The Gray Wolf (Canis lupus), known in Europe as the Grey Wolf, is a mammal of the Canidae family. Depending on researcher, the wolf either shares a common ancestry with, or is a member of, the same species as the domestic dog (Canis familiaris or C. lupus familiaris). Wolves once had a nearly worldwide range, but are now limited primarily to North America, Eurasia, and the Middle East.
The habitat of wolves include forests, tundra, taigas, plains, and mountains. In the Northern Hemisphere, human habitat destruction and hunting have drastically reduced their range. The wolf is frequently involved in conflicts between competing interests: tourism versus industry, city versus country, as well as conservationism versus urban development.
Since the wolf is an apex predator, its state usually depends on the state of its habitat. Wolves are still endangered after being hunted to near extinction in many parts of the world in the 17th century. Carolus Linnaeus gave the wolf the scientific name Canis lupus in the 18th century
Anatomy
Gray Wolf (Canis lupus).The wolf's anatomy differs from the dog in several ways. The wolf usually has golden-yellow eyes, longer legs, larger paws, more-pronounced jaws, a longer muzzle, and a brain that is typically 30 percent larger than that of a dog.[2] Also noticeable is a pre-caudal gland on the over side of the tail, close to the base, that is not present on dogs. Wolves are also distinguished from dogs by characteristics of the skull, particularly the orbital angle, which is the angle formed between lines drawn across the top and side of the skull at the eye socket. This angle is larger (53 degrees or more) in dogs, and smaller (45 degrees or less) in wolves. Lastly, while the elbows of many dogs stick more out to the sides of their bodies, the elbows of a wolf point inwards towards their stomach, almost touching. This allows wolves to run at speeds of 8 kilometers per hour (km/h) (5 miles per hour) (mph) for hours on end.[3]
A wolf often seems more massive than a dog of comparable weight due to the extra bulk of the coat. The coat is built up of two layers, with hard guard hairs to repel water and dirt and a thick, woolly undercoat to keep the animal warm. The wolf changes coat two times a year, in spring and autumn. Females tend to keep the winter coat further into the spring than males.
Wolves and most larger dogs share the same tooth configuration: The upper jaw has six incisors, two canines, eight premolars, and four molars. The bottom jaw has six incisors, two canines, eight premolars, and six molars.[4] The canine teeth are by far most important, as they are used to catch and hold prey. One common reason that wolves starve is due to tooth damage after suffering a kick by larger prey.
Wolves stand approximately 0.66–0.8 meters (26–32 in) at the shoulder and weigh 25–52 kilograms (55–115 lb, with extremes being 195 pounds [88 kg]). Females are about twenty percent smaller than males.[5][6] They measure 1–1.5 meters (40–58 in) long, with the tail consisting roughly a third of their body length (0.67–0.5 meter, 26–20 in). The body of the wolf is built for long-distance running, with a rather thin chest and powerful back and leg muscles which allow them to run at 72 km/h (45 mph) with strides of up to sixteen feet. Wolves can also travel over great distances, and their wide paws ensure deep snow hampers them less than their prey.
Coloration runs from gray to gray-brown but can vary through the canine spectrum of white, red, brown, and black.A wolf's coat usually lacks any clear patterns save for markings around the eyes. Fur colors often mimic the colors of a wolf's surroundings; for example, in regions where there is continual snowfall, white wolves are far more common.[7] Aging wolves acquire a grayish tint in their coat.
Social structure
Packs
A wolf pack baiting an American Bison.Wolves function as social predators and hunt in packs organized according to a strict social hierarchy and led by an alpha male and alpha female. This social structure was originally thought to allow the wolf to take prey many times its size. However, emerging new theories suggest the pack strategy has less to do with hunting than with reproductive success.
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 two and 20 wolves, though an average pack consists of six or seven.[8][9] The hierarchy of the pack is relatively strict, with the alphas at the top and the omega at the bottom. The hierarchy affects all activity in the pack, from which wolf eats first to which is allowed to breed (generally only the alpha pair).
New packs are formed when a wolf leaves its birth pack and claims a territory. Wolves searching for other wolves with which to form packs can travel very long distances in search of suitable territories. Dispersing individuals must avoid the territories of other wolves because intruders on "owned" territories are chased away or killed. This possibly explains wolf "predation" of dogs. Most dogs, except perhaps large, specially bred attack dogs, do not have much of a chance against a wolf protecting its territory from the unwanted intrusion.
Rank order
The alpha pair has the most social freedom of all the animals in a pack, but they are not "leaders" in the sense humans usually think of the term. They do not give the other wolves orders; the alphas simply have the most liberty to choose where they would like to go and what they would like to do, and the rest of the pack usually follows. In larger packs, there may be betas, a second in command to the alphas, and the omegas, the lowest-ranking member of the pack.[10]
While most alpha pairs are monogamous with each other, there are exceptions.[11] 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 usually take another mate. Usually, only the alpha pair is able to successfully rear a litter of pups. (Other wolves in a pack may breed, and may even produce pups, but usually they lack the freedom or the resources to raise the pups to maturity.) All the wolves in the pack assist in raising wolf pups. Some pups may choose to stay in the original pack to reinforce it and help rear more pups while others disperse.
Rank order is established and maintained through a series of ritualized fights and posturing best described as ritual bluffing. Wolves prefer psychological warfare to actual fighting, and high-ranking status is based more on personality or attitude than on size or physical strength. Rank, who holds it, and how it is enforced varies widely between packs and between individual animals. In large packs full of easygoing wolves, or in a group of juvenile wolves, rank order may shift almost constantly, or even be circular (e.g., animal A dominates animal B, who dominates animal C, who dominates animal A).
Loss of rank can happen gradually or suddenly. An older wolf may simply choose to give way when an ambitious challenger presents itself, and rank will shift without bloodshed. On the other hand, the older animal may choose to fight back, with varying degrees of intensity. While an extremely high percentage of wolf aggression is non-damaging and ritualized, a high-stakes fight can result in injury. The loser of such a damaging fight is frequently chased away from the pack or, rarely, may be killed as other aggressively aroused wolves attempt to join in. This kind of dominance fight is more common in the winter months, when mating occurs.
Body language
See also: Dog communication
This facial expression is defensive and gives warning to other wolves to be cautious.
This facial expression shows fear.Wolves communicate not only by sound (such as yipping, growling, and howling), but also by body language. This ranges from subtle signals–such as a slight shift in weight–to the obvious, like rolling on the back as a sign of submission.[12]
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 vertical and curled toward the back. This display shows the wolf's rank to all others in the pack. A dominant lupine may stare penetratingly at a submissive one, pin the other to the ground, or even stand on its hind legs.
Submission (active) – In active submission, the entire body is lowered, and the lips and ears are drawn back. Sometimes active submission is accompanied by a 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 lupine'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 snarl.
Fear – A frightened wolf tries to make its body look small and therefore less conspicuous. The ears flatten down 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 lupine is suspicious. In addition, the wolf 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 sphinxlike or on its side. The wolf's tail may also wag. 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 lupine may wag its tail if it is 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 lupine 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 is reminiscent of the playful behavior executed in domestic dogs.
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Howling
Howling adult wolf on glacial erratic at Little America Flats.Wolves are noted for their distinctive howl. There are several possible reasons for the howling. It can be said at the outset that wolves do not howl when attacking their prey. In fact, it has been shown that prey animals do not even react to the sound. Perhaps they simply fail to make the connection between noise and predator.
The most obvious reason for wolves to howl is to keep in touch; it is difficult to think of a better way for a lupine pack to communicate in a thickly forested area or over great distances. Howls are also employed to summon pack members to a location.[13] However, howling also occurs when a pack is together, so there must be some other purpose. Observations of wolf packs suggest that howling often occurs at summer sunsets preceding the adults' departure to the hunt. This is repeated when they return at sunup.
Some scientists speculate that these group howling sessions strengthen the wolves' social bonds and comradeship—similar to community singing among humans. Howling may also be a form of territorial advertisement and declaration. Studies have shown that the dominant animals in a pack are more likely to answer a human imitation of a "rival" pack when residing in an area that is indisputably theirs.
Wolves howl more frequently in the evening and the early morning, especially during winter and spring breeding and pup rearing. The pups themselves, however, towards the end of July and on into the next two months, are a different matter entirely. They howl at the least provocation and stimulus. This may be because the adults often leave them at a "rendezvous site" to go off hunting. Their loneliness may cause them to try to make contact with what they interpret to be a returning pack member.
Wolves also howl when they have something to protect, such as a fresh kill. When they wish to avoid conflict with other packs, they howl less frequently.
Hunting
The wolf is a carnivore. Packs of wolves hunt any large herbivores in their range, while lone wolves are more prone to consume smaller animals. The hunting methods range from surprise attacks to long-lasting chases. Through the cooperation of a pack, wolves are able to pursue large prey for several hours before relenting, but the success rate is rather low. Solitary wolves catch small animals by pouncing and pinning them to the ground with their front paws, a technique also exhibited by foxes and coyotes. Wolves' diets include but are not limited to large mammals such as elk, caribou, moose and deer; they also prey on beavers, hares, rodents, and other small animals. A wolf needs between three and ten pounds (1.35 to 4.5 kg) of meat per day to survive, but as a wolf may not get a chance to eat every day, they can eat up to twenty pounds (9 kg) of meat in a sitting. [14]
When attacking, wolves generally target the neck, throat, and sides of an animal. Wolf packs mostly kill and feast on the weak, elderly, and sick animals, since large, healthy mammals can and will fight against wolves possibly injuring and even killing a great many wolves. In one study, less than 1 out of 10 chases of moose resulted in a successful kill.[15]
Wolves also have a scent masking instinct whereby they roll in decomposing carcasses or scat. The same behavior can occasionally be seen in their domesticated counterparts as well.[16]
Reproduction and mortality
A wolf cub looks up to others in the pack for protection.Normally, only the alpha pair of the pack breeds. This kind of organization also occurs in other pack-hunting canids, such as the Dhole and the African Hunting Dog. Mating usually occurs in February to May, and wolves, unlike dogs, only mate once a year. Another interesting fact about the social economy of wolves is that they are usually monogamous: the alpha pair will ordinarily mate exclusively with each other so long as they both remain alphas. There are times when one of the alphas will attempt to mate with a subordinate wolf, and if the other alpha is unable to prevent it, multiple litters can be born. This has been documented in Yellowstone amongst other places and usually occurs in large packs with plenty of available prey.
The gestation period is 60 to 63 days, and the pups are born blind and completely dependent on their mother. There are 1–14 pups per litter, with the average litter size being 6 or 7 pups. Pups reside in the den in which they are born until they reach 8–10 weeks of age. The mother usually stays with her litter alone for the first 3 weeks, but all members of the pack eventually help rear the pups. Pups consume food regurgitated by older wolves until they are 45 days old. They are fed meat provided by pack members after that age.[17]
Wolf pups reach sexual maturity at 2 years for females, and 3 years for males. Most wolves leave their birth pack when they are 1–3 years old.
Wolves typically live 6–9 years in the wilderness, although in captivity they live 16 years on average. The record lifespan of a wolf is about 20 years of age.[18] However, the mean age of wolves is rather low. The mortality among pups is high, and few survive the first winter. The most significant mortality factors for grown wolves are hunting and poaching by humans, car accidents, and wounds from hunting prey. Wolves are suceptible to the same infections that affect domestic dogs, such as mange, heartworm, rabies and canine distemper, and such diseases can become epidemic, drastically reducing the wolf population in an area. Wolves readily adjust to fluctuations in prey populations, so mass starvation is unusual. Wolves are able to sustain their population under a heavy pressure, as long as the alpha pairs survive.
Human attitudes towards wolves
A Fish and Wildlife Service poster urging hunters to report Gray Wolf sightings.The relationship between people and wolves has had a very long and turbulent history. Historically, humans have often viewed wolves as a great danger or as a nuisance to be destroyed. An opposing view, held by most biologists and naturalists, postulates that wolves form a valuable part of the ecosystem by hunting down animals such as deer—whose population would grow out of control if it were not for wolves—and require protection. Often, these views occur simultaneously and cause conflicts among differing groups of people, as one sees when a wildlife service or organization attempts to preserve endangered wolves or to reintroduce wolves to a habitat, like the rare and almost extinct Red Wolf.
Changing attitudes
In the late 20th century, an increased awareness of the beneficial nature of wolves arose, encouraged by books like Never Cry Wolf by Farley Mowat and nature documentaries as well as by classification of the species as endangered. Accordingly, while the stereotype of wolves still has influence, a significant portion of the public has gained a positive opinion of wolves as interesting, valuable, and even noble animals. Thus, parks with a visible wolf population have often become popular tourist attractions. For instance, visitation to Yellowstone National Park has shown an increase partially due to the wolf reintroduction program and the hope of spotting a wolf.
Original distribution of gray wolf subspecies.Such organizations as the International Wolf Center and Mission: Wolf attempt to educate people about the true nature of wolves, and such action proves helpful to the reintroduction process, especially in places such as Yellowstone National Park.
In other parks, tourists often participate in wolf howls, trying to produce wolflike howls in hopes that the resident wolves will answer. In fact, some nature lovers have complained that this popularity has drawbacks, since tourists sometimes intrude into wolf habitats and disturb them.
The large amount of research done on the wolf in the past half century has also helped to educate people and make them realize how sociologically similar humans are to wolves, and how they have nothing to fear from these shy, majestic animals. Biologists such as L. David Mech and Luigi Boitani have been major leaders in wolf research.
Nature documentaries have also played a role in changing attitudes. For instance, the film evidence of the wolf being a very social animal and devoted parent to its young enlightened and charmed many viewers to a softer side to the feared predator.
Reintroduction
In the United States, wolves are repopulating where they were eradicated, and numbers have been increasing in Alaska and Minnesota, where some packs remained in the deep forests despite bounty hunting and other past eradication efforts. Not only are they slowly but surely coming back naturally from Canada, they are also being successfully reintroduced in some states such as Idaho and Wyoming. It is curious to note that some ranchers prefer reintroduction, as they can kill wolves that
参考资料：http://en.wikipedia.org/wiki/Gray_Wolf