The wolf (Canis lupus), more specifically the gray wolf, is a mammal in the canine family (Canidae), belonging to the predators (Carnivora). The wolf is the largest recent predator of the dog family (Canidae). Wolves usually live in packs, which are family groups. Main prey in most regions are medium to large ungulates. A wolf and a dog can produce fertile offspring together, so that, according to a common species term in biology, they can be considered the same species.
Wolves have a head-rump length of 1 to 1.5 m, and a tail of 30 to 50 cm. The shoulder height is 65 to 80 cm. Females are about 10 percent smaller than males; males weigh 20 to 80 kg, females average 18 to 50 kg. At rest, the wolf has a heart rate of 90 beats per minute and a respiratory rate of 15 to 20 per minute. With great exertion, this can increase to a heart rate of 200 per minute and a respiratory rate of 100 per minute. The sense of hearing, smell and sight are well developed. Against the wind, a wolf can detect other animals within 300 meters of it. It can also see excellently in the dark. The wolf has a vision angle of 250° (for comparison, 180° in humans). The wolf can hear tones up to 40 kHz, tones too high for human hearing. Special dog whistles have been developed, which cannot be heard by humans, but can be heard by dogs and wolves.
A wolf’s teeth consist of a total of 42 teeth, including 12 incisors, 4 canines, 16 anterior molars, and 10 tearing and common molars. The wolf’s canines are 2.5 cm long and are strong, sharp and slightly curved. These canines allow them to grab and hold their prey. The pressure a wolf can exert with the canines while biting is 15 MPa. A wolf can thus bite through an elk’s leg in one bite. A wolf does not chew its prey, but tears the meat into pieces and swallows it. It tears this meat with its small incisors. With stringy components of the meat, the wolf naturally flosses its teeth. This activates the salivary glands and also rinses the mouth.
The wolf has a very dense and soft winter coat, with a short undercoat and long, coarse, cover hair. Most of the undercoat and some of the cover hair are shed in the spring and grow back in the fall. The wolf’s longest hairs are located on the back and especially on the front and neck. In particular, there are long hairs on the shoulders and they form a crest in the upper part of the neck. The hairs on the cheeks are elongated and form bunches. The ears are covered with short hairs very similar to the fur. On the limbs from the elbows to the calcaneal tendons there are short, elastic and closely spaced hairs. The winter coat resists cold well. Wolves in northern climates can rest comfortably in open areas at -40°C by placing their muzzle between the hind legs and covering their face with the tail. A wolf’s fur provides better insulation than dog fur and, like wolverines, the fur does not freeze when a wolf breathes against its fur. In warm climates, the fur is coarser and thinner than in northern wolves. Females have smoother-haired legs than males, and in general, as they age, they develop a more sleek and soft coat. Older wolves generally have more white hair at the tip of the tail, along the nose and on the forehead. The winter coat is retained longest in lactating females, where they do lose some hair around the nipples. The length of the hair on the middle of the back is 6 to 7 cm. The length of the cover hairs on the shoulders generally does not exceed 9 cm, but can reach 11 to 13 cm.
The color of the coat varies from almost pure white to various shades of blond, cream and ochre to gray, brown and black. The variation in coat color tends to increase in higher latitudes. There are almost no differences in coat color between the sexes, although a female’s coat may be redder in color. Coat color does not appear to serve camouflage purposes. Some experts conclude that the mixed colors have more to do with emphasis on certain gestures during interaction. Black-colored wolves (resulting from wolf-dog hybridization) are rare in Eurasia, where interactions with domestic dogs have been reduced over the past thousand years due to the depletion of the wild wolf. Black specimens are more common in North America. About half of the wolves in Yellowstone National Park are black.
The wolf has highly developed senses. A wolf’s eyes are better than those of humans. Wolves, like felines, can see better in the dark. Humans have more cones in their eyes, but fewer rods. Wolves see depth less well at a distance than humans, but wolves, like dogs, are more likely to recognize moving objects. If a person were to stand still in front of a wolf, there is a chance that the wolf could see through the person. When the person moves, the wolf sees the person again. Wolves see better in the dark because there is a layer of pigment made up of refractive small crystals behind the retina. This pigment layer reflects the light. This is also why the eyes of a wolf or dog light up when one shines light on them. Wolves can see almost all the way around themselves at a 270-degree angle. Humans can only see 180 degrees around them.
The wolf is a specialist when it comes to prey animals. In packs, it prefers to hunt the larger ungulates, such as elk, red deer, roe deer and wild boar, depending on the supply in an area. It also eats rodents, lagomorphs, and birds, as well as carrion and garbage. A study of the menu of Polish-German wolves found that roe deer occupy about half the menu, red deer 30 percent, and wild boar about 15 percent. Smaller animals occupy only five percent of the menu. In Scandinavia, prey in winter consists mainly of deer and in summer of (young) elk. Cattle and even dogs are also seized. An unprotected sheep is easy prey for a wolf. Thus, the wolf is carnivorous and hardly eats any plant food.
Success in hunting depends only to a limited extent on the number of animals in the pack. At more than four individuals, success seems to stagnate. This is because during hunting the work is done mainly by the single individuals of the pack who are engaged in reproduction. Those who do not engage in reproduction, and thus do not have to risk their lives for their offspring, may behave in the pack as free riders. They appear to cooperate, but in fact do little.
The effect of wolves on the populations of their prey animals is a source of misunderstanding. Wolves will never be able to exterminate their prey animals as long as the prey animals have freedom of migration. Wolves do affect the migration behavior and condition of the prey animal population. In regions where wolves are present, the prey animals will be very alert and will always try to move out of the wolves’ reach. Less healthy animals will then prey earlier than healthy animals, keeping the prey animal population “in condition.” The healthier the prey animals are, or the lower their densities, the more the wolf will be required to obtain food, which has its effect on the fitness and reproductive success of the wolves. Ultimately, the prey animals thus affect the wolf population more than the other way around.
If wolves can easily get to farm animals, they will feast on them. Wolves will increase in numbers in such food-rich areas. Then, if the farm animals in question are no longer available due to better protection, wolves will seek other sources of food, which may involve brutal-looking garbage eating. Foxes exhibit similar behavior, for example, in the dunes. Such human-wolf interactions reinforce the negative image that exists toward wolves.
Behavior and social structure.
Wolves are diurnal and twilight animals, but fierce hunting has caused them to adopt a nocturnal lifestyle in many areas (including Europe). The wolf is a good runner, but can also swim well. They are capable of moving quickly, with a top speed of 50 to 60 mph. On average, an established wolf covers 20-25 kilometers per day and a “walking wolf” covers 60 to as much as 70 kilometers per day, but there has been a case where a wolf covered 190 kilometers in one day. Typically, they will stay within their territory, but if necessary they can explore new areas at a rapid pace.
Pack and territory
Wolves are social animals that live in packs that are strictly organized. Nowadays, family groups are preferred. A family group is led by a male and a female usually referred to as alpha. Usually they have the sole right to reproduce. The remaining animals are usually (adult) offspring of the alpha pair. A similar system can also be found in other group-hunting canine species such as the dhole (Cuon alpinus) from India and the African wild dog (Lycaon pictus). The offspring of the alpha pair remain in the pack for at most two years. With an average litter of 4 animals, the pack may consist of 10 animals after 2 years. Food supply affects pack size. Where food is plentiful (for example, Alaska, where wolves hunt elk), wolves live in large packs that may consist of as many as 30 animals. In areas with little food, such as Italy and Spain, the animals live in small family groups consisting of the alpha pair and their cubs.
The older cubs may or may not voluntarily leave the pack, often moving in with their siblings for a period of time. When they have found their own territory and a mate, they form their own pack. Research in Scandinavia has shown that a bitch who has moved away from the pack determines the location of a new territory. A roaming male dog goes in search of such an annexed territory.
The size of a territory depends on the food situation, but will be between 200 and 2000 km². Territories of 350 km² have been measured in the Alps; in Alaska they are larger. Lone wolves in search of a mate or new territory can travel long distances – from tens of kilometers to more than a thousand kilometers.
The wolf has a wide variety of modes of expression, including sounds. The familiar howl is primarily for communicating over longer distances and is more intense in animals where the social bond is greater. Depending on conditions, wolves can hear this howling at distances of six to 10 kilometers. Marking the territory, by urinating with a raised hind leg, is reserved for dominant animals. Within the pack, communication is primarily through body language. Submissive wolves, for example, greet others by submission, with averted eyes, tail between hind legs, low posture, ears back and a soft howl. When wolves are angry or frightened, they usually show it with bared teeth and growling.
Wolves howl to keep the pack together (usually before and after hunting), to alert other wolves (mainly at the litter), to find each other during a storm or in an unfamiliar area, and to communicate over long distances. A wolf’s howl can be heard over an area of up to 130 km² under certain circumstances. A wolf’s howl is generally indistinguishable from that of large dogs. Male wolves have a range of about an octave and their call ends in a deep bass with emphasis on “O,” while female wolves produce a nasal baritone, with emphasis on “U.” Pups almost never howl; the howl of wolves one year old ends in a dog-like howl.
The howl consists of a fundamental tone that may be between 150 and 780 Hz, with a series of up to 12 harmonic overtones. The pitch usually remains constant or varies slightly. A howling wolf can alternately drop and then rise the pitch up to 5 times. Howls used to call other wolves in the pack to a killed prey consist of elongated, soft sounds somewhat like the beginning of an eagle owl’s cry. When chasing prey, they emit higher pitched tones that go back and forth between two notes. When trapping their prey, they use a combination of short barks and howls. When howling together, they howl in unison rather than in chorus on the same note, giving the impression that there are more wolves than the actual number. Solitary wolves usually do not howl in areas where other packs are present. Wolves do not answer howls in rainy weather or when they are full.
The howls of wolves from different areas can differ from each other. European wolves howl much longer and more melodiously than those from North America, which howl much louder and place a stronger emphasis on the first syllable. The two do understand each other’s language, as evidenced by observations in which North American wolves responded to biologists imitating European wolves.
Relationship with ravens
Wolves and ravens have a special social and ecological relationship. Ravens and wolves are sometimes observed playing, but there is also a feeding relationship between the two species. Ravens hang out near wolves allowing them to take advantage of their prey. The relationship also works in the other direction: ravens can lure wolves to potential prey or carrion, which both species can eat from. Ravens show a specific preference to follow wolves.
Reproduction and development
The wolf is generally monogamous: pairs usually stay together until one of the two dies. After the death of a wolf, a new pair is quickly formed. Because there are usually more males in a group, unpaired females are a rarity. If a male wolf is unable to make a territory or find a mate, he will mate with the daughters of an already established breeding pair from another group. Such wolves are called “casanova wolves,” after Giacomo Casanova. Unlike males of established groups, they do not form breeding pairs with the females they mate with. Some groups may have multiple females fertilized in this way, as is the case in Yellowstone National Park.
The age at which a wolf first mates depends largely on environmental factors: when food is abundant or when wolf populations are heavily managed, wolves may raise cubs at a younger age to better utilize the abundant resources. This is also demonstrated by the fact that wolves in captivity are ready to mate as soon as 9 to 10 months of age, while the youngest recorded mating in the wild occurred in wolves two years old. Females can have cubs every year, averaging one litter per year. Unlike the coyote, the wolf never reaches reproductive aging. The rutting period usually occurs in late winter. In older females, this period begins 2-3 weeks earlier than younger females. When the female is ready to mate, she moves her tail to one side to expose her vulva. During mating, the male’s penis gets stuck in the vagina, something that can last 5-36 minutes. Because the rutting season in wolves lasts only a month, male wolves do not leave their females to fertilize other females, which dogs do.
The mating season of wolves varies by area. In Scandinavia, it lasts from February to April. A wolf’s nest is in a cave or den, hidden under tree roots or among rocks. Sometimes he digs his own den, or enlarges a fox den or badger sett. The other females howl at the entrance, seeming to cheer him on. During gestation, female wolves stay near their territories, where violent encounters are less likely. Older females usually gestate in the den of their previous litter, while younger females usually stay near their birthplace. The gestation period lasts 62-75 days. Cubs are usually born in the summer period. Wolves give birth to relatively large cubs in small litters compared to other canine species. The average litter consists of 5 or 6 cubs. Where prey is abundant, large litters are usually thrown. Exceptionally large litters of 14-17 cubs occur only in 1% of cases. The cubs are usually born in the spring, which coincides with a corresponding increase in the population of prey. The cubs are born blind and deaf and have short and soft, gray-brown fur. At birth, they weigh 300-500 grams. They begin to see after 9-12 days. The milk canine teeth come out after a month. The cubs leave the nest for the first time after three weeks. When they are 1.5 months old, they are strong enough to flee from danger. Mother wolves do not leave the den for the first few weeks; the fathers fetch food for them and their cubs. Cubs begin eating solid food at 3 to 4 weeks of age. The cubs show the fastest growth during the first four months: during this period, the cub’s weight increases about thirty-fold. By autumn, the cubs are large enough to join adults in hunting large prey.
The cubs stay with the pack for at least a year. They often stay with the pack longer, but sometimes one- or two-year-olds leave the group, especially if dominated by other pack members and also depending on the food supply. In areas with larger prey animals, such as elk and red deer, it is advantageous to have a large pack. Wolves can live from fifteen to twenty years in captivity, but in the wild about ten years is the maximum.
Enemies and competitors
Wolves usually dominate other members of the canine family in areas where they both occur. In North America, it is common for wolves to kill coyotes, especially in winter, when coyotes try to get food from animals that wolves have killed. Wolves often attack coyotes’ nests by digging them out and killing the pups, but they rarely eat them. There are no records of coyotes killing wolves, but coyotes can chase wolves when they outnumber them. Almost identical interactions have also been observed in Eurasia between wolves and jackals, which are considerably outnumbered in areas where wolves are abundant.
Wolves are the main enemy of raccoon dogs. They kill large numbers of them during the spring and summer seasons. Wolves also kill red, polar and steppe foxes, sometimes eating them. In Asia, they can compete with dholes. Wolves run into brown bears in Eurasia and North America. Brown bears usually dominate wolf packs, while wolves usually prevail against bears when defending their dens. Both species kill each other’s cubs. Wolves eat brown bears after killing them, while brown bears seem to eat only young wolves.
Interactions of wolves with black bears are much rarer than with brown bears, partly due to differences between habitat preferences. The majority of black bear-wolf encounters occur in the north. No interactions have been observed in Mexico. Wolves have been observed on numerous occasions where they actively seek out black bears in their dens to kill them, without eating them. Compared to brown bears, black bears appear to be killed more frequently by wolves. While encounters with brown and black bears appear to be common, it is rare for polar bears to interact with wolves, but two images were recorded in which wolf groups kill polar bear cubs. Wolves may also kill the cubs of Asiatic black bears.
Wolves can encounter striped hyenas in Israel and Central Asia. Striped hyenas feed on the bodies of wolves in areas where the two species encounter each other. On a one-to-one basis, hyenas dominate wolves, although groups with wolves can chase away a hyena that is alone.
Large wolf populations produce low numbers of small- to medium-sized felines. Wolves encounter cougars along parts of the Rocky Mountains and adjacent mountain ranges. When hunting at different elevations, wolves and cougars usually avoid each other. In winter, however, when the snow forces their prey into the valleys, the two species are more likely to interact. Although they rarely interact, wolves and pumas will kill each other when one party is in the majority. They hunt manoels and can pose a threat to snow leopards. Wolves also limit the population of the Eurasian lynx. Outside of humans, tigers appear to be the only serious predators of wolves. In areas where wolves and tigers co-occur, such as the Russian Far East, the two species have overlapping diets, resulting in competition.
Interactions between wolves and tigers are well documented in Sichote-Alin, which had few wolves until the early 20th century. The number of wolves in the region increased only after tigers were largely eliminated during Russian colonization in the late 19th and early 20th centuries. This is confirmed by the indigenous people of the region who claim they have no knowledge of wolves inhabiting Sikhote-Alin before the year 1930, when tiger numbers declined. Tigers keep wolf numbers low, to the point of local extinction or at least to such low numbers that they are a functionally insignificant component of the ecosystem. Only if humans keep tiger numbers low do wolves seem to have a chance. Wolves today are scarce in areas where tigers occur; they live there individually or in small groups. Based on interactions between the two species, it can be seen that tigers occasionally hunt and kill wolves while wolves only eat the carrion of dead tigers. Proven cases of tigers killing wolves are rare and attacks seem to be aimed at eliminating competition rather than predation. This competitive drive has been used by Russian conservationists to convince hunters in the Far East to tolerate the big cats because they have less impact on ungulate numbers than wolves and because they reduce wolf numbers.
The Swedish botanist and zoologist Carl Linnaeus published the dual nomenclature in his Systema Naturae in 1758. Canis is the Latin word for “dog” and Linnaeus listed dog-like carnivores under this genus, including domestic dogs, wolves, and coyotes. He classified the domestic dog as Canis familiaris and the wolf as Canis lupus. Linnaeus made this classification thinking that the domestic dog was a separate species from the wolf, since the upward curving tail of the domestic dog was not seen in other dog-like species other than the domestic dog.
Before humans developed agriculture and herding, the wolf was the world’s most common predator. It was widespread throughout Eurasia, North Africa and North America. However, they were exterminated by humans, especially in densely populated developed countries such as Western Europe. Today, large areas of wolves can be found in Eastern Europe, the Balkan Peninsula, Canada, Siberia, Mongolia and Iran. Outside of these, there are only small, isolated areas (sometimes with fewer than 100 animals).
A very adaptable animal, the wolf can live in different habitats, from the ice deserts of the Arctic to the sand deserts of Central Asia and North America. Most wolves live in steppes and forests. Since early times, it has been recognized as a forest animal because it escapes from the open spaces claimed by humans into forests.
Relationship with humans
From the time humans began raising sheep and goats for a living, wolves have been considered harmful animals because they preyed on animals from herds. Over time, the animal was hunted and exterminated in many places for this reason. Stories and fairy tales also depicted the wolf as an animal that attacked humans. Probably no story has been as bad for the wolf’s image as a human devourer as the fairy tale of Little Red Riding Hood, written down in 1697 by Charles Perrault but probably older.
In practice, a wolf usually flees from a human. Humans and children are attacked only on rare occasions, almost only when they venture near a nest with young. Many cases have been documented in which wolves killed humans. Compared to carnivores of about the same size, however, the wolf kills relatively few humans. About half of the cases involve rabid wolves. The dog, the wolf’s closest relative, kills several tens of thousands worldwide each year. Wolfhounds can be bolder than true wolves. They are also more likely to live near inhabited places, making them potentially much more dangerous to livestock and humans.
Individual wolves are shy. The larger the pack is, the more the wolf dares to hunt. An elk is never attacked by one or two wolves; that only happens with a pack of six or more. On the other hand, the wolf prefers to live in small groups of two or three animals in landscapes where there are plenty of small prey to be had. The formation of large packs seems to occur especially in areas with long cold winters with lots of snow. During such a period, large prey are still easy to find; the small prey are then hibernating or living deeply hidden under the snow. Large packs also usually avoid places where they might encounter humans.
How wolves react to humans depends largely on their previous experiences with humans: wolves that have no negative experiences with humans and do not depend on humans for food show little fear. They are generally not dangerous to a human as long as they are few in number, have adequate food, have little contact with humans and are occasionally hunted. Although wolves can react aggressively when taunted, such attacks are usually limited to superficial bites to the limbs.
Actual predatory attacks are usually made by an individual wolf or pack that has experience attacking humans. Such attacks may be preceded by a long period of habituation during which wolves gradually lose their fear of humans. The wolf generally attacks its victim by grabbing him by the neck and dragging him away to eat him unless disturbed. Such attacks appear to occur clustered in time and place, and usually continue until animals conditioned in this way are killed. Predatory attacks can occur at any time of the year, with a peak in the June-August period, when people are more likely to enter forested areas (in connection with grazing livestock or to pick berries and mushrooms), although attacks by non-dog wolves have also been known to occur in winter, specifically in Belarus and Ukraine and in Russia’s Kirovsk, Irkutsk and Karelia districts. Wolves with cubs have more problems obtaining food in summer. The majority of victims of predatory attacks are children; in the rare cases where adults are killed, the victims are almost always women.
Wolves in folklore and mythology
Wolves have traditionally had a bad reputation, which is only partly true. Of course, wolves, like other predators, can be dangerous, especially if handled improperly. However, the many horror stories about their malevolence (as in the fairy tales Little Red Riding Hood, The Wolf and the Three Little Pigs and The Wolf and the Seven Goats) seem unjustified. Yet conservationists everywhere struggle to reinstate the species anywhere because of these myths.
In the 20th century, attitudes toward wolves have gradually changed somewhat, as the realization has dawned that these animals are also an inseparable part of the few truly wild parts of the world that remain.