|The wolf (Canis lupus), also known as the timber wolf or gray wolf, is a mammal of the order Carnivora. The gray wolf is the largest member of the genus Canis. Its shoulder height ranges from 0.6 to 0.9 meters (26-36 inches) and its weight typically varies between 32 and 62 kilograms (70-135 pounds). As evidenced by DNA sequencing and genetic drift studies, the gray wolf shares a common ancestry with the domestic dog (Canis lupus familiaris)
The gray wolf was once abundant over much of North America and Eurasia. However, as a result of habitat destruction and widespread hunting, it now inhabits a very limited portion of its former range. In some regions, gray wolves are listed as endangered or threatened, although considered as a whole, wolves are regarded as a species of least concern for extinction according to the International Union for the Conservation of Nature and Natural Resources. Wolves are still hunted in many areas of the world for sport and as perceived threats to livestock. Kazakhstan is currently thought to have the largest wolf population of any nation in the world, with as many as 90,000, versus some 60,000 for Canada, which is three and a half times larger.
Being apex predators, gray wolves are integral components of the ecosystems they typically occupy. The diversity of such ecosystems reflects its adaptability as a species, as the ecosystems in which wolves have been known to thrive include, but are not limited to, temperate forests, deserts, mountains, tundra, taiga, and grasslands.
Wolves feature in folklore and mythology of cultures ancient to modern across the northern hemisphere; from the Norse legend of the giant Fenrir to more sympathetic depictions in Central Asia and the suckling of Romulus and Remus in the foundation of Rome. More familiar still are the fairy tales where the wolf appears as a villain such as Little Red Riding Hood and the Three Little Pigs. Wolf legends have also given rise to the popular horror figure of the werewolf.
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 0.95 meters (26-38 inches) at the shoulder and weight ranges from 32 to 62 kilograms (70-135 pounds), which together make the gray wolf the largest of all wild canids. Although rarely encountered, extreme specimens of more than 77 kg (170 lb) have been recorded in Alaska and Canada. The heaviest wild wolf on record, killed in Alaska in 1939, was 80 kg (175 lb). The smallest wolves come from the Arabian Wolf subspecies, the females of which may weigh as little as 10 kg (22 lb) at maturity. Females in any given wolf population typically weigh about 20% less than their male counterparts. 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.
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. While thus sprinting, wolves can cover up to 5 meters (16 ft) per bound.
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. 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. Bristled hairs and blunt claws enhance grip on slippery surfaces, and special blood vessels keep paw pads from freezing. 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. Unlike dogs and coyotes, wolves lack sweat glands on their paw pads. 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 designed to 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. North American wolves typically have longer, silkier fur than their Eurasian counterparts.
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 certainly not uncommon for an individual or an entire population to be entirely one color (usually all black or all white). 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.
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. Though extremely unusual, it is possible for an adult wolf to retain its blue-colored irises.
Wolves' long, powerful muzzles help distinguish them from other canids, particularly coyotes and golden jackals, which have more narrow, pointed muzzles. 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 degrees for wolves) and a comparatively larger brain capacity. Larger paw size, yellow eyes, longer legs, and bigger teeth further distinguish adult wolves from other canids, especially dogs. Also, precaudal glands at the base of the tail are present in wolves but not in dogs.
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. 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 are designed to hold and subdue the prey. Capable of delivering up to 10,000 kPa (1450 lb/sq. inch) of pressure, a wolf's teeth are its main weapons as well as its primary tools. Therefore, any injury to the jaw line or teeth could devastate a wolf, dooming it to starvation or incapacity.
Reproductive physiology and life cycle
Usually, the instinct to reproduce drives young wolves away from their birth packs, leading them to seek out mates and territories of their own. Dispersals occur at all times during the year, typically involving wolves that have reached sexual maturity prior to the previous breeding season. 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. 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. The bond that forms between these wolves oftentimes lasts until one of them dies.
Generally, mating occurs between January and April, the higher the latitude, the later it occurs. A pack usually produces a single litter unless the alpha 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, in fact, the alpha male and alpha female may be forced to prevent other wolves from mating with one another. Under normal circumstances, a pack can only support one litter per year, so this dominance behavior is beneficial in the long run.
When the alpha female goes into estrus (which occurs once per year and lasts 5-14 days), 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 male wolf will mount the female firmly from behind. After achieving coitus, the two form a copulatory tie once the male's bulbus glandis, an erectile tissue located near the base of the canine penis, swells and the female's vaginal muscles tighten. Ejaculation is induced by the thrusting of the male's pelvis and the undulation of the female's cervix. The two become physically inseparable for anywhere from 10 to 30 minutes, during which the male will ejaculate multiple times. After the initial ejaculation, the male may lift one of his legs over the female such that they are standing end-to-end; this is believed to be a defensive measure. The mating ritual is repeated many times throughout the female's brief ovulation period, which occurs once per year per female, unlike female dogs, whose estrus usually occurs twice per year.
The gestation period lasts between 60 and 63 days. The pups, at a weight of 0.5 kg (1 lb), are born blind, deaf, and completely dependent on their mother. There can be anywhere from 1 to 14 pups per litter, with the average litter size being about 4 to 6. Pups reside in the den and stay there for no longer than two months. The den is usually on high ground near an open water source, and has an open "room" at the end of an underground or hillside tunnel that can be up to a few meters long. 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. They begin eating regurgitated foods after 2 weeks - by which 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.
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. 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. Wolves that reach maturity generally live 6 to 8 years in the wild, although in captivity they can live to twice that age. 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, or, less often, coyotes, foxes, 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 be killed by other predators occasionally, rival wolf packs are often their most dangerous non-human enemy. A study on wolf mortality concluded that 14-65% of wolf deaths were inflicted by other wolves.
Wolves are susceptible to the same infections that affect domestic dogs, such as mange, heartworm, rabies, parvovirus and canine distemper. Epidemics of these can drastically reduce wolf populations in a given area. Wolves are reported to carry over 50 types of parasites, including echinococci, cysticercocci, coeruni (all of which can attach humans) and the trichinellidae family.
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.
* 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.
* Relaxedness - 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 loll 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 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.
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. 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 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. 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. Howling becomes less indiscriminate as wolves learn to distinguish howling pack members from rival wolves.
Wolves, like other canines, use scent marking to lay claim to anything—from territory to fresh kills. Alpha wolves scent mark the most often, with males doing so more than females. The most widely used scent marker is urine. Male and female alpha 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. 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' heavy reliance on odoriferous signals testifies greatly to their olfactory capabilities. Wolves can detect virtually any scent, including marks, from great distances, and can distinguish among them as well or better than humans can distinguish other humans visually.
Wolves function as social predators and hunt in packs organized according to strict, rank-oriented social hierarchies. It was originally believed that this comparatively high level of social organization was related to hunting success, and while this still may be true to a certain extent, emerging theories suggest that the pack has less to do with hunting and more to do with reproductive success.
The pack is led by the two individuals that sit atop the social hierarchy: the alpha male and the alpha female. The alpha pair has the greatest amount of social freedom compared to the rest of the pack. Although they are not "leaders" in the human sense of the term, they help to resolve any disputes within the pack, have the greatest amount of control over resources (such as food), and, most importantly, they help keep the pack cohesive and functional.
While most alpha pairs are monogamous, there are exceptions. An alpha animal may preferentially mate with a lower-ranking animal, especially if the other alpha is closely related (a brother or sister, for example). The death of one alpha does not affect the status of the other alpha, who will quickly take another mate.
Usually, only the alpha pair is able to rear a litter of pups successfully. Other wolves in a pack may breed, but when resources are limited, time, devotion, and preference will be given to the alpha pair's litter. Therefore, non-alpha parents of other litters within a single pack may lack the means to raise their pups to maturity of their own accord. All wolves in a pack assist in raising wolf pups. Some mature individuals choosing not to disperse may stay in their original packs so as to reinforce it and help rear more pups.
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. New packs are formed when a wolf leaves its birth pack, finds a mate, and claims a territory. Lone wolves searching for other individuals can travel very long distances seeking out suitable territories. Dispersing individuals must avoid the territories of other wolves because intruders on occupied territories are chased away or killed. It is taboo for one wolf to travel into another wolf's territory unless invited. Most dogs, except perhaps large, specially bred attack dogs, do not stand much of a chance against a pack of wolves protecting its territory from an intrusion.
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.
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 Canadian Wolf (Canis lycaon) and the Ethiopian Wolf (Canis simensis). Also related are the Coyote (Canis latrans) and the Golden Jackal (Canis aureus).
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 oftentimes simply referred to as wolves. It was one of the many species originally described by Carolus Linnaeus in his eighteenth-century work, Systema Naturae, and it still bears its original classification, Canis lupus. The binomial name is derived from the Latin Canis, meaning "dog", and lupus, "wolf".
Desert dwelling grey wolf subspecies, such as this Arabian wolf, tend to be smaller than their more northern cousins.
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. Indeed, only a single wolf species may exist. Taxonomic modification will likely continue for years to come.
Although the species' origins are still under debate, current theories propose that they first evolved in South East Asia during the Pleistocene epoch. DNA analysis from the cell's mitochondria on Asiatic subspecies have allowed scientists to put a time to the point at which the wolf lineage originated. The rate of changes observed in the DNA sequence dates the Asian lineage to about 800,000 years, as opposed to European and North American bloodlines which stretch back to 150,000 years. The wolf likely crossed into North America from the Old World via the Bering land bridge (that once joined Alaska and Siberia) and traveled south of the ice sheets prior to the last glacial maximum 18,000 years ago.
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