Post by Runic on Aug 29, 2013 21:52:00 GMT 5
Grey wolf (Canis lupus)
Scientific classification
Domain: Eukarya
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Subclass: Theria
Order: Carnivora
Suborder: Caniformia
Family: Canidae
Subfamily: Caninae
Tribe: Canini
Genus: Canis
Species: Canis lupus
The grey wolf or gray wolf (Canis lupus), also known as simply wolf, is the largest wild member of the Canidae family. It is an ice age survivor originating during the Late Pleistocene around 300,000 years ago. DNA sequencing and genetic drift studies reaffirm that the gray wolf shares a common ancestry with the domestic dog (Canis lupus familiaris). Although certain aspects of this conclusion have been questioned, including recently, the main body of evidence confirms it. A number of other gray wolf subspecies have been identified, though the actual number of subspecies is still open to discussion. Gray wolves are typically apex predators in the ecosystems they occupy. Though not as adaptable as more generalist canid species, wolves have thrived in temperate forests, deserts, mountains, tundra, taiga, grasslands, and even urban areas.
Distribution
Though once abundant over much of Eurasia and North America, the gray wolf inhabits a very small portion of its former range because of widespread destruction of its territory, human encroachment, and the resulting human-wolf encounters that sparked broad extirpation. Even so, the gray wolf is regarded as being of least concern for extinction according to the International Union for Conservation of Nature, when the entire gray wolf population is considered as a whole. Today, wolves are protected in some areas, hunted for sport in others, or may be subject to extermination as perceived threats to livestock and pets.
Physical characteristics
Gray wolf weight and size can vary greatly worldwide, tending to increase proportionally with latitude as predicted by Bergmann's Rule. In general, height varies from 0.6 to .95 meters and (26–38 inches) at the shoulder. Wolf weight varies geographically; on average, European wolves may weigh 38.5 kg (85 lbs), North American wolves 80 lbs - 130lbs, and Indian and Arabian wolves 25 kg (55 lbs). Though rarely encountered, extreme specimens of more than 77 kg (170 lb.) have been recorded in Alaska, Canada, and the former Soviet Union. The heaviest recorded gray wolf in the New World was killed on 70 Mile River in east-central Alaska on July 12, 1939 and weighed 79 kg (175 lb.), while the heaviest recorded wolf in the Old World was killed after World War II in the Kobelyakski Area of the Poltavskij Region in the Ukrainian SSR, and weighed 86 kg (189 lb.). Grey wolves are sexually dimorphic, with females in any given wolf population typically weighing 20% less than males. Females also have narrower muzzles and foreheads; slightly shorter, smoother furred legs; and less massive shoulders. Gray wolves can measure anywhere from 1.3 to 2 meters (4.5–6.5 feet) from nose to the tip of the tail, which itself accounts for approximately one quarter of overall body length.
Gray wolves rely on their stamina rather than speed for hunting. 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. One female gray wolf was recorded to have made 7 metre bounds when chasing prey.
Gray wolf paws are able to tread easily on a wide variety of terrains, especially snow. There is a slight webbing between each toe, which allows them to move over snow more easily than comparatively hampered prey. Gray wolves are digitigrade, which, with the relative largeness of their feet, helps them to distribute their weight well on snowy surfaces. The front paws are larger than the hind paws, and have a fifth digit, the dewclaw, that is absent on hind paws. 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 western coyotes, gray wolves have a lower density of sweat glands on their paws. This trait is also present in Eastern Canadian Coyotes which have been shown to have recent wolf ancestry. 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.
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.
Adolescent wolf with golden-yellow eyes.Wolves' long, powerful muzzles help distinguish them from other canids, particularly coyotes and Golden Jackals, which have more narrow, pointed muzzles. In wolves, the anterior incisure of the nasal bones does not have a medial protrusion, unlike jackals. The cingulum on the external edge of the first upper molar is only slightly expressed, while it is broad and distinctly marked in jackals.
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 hold and subdue the prey. Capable of delivering up to 10,000 kPa (1450 lbf/in²) of pressure, a wolf's teeth are its main weapons as well as its primary tools.[6] This is roughly twice the pressure that a domestic dog of similar size can deliver. The dentition of grey wolves is better suited to bone crushing than those of other modern canids, though it is not as specialised as that found in hyenas.
Wolf saliva has been shown to reduce bacterial infection in wounds and accelerate tissue regeneration.
Reproduction and life cycle
Wolf nursing her pupsGenerally, mating occurs between January and April — the higher the latitude, the later it occurs. A pack usually produces a single litter unless the breeding male mates with one or more subordinate females. During the mating season, breeding wolves become very affectionate with one another in anticipation of the female's ovulation cycle. The pack tension rises as each mature wolf feels urged to mate. During this time, the breeding pair may be forced to prevent other wolves from mating with one another. Incest rarely occurs, though inbreeding depression has been reported to be a problem for wolves in Saskatchewan and Isle Royale. When the breeding 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 gestation period lasts between 60 and 63 days. The pups, which weigh 0.5 kg (1 lb) at birth, are born blind, deaf, and completely dependent on their mother. The average litter size is 5-6 pups, though there are two Soviet records of litters consisting of 17 pups. The pups reside in the den and stay there for two months. The den is usually on high ground near an open water source, and has an open chamber at the end of an underground or hillside tunnel that can be up to a few meters long. During this time, the pups will become more independent, and will eventually begin to explore the area immediately outside the den before gradually roaming up to a mile away from it at around 5 weeks of age. Wolf growth rate is slower than that of coyotes and dholes. They begin eating regurgitated foods after 2 weeks of feeding on milk, which in wolves has less fat and more protein and arginine than dog milk. By this time, their milk teeth have emerged — and are fully weaned by 10 weeks. During the first weeks of development, the mother usually stays with her litter alone, but eventually most members of the pack will contribute to the rearing of the pups in some way. 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 10 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, tigers, or other wolves. The most significant causes of mortality for grown wolves are hunting and poaching, car accidents, and wounds inflicted while hunting prey. Although adult wolves may occasionally be killed by other predators, rival wolf packs are often their most dangerous non-human enemy.
Social structure
Occasionally, single wolves are found in the wild, though packs are more common. Lone wolves are typically old specimens driven from their pack or young adults in search of new territory. Wolf packs in the northern hemisphere tend not to be as compact or unified as those of African Wild Dogs and Spotted Hyenas, though they are not as unstable as those of coyotes. Normally, the pack consists of a male, a female, and their offspring, essentially making the pack a nuclear family. 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. An unusually large pack consisting of 36 wolves was reported in 1967 in Alaska. While most breeding pairs are monogamous, there are exceptions. Wolves will usually remain with their parents until the age of two years. Young from the previous season will support their parents in nursing pups of a later year. Wolf cubs are very submissive to their parents, and remain so after reaching sexual maturity. On occasion in captivity, subordinate wolves may rise up and challenge the dominant pair; such revolts may result in daughters killing mothers and sons killing fathers. This behavior has never been documented in the wild, and it is hypothesized that it only happens in captivity because dispersal is impossible. There are no documented cases of subordinate wolves challenging the leadership of their parents. Instead of openly challenging the leadership of the pack leaders, most young wolves between the ages of 1–4 years leave their family in order to search for, or start, a pack of their own. Wolves acting unusually, such as epileptic pups or thrashing adults crippled by a trap or a gunshot, are usually killed by other members of their own pack. Asiatic and Middle Eastern wolves tend to be less inclined to socialising with any other member of their species outside their own nuclear family, passing their lives more frequently either in pairs or as social individuals, much like coyotes and dingoes.
In literature, wolf packs are commonly portrayed as strongly hierarchic communities, with a dominant breeding "Alpha pair", a group of subordinate "Beta" individuals, and the scapegoat "Omega wolf" on the lowest end of the hierarchy. These descriptions are heavily based on research on captive wolf packs composed of unrelated individuals and cannot be extrapolated to wild wolf packs. In captivity, dispersal of mature individuals is impossible, resulting in frequent aggressive hierarchic encounters. According to wolf biologist L. David Mech, "Calling a wolf an alpha is usually no more appropriate than referring to a human parent or a doe deer as an alpha. Any parent is dominant to its young offspring, so alpha adds no information." and that basing observations on captive living arrangements would be like “…trying to draw inferences about human family dynamics by studying humans in refugee camps”. The term may be valid under certain circumstances, such as when a pack adopts an unrelated dispersed wolf, when the breeding pair die, thus leaving the alpha position open, or when siblings disperse from a pack together. In these cases, the standard nuclear family model does not apply, which may cause wild wolves to behave more like they do in captivity.
Dietary habits
Wolves feed primarily on medium to large sized ungulates, though they are opportunistic feeders, and will generally eat any meat that is available, including non-ungulate species, carrion and garbage. Cannibalism is not uncommon in wolves, and has been recorded to occur in times of food scarcity, when a pack member dies, and during territorial disputes. Some wolf packs in Alaska and Western Canada have been observed to feed on salmon. Humans are rarely, but occasionally preyed upon. Wolves will typically avoid a potential prey item which does not conform to what they experienced during their lives. Generally, the greater the discrepancy to what wolves are accustomed to, the greater their resistance to exploring it. This is only increased should the new prey act bold, assertive, and fearless. Nevertheless, even if there is no food shortage, wolves will explore alternative prey if they continually come into close contact with it and habituate themselves.
Unlike lion prides, wolf packs numbering above 2 individuals show little strategic cooperation in hunting large prey. Wolves typically attempt to conceal themselves as they approach their prey. Often, they will wait for the prey to graze, when it is distracted. If the prey animal stands its ground or confronts the pack, the wolves will approach and threaten it. The wolves will eventually leave if their prey does not run, though the length of time can range from hours to days. If their prey attempts to flee, the wolves will give chase. Wolves generally do not engage in long chases, and will usually stop a pursuit after a chase of 10-180 metres, though there has been one documented case of a wolf chasing a moose for 36 km. Female wolves tend to be better at chasing prey than males, while the latter are more adept at wrestling large prey to the ground once it is caught. Packs composed largely of female wolves thrive on fleet footed prey such as elk, while packs specialising in bison tend to have a greater number of males. Though commonly portrayed as targeting solely sick or infirm animals, there is little evidence that they actively limit themselves to such targets. Rather, the evidence shows that wolves will simply target the easiest options available, which as well as sick and infirm animals, can also include young animals and pregnant females. Though wolves commonly hunt large prey in packs, there are cases in which single wolves have successfully killed large animals unaided. One wolf was recorded to have killed moose 11 times singlehandedly.
Wolves will typically attempt to disable large prey by tearing at the haunches and perineum, causing massive bleeding and loss of coordination. A single bite can cause a wound up to 10–15 cm in length. A large deer in optimum health generally succumbs to three bites at the perineum area after a chase of 150 metres. Once their prey is sufficiently weakened, the wolves will grab it by the flanks and pull it down.Sometimes, with medium sized prey such as dall sheep, wolves will bite the throat, severing the windpipe or jugular. When attacking canid prey, such as dogs, coyotes or other wolves, wolves will kill by biting the back, neck or head. With prey of equal or lesser weight to the wolf, such as lambs or small children, wolves will grab their quarry by the neck, chest, head or thigh and carry them off to a secluded spot. Once the prey collapses, the wolves will tear open the abdominal cavity and commence feeding on the animal, sometimes before it has died. On some occasions, wolves will not press an attack, and will wait for their prey to die from their wounds before feeding begins. Wolves will occasionally attack pregnant ungulates to feed on the fetus(es), leaving the mother uneaten. Usually, it is the dominant pair that works the hardest in killing the pack's target. Wolves have on occasion been observed to engage in acts of surplus killing. This phenomenon is common when wolves target livestock. In the wild, this usually occurs in late winter or spring when deep snow impedes their prey's escape.
Pack status is reinforced during feeding. The breeding pair usually eats first, starting with the heart, liver, and lungs. Wolves of intermediate rank will prevent lower ranking pack members from feeding until the dominant pair finishes eating. The stomach of prey is eaten, though the contents are left untouched if the killed animal is a herbivore. The leg muscles are eaten next, with the hide and bones being the last to be consumed. If they are disturbed while feeding, they will instead focus their attention on their prey's fat deposits rather than internal organs. A single wolf can eat up to 3.2–3.5 kg of food at a time, though they can eat as much as 13–15 kg when sufficiently hungry. A wolf's yearly requirement is 1.5 tons of meat. Wolves can go without sustenance for long periods, with a Russian record showing how one specimen survived for 17 days without food. Research has shown that 2 weeks without food will not weaken a wolf's muscle activity. After eating, wolves will drink large quantities of water to prevent uremic poisoning. A wolf's stomach can hold up to 7.5 litres of water. Wolves supplement their diet with vegetation. Scat analysis found 75% of samples found Yellowstone National Park wolves’ summer diet contained plants mostly grass (Graminae). In some areas of the former Soviet Union wolves have been reported to cause serious damage to watermelon plantations.
Studies on how wolves affect prey populations tend to vary considerably, with some results indicating that wolves dramatically reduce, sometimes locally extirpate some prey species, while others indicate that wolf predation simply takes over from other mortality factors present in wolf-free zones. Wolves are not essential for the presence of many other species.
Interspecific predatory relationships
Wolves typically dominate other canid species in areas where they are sympatric. In North America, wolves are generally intolerant of coyotes in their territory; two years after their reintroduction to the Yellowstone National Park, the wolves were responsible for a near 50% drop in coyote populations through both competition and predation. Wolves have been reported to dig coyote pups from their dens and kill them. Wolves typically do not consume the coyotes they kill. There are no records of coyotes killing wolves, though they have been known to gang up on wolves if they outnumber them. Wolves have been observed to allow coyotes to approach their kills, only to chase them down and kill them. Coyote specialist Robert Crabtree of the Yellowstone Ecological Research Center suggested that this behaviour could be linked to the intraspecific territoriality of wolves, even though coyote represent no danger: "Maybe you want to teach your pups tricks of the trade... Maybe wolves are killing coyotes to practice for conflicts with other wolves later in life."[89] Near identical interactions have been observed in Greece between wolves and Golden Jackals. Wolves may kill foxes on kill sites, though not as frequently as they do with coyotes. Raccoon Dogs are also reportedly preyed upon.
Brown Bears are encountered in both Eurasia and North America. The majority of interactions between wolves and Brown Bears usually amount to nothing more than mutual avoidance. Serious confrontations depend on the circumstances of the interaction, though the most common factor is defence of food and young. Brown Bears will use their superior size to intimidate wolves from their kills and when sufficiently hungry, will raid wolf dens. Brown Bears usually dominate wolves on kills, though they rarely prevail against wolves defending den sites. Wolves in turn have been observed killing bear cubs, to the extent of even driving off the defending mother bears. Deaths in wolf/bear skirmishes are considered very rare occurrences, the individual power of the brown bear and the collective strength of the wolf pack usually being sufficient deterrents to both sides. Encounters with American Black Bears occur solely in the Americas; their interactions with wolves are much rarer than those of Brown Bears, due to differences in habitat preferences. The majority of Black Bear encounters with wolves occur in the species' northern range, with no interactions being recorded in Mexico. Wolves have been recorded to kill Black Bears on numerous occasions without eating them. Unlike Brown Bears, Black Bears frequently lose against wolves in disputes over kills. While encounters with brown and black bears appear to be common, polar bears are rarely encountered by wolves, though there are two records of wolf packs killing polar bear cubs.
Large wolf populations limit the numbers of small to medium sized felines. Wolf predation is recorded to reduce lynx populations wherever the two species are sympatric. Lynx populations in Slovakia plummeted during World War II, when large numbers of wolves entered the cat's range. Similarly, in Russia, lynx populations drop in areas with high wolf densities. In the Rocky Mountains and adjacent mountain areas of North America, wolves are usually hostile toward cougars and will kill cubs if given the opportunity. A pack will on occasion appropriate the kills of adult cougars, which respond by increasing their kill rate. Both species have been recorded to kill each other. National Park Service cougar specialist Kerry Murphy stated that the cougar usually is at an advantage on a one to one basis, considering it can effectively use its claws, as well as its teeth, unlike the wolf which relies solely on its teeth. Yellowstone officials have reported that attacks between cougars and wolves are not uncommon. Multiple incidents of cougars taking wolves and vice versa have been recorded in Yellowstone National Park. Researchers in Montana have found that wolves regularly kill cougars in the area. Similarly, large numbers of wolves have been reported to reduce leopard populations in Tibet. However, the reverse is true for larger cats such as tigers. In areas where wolves and tigers share ranges, such as the Russian Far East, the two species typically display a great deal of dietary overlap, resulting in intense competition. Wolf and tiger interactions are well documented in Sikhote-Alin, which until the beginning of the 20th century, held very few wolves. It is thought by certain experts that wolf numbers increased in the region after tigers were largely eliminated during the Russian colonization in the late 1800s and early 1900s. This is corroborated by native inhabitants of the region claiming that they had no memory of wolves inhabiting Sikohte-Alin until the 1930s, when tiger numbers decreased. Tigers depress wolf numbers, either to the point of localized extinction or to such low numbers as to make them a functionally insignificant component of the ecosystem. Wolves appear capable of escaping competitive exclusion from tigers only when human persecution decreases the latter's numbers. Today wolves are considered scarce in tiger inhabited areas, being found in scattered pockets, and usually seen traveling as loners or in small groups. First hand accounts on interactions between the two species indicate that tigers occasionally chase wolves from their kills, while wolves will scavenge from tiger kills. Tigers are not known to prey on wolves, though there are four records of tigers killing wolves without consuming them. This competitive exclusion of wolves by tigers has been used by Russian conservationists to convince hunters in the Far East to tolerate the big cats, as they limit ungulate populations less than wolves, and are effective in controlling the latter's numbers.
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Scientific classification
Domain: Eukarya
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Subclass: Theria
Order: Carnivora
Suborder: Caniformia
Family: Canidae
Subfamily: Caninae
Tribe: Canini
Genus: Canis
Species: Canis lupus
The grey wolf or gray wolf (Canis lupus), also known as simply wolf, is the largest wild member of the Canidae family. It is an ice age survivor originating during the Late Pleistocene around 300,000 years ago. DNA sequencing and genetic drift studies reaffirm that the gray wolf shares a common ancestry with the domestic dog (Canis lupus familiaris). Although certain aspects of this conclusion have been questioned, including recently, the main body of evidence confirms it. A number of other gray wolf subspecies have been identified, though the actual number of subspecies is still open to discussion. Gray wolves are typically apex predators in the ecosystems they occupy. Though not as adaptable as more generalist canid species, wolves have thrived in temperate forests, deserts, mountains, tundra, taiga, grasslands, and even urban areas.
Distribution
Though once abundant over much of Eurasia and North America, the gray wolf inhabits a very small portion of its former range because of widespread destruction of its territory, human encroachment, and the resulting human-wolf encounters that sparked broad extirpation. Even so, the gray wolf is regarded as being of least concern for extinction according to the International Union for Conservation of Nature, when the entire gray wolf population is considered as a whole. Today, wolves are protected in some areas, hunted for sport in others, or may be subject to extermination as perceived threats to livestock and pets.
Physical characteristics
Gray wolf weight and size can vary greatly worldwide, tending to increase proportionally with latitude as predicted by Bergmann's Rule. In general, height varies from 0.6 to .95 meters and (26–38 inches) at the shoulder. Wolf weight varies geographically; on average, European wolves may weigh 38.5 kg (85 lbs), North American wolves 80 lbs - 130lbs, and Indian and Arabian wolves 25 kg (55 lbs). Though rarely encountered, extreme specimens of more than 77 kg (170 lb.) have been recorded in Alaska, Canada, and the former Soviet Union. The heaviest recorded gray wolf in the New World was killed on 70 Mile River in east-central Alaska on July 12, 1939 and weighed 79 kg (175 lb.), while the heaviest recorded wolf in the Old World was killed after World War II in the Kobelyakski Area of the Poltavskij Region in the Ukrainian SSR, and weighed 86 kg (189 lb.). Grey wolves are sexually dimorphic, with females in any given wolf population typically weighing 20% less than males. Females also have narrower muzzles and foreheads; slightly shorter, smoother furred legs; and less massive shoulders. Gray wolves can measure anywhere from 1.3 to 2 meters (4.5–6.5 feet) from nose to the tip of the tail, which itself accounts for approximately one quarter of overall body length.
Gray wolves rely on their stamina rather than speed for hunting. 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. One female gray wolf was recorded to have made 7 metre bounds when chasing prey.
Gray wolf paws are able to tread easily on a wide variety of terrains, especially snow. There is a slight webbing between each toe, which allows them to move over snow more easily than comparatively hampered prey. Gray wolves are digitigrade, which, with the relative largeness of their feet, helps them to distribute their weight well on snowy surfaces. The front paws are larger than the hind paws, and have a fifth digit, the dewclaw, that is absent on hind paws. 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 western coyotes, gray wolves have a lower density of sweat glands on their paws. This trait is also present in Eastern Canadian Coyotes which have been shown to have recent wolf ancestry. 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.
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.
Adolescent wolf with golden-yellow eyes.Wolves' long, powerful muzzles help distinguish them from other canids, particularly coyotes and Golden Jackals, which have more narrow, pointed muzzles. In wolves, the anterior incisure of the nasal bones does not have a medial protrusion, unlike jackals. The cingulum on the external edge of the first upper molar is only slightly expressed, while it is broad and distinctly marked in jackals.
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 hold and subdue the prey. Capable of delivering up to 10,000 kPa (1450 lbf/in²) of pressure, a wolf's teeth are its main weapons as well as its primary tools.[6] This is roughly twice the pressure that a domestic dog of similar size can deliver. The dentition of grey wolves is better suited to bone crushing than those of other modern canids, though it is not as specialised as that found in hyenas.
Wolf saliva has been shown to reduce bacterial infection in wounds and accelerate tissue regeneration.
Reproduction and life cycle
Wolf nursing her pupsGenerally, mating occurs between January and April — the higher the latitude, the later it occurs. A pack usually produces a single litter unless the breeding male mates with one or more subordinate females. During the mating season, breeding wolves become very affectionate with one another in anticipation of the female's ovulation cycle. The pack tension rises as each mature wolf feels urged to mate. During this time, the breeding pair may be forced to prevent other wolves from mating with one another. Incest rarely occurs, though inbreeding depression has been reported to be a problem for wolves in Saskatchewan and Isle Royale. When the breeding 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 gestation period lasts between 60 and 63 days. The pups, which weigh 0.5 kg (1 lb) at birth, are born blind, deaf, and completely dependent on their mother. The average litter size is 5-6 pups, though there are two Soviet records of litters consisting of 17 pups. The pups reside in the den and stay there for two months. The den is usually on high ground near an open water source, and has an open chamber at the end of an underground or hillside tunnel that can be up to a few meters long. During this time, the pups will become more independent, and will eventually begin to explore the area immediately outside the den before gradually roaming up to a mile away from it at around 5 weeks of age. Wolf growth rate is slower than that of coyotes and dholes. They begin eating regurgitated foods after 2 weeks of feeding on milk, which in wolves has less fat and more protein and arginine than dog milk. By this time, their milk teeth have emerged — and are fully weaned by 10 weeks. During the first weeks of development, the mother usually stays with her litter alone, but eventually most members of the pack will contribute to the rearing of the pups in some way. 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 10 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, tigers, or other wolves. The most significant causes of mortality for grown wolves are hunting and poaching, car accidents, and wounds inflicted while hunting prey. Although adult wolves may occasionally be killed by other predators, rival wolf packs are often their most dangerous non-human enemy.
Social structure
Occasionally, single wolves are found in the wild, though packs are more common. Lone wolves are typically old specimens driven from their pack or young adults in search of new territory. Wolf packs in the northern hemisphere tend not to be as compact or unified as those of African Wild Dogs and Spotted Hyenas, though they are not as unstable as those of coyotes. Normally, the pack consists of a male, a female, and their offspring, essentially making the pack a nuclear family. 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. An unusually large pack consisting of 36 wolves was reported in 1967 in Alaska. While most breeding pairs are monogamous, there are exceptions. Wolves will usually remain with their parents until the age of two years. Young from the previous season will support their parents in nursing pups of a later year. Wolf cubs are very submissive to their parents, and remain so after reaching sexual maturity. On occasion in captivity, subordinate wolves may rise up and challenge the dominant pair; such revolts may result in daughters killing mothers and sons killing fathers. This behavior has never been documented in the wild, and it is hypothesized that it only happens in captivity because dispersal is impossible. There are no documented cases of subordinate wolves challenging the leadership of their parents. Instead of openly challenging the leadership of the pack leaders, most young wolves between the ages of 1–4 years leave their family in order to search for, or start, a pack of their own. Wolves acting unusually, such as epileptic pups or thrashing adults crippled by a trap or a gunshot, are usually killed by other members of their own pack. Asiatic and Middle Eastern wolves tend to be less inclined to socialising with any other member of their species outside their own nuclear family, passing their lives more frequently either in pairs or as social individuals, much like coyotes and dingoes.
In literature, wolf packs are commonly portrayed as strongly hierarchic communities, with a dominant breeding "Alpha pair", a group of subordinate "Beta" individuals, and the scapegoat "Omega wolf" on the lowest end of the hierarchy. These descriptions are heavily based on research on captive wolf packs composed of unrelated individuals and cannot be extrapolated to wild wolf packs. In captivity, dispersal of mature individuals is impossible, resulting in frequent aggressive hierarchic encounters. According to wolf biologist L. David Mech, "Calling a wolf an alpha is usually no more appropriate than referring to a human parent or a doe deer as an alpha. Any parent is dominant to its young offspring, so alpha adds no information." and that basing observations on captive living arrangements would be like “…trying to draw inferences about human family dynamics by studying humans in refugee camps”. The term may be valid under certain circumstances, such as when a pack adopts an unrelated dispersed wolf, when the breeding pair die, thus leaving the alpha position open, or when siblings disperse from a pack together. In these cases, the standard nuclear family model does not apply, which may cause wild wolves to behave more like they do in captivity.
Dietary habits
Wolves feed primarily on medium to large sized ungulates, though they are opportunistic feeders, and will generally eat any meat that is available, including non-ungulate species, carrion and garbage. Cannibalism is not uncommon in wolves, and has been recorded to occur in times of food scarcity, when a pack member dies, and during territorial disputes. Some wolf packs in Alaska and Western Canada have been observed to feed on salmon. Humans are rarely, but occasionally preyed upon. Wolves will typically avoid a potential prey item which does not conform to what they experienced during their lives. Generally, the greater the discrepancy to what wolves are accustomed to, the greater their resistance to exploring it. This is only increased should the new prey act bold, assertive, and fearless. Nevertheless, even if there is no food shortage, wolves will explore alternative prey if they continually come into close contact with it and habituate themselves.
Unlike lion prides, wolf packs numbering above 2 individuals show little strategic cooperation in hunting large prey. Wolves typically attempt to conceal themselves as they approach their prey. Often, they will wait for the prey to graze, when it is distracted. If the prey animal stands its ground or confronts the pack, the wolves will approach and threaten it. The wolves will eventually leave if their prey does not run, though the length of time can range from hours to days. If their prey attempts to flee, the wolves will give chase. Wolves generally do not engage in long chases, and will usually stop a pursuit after a chase of 10-180 metres, though there has been one documented case of a wolf chasing a moose for 36 km. Female wolves tend to be better at chasing prey than males, while the latter are more adept at wrestling large prey to the ground once it is caught. Packs composed largely of female wolves thrive on fleet footed prey such as elk, while packs specialising in bison tend to have a greater number of males. Though commonly portrayed as targeting solely sick or infirm animals, there is little evidence that they actively limit themselves to such targets. Rather, the evidence shows that wolves will simply target the easiest options available, which as well as sick and infirm animals, can also include young animals and pregnant females. Though wolves commonly hunt large prey in packs, there are cases in which single wolves have successfully killed large animals unaided. One wolf was recorded to have killed moose 11 times singlehandedly.
Wolves will typically attempt to disable large prey by tearing at the haunches and perineum, causing massive bleeding and loss of coordination. A single bite can cause a wound up to 10–15 cm in length. A large deer in optimum health generally succumbs to three bites at the perineum area after a chase of 150 metres. Once their prey is sufficiently weakened, the wolves will grab it by the flanks and pull it down.Sometimes, with medium sized prey such as dall sheep, wolves will bite the throat, severing the windpipe or jugular. When attacking canid prey, such as dogs, coyotes or other wolves, wolves will kill by biting the back, neck or head. With prey of equal or lesser weight to the wolf, such as lambs or small children, wolves will grab their quarry by the neck, chest, head or thigh and carry them off to a secluded spot. Once the prey collapses, the wolves will tear open the abdominal cavity and commence feeding on the animal, sometimes before it has died. On some occasions, wolves will not press an attack, and will wait for their prey to die from their wounds before feeding begins. Wolves will occasionally attack pregnant ungulates to feed on the fetus(es), leaving the mother uneaten. Usually, it is the dominant pair that works the hardest in killing the pack's target. Wolves have on occasion been observed to engage in acts of surplus killing. This phenomenon is common when wolves target livestock. In the wild, this usually occurs in late winter or spring when deep snow impedes their prey's escape.
Pack status is reinforced during feeding. The breeding pair usually eats first, starting with the heart, liver, and lungs. Wolves of intermediate rank will prevent lower ranking pack members from feeding until the dominant pair finishes eating. The stomach of prey is eaten, though the contents are left untouched if the killed animal is a herbivore. The leg muscles are eaten next, with the hide and bones being the last to be consumed. If they are disturbed while feeding, they will instead focus their attention on their prey's fat deposits rather than internal organs. A single wolf can eat up to 3.2–3.5 kg of food at a time, though they can eat as much as 13–15 kg when sufficiently hungry. A wolf's yearly requirement is 1.5 tons of meat. Wolves can go without sustenance for long periods, with a Russian record showing how one specimen survived for 17 days without food. Research has shown that 2 weeks without food will not weaken a wolf's muscle activity. After eating, wolves will drink large quantities of water to prevent uremic poisoning. A wolf's stomach can hold up to 7.5 litres of water. Wolves supplement their diet with vegetation. Scat analysis found 75% of samples found Yellowstone National Park wolves’ summer diet contained plants mostly grass (Graminae). In some areas of the former Soviet Union wolves have been reported to cause serious damage to watermelon plantations.
Studies on how wolves affect prey populations tend to vary considerably, with some results indicating that wolves dramatically reduce, sometimes locally extirpate some prey species, while others indicate that wolf predation simply takes over from other mortality factors present in wolf-free zones. Wolves are not essential for the presence of many other species.
Interspecific predatory relationships
Wolves typically dominate other canid species in areas where they are sympatric. In North America, wolves are generally intolerant of coyotes in their territory; two years after their reintroduction to the Yellowstone National Park, the wolves were responsible for a near 50% drop in coyote populations through both competition and predation. Wolves have been reported to dig coyote pups from their dens and kill them. Wolves typically do not consume the coyotes they kill. There are no records of coyotes killing wolves, though they have been known to gang up on wolves if they outnumber them. Wolves have been observed to allow coyotes to approach their kills, only to chase them down and kill them. Coyote specialist Robert Crabtree of the Yellowstone Ecological Research Center suggested that this behaviour could be linked to the intraspecific territoriality of wolves, even though coyote represent no danger: "Maybe you want to teach your pups tricks of the trade... Maybe wolves are killing coyotes to practice for conflicts with other wolves later in life."[89] Near identical interactions have been observed in Greece between wolves and Golden Jackals. Wolves may kill foxes on kill sites, though not as frequently as they do with coyotes. Raccoon Dogs are also reportedly preyed upon.
Brown Bears are encountered in both Eurasia and North America. The majority of interactions between wolves and Brown Bears usually amount to nothing more than mutual avoidance. Serious confrontations depend on the circumstances of the interaction, though the most common factor is defence of food and young. Brown Bears will use their superior size to intimidate wolves from their kills and when sufficiently hungry, will raid wolf dens. Brown Bears usually dominate wolves on kills, though they rarely prevail against wolves defending den sites. Wolves in turn have been observed killing bear cubs, to the extent of even driving off the defending mother bears. Deaths in wolf/bear skirmishes are considered very rare occurrences, the individual power of the brown bear and the collective strength of the wolf pack usually being sufficient deterrents to both sides. Encounters with American Black Bears occur solely in the Americas; their interactions with wolves are much rarer than those of Brown Bears, due to differences in habitat preferences. The majority of Black Bear encounters with wolves occur in the species' northern range, with no interactions being recorded in Mexico. Wolves have been recorded to kill Black Bears on numerous occasions without eating them. Unlike Brown Bears, Black Bears frequently lose against wolves in disputes over kills. While encounters with brown and black bears appear to be common, polar bears are rarely encountered by wolves, though there are two records of wolf packs killing polar bear cubs.
Large wolf populations limit the numbers of small to medium sized felines. Wolf predation is recorded to reduce lynx populations wherever the two species are sympatric. Lynx populations in Slovakia plummeted during World War II, when large numbers of wolves entered the cat's range. Similarly, in Russia, lynx populations drop in areas with high wolf densities. In the Rocky Mountains and adjacent mountain areas of North America, wolves are usually hostile toward cougars and will kill cubs if given the opportunity. A pack will on occasion appropriate the kills of adult cougars, which respond by increasing their kill rate. Both species have been recorded to kill each other. National Park Service cougar specialist Kerry Murphy stated that the cougar usually is at an advantage on a one to one basis, considering it can effectively use its claws, as well as its teeth, unlike the wolf which relies solely on its teeth. Yellowstone officials have reported that attacks between cougars and wolves are not uncommon. Multiple incidents of cougars taking wolves and vice versa have been recorded in Yellowstone National Park. Researchers in Montana have found that wolves regularly kill cougars in the area. Similarly, large numbers of wolves have been reported to reduce leopard populations in Tibet. However, the reverse is true for larger cats such as tigers. In areas where wolves and tigers share ranges, such as the Russian Far East, the two species typically display a great deal of dietary overlap, resulting in intense competition. Wolf and tiger interactions are well documented in Sikhote-Alin, which until the beginning of the 20th century, held very few wolves. It is thought by certain experts that wolf numbers increased in the region after tigers were largely eliminated during the Russian colonization in the late 1800s and early 1900s. This is corroborated by native inhabitants of the region claiming that they had no memory of wolves inhabiting Sikohte-Alin until the 1930s, when tiger numbers decreased. Tigers depress wolf numbers, either to the point of localized extinction or to such low numbers as to make them a functionally insignificant component of the ecosystem. Wolves appear capable of escaping competitive exclusion from tigers only when human persecution decreases the latter's numbers. Today wolves are considered scarce in tiger inhabited areas, being found in scattered pockets, and usually seen traveling as loners or in small groups. First hand accounts on interactions between the two species indicate that tigers occasionally chase wolves from their kills, while wolves will scavenge from tiger kills. Tigers are not known to prey on wolves, though there are four records of tigers killing wolves without consuming them. This competitive exclusion of wolves by tigers has been used by Russian conservationists to convince hunters in the Far East to tolerate the big cats, as they limit ungulate populations less than wolves, and are effective in controlling the latter's numbers.
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