New Page 1

   TORNA ALLA HOME DI ENGLISH GRATIS    Tel. 02-78622122  •  info@englishgratis.com  •  INFORMATIVA PRIVACY

 

WIKIBOOKS
DISPONIBILI
•••••••••

ART
- Great Painters
BUSINESS&LAW
- Accounting
- Fundamentals of Law
- Marketing
- Shorthand
CARS
- Concept Cars
GAMES&SPORT
- Videogames
- The World of Sports

COMPUTER TECHNOLOGY
- Blogs
- Free Software
- Google
- My Computer

- PHP Language and Applications
- Wikipedia
- Windows Vista

EDUCATION
- Education
LITERATURE
- Masterpieces of English Literature
LINGUISTICS
- American English

- English Dictionaries
- The English Language

MEDICINE
- Medical Emergencies
- The Theory of Memory
MUSIC&DANCE
- The Beatles
- Dances
- Microphones
- Musical Notation
- Music Instruments
SCIENCE
- Batteries
- Nanotechnology
LIFESTYLE
- Cosmetics
- Diets
- Vegetarianism and Veganism
TRADITIONS
- Christmas Traditions
NATURE
- Animals

- Fruits And Vegetables


 


ARTICLES IN THE BOOK

  1. Alligator
  2. Alpaca
  3. Anaconda
  4. Ant
  5. Anteater
  6. Antelope
  7. Baboon
  8. Badger
  9. Bat
  10. Bear
  11. Bee
  12. Boa
  13. Butterfly
  14. Camel
  15. Canary
  16. Cat
  17. Cheeta
  18. Chicken
  19. Chimpanzee
  20. Cobra
  21. Cod
  22. Condor
  23. Cormorant
  24. Cow
  25. Crab
  26. Cricket
  27. Crocodile
  28. Crow
  29. Deer
  30. Dog
  31. Dolphin
  32. Donkey
  33. Dove
  34. Duck
  35. Eagle
  36. Elephant
  37. Emu
  38. Falcon
  39. Ferret
  40. Fly
  41. Fox
  42. Gazelle
  43. Giraffe
  44. Goat
  45. Goose
  46. Gorilla
  47. Hare
  48. Hedgehog
  49. Heron
  50. Hippopotamus
  51. Horse
  52. Hyena
  53. Ibis
  54. Jackal
  55. Kangaroo
  56. Kingfisher
  57. Koala
  58. Leopard
  59. Lion
  60. Llama
  61. Lobster
  62. Louse
  63. Mantodea
  64. Mink
  65. Mole
  66. Mongoose
  67. Mosquito
  68. Mule
  69. Nightingale
  70. Octopus
  71. Opossum
  72. Orangutan
  73. Ostrich
  74. Otter
  75. Owl
  76. Panda
  77. Parrot
  78. Partridge
  79. Peacock (Peafowl)
  80. Pelican
  81. Penguin
  82. Pheasant
  83. Pig
  84. Pigeon
  85. Prawn
  86. Puffin
  87. Quail
  88. Rabbit
  89. Reindeer
  90. Rhinoceros
  91. Salmon
  92. Seagull
  93. Seal
  94. Shark
  95. Sheep
  96. Shrimp
  97. Silk worm
  98. Skunk
  99. Sparrow
  100. Spider
  101. Squid
  102. Squirrel
  103. Stork
  104. Swallow
  105. Swan
  106. Tarantula
  107. Termite
  108. Tiger
  109. Toucan
  110. Tuna
  111. Turkey
  112. Turtle
  113. Violet-ear
  114. Vulture
  115. Walrus
  116. Wasp
  117. Whale
  118. Wolf
  119. Woodpecker
  120. Yak
  121. Zebra
 



ANIMALS
This article is from:
http://en.wikipedia.org/wiki/Wolf

All text is available under the terms of the GNU Free Documentation License: http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License 

Gray Wolf

From Wikipedia, the free encyclopedia

(Redirected from Wolf)

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.

The Gray Wolf, being a keystone predator, is an integral component of the ecosystems to which it typically belongs. The wide range of habitats in which wolves can thrive reflects their adaptability as a species, and includes temperate forests, mountains, tundra, taiga, and grasslands. In the contiguous United States, with the exception of Minnesota and Wisconsin (where they have a threatened status), they are listed as endangered under the Endangered Species Act of 1973. They continue to be hunted in many areas of the world as perceived threats to livestock and humans, as well as for sport.

Anatomy, physiology, and reproduction

Features and adaptations

Wolf weight and size can vary greatly worldwide, though both tend to increase proportionally with higher latitudes. Generally speaking, height varies from 0.6–0.8 meters (26–32 inches) at the shoulder, and weight can range anywhere from 23–59 kilograms (50–130 pounds), making wolves the largest among all wild canids.[3] Although rarely encountered, extreme specimens reaching over 77 kg (170 lb) have been recorded in Alaska and Canada,[4] and the heaviest wolf on record, which was killed in Alaska in 1939, weighed 80 kg (175 lb).[5] The smallest wolves come from the Arabian Wolf subspecies, the females of which may weigh as little as 10 kg (22 lb) at maturity. Customarily, however, wolves will be of a more typical physical capacity, with the females in a given population weighing about 20% less than their male counterparts.[6] Wolves can measure anywhere from 1.3–2 meters (4.5–6.5 feet) from nose to tail tip, with the tail itself consisting of approximately one quarter of overall body length.[7]

Wolves are built for stamina, possessing features tailored for long-distance travel. Narrow chests and powerful backs and legs contribute to the wolf's proficiency for efficient locomotion. They are capable of covering several miles trotting at about a 10 km/h (6 mph) pace, though they have been known to reach speeds approaching 65 km/h (40 mph) during a chase (wolves only run fast when testing potential prey).[8] While sprinting thus, wolves can cover up to 5 meters (16 ft) per bound.[9]

Wolves usually have blended pelages.
Enlarge
Wolves usually have blended pelages.

Wolf paws are able to traverse easily through 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, so the relative largeness of their feet helps to better distribute their weight on snowy surfaces. The front paws are larger than the hind paws, and feature 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] Furthermore, scent glands located between a wolf's toes leave trace chemical markers behind, thereby helping the wolf to effectively navigate over large expanses while concurrently keeping others informed of its whereabouts.[10]

A wolf sometimes seems more massive 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. 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, and 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.

Adolescent wolf with golden-yellow eyes.
Enlarge
Adolescent wolf with golden-yellow eyes.

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) while possessing 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.[5] Therefore, any injury to the jaw line or teeth could devastate an individual, dooming it to starvation or incompetence.

Courtship and mating

Usually, the instinct to pass on genetic material 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 who reached sexual maturity during the previous breeding season. It takes two such dispersals from two different packs for the process to take place, as 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, preferentially doing so in time for the next mating season. The bond that forms between such wolves often lasts for the shorter of the two lifetimes, with few exceptions.[16]

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

When the alpha female goes into estrus, a phenomenon that 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 let the male know when his mate is in heat. She will be unreceptive for the first few days of estrus, during which time she sheds the lining of her uterus. Once the female begins to ovulate, mating occurs.

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 10–30 minutes, during which period 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 ordeal is repeated many times throughout the female's brief ovulation period, which occurs once per year per female, unlike female dogs, with whom estrus usually occurs twice per year.

Breeding and life cycle

A wolf pup looks up to others in the pack for protection.
Enlarge
A wolf pup looks up to others in the pack for protection.

Normally, only the alpha pair of the pack breeds, which is a kind of organization not uncommon to other pack-hunting canids including the Dhole and the African Hunting Dog. Mating occurs between January and April, happening later in the year as latitude increases.[16] A pack usually produces a single litter, though sometimes multiple litters will be born if the alpha male mates with one or more subordinate females. Under normal circumstances, the alpha female will try to prevent this by aggressively dominating other females and physically separating them from the alpha male during the mating season.

A wolf resting at the entrance to its den; also note how its coloration blends in with the environment.
Enlarge
A wolf resting at the entrance to its den; also note how its coloration blends in with the environment.

The gestation period lasts 60–63 days, and at the weight of 0.5 kg (1 lb), the pups are born blind, deaf, and completely dependent on their mother.[16][3] There are 1–14 pups per litter, with the average litter size being about 4–6.[20] Pups reside in the den, where they are born, and stay there until they reach about 3 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 2 months, the restless pups will be moved to a rendezvous site, which gives them a safe place to reside while most of the adults go out to hunt.[11] An adult or two will 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 (they tag along as observers until about 8 months, by which time they are large enough to actively participate),[11] and will receive first 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.[16]

Wolves typically reach sexual maturity after 2 or 3 years, at which point many of them will feel compelled to leave their birth packs and search out mates and territories of their own.[16][21] Wolves that reach maturity generally live 6–8 years in the wild, although in captivity they can live to be twice that age.[20] High mortality rates result in a relatively low life expectancy for wolves on an overall basis. Pups die when food is scarce; they can also fall prey to other predators such as bears, or, less likely, coyotes, foxes, or other wolves. The most significant mortality factors for grown wolves are hunting and poaching by humans, car accidents, and wounds suffered while hunting prey. Wolves are susceptible 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.

Behavior

Body language

See also: Dog communication
This facial expression is defensive and gives warning to other wolves to be cautious.
Enlarge
This facial expression is defensive and gives warning to other wolves to be cautious.
This facial expression shows fear.
Enlarge
This facial expression shows fear.
This wolf's submissive posture, wagging tail and horizontal ears show a friendly greeting.
Enlarge
This wolf's submissive posture, wagging tail and horizontal ears show a friendly greeting.

Wolves can visually communicate an impressive variety of expressions and moods that range from subtler signals, such as a slight shift in weight, to the more obvious ones, like rolling on the back as a sign of 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 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 it to the ground, "ride up" on its shoulders, 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 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 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 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 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 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 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 demonstrated by domestic dogs.

Howling

Wolves howl for several reasons. Howling helps pack members keep in touch, allowing them to effectively communicate in thickly forested areas or over great distances. Furthermore, howling helps to summon pack members to a specific location. Howling can also serve as a declaration of territory, as portrayed by a dominant wolf's tendency to respond to a human imitation of a "rival" individual in an area that the wolf considers its own. This behavior is also 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. Thus, wolves tend to howl with great care.[23]

Howling adult wolf on glacial erratic at Little America Flats.
Enlarge
Howling adult wolf on glacial erratic at Little America Flats.

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, which tends to prevent a listener from accurately estimating the number of wolves involved. This concealment of numbers makes a listening rival pack wary of what action to take. For example, confrontation could mean bad news if the rival pack gravely underestimates the howling pack's numbers.

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 relatively easily over the following two months. Such indiscriminate howling usually has a communicative intent, and has no adverse consequences so early in a wolf's life.[23] Howling becomes less indiscriminate as wolves learn to distinguish howling pack members from rival wolves.

Other vocalizations

Growling, used in tandem with bared teeth, is the most visual and effective warning wolves use. Wolf growls have a distinct, deep, bass-like quality, and are used much of the time as a threat, though they are not always necessarily used for defense. Wolves will also growl at other wolves while being aggressively dominant.

Wolves also bark, which they do when nervous or to warn other wolves of danger. Wolves bark very discreetly, and will not generally bark loudly or repeatedly as dogs do; rather, they use a low-key, breathy "whuf" sound to get attention immediately from other wolves. Wolves will also "bark-howl" by adding a brief howl to the end of a bark. Wolves bark-howl for the same reasons they normally bark. Actually, pups bark and bark-howl much more frequently than adults, using such vocalizations as cries for attention, care, or food.

Wolves can also whimper, which they usually do only while submitting to other wolves. Wolf pups will whimper when they need a reassurance of security from their parents or other wolves.

Scent marking

Wolves, like other canines, use scent marking to lay claim to anything from territory to fresh kills.[24] Alpha wolves scent mark the most often, with males doing so more than females. The most widely used scent marker is urine. Male alpha wolves urine-mark objects using a raised-leg stance (all females squat) so as to enforce rank and territory. They will also use such marks to identify food caches and to claim kills on behalf of the whole pack. Defecation markers are used for the same purposes as urine marks, and serve as a more visual warning, as well.[24] These types of scent markings are particularly useful for navigational purposes, keeping the pack from traversing the same terrain too often while also allowing each individual to be aware of the whereabouts of its pack members. Above all, though, scent marking is used to notify other wolves and packs that a given 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.[24] Pheromones secreted by these glands identify each individual wolf. A dominant wolf will "rub" his or her body against subordinate wolves to mark such individuals as being members of a particular pack. Wolves may also "paw" dirt to release pheromones in lieu of urine marking.[25]

Wolves' heavy reliance on odoriferous signals testifies greatly to their olfactory capabilities. Wolves can pick up any scent, including marks, from great distances, and can distinguish among them just as well or better than humans can distinguish other humans visually.

Social structure and hunting

The pack

Wolves function as social predators and hunt in packs organized according to strict, rank-oriented social hierarchies.[16] It was originally thought that this comparatively high level of social organization had more to do with 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 (of whom only one may be the "top" alpha) has the greatest amount of social freedom compared to the rest of the pack, but they are not "leaders" in the human sense of the term. The alphas do not give the other wolves orders; rather, they simply have the most freedom in choosing where to go, what to do, and when to do it. Possessing strong instincts for fellowship, the rest of the pack usually follows.

While most alpha pairs are monogamous with each other, there are exceptions.[26] 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.[16]

Usually, only the alpha pair is able to successfully rear a litter of pups. Other wolves in a pack may breed, but will usually lack the resources required to raise the pups to maturity. All the wolves in the pack assist in raising wolf pups. Some mature individuals, usually females, may choose to stay in the original pack so as to reinforce it and help rear more pups. However, most will disperse, males particularly.

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 2–20 wolves, though an average pack consists of 6 or 7.[27][28] New packs are formed when a wolf leaves its birth pack 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, a behavior that may explain wolf "predation" of dogs. 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 unwanted intrusion.

Hierarchy

A wolf pack in Yellowstone National Park, with the alphas leading and the omega in the rear.
Enlarge
A wolf pack in Yellowstone National Park, with the alphas leading and the omega in the rear.

The hierarchy, led by the alpha male and female, affects all activity in the pack to some extent. In most larger packs, there are two separate hierarchies in addition to an overbearing one: the first consists of the males, led by the alpha male, and the other consists of the females, led by the alpha female.[10] In this situation, the alpha male usually assumes the "top" alpha position, though alpha females have been known to take control over entire packs in some cases. The male and female hierarchies are interdependent, and are maintained constantly by aggressive and elaborate displays of dominance and submission.

After the alpha pair, there may also, especially in larger packs, be a beta wolf or wolves, a "second-in-command" to the alphas. Betas typically assume a more prominent role in assisting with the upbringing of the alpha pair's litter, often serving as surrogate mothers or fathers while the alpha pair is away. Beta wolves are the most likely to challenge their superiors for the role of the alpha, though some betas seem content with being second, and will sometimes even let lower ranking wolves leapfrog them for the position of alpha should circumstances necessitate such a happening, such as the death of the alpha. More ambitious beta wolves, however, will only wait so long before challenging for the top spot unless they choose to disperse and create their own pack instead.

Loss of rank can happen gradually or suddenly. An older wolf may simply choose to give way when a motivated challenger presents itself, yielding its position without bloodshed. On the other hand, the challenged individual may choose to fight back, with varying degrees of intensity. While the majority of wolf aggression is non-damaging and ritualized, a high-stakes fight can easily result in injury for either or both parties. The loser of such a confrontation is frequently chased away from the pack or, rarely, may be killed as other aggressive wolves contribute to the insurgency. This kind of dominance encounter is more common during the mating season.

Rank order within a pack is established and maintained through a series of ritualized fights and posturing best described as "ritual bluffing". Wolves prefer psychological warfare to physical confrontations, meaning that 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).

In a more typical pack, however, only one wolf will assume the role of the omega: the lowest-ranking member of a pack.[24] These individuals absorb the greatest amount of aggression from the rest of the pack, and may be subjected to different forms of truculence at any given point— anything from constant dominance from other pack members to inimical, physical harassment. Although this arrangement may seem objectionable after cursory analysis, the nature of pack dynamics demands that one wolf be at the bottom of the ranking order, and such individuals are perhaps better suited for constant displays of active and passive submission than they are for living alone. For wolves, camaraderie— no matter what the form— is preferable to solitude, and, indeed, submissive wolves tend to choose low rank over potential starvation.

Cooperative hunting and diet

An American Bison standing its ground, thereby increasing its chance for survival.
Enlarge
An American Bison standing its ground, thereby increasing its chance for survival.

Packs of wolves cooperatively hunt any large herbivores in their range. Pack hunting revolves around the chase, as wolves are able to run for long periods before relenting. It takes meticulous cooperation for a pack to take down a large prey animal, but the success rate of such chases is actually very low. Wolves, in the interest of saving energy, will only chase any one potential prey animal for the first thousand or so meters before giving up and trying again at a different time with a different prey.[29] Hence, like most other pack species, wolves must hunt continually to sustain themselves. Solitary wolves depend more on smaller animals, capturing them by pouncing and pinning them to the ground with their front paws— a common technique among canids such as foxes and coyotes.

Wolves' diets include, but are not limited to, elk, caribou, moose, deer, and other large ungulates. The American Bison is probably the largest animal wolves prey on, with bison exceeding a ton having been taken down by a pack. They also prey on rodents and small animals in a limited manner, as a typical adult wolf requires a minimum of 1.1 kg (2.5 lb) of food per day for sustenance, but approximately 2.2 kg (5 lb) to reproduce successfully;[20] however, this certainly doesn't mean that a wolf will get the chance to eat everyday. In fact, wolves rarely eat on a daily basis, so they compensate by eating up to a maximum of 10 kg (22 lb) at a single sitting when they get the chance.[20]

When pursuing large prey, wolves generally attack from all angles, targeting the necks and sides of such animals. Wolf packs test large populations of prey species by inducing a chase, targeting less-fit individuals; such animals typically include the elderly, diseased, and young.[21] Healthy animals may also succumb through circumstance or by chance. However, most healthy, fit individuals will stand their ground against wolves, increasing the possibility of injury for the wolves involved, which makes the weaker members of a species comparatively easier and safer to hunt.

Like many other keystone predators, wolves are sensitive to fluctuations in prey abundance, making them likely to experience minor changes within their own populations as the abundance of their primary prey species gradually rises and drops over long periods of time. This balance between wolves and their prey prevents the mass starvation of all species involved.


 

Historical perceptions

Main article: Attitudes toward wolves
Original distribution of gray wolves by subspecies.
Enlarge
Original distribution of gray wolves by subspecies.
Present distribution of gray wolves by subspecies.
Enlarge
Present distribution of gray wolves by subspecies.

The relationship between humans and wolves has had a very long and turbulent history. Traditionally, humans have viewed wolves negatively, perceiving them to be dangerous or as nuisances to be destroyed – a perception now known to be extremely undeserved. European folklore exacerbated this negative image, which was brought over to North America with migrating Europeans. In brief, the gray wolf, which, at one point, could be found in any ecosystem on every continent in the Northern Hemisphere, was persistently one of the first species to go once a significant population of humans settled in a given area. As technology made the killing of wolves and other predators easier, simple control gave way to complete annihilation.

Historically, unwarranted fear of the wolf has been responsible for most of the trouble the species has received, including why it was nearly hunted out of existence in the U.S. and Europe prior to the 20th century. However, ecological research conducted during the 20th century shed new light on wolves and other predators, specifically with regard to the critical role they play in maintaining the ecosystems to which they belong. As a result of this and other important factors, wolves have come to be viewed in a much more positive way.

A general environmental awareness began to take root sometime in the middle of the 20th century that forced people to re-think former notions, including those regarding predators. In North America, people realized that in over one hundred years of documentation, there had been no verified human fatality caused by an attack from a healthy wolf.[30][31] Wolves are actually naturally cautious and will almost always flee from humans, perhaps only carefully approaching a person out of curiosity. There are, however, some reported attacks in North America where it is thought that the wolves involved had become habituated to humans.[32] Although attitudes have significantly changed, there are still many who hold more cautious views of the wolf.

Reintroduction

Main article: Wolf reintroduction

In certain parts of the world, debate about wolf reintroduction is ongoing and oftentimes heated, both where reintroduction is being considered and where it has already occurred. Where wolves have been successfully reintroduced, as in the greater Yellowstone area and Idaho, reintroduction opponents continue to cite livestock predation, surplus killing, and economic hardships caused by wolves as reason why they should never have been reintroduced to begin with, as well as why they should be removed or severely reduced.[33][34] Opponents in prospective areas echo these same concerns.

However, what the Yellowstone and Idaho reintroductions demonstrate is how compromise can be used to satisfy relevant interests. These reintroductions were the culmination of over two decades of research and debate. Ultimately, the economic concerns of the local ranching industry, arguably the single best reason used against reintroduction, was dealt with when Defenders of Wildlife decided to establish a fund that would compensate ranchers for livestock lost to wolves, thereby shifting the economic burden from industry to the wolf proponents themselves.[35] Indeed, the majority of the organizations opposing reintroduction relented their "no wolf, no way" stance when this crucial deal breaker was resolved.

Today, there are over 300 wolves in the Greater Yellowstone Ecosystem and over 500 in Idaho. Both populations have long since met their recovery goals and the reintroduction experiment has been a resounding success. Still, lessons learned from this ordeal may yet prove useful where wolf reintroduction continues to create a sharp divide between industry and environmental interests, as it has in Arizona (where Mexican wolves were released beginning in 1998) and Scandinavia (where an inexplicable, isolated population has established itself over the past few decades). In some other Western and Central European countries, the debate will likely impair wolf reintroduction efforts where they are being considered, but, as history has validated, industry need not be ignored for a reintroduction effort to be successful.

Wolf hunting

Main article: Wolf hunting

Livestock predation

As long as there is enough prey, wolves seem to avoid taking livestock, often ignoring them entirely.[36] However, some wolves or packs can specialize in hunting livestock once the behavior is learned despite natural prey abundance. In such situations, sheep are usually the most vulnerable, but horses and cattle are also at risk. Wolf-secure fences, relocation where applicable, and local wolf extermination are the only known methods to effectively stop livestock predation.

Over several centuries, shepherds and dog breeders have used selective breeding to "create" large livestock-guarding dogs that can stand up to wolves preying on flocks.[37] In the U.S., in light of the gray wolf and other large predators having recently been reintroduced to certain areas, the United States Department of Agriculture has been looking into the use of breeds such as the Akbash from Turkey, the Maremma from Italy, the Great Pyrenees from France, and the Kuvasz from Hungary, among others, to help limit wolf-livestock interactions.

In some areas across the world, hunters or state officials will hunt wolves from helicopters or light planes to control populations (or for sport in some instances), citing it as the most effective way to control wolf numbers, given that traditional poisons are largely banned. The method is used where interactions between livestock and wolves are common, or where sport or subsistence hunters desire more game animals with less competition. Aerial hunting is seen as highly controversial. In areas where aerial hunting is used to limit livestock-wolf interactions or to boost populations of game animals, arguments against it are usually centered around whether or not the reasons behind such predator elimination are scientifically valid.

Other, non- or less-lethal methods of protecting livestock from wolves have been under development for the past decade. Such methods include rubber ammunition and use of guard animals.[38]

Trapping and breeding for fur

"How Wolves may be caught with a Snare," 15th century.
Enlarge
"How Wolves may be caught with a Snare," 15th century.

Wolves are frequently trapped, in the areas where it is legal, using snares or leg hold traps. The economic value of wolf pelts is limited, so it is mainly a recreation activity. Wolf trapping has come under heavy fire from animal rights groups, who allege that unskilled trappers can create unnecessary suffering for the animal involved.[39] Proponents counter that trapping, using the right tools and equipment, can be considered as humane as traditional hunting.[40]

A radio-collared wolf.
Enlarge
A radio-collared wolf.

Wolves are also bred for their fur in a very few locations, but they are considered as a rather problematic animal to breed, and, combined with the low value of the pelt, most fur farms utilize other animals.

Biologists may also trap wolves for research purposes. Darting and box traps are the tools of choice for such professionals, who often use these and similar techniques to fit wolves and other animals with collars holding radio transmitters and to check their health before releasing them. Use of such technology also allows them to keep track of population numbers and dispersal trends, among other things. Radio collars can also be used to monitor wolves when they come near livestock, and to identify a wolf or a pack that preys on livestock, allowing proper action to be prompter and more accurate.

Taxonomy

Classification and relation to the dog

Much debate has occurred over the relationship between the wolf and the domestic dog. Most authorities see the wolf as the dog's direct ancestor, but others have postulated descent from the Golden Jackal. Because the canids have evolved recently and different canids interbreed readily, untangling the true relationships has presented difficulties. However, molecular systematics now indicate very strongly that domestic dogs and wolves are more closely related than either is to any other canid, and the domestic dog is now normally classified as a subspecies of the wolf: Canis lupus familiaris. The main differences between wolves and domestic dogs are that wolves have, on average, 30% larger brains, a better immune system, better sense of smell, and are generally much larger than domestic dogs.[41]

The classification of wolves and closely related creatures offers many challenges. Although taxonomists have proposed many species over the years, most types clearly do not comprise true species. Indeed, only a single wolf species may exist. While scientists have proposed a host of subspecies, wolf taxonomy at this level remains controversial.[42] Further taxonomic modification will continue for years to come.

Subspecies of the wolf

It was once believed there were up to 50 subspecies. However, the last decade has seen a new and widely accepted list that has been condensed to 13 living subspecies, 14 including the common dog, and 2 recently extinct subspecies. This takes into account the anatomy, distribution, and migration of various wolf colonies.

Media

  • Wolf howl recording (file info) — play in browser (beta)
  • Problems playing the files? See media help.

See also

  • Werewolf
  • Wolves in fiction
  • Dog communication
  • Attitudes toward wolves
  • Wolf reintroduction
  • Wolf hunting
  • International Wolf Center
  • Wild Canid Survival and Research Center
  • L. David Mech
  • Wiktionary:Wolf

Three other extant canid species also known as wolves:

  • Red Wolf
  • Eastern Canadian Wolf
  • Ethiopian Wolf

Extinct species of wolf:

  • Dire Wolf

References

External links

Commons logo
Wikimedia Commons has media related to:
Canis lupus
  • Canids.org
  • Defenders of Wildlife
  • Enature.com
  • International Wolf Center
  • Mission: Wolf
  • Sinapu
  • Wild Animals Online
  • WolfSource
  • Wolf Park
  • Wolf Song of Alaska
  • Wolf Web

Retrieved from "http://en.wikipedia.org/wiki/Gray_Wolf"

 



Siti amici:  Lonweb Daisy Stories English4Life
 
Sito segnalato da INGLESE.IT

 

 
CONDIZIONI DI USO DI QUESTO SITO
L'utente può utilizzare il nostro sito solo se comprende e accetta quanto segue:

  • Le risorse linguistiche gratuite presentate in questo sito si possono utilizzare esclusivamente per uso personale e non commerciale con tassativa esclusione di ogni condivisione comunque effettuata. Tutti i diritti sono riservati. La riproduzione anche parziale è vietata senza autorizzazione scritta.
  • Il nome del sito EnglishGratis è esclusivamente un marchio e un nome di dominio internet che fa riferimento alla disponibilità sul sito di un numero molto elevato di risorse gratuite e non implica dunque alcuna promessa di gratuità relativamente a prodotti e servizi nostri o di terze parti pubblicizzati a mezzo banner e link, o contrassegnati chiaramente come prodotti a pagamento (anche ma non solo con la menzione "Annuncio pubblicitario"), o comunque menzionati nelle pagine del sito ma non disponibili sulle pagine pubbliche, non protette da password, del sito stesso.
  • La pubblicità di terze parti è in questo momento affidata al servizio Google AdSense che sceglie secondo automatismi di carattere algoritmico gli annunci di terze parti che compariranno sul nostro sito e sui quali non abbiamo alcun modo di influire. Non siamo quindi responsabili del contenuto di questi annunci e delle eventuali affermazioni o promesse che in essi vengono fatte!
  • Coloro che si iscrivono alla nostra newsletter (iscrizione caratterizzatalla da procedura double opt-in) accettano di ricevere saltuariamente delle comunicazioni di carattere informativo sulle novità del sito e, occasionalmente, delle offerte speciali relative a prodotti linguistici a pagamento sia nostri che di altre aziende. In ogni caso chiunque può disiscriversi semplicemente cliccando sulla scritta Cancella l'iscrizione che si trova in fondo alla newsletter, non è quindi necessario scriverci per chiedere esplicitamente la cancellazione dell'iscrizione.
  • L'utente, inoltre, accetta di tenere Casiraghi Jones Publishing SRL indenne da qualsiasi tipo di responsabilità per l'uso - ed eventuali conseguenze di esso - degli esercizi e delle informazioni linguistiche e grammaticali contenute sul siti. Le risposte grammaticali sono infatti improntate ad un criterio di praticità e pragmaticità più che ad una completezza ed esaustività che finirebbe per frastornare, per l'eccesso di informazione fornita, il nostro utente.

     

    ENGLISHGRATIS.COM è un sito di Casiraghi Jones Publishing SRL
    Piazzale Cadorna 10 - 20123 Milano - Italia
    Tel. 02-78622122 - email:
    Iscritta al Registro Imprese di MILANO - C.F. e PARTITA IVA: 11603360154
    Iscritta al R.E.A. di Milano n.1478561 • Capitale Sociale
    10.400 interamente versato

    Roberto Casiraghi                                                                                Crystal Jones