starting with the heart, liver, and lungs. Wolves of intermediate rank will prevent lower ranking pack members from feeding until the dominant pair finishes eating.[25] The stomach of prey is eaten, though the contents are left untouched if the killed animal is a herbivore. The leg muscles are eaten next, with the hide and bones being the last to be consumed.[64] If they are disturbed while feeding, they will instead focus their attention on their prey's fat deposits rather than internal organs.[81][82] A single wolf can eat up to 3.2-3.5 kg of food at a time, though they can eat as much as 13–15 kg when sufficiently hungry. A wolf's yearly requirement is 1.5 tons of meat.[9] Wolves can go without sustenance for long periods of time, with one Russian record showing how one specimen survived for 17 days without food.[6] Research has shown that 2 weeks without food will not weaken a wolf's muscle activity.[9] After eating, wolves will drink large quantities of water to prevent uremic poisoning.[6] A wolf's stomach can hold up to 7.5 litres of water.[9] Wolves will on occasion supplement their diet with vegetation, with some areas of the former Soviet Union reporting that wolves cause serious damage to watermelon plantations.[71]

Studies on how wolves affect prey populations tend to vary considerably, with some results indicating that wolves dramatically reduce, sometimes locally extirpate some prey species, while others indicate that wolf predation simply takes over from other mortality factors present in wolf-free zones.[66][80] Wolves are not a keystone species, as they are not essential for the presence or survival of other species.[83]

Interspecific predatory relationships
Rolf Peterson investigating coyote carcass killed by a wolf in Yellowstone National Park, January 1996

Wolves typically dominate other canid species in areas where they are sympatric. In North America, wolves are generally intolerant of coyotes in their territory; two years after their reintroduction to the Yellowstone National Park, the wolves were responsible for a near 50% drop in coyote populations through both competition and predation.[84] Wolves have been reported to dig coyote pups from their dens and kill them. Wolves typically do not consume the coyotes they kill. There are no records of coyotes killing wolves,[75] though they have been known to gang up on wolves if they outnumber them.[84] Near identical interactions have been observed in Greece between wolves and Golden Jackals.[85] Wolves may kill foxes on kill sites, though not as frequently as they do with coyotes. Raccoon Dogs are also reportedly preyed upon.[75]
Wolf following a brown bear

Brown Bears are encountered in both Eurasia and North America. The majority of interactions between wolves and Brown Bears usually amount to nothing more than mutual avoidance. Serious confrontations depend on the circumstances of the interaction, though the most common factor is defence of food and young. Brown Bears will use their superior size to intimidate wolves from their kills and when sufficiently hungry, will raid wolf dens. Brown Bears usually dominate wolves on kills, though they rarely prevail against wolves defending den sites. Wolves in turn have been observed killing bear cubs, to the extent of even driving off the defending mother bears. Deaths in wolf/bear skirmishes are considered very rare occurrences, the individual power of the brown bear and the collective strength of the wolf pack usually being sufficient deterrents to both sides.[75] Encounters with American Black Bears occur solely in the Americas; their interactions with wolves are much rarer than those of Brown Bears, due to differences in habitat preferences. The majority of Black Bear encounters with wolves occur in the species' northern range, with no interactions being recorded in Mexico. Wolves have been recorded to kill Black Bears on numerous occasions without eating them. Unlike Brown Bears, Black Bears frequently lose against wolves in disputes over kills.[75] While encounters with brown and black bears appear to be common, polar bears are rarely encountered by wolves, though there are two records of wolf packs killing polar bear cubs.[86]

Large wolf populations limit the numbers of small to medium sized felines. Wolf predation is recorded to reduce lynx populations wherever the two species are sympatric. Lynx populations in Slovakia plummetted during World War II, when large numbers of wolves entered the cat's range. Similairly, in Russia, lynx populations drop in areas with high wolf densities.[87] In the Rocky Mountains and adjacent mountain areas of North America, wolves are usually hostile toward cougars and will kill cubs if given the opportunity. A pack will on occasion appropriate the kills of adult cougars, which respond by increasing their kill rate. Both species have been recorded to kill each other.[75] National Park Service cougar specialist Kerry Murphy stated that the cougar usually is at an advantage on a one to one basis, considering it can effectively use its claws, as well as its teeth, unlike the wolf which relies solely on its teeth. Yellowstone officials have reported that attacks between cougars and wolves are not uncommon. Multiple incidents of cougars taking wolves and vice versa have been recorded in Yellowstone National Park. Researchers in Montana have found that wolves regularly kill cougars in the area.[88] Similarly, large numbers of wolves have been reported to reduce leopard populations in Tibet[89]. However, the reverse is true for larger cats such as tigers. In areas where wolves and tigers share ranges, such as the Russian Far East, the two species typically display a great deal of dietary overlap, resulting in intense competition. Wolf and tiger interactions are well documented in Sikhote-Alin, which until the beginning of the 20th century, held very few wolves. It is thought by certain experts that wolf numbers increased in the region after tigers were largely eliminated during the Russian colonization in the late 1800s and early 1900s. This is corroborated by native inhabitants of the region claiming that they had no memory of wolves inhabiting Sikohte-Alin until the 1930s, when tiger numbers decreased.[90] Tigers depress wolf numbers, either to the point of localized extinction or to such low numbers as to make them a functionally insignificant component of the ecosystem. Wolves appear capable of escaping competitive exclusion from tigers only when human persecution decreases the latter's numbers.[91] Today wolves are considered scarce in tiger inhabited areas, being found in scattered pockets, and usually seen traveling as loners or in small groups. First hand accounts on interactions between the two species indicate that tigers occasionally chase wolves from their kills, while wolves will scavenge from tiger kills. Tigers are not known to prey on wolves, though there are four records of tigers killing wolves without consuming them.[90] This competitive exclusion of wolves by tigers has been used by Russian conservationists to convince hunters in the Far East to tolerate the big cats, as they limit ungulate populations less than wolves, and are effective in controlling the latter's numbers.[92]

Wolves may occasionally encounter Striped Hyenas in the Middle East and Central and South Asia, mostly in disputes over carcasses. Though hyenas usually dominate wolves on a one to one basis, wolf packs have been reported to displace lone hyenas from carcasses.[93] Wolf remains have been found in Cave Hyena den sites, though it is unknown if the wolves were killed or scavenged upon.[94] Unlike cave hyenas, which preferentially preyed on lowland animals such as horses, wolves relyed more on slope-dwelling ibex and Roe Deer, thus minimising competition. Wolves and Cave Hyenas seem to display negative abundance relations over time, with wolf populations expanding their ranges as hyenas disappeared.
Body language
See also: Dog communication
The posture and facial expression of this Arabian wolf is defensive and gives warning to other wolves to be cautious.
This facial expression shows fear.

Wolves can communicate visually through a wide variety of expressions and moods ranging from subtle signals, such as a slight shift in weight, to more obvious ones, such as rolling on their backs to indicate complete submission.[96]

* Dominance – A dominant wolf stands stiff legged and tall. The ears are erect and forward, and the hackles bristle slightly. Often the tail is held vertically and curled toward the back. This display asserts the wolf's rank to others in the pack. A dominant wolf may stare at a submissive one, pin it to the ground, "ride up" on its shoulders, or even stand on its hind legs.
* Submission (active) – During active submission, the entire body is lowered, and the lips and ears are drawn back. Sometimes active submission is accompanied by muzzle licking, or the rapid thrusting out of the tongue and lowering of the hindquarters. The tail is placed down, or halfway or fully between the legs, and the muzzle often points up to the more dominant animal. The back may be partly arched as the submissive wolf humbles itself to its superior; a more arched back and more tucked tail indicate a greater level of submission.
* Submission (passive) – Passive submission is more intense than active submission. The wolf rolls on its back and exposes its vulnerable throat and underside. The paws are drawn into the body. This posture is often accompanied by whimpering.
* Anger – An angry wolf's ears are erect, and its fur bristles. The lips may curl up or pull back, and the incisors are displayed. The wolf may also arch its back, lash out, or snarl.
* Fear – A frightened wolf attempts to make itself look small and less conspicuous; the ears flatten against the head, and the tail may be tucked between the legs, as with a submissive wolf. There may also be whimpering or barks of fear, and the wolf may arch its back.
* Defensive – A defensive wolf flattens its ears against its head.
* Aggression – An aggressive wolf snarls and its fur bristles. The wolf may crouch, ready to attack if necessary.
* Suspicion – Pulling back of the ears shows a wolf is suspicious. The wolf also narrows its eyes. The tail of a wolf that senses danger points straight out, parallel to the ground.
* Relaxation – A relaxed wolf's tail points straight down, and the wolf may rest sphinx-like or on its side. The wolf may also wag its tail. The further down the tail droops, the more relaxed the wolf is.
* Tension – An aroused wolf's tail points straight out, and the wolf may crouch as if ready to spring.
* Happiness – As dogs do, a wolf may wag its tail if in a joyful mood. The tongue may roll out of the mouth.
* Hunting – A wolf that is hunting is tensed, and therefore the tail is horizontal and straight.
* Playfulness – A playful wolf holds its tail high and wags it. The wolf may frolic and dance around, or bow by placing the front of its body down to the ground, while holding the rear high, sometimes wagged. This resembles the playful behavior of domestic dogs.

Howling and other vocalisations
Howling adult wolf at the UK Wolf Conservation Trust

Wolf howls, which can last from 0.5–11 seconds, typically have a frequency of 150-780 Hz.[17] Howling helps pack members keep in touch, allowing them to communicate effectively in thickly forested areas or over great distances. Howling also helps to call pack members to a specific location. Howling can also serve as a declaration of territory, as shown in a dominant wolf's tendency to respond to a human imitation of a "rival" wolf in an area the wolf considers its own. This behavior is stimulated when a pack has something to protect, such as a fresh kill. As a rule of thumb, large packs will more readily draw attention to themselves than will smaller packs. Adjacent packs may respond to each others' howls, which can mean trouble for the smaller of the two. Wolves therefore tend to howl with great care.[97] Wolves will also howl for communal reasons. Some scientists speculate that such group sessions strengthen the wolves' social bonds and camaraderie—similar to community singing among humans.[97] During such choral sessions, wolves will howl at different tones and varying pitches, making it difficult to estimate the number of wolves involved. This confusion of numbers makes a listening rival pack wary of what action to take. For example, confrontation could be disastrous if the rival pack gravely underestimates the howling pack's numbers. A wolf's howl may be heard from up to ten miles (16 km) away, depending on weather conditions. Observations of wolf packs suggest that howling occurs most often during the twilight hours, preceding the adults' departure to the hunt and following their return. Studies also show that wolves howl more frequently during the breeding season and subsequent rearing process.[98] The pups themselves begin howling soon after emerging from their dens and can be provoked into howling sessions easily over the following two months. Such indiscriminate howling usually is intended for communication, and does not harm the wolf so early in its life.[97] Howling becomes less indiscriminate as wolves learn to distinguish howling pack members from rival wolves. The Arabian and Iranian wolf subspecies are unusual as they are not known to howl.[6][99]

Growling, while teeth are bared, is the most visual warning wolves use. Wolf growls have a distinct, deep, bass-like quality which can range from 250-1,500 Hz.[17] It is often used to threaten rivals, though not necessarily to defend themselves. Wolves also growl at other wolves while being aggressively dominant. Wolves bark when nervous or when alerting other wolves of danger but do so very discreetly and will not generally bark loudly or repeatedly as dogs do. Instead they use a low-key, breathy "whuf" sound which can measure from 320-904 Hz[17] to immediately get attention from other wolves. Wolves also "bark-howl" by adding a brief howl to the end of a bark. Wolves bark-howl for the same reasons they normally bark. Generally, pups bark and bark-howl much more frequently than adults, using these vocalizations to cry for attention, care, or food. A lesser known sound is the rally. Wolves will gather as a group and, amidst much tail-wagging and muzzle licking, emit a high-pitched wailing noise interspersed with something similar to (but not the same as) a bark. Rallying is often a display of submission to an alpha by the other wolves.[100] Wolves also whimper, a sound with a maximum range of 3,500 Hz[17], usually when submitting to other wolves. Wolf pups whimper when they need a reassurance of security from their parents or other wolves.

Taxonomy

The gray wolf is a member of the genus Canis, which comprises between 7 and 10 species. It is one of six species termed 'wolf', the others being the Red Wolf (Canis rufus), the Indian Wolf (Canis indica), the Himalayan Wolf (Canis himalayaensis), the Eastern Wolf (Canis lycaon), and the Ethiopian Wolf (Canis simensis), although concerning a couple of these there is still some uncertainty as to whether they should be considered subspecies of Canis lupus or species in their own right. Recent genetic research suggests that the Indian Wolf, originally considered only as a subpopulation of the Iranian Wolf (Canis lupus pallipes), represents a distinct species (Canis indica). Similar results were obtained for the Himalayan Wolf, which is traditionally placed into the Tibetan Wolf (Canis lupus laniger) [101].

With respect to common names, spelling differences result in the alternative spelling grey wolf. As the first-named and most widespread of species termed "wolf", gray wolves are often simply referred to as wolves. It was one of the many species originally described by Carl Linnaeus in his eighteenth-century work, Systema Naturae, and it still bears its original classification, Canis lupus.[102] The binomial name is derived from the Latin Canis, meaning "dog", and lupus, "wolf".[103]
Desert dwelling grey wolf subspecies, such as this Arabian wolf, tend to be smaller than their more northern cousins.

Classifying gray wolf subspecies can be challenging. Although scientists have proposed a host of subspecies, wolf taxonomy at this level remains controversial.[104] Indeed, only a single wolf species may exist. Taxonomic modification will likely continue for years to come.

Current theories propose that the gray wolf first evolved in Eurasia during the early Pleistocene. The rate of changes observed in DNA sequence date the Asiatic lineage to about 800,000 years, as opposed to the American and European lineages which stretch back only 150,000.[105] The gray wolf migrated into North America from the Old World, probably via the Bering land bridge, around 400,000 years ago. However, they did not become widespread until 12,000 years ago, when the native American megafauna began dying out. It is thought by certain experts that the wolf's Eurasian origin could account for its relative inability to modify its behaviour in light of human encroachment, compared to native American predators like black bears, cougars and coyotes which were under greater predation pressure from larger, now extinct predators.[106] The gray wolf then coexisted with the Dire Wolf (Canis dirus). Although more heavily built and possessing a stronger bite, the dire wolf's dentition was less adept at crushing bones than the grey wolf was.[24] The Dire Wolf ranged from southern Canada to South America until about 8,000 years ago when climate changes are thought to have caused it to become extinct. After that the gray wolf is thought to have become the prime canine predator in North America.

The International Commission on Zoological Nomenclature has conserved the name Canis lupus; see Opinion 2027.

Subspecies
Main article: Subspecies of Canis lupus
Skull of a European wolf
Skull of a Canadian wolf

At one point, up to 50 gray wolf subspecies were recognized. Though no true consensus has been reached, this list can be condensed to 13–15 general extant subspecies. Modern classifications take into account the DNA, anatomy, distribution, and migration of various wolf colonies. As of 2005[update], 37 subspecies are currently described, including the dingo and the domestic dog.[107] Wolves show a great deal of dimorphism geographically. For example, North American wolves are, overall, generally the same size as European breeds, but have have larger, rounder heads, broader, more obtuse muzzles, shorter legs and are usually more robust. European wolves on the contrary tend to have longer, more higher placed ears, narrower heads, more slender loins and coarser, less luxuriant fur[108][109]. However, wolves of different geographical locations can interbreed. The Zoological Gardens of London for example once successfully managed to mate a male European wolf to an Indian female, resulting in a cub bearing an almost exact likeness to its sire.[110]

Relation to the dog

Much debate has centered on the relationship between the wolf and the domestic dog, though most authorities see the wolf as the dog's direct ancestor (see Origin of the domestic dog). Because canids have evolved recently and different species interbreed readily, untangling the relationships has been difficult. However, molecular systematics now indicate very strongly that domestic dogs and wolves are closely related, and the domestic dog is now normally classified as a subspecies of the wolf: Canis lupus familiaris. Additionally, breeding experiments in Germany with poodles, wolves, and later on with the resulting wolf-dogs showed unrestricted fertility, mating via free choice and no significant communication problems (even after a few generations). This contrasted with the hybrid offspring of poodles crossed with coyotes and jackals, which all showed a decrease in fertility and significant communication problems, as well as an increase in genetic diseases after three generations of interbeeding. The researchers therefore concluded that domestic dogs and grey wolf are the same species.[111] DNA evidence has demonstrated that canis lupus lupus and canis lupus familiaris are genetically very similar. Both have 39 chromosomes, representing roughly 19000 genes spread over 2.4 billion base pairs [112] In a 2005 study reported in Nature, genetic similarity was assessed within breed, between breeds, and between subspecies by measuring the frequency of single nucleotide polymorphisms. The dogs studies were genetically most similar to others of the same breed (SNP frequency roughly 1/1600). The primary breed studied, the boxer, was also genetically similar to other breeds (SNP frequency roughly 1/900), although there was some variance depending on breed. For instance, the boxer was found to be significantly less similar to Alaskan Malamutes (SNP frequency roughly 1/750). The boxer was found to be least similar to other canids, including canis lupus lupus (SNP frequency roughly 1/580) and coyotes (SNP frequency roughly 1/400). From these analyses, it can be estimated that the variance between canis lupus lupus and canis lupus familiaris is roughly twice as great as the variance within the subspecies canis lupus familiaris, and four times as great as the variance within an individual breed.[112]

Domestication
Main article: Dog taxonomy and evolution

There is a great deal of controversy surrounding the divergence of domestic dogs from wolves. The number of divergence events, the approximate date of these events, and the location of these events have not been conclusively determined. Archaeological evidence clearly shows that dogs diverged from wolves more than 15,000 years ago, but it could have been much earlier. Genetic studies suggest that dogs were domesticated in three or four events, including relatively small wolf populations, in East Asia upwards of 100,000 years ago. These studies, however, depend on assumptions that are likely to be violated; the date could be much earlier or later. Most archaeologists believe that dogs diverged from wolves between 15,000 and 35,000 years ago, and that domestication events were caused by human lifestyle changes (e.g., establishment of permanent towns). It is agreed that all domestication events occurred in Eurasia, and that domestic dogs likely entered North America with one of the subsequent waves of humans roughly 12,000 years ago. Thus, dogs are believed to have spread very quickly throughout the world[113]. Which exact subspecies of wolf gave rise to dogs is still debated. Some scientists point to the Tibetan wolf, noting that the uppermost part of the lower jaw is turned back as in the dog, though not so in other grey wolf subspecies, while others state that the Indian Wolf was more likely, due to its small size and more docile behaviour.[114]

Physical and behavioural differences

Despite their close relationship, wolves and dogs show a number of physical and behavioural differences. Some experts cite these differences as a basis for rejecting the ancestral wolf hypothesis,[4] while others theorise that the lack of characteristics in some domestic dogs (e.g. regurgitating of food or strict pack structure) present in wolves is not a distinguishing feature between the two species, but a degeneration caused through irresponsible breeding or lack of knowledge as several domestic dogs (especially among those who reverted to the wild) show these characteristics while others do not.[115][116]

Certain instinctive and social behaviors displayed by wolves may not be expressed in dogs simply because the opportunity never arises in their captive social setting. However, even when dogs range freely in wild or in semi-wild circumstances, they show marked divergences from their wild ancestors. In a comparative study on poodles and wolves, wolf biologist Eric Zimen and his colleagues recorded 362 specific behaviors displayed by wolves, 64% of which were displayed by poodles with little or no change, while 13% of wolf behaviors had vanished altogether. 23% of wolf-like mannerisms persisted but in markedly modified forms. In performing many of these modified wolf-like behaviors, the poodles lacked a seriousness of purpose, being indiscriminate and ineffectual in their choice of "prey", similairly to young wolves at play. In the poodles, many of the subtle facial and body expressions characteristic of wolves were greatly simplified, while many were absent altogether. Aggressive and defensive postures were greatly muted, due to poodles being generally less fearful, less aggressive and are more tolerant to invasions of personal space. Unlike adult wolves, which avoid physical contact with each other when sleeping, the poodles continued to frequently lie together through the age of eight months or older, even in hot weather when there was no conceivable reason for huddling to preserve body heat.[117]

Compared to equally sized wolves, dogs tend to have 20% smaller skulls and 10% smaller brains, as well as proportionately smaller teeth than other canid species.[15] The premolars and molars of dogs are much more crowded. Dog's teeth also have less complex cusp patterns, and their tympanic bulla is much smaller than in wolves.[118] As the brains of domestic dogs are smaller than those of wolves, they require fewer calories to survive. The dog's diet of human refuse in antiquity made the large brains and jaw muscles needed for hunting unnecessary. It is thought by certain experts that the dog's limp ears are a result of atrophy of the jaw muscles.[15] The paws of a dog are half the size of those of a wolf, and their tails tend to curl upwards, another trait not found in wolves.[6]

Interspecific hybridization
Main articles: Canid hybrid, Wolf-dog hybrid, Black wolf (animal), and Coywolf
A wolf-dog hybrid with malamute ancestry

Wolves can interbreed with domestic dogs and produce fertile offspring. Wolf-dog hybrids are generally said to be naturally healthy animals, and are affected by less inherited diseases than most breeds of dog. Wolfdogs are usually healthier than either parent due to heterosis.[119] According to the National Wolfdog Alliance, 40 U.S. states effectively forbid the ownership, breeding and importation of wolfdogs, while others impose some form of regulation upon ownership.[120] Most European nations, as well as many U.S. counties and municipalities, also either outlaw the animal entirely or put restrictions on ownership.[121]. Although wolves in the wild will usually kill dogs, matings of dogs and wild wolves has been confirmed in some populations through genetic testing. As the survival of some continental wolf packs is severely threatened, scientists fear that the creation of wolf-dog hybrid populations in the wild is a threat to the continued existence of some isolated wolf populations. Hybridization in the wild usually occurs near human habitations where wolf density is low and dogs are common. However, extensive wolf-dog hybridization is not supported by morphological evidence, and analyses of mtDNA sequences have revealed that such matings are rare.[10] In some cases, the presence of dewclaws is considered a useful, but not absolute indicator of dog gene contamination in wild wolves. Dewclaws are the vestigial fifth toes of the hind legs common in domestic dogs but thought absent from pure wolves, which only have four hind toes.[13] Observations on wild wolf hybrids in the former Soviet Union indicate that wolf hybrids in a wild state may form larger packs than pure wolves, and have greater endurance when chasing prey.[8] Genetic research from the University of California, Los Angeles revealed that wolves with black pelts owe their distinctive coloration to a mutation that first arose in domestic dogs.[18]
The Red Wolf has been shown through various genetic testing techniques to be a wolf/coyote hybrid[122]

Wolves and coyotes can interbreed and produce fertile offspring, a fact which calls into question their status as two separate species.[123] The offspring, known as a coywolf, is generally intermediate in size to both parents, being larger than a pure coyote, but smaller than a pure wolf. A study showed that of 100 coyotes collected in Maine, 22 had half or more wolf ancestry, and one was 89 percent wolf. A theory has been proposed that the large eastern coyotes in Canada are actually hybrids of the smaller western coyotes and wolves that met and mated decades ago as the coyotes moved toward New England from their earlier western ranges.[124] The Red Wolf is thought by certain scientists to be in fact a wolf/coyote hybrid rather than a unique species. Strong evidence for hybridization was found through genetic testing which showed that red wolves have only 5% of their alleles unique from either grey wolves or coyotes. Genetic distance calculations have indicated that red wolves are intermediate between coyotes and grey wolves, and that they bear great similarity to wolf/coyote hybrids in southern Quebec and Minnesota. Analyses of mitochondrial DNA showed that existing Red Wolf populations are predominantly coyote in origin.[122]

Current & Historical status
Main article: List of grey wolf populations by country
Present distribution of the various wolf subspecies

The Gray Wolf was once the world's most widely distributed mammal, living north of 15°N latitude in North America and 12°N in Eurasia[125]. Though once abundant, the gray wolf inhabits a very small portion of its former range because of widespread destruction of its habitat, human encroachment of its habitat, and the resulting human-wolf encounters that sparked broad extirpation[125]. This reduction has been greatest in developed areas of Europe, Asia, Mexico and the United States because of poisoning and deliberate persecution[125].

In 1982 through 1994, the grey wolf was listed as vulnerable to extinction by the International Union for Conservation of Nature (IUCN). Changes is legal protections, land-use and population shifts to urban areas have stopped the decline in wolf population[125]. Additionally, recolonization and reintroduction programs have increased wolf populations in Western Europe and the western United States[125].As a result, in 1996, the IUCN reduced the risk status of the gray wolf to being of least concern [125]. Today, the conservational status of wolves varies greatly. They are protected in some areas, hunted for sport in others, or may be subject to extermination as perceived threats to livestock and pets.

Despite not being at risk for extinction, local populations of wolves are still threatened. One such threat is genetic bottlenecking caused by population fragmentation[126]. Human populations have isolated small pockets of animals, which then suffer the effects of inbreeding. Studies have shown that the reproduction rate in wolves is strongly related to genetic diversity[127]. Isolated wolf populations are greatly affected by the introduction of the alleles of even a single additional wolf[126]. A small, isolated group of wolves on Isle Royale is believed to be suffering from the effects of reduced genetic variability. In 1991, the population was reduced from 50 to 12 wolves. Studies have shown that this reduction has coincided with a 50% loss of allozyme heterozygosity[128].

Wolves tend to have difficulty adapting to change, and are often referred to as an indicator species; a species delineating an ecoregion or indicating an environmental condition such as a disease outbreak, pollution, species competition, or climate change. Wolves do not seem to be able to adapt as readily to expanding civilization the way coyotes do. While human expansion has seen an increase in the latter's numbers, it has caused a drop in those of the former.