Bears are of the family Ursidae (). They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of throughout most of the Northern Hemisphere and partially in the Southern Hemisphere. Bears are found on the continents of North America, South America, and Eurasia. Common characteristics of modern bears include large bodies with stocky legs, long snouts, small rounded ears, shaggy hair, plantigrade paws with five nonretractile claws, and short tails.
While the polar bear is mostly carnivorous, and the giant panda is mostly herbivorous, the remaining six species are omnivorous with varying diets. With the exception of courting individuals and mothers with their young, bears are typically solitary animals. They may be diurnality or nocturnal and have an excellent sense of smell. Despite their heavy build and awkward gait, they are adept runners, climbers, and swimmers. Bears use shelters, such as caves and logs, as their dens; most species occupy their dens during the winter for a long period of hibernation, up to 100 days.
Bears have been hunted since prehistoric times for bear meat and fur; they have also been used for bear-baiting and other forms of entertainment, such as being tame bear. With their powerful physical presence, they play a prominent role in the arts, mythology, and other cultural aspects of various human societies. In modern times, bears have come under pressure through encroachment on their habitats and illegal trade in bear parts, including the Asian bile bear market. The IUCN lists six bear species as vulnerable or endangered, and even least concern species, such as the brown bear, are at risk of extirpation in certain countries. The poaching and international trade of these most threatened populations are prohibited, but still ongoing.
Bear taxon names such as Arctoidea and Helarctos come from the ancient Greek ἄρκτος ( arktos), meaning bear, as do the names "arctic" and "antarctic", via the name of the constellation Ursa Major, the "Great Bear", prominent in the northern sky.
Bear taxon names such as Ursidae and Ursus come from Latin Ursus/Ursa, he-bear/she-bear. The female first name "Ursula", originally derived from a Christian saint's name, means "little she-bear" (diminutive of Latin ursa). In Switzerland, the male first name "Urs" is especially popular, while the name of the canton and city of Bern is by legend derived from Bär, German for bear. The Germanic name Bernard (including Bernhardt and similar forms) means "bear-brave", "bear-hardy", or "bold bear". The Old English name Beowulf is a kenning, "bee-wolf", for bear, in turn meaning a brave warrior.Sweet, Henry (1884) Anglo-Saxon Reader in Prose and Verse. The Clarendon Press, p. 202.
The New World short-faced bears (Tremarctinae) differentiated from Ursinae following a dispersal event into North America during the mid-Miocene (about 13 Mya). They invaded South America (≈2.5 or 1.2 Ma) following formation of the Isthmus of Panama. Their earliest fossil representative is Plionarctos in North America (c. 10–2 Ma). This genus is probably the direct ancestor to the Arctodus (genus Arctodus), the Arctotherium ( Arctotherium), and the spectacled bears, Tremarctos, represented by both an extinct North American species ( T. floridanus), and the lone surviving representative of the Tremarctinae, the South American spectacled bear ( T. ornatus).
The subfamily Ursinae experienced a dramatic proliferation of taxa about 5.3–4.5 Mya, coincident with major environmental changes; the first members of the genus Ursus appeared around this time. The sloth bear is a modern survivor of one of the earliest lineages to diverge during this radiation event (5.3 Mya); it took on its peculiar morphology, related to its diet of termites and ants, no later than by the early Pleistocene. By 3–4 Mya, the species Ursus minimus appears in the fossil record of Europe; apart from its size, it was nearly identical to today's Asian black bear. It is likely ancestral to all bears within Ursinae, perhaps aside from the sloth bear. Two lineages evolved from U. minimus: the black bears (including the sun bear, the Asian black bear, and the American black bear); and the brown bears (which includes the polar bear). Modern evolved from U. minimus via Ursus etruscus, which itself is ancestral to the extinct Pleistocene cave bear. Species of Ursinae have migrated repeatedly into North America from Eurasia as early as 4 Mya during the early Pliocene. The polar bear is the most recently evolved species and descended from a population of brown bears that became isolated in northern latitudes by glaciation 400,000 years ago.
Note that although they are called "bears" in some languages, and Procyonidae are not bears, but rather Musteloidea.
There are two phylogenetic hypotheses on the relationships among extant and fossil bear species. One is all species of bears are classified in seven subfamilies as adopted here and related articles: Amphicynodontinae, Hemicyoninae, Ursavinae, Agriotheriinae, Ailuropodinae, Tremarctinae, and Ursinae. Below is a cladogram of the subfamilies of bears after McLellan and Reiner (1992) and Qiu et al.. (2014):
The second alternative phylogenetic hypothesis was implemented by McKenna et al. (1997) to classify all the bear species into the superfamily Ursoidea, with Hemicyoninae and Agriotheriinae being classified in the family "Hemicyonidae". Amphicynodontinae under this classification were classified as stem-pinnipeds in the superfamily Pinnipedia. In the McKenna and Bell classification, both bears and pinnipeds are in a parvorder of mammals known as Ursida, along with the extinct bear dogs of the family Amphicyonidae. Below is the cladogram based on McKenna and Bell (1997) classification:
Unlike most other land carnivorans, bears are plantigrade. They distribute their weight toward the hind feet, which makes them look lumbering when they walk. They are capable of bursts of speed but soon tire, and as a result mostly rely on ambush rather than the chase. Bears can stand on their hind feet and sit up straight with remarkable balance. Their front paws are flexible enough to grasp fruit and leaves. Bears' non-retractable claws are used for digging, climbing, tearing, and catching prey. The claws on the front feet are larger than those on the back and may be a hindrance when climbing trees; black bears are the most arboreal of the bears, and have the shortest claws. Pandas are unique in having a bony extension on the wrist of the front feet which acts as a thumb, and is used for gripping bamboo shoots as the animals feed.
Most mammals have agouti hair, with each individual hair shaft having bands of color corresponding to two different types of melanin pigment. Bears however have a single type of melanin and the hairs have a single color throughout their length, apart from the tip which is sometimes a different shade. The coat consists of long guard hairs, which form a protective shaggy covering, and short dense hairs which form an insulating layer trapping air close to the skin. The shaggy coat helps maintain body heat during winter hibernation and is shed in the spring leaving a shorter summer coat. Polar bears have hollow, translucent guard hairs which gain heat from the sun and conduct it to the dark-colored skin below. They have a thick layer of blubber for extra insulation, and the soles of their feet have a dense pad of fur. While bears tend to be uniform in color, some species may have markings on the chest or face and the giant panda has a bold black-and-white pelage.
Bears have small rounded ears so as to minimize heat loss, but neither their hearing nor sight are particularly acute. Unlike many other carnivorans they have color vision, perhaps to help them distinguish ripe nuts and fruits. They are unique among carnivorans in not having touch-sensitive whiskers on the muzzle; however, they have an excellent olfaction, better than that of the dog, or possibly any other mammal. They use smell for signalling to each other (either to warn off rivals or detect mates) and for finding food. Smell is the principal sense used by bears to locate most of their food, and they have excellent memories which helps them to relocate places where they have found food before.
The skulls of bears are massive, providing anchorage for the powerful Masseter muscle and temporal muscle jaw muscles. The canine tooth are large but mostly used for display, and the molar teeth flat and crushing. Unlike most other members of the Carnivora, bears have relatively undeveloped carnassial teeth, and their teeth are adapted for a diet that includes a significant amount of vegetable matter. Considerable variation occurs in dentition even within a given species. This may indicate bears are still in the process of evolving from a mainly meat-eating diet to a predominantly herbivorous one. Polar bears appear to have secondarily re-evolved carnassial-like cheek teeth, as their diets have switched back towards carnivory. Sloth bears lack lower central incisors and use their protrusible lips for sucking up the termites on which they feed. The general dental formula for living bears is: . The structure of the larynx of bears appears to be the most basal of the caniforms. They possess air pouches connected to the pharynx which may vocal resonance their vocalizations.
Bears have a fairly simple digestive system typical for carnivorans, with a single stomach, short undifferentiated intestines and no cecum. Even the herbivorous giant panda still has the digestive system of a carnivore, as well as carnivore-specific genes. Its ability to digest cellulose is ascribed to the microbes in its gut. Bears must spend much of their time feeding in order to gain enough nutrition from foliage. The panda, in particular, spends 12–15 hours a day feeding.
The most widespread species is the brown bear, which occurs from Western Europe eastwards through Asia to the western areas of North America. The American black bear is restricted to North America, and the polar bear is restricted to the Arctic Ocean. All the remaining species of bear are Asian. They occur in a range of habitats which include tropical lowland rainforest, both coniferous and broadleaf forests, prairies, steppes, montane grassland, alpine scree slopes, Arctic tundra and in the case of the polar bear, Drift ice. Bears may dig their dens in hillsides or use caves, hollow logs and dense vegetation for shelter.
When foraging for plants, bears choose to eat them at the stage when they are at their most nutritious and digestible, typically avoiding older grasses, sedges and leaves. Hence, in more northern temperate areas, browsing and grazing is more common early in spring and later becomes more restricted. Knowing when plants are ripe for eating is a learned behavior. Berries may be foraged in bushes or at the tops of trees, and bears try to maximize the number of berries consumed versus foliage. In autumn, some bear species forage large amounts of naturally fermentation fruits, which affects their behavior. Smaller bears climb trees to obtain mast (edible reproductive parts, such as acorns). Such masts can be very important to the diets of these species, and mast failures may result in long-range movements by bears looking for alternative food sources. Brown bears, with their powerful digging abilities, commonly eat roots. The panda's diet is over 99% bamboo, of 30 different species. Its strong jaws are adapted for crushing the tough stems of these plants, though they prefer to eat the more nutritious leaves. can make up to 50% of the diet of the spectacled bear, which also has strong jaws to bite them open.
The sloth bear is not as specialized as polar bears and the panda, has lost several front teeth usually seen in bears, and developed a long, suctioning tongue to feed on the ants, termites, and other burrowing insects. At certain times of the year, these insects can make up 90% of their diets. Some individuals become addicted to sweets in garbage inside towns where tourism-related waste is generated throughout the year. Some species may raid the nests of and bees for the honey and immature insects, in spite of stinging from the adults. Sun bears use their long tongues to lick up both insects and honey. Fish are an important source of food for some species, and brown bears in particular gather in large numbers at . Typically, a bear plunges into the water and seizes a fish with its jaws or front paws. The preferred parts to eat are the brain and eggs. Small burrowing mammals like may be dug out and eaten.
The brown bear and both species of black bears sometimes take large ungulates, such as deer and , mostly the young and weak. These animals may be taken by a short rush and ambush, though hiding young may be sniffed out and pounced on. The polar bear mainly preys on seals, stalking them from the ice or breaking into their dens. They primarily eat the highly digestible blubber. Large mammalian prey is typically killed with raw strength, including bites and paw swipes, and bears do not display the specialized killing methods of felids and canids. Predatory behavior in bears is typically taught to the young by the mother.
Bears are prolific and , stealing food caches from rodents, and carcasses from other predators. For hibernating species, weight gain is important as it provides nourishment during winter dormancy. A brown bear can eat of food and gain of fat a day prior to entering its den.
Bears sometimes communicate with visual displays such as standing upright, which exaggerates the individual's size. The chest markings of some species may add to this intimidating display. Staring is an aggressive act and the facial markings of spectacled bears and giant pandas may help draw attention to the eyes during agonistic encounters. Individuals may approach each other by stiff-legged walking with the head lowered. Dominance between bears is asserted by making a frontal orientation, showing the canine teeth, muzzle twisting and neck stretching. A subordinate may respond with a lateral orientation, by turning away and dropping the head and by sitting or lying down.
Bears also communicate with their scent by urinating on or rubbing against trees and other objects. This is usually accompanied by clawing and biting the object. Bark may be spread around to draw attention to the marking post. Pandas establish territories by marking objects with urine and a waxy substance from their anal glands. Polar bears leave behind their scent in their tracks which allow individuals to keep track of one another in the vast Arctic wilderness.
Gestation typically lasts six to nine months, including delayed implantation, and litter size numbers up to four cubs. Giant pandas may give birth to twins but they can only suckle one young and the other is left to die. In northern living species, birth takes place during winter dormancy. Cubs are born blind and helpless with at most a thin layer of hair, relying on their mother for warmth. The milk of the female bear is rich in fat and antibodies and cubs may suckle for up to a year after they are born. By two to three months, cubs can follow their mother outside the den. They usually follow her on foot, but sloth bear cubs may ride on their mother's back. Male bears play no role in raising young. Infanticide, where an adult male kills the cubs of another, has been recorded in polar bears, brown bears and American black bears but not in other species. Males kill young to bring the female into estrus. Cubs may flee and the mother defends them even at the cost of her life.
In some species, offspring may become independent around the next spring, though some may stay until the female successfully mates again. Bears reach sexual maturity shortly after they disperse; at around three to six years depending on the species. Male Alaskan brown bears and polar bears may continue to grow until they are 11 years old. Lifespan may also vary between species. The brown bear can live an average of 25 years.
Bears are parasitized by eighty species of parasites, including single-celled protozoans and gastro-intestinal worms, and nematodes and flukes in their heart, liver, lungs and bloodstream. Externally, they have ticks, fleas and lice. A study of American black bears found seventeen species of endoparasite including the protozoan Sarcocystis, the parasitic worm Diphyllobothrium mansonoides, and the nematodes Dirofilaria immitis, Capillaria aerophila, Physaloptera sp., Strongyloides sp. and others. Of these, D. mansonoides and adult C. aerophila were causing pathological symptoms. By contrast, polar bears have few parasites; many parasitic species need a secondary, usually terrestrial, host, and the polar bear's life style is such that few alternative hosts exist in their environment. The protozoan Toxoplasma gondii has been found in polar bears, and the nematode Trichinella nativa can cause a serious infection and decline in older polar bears. Bears in North America are sometimes infected by a Morbillivirus similar to the Canine distemper. They are susceptible to infectious canine hepatitis (CAV-1), with free-living black bears dying rapidly of encephalitis and hepatitis.
Laws have been passed in many areas of the world to protect bears from habitat destruction. Public perception of bears is often positive, as people identify with bears due to their omnivorous diets, their ability to stand on two legs, and their symbolic importance. Support for bear protection is widespread, at least in more affluent societies. The giant panda has become a worldwide symbol of conservation. The Sichuan Giant Panda Sanctuaries, which are home to around 30% of the wild panda population, gained a UNESCO World Heritage Site designation in 2006. Where bears raid crops or attack livestock, they may come into conflict with humans. In poorer rural regions, attitudes may be more shaped by the dangers posed by bears, and the economic costs they cause to farmers and ranchers.
Bear hunting for sport, food, and folk medicine. Their meat is dark and stringy, like a tough cut of beef. In Cantonese cuisine, bear paws are considered a delicacy. Bear meat should be cooked thoroughly, as it can be infected with the parasite Trichinella spiralis.
The peoples of eastern Asia use bears' body parts and secretions (notably their gallbladders and bile) as part of traditional Chinese medicine. More than 12,000 bears are thought to be kept on farms in China, Vietnam, and South Korea for the production of bile. Trade in bear products is prohibited under CITES, but bear bile has been detected in shampoos, wine and herbal medicines sold in Canada, the United States and Australia.
There is evidence of prehistoric bear worship, though this is disputed by archaeologists. It is possible that bear worship existed in early Chinese and Ainu religion. The prehistoric Finns, Siberian peoples and more recently Koreans considered the bear as the spirit of their forefathers. Artio ( Dea Artio in the Gallo-Roman religion) was a Celtic bear goddess. Evidence of her worship has notably been found at Bern, itself named for the bear. Her name is derived from the Celtic word for "bear", artos. In ancient Greece, the archaic cult of Artemis in bear form survived into Classical times at Brauron, where young Athenian girls passed an initiation rite as arktoi "she bears".Burkert, Walter, Greek Religion, 1985:263.
The constellations of Ursa Major and Ursa Minor, the great and little bears, are named for their supposed resemblance to bears, from the time of Ptolemy. The nearby star Arcturus means "guardian of the bear", as if it were watching the two constellations. Ursa Major has been associated with a bear for as much as 13,000 years since Paleolithic times, in the widespread Cosmic Hunt myths. These are found on both sides of the Beringia, which was lost to the sea some 11,000 years ago. reviewed at
Bears are popular in children's stories, including Winnie the Pooh, Paddington Bear, Gentle Ben and "The Brown Bear of Norway". An early version of "Goldilocks and the Three Bears", was published as "The Three Bears" in 1837 by Robert Southey, many times retold, and illustrated in 1918 by Arthur Rackham. The Hanna-Barbera character Yogi Bear has appeared in numerous comic books, animated television shows and films. The Care Bears began as greeting cards in 1982, and were featured as toys, on clothing and in film. Around the world, many children—and some adults—have , stuffed toys in the form of bears, named after the American statesman Theodore Roosevelt when in 1902 he had refused to shoot an American black bear tied to a tree.
Bears, like other animals, may symbolize nations. The Russian Bear has been a common national personification for Russia from the 16th century onward. Smokey Bear has become a part of American culture since his introduction in 1944, with his message "Only you can prevent forest fires".
Specialty organizations for each of the eight species of bears worldwide include:
Taxonomy
Evolution
Phylogeny
Physical characteristics
Size
Morphology
Distribution and habitat
Behavior and ecology
Feeding
Communication
Reproduction and development
Hibernation
Mortality
Relationship with humans
Conservation
Attacks
Entertainment, hunting, food and folk medicine
Cultural depictions
Organizations
See also
Notes
Citations
General and cited references
Further reading
External links
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