Gray Wolf

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Gray Wolf
Conservation status
Least Concern [1]
Scientific classification
Kingdom: Animalia   Phylum: Chordata   Class: Mammalia   Order: Carnivora   Family: Canidae   Genus: Canis   Species: C. lupus
Binomial name
Canis lupus Linnaeus, 1758
Range map

The Gray Wolf (Canis lupus; also spelled Grey Wolf, see spelling differences; also known as Timber Wolf or Wolf) is a mammal in the order Carnivora. The Gray Wolf shares a common ancestry with the domestic dog (Canis lupus familiaris), as evidenced by DNA sequencing and genetic drift studies.^[2] Gray wolves were once abundant and distributed over much of North America, Eurasia, and the Middle East. Today, for a variety of human-related reasons, including widespread habitat destruction and excessive hunting, wolves inhabit only a very limited portion of their former range. Though listed as a species of least concern for extinction worldwide, for some regions including the Continental United States, the species is listed as endangered or threatened.^[3]

The Gray Wolf, being a keystone predator, is an important part of the ecosystems to which it typically belongs. The wide range of habitats where wolves thrive reflects their adaptability as a species, and includes temperate forests, mountains, tundra, taiga, and grasslands. In much of the world, with the exception of Northern regions, they are listed as endangered. They continue to be hunted in many areas of the world for their perceived threat to livestock, as well as for sport.

Contents 1 Anatomy, physiology, and reproduction 1.1 Features and adaptations 1.2 Courtship and mating 1.3 Breeding and life cycle 2 Behavior 2.1 Body language 2.2 Howling 2.3 Other vocalizations 2.4 Scent marking 3 Social structure and hunting 3.1 The pack 3.2 Hierarchy 3.3 Cooperative hunting and diet 4 Historical perceptions 5 Reintroduction 6 Wolf hunting 6.1 Livestock predation 6.2 Trapping and breeding for fur 7 Taxonomy 7.1 Classification and relation to the dog 7.2 Subspecies of the wolf 8 Media 9 See also 10 References 11 External links

Anatomy, physiology, and reproduction

 Features and adaptations

The weight and size of the Gray Wolf can vary greatly worldwide, and tend to increase proportionally with latitude. Generally speaking, height varies from 0.6–0.9 meters (26–34 inches) at the shoulder, and weight from 32–62 kilograms (70–135 pounds), which together make Gray Wolves the largest of all wild canids.^[4] Although rarely encountered, extreme specimens of more than 77 kg (170 lb) have been recorded in Alaska and Canada;^[5] the heaviest wild wolf on record, which was killed in Alaska in 1939, was 80 kg (175 lb).^[6] 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 a given population typically weigh about 20% less than their male counterparts.^[7] Wolves can measure anywhere from 1.3–2 meters (4.5–6.5 feet) from nose to the tip of the tail, which itself accounts for approximately one.

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.^[8] While thus sprinting, wolves can cover up to 5 meters (16 ft) per bound.^[9]

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 wolves 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, a 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.^[10] 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.^[10]

A wolf sometimes seems heavier than it actually is due to its bulky coat, which is made of two layers. The first layer consists of tough guard hairs designed to repel water and dirt. The second is a dense, water-resistant undercoat that insulates the wolf. 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.

Coloration varies greatly: it runs 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.

At birth, wolf pups tend to have darker fur and blue eyes that will change to a yellow-gold or orange color when the pups are 8–16 weeks old.^[11] Though extremely unusual, it is possible for an adult wolf to retain its blue-colored eyes.^[12]

Wolves have stout, blocky muzzles that help distinguish them from coyotes and dogs. Wolves also differ in certain skull dimensions, having a smaller orbital angle, for example, than dogs (>53 degrees for dogs compared to <45 degrees for wolves) and a comparatively larger brain capacity.^[13] Larger paw size, yellow eyes, longer legs, and bigger teeth further distinguish adult wolves from other canids, particularly 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.^[14] 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. Powered by 1500 lb/sq. inch of pressure, a wolf's teeth are its main weapons as well as its primary tools.^[6] Therefore, any injury to the jaw line or teeth could devastate a wolf, dooming it to starvation or incapacity.

 Courtship and mating

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 of wolves who have reached sexual maturity in the previous breeding season. It takes two such dispersals from two packs for the process to take place, for dispersing wolves from the same maternal pack tend not to mate.^[15] 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 often lasts until one of them dies — with few exceptions.^[16]

During the mating season, breeding wolves become very affectionate with one another in anticipation of the female's ovulation cycle. Overall, pack tension rises as each mature wolf feels urged to mate. In fact, during this time, the alpha male and alpha female may be forced to aggressively prevent other wolves from mating with one other.^[15] Under normal circumstances, a pack can only support one litter per year; so the dominance of the alpha wolves is beneficial in the long run.^{[specify][15]}

When the alpha female goes into estrus—which occurs once per year and lasts 5–14 days,^[17]—she and her mate will spend an increased amount of time in seclusion. Pheromones in the female's urine and the swelling of her vulva make it 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, 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.^[18][19] 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.^[19] 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.

 Breeding and life cycle

Normally, only the alpha pair of the pack breeds (this is a kind of organization also found in other pack-hunting canids, including the Dhole and the African Hunting Dog). Mating occurs between January and April — the higher the latitude, the later it occurs.^[16] A pack usually produces a single litter, unless the alpha male mates with one or more subordinate females. Under normal circumstances, the alpha female tries to prevent this during mating season by dominating the other females and keeping them away from the alpha male.

The gestation period lasts 60–63 days. The pups, at a weight of 0.5 kg (1 lb), are born blind, deaf, and completely dependent on their mother.^[16][4] There are 1 to 14 pups per litter; the average litter size is about 4 to 6.^[20] Pups reside in the den, where they are born deaf with their eyes closed, and stay there until they reach about three weeks of age.^[11] 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.^[10] 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.^[11] They begin eating regurgitated foods after 2 weeks— by which time their milk teeth have emerged—and are fully weaned by 8–10 weeks.^[11] 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.^[16]

After two months, the restless pups will be moved to a rendezvous site, where they can safely stay while most of the adults go out to hunt.^[11] 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, despite their low ranks. The pups tag along as observers until about 8 months, when they are large enough to actively participate.^[11] The fighting over eating privileges results in a secondary ranking being formed among them, which allows them to practice the dominance/submission rituals essential to their later survival within packs.^[16]

Wolves typically reach sexual maturity after two or three years, when many of them will be compelled to leave their birth packs and seek out mates and their own territories.^[16][21] Wolves that reach maturity generally live 6 to 8 years in the wild, although in captivity they can live to twice that age.^[20] 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. Grown wolves are occasionally killed by bears or big cats, but rival wolf packs are by far their most dangerous non-human predator.^{[citation needed]} Wolves are susceptible to the same infections that affect domestic dogs, such as mange, heartworm, rabies and canine distemper. Epidemics of these can drastically reduce the population in an area.

 Behavior

 Body language

See also: Dog communication

Wolves can visually communicate with an impressive 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.^[22]

• 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 penetratingly 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 partially 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 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 tries to make its body look small and therefore 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.

[edit] Howling

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.^[23]

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.^[23] 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.^[23] Howling becomes less indiscriminate as wolves learn to distinguish howling pack members from rival wolves.