Bears have been hunted and persecuted throughout human history. Most bear populations continue to face hunting pressure and have become fragmented as a result of human habitat destruction and hunting.
The IUCN ranks Malayan sun bears (Helarctos malayanus) as data deficient, polar bears (Ursus maritimus) as lower risk, Asiatic black bears (Ursus thibetanus), sloth bears (Melursus ursinus), and spectacled bears (Tremarctos ornatus) as vulnerable, and giant pandas (Ailuropoda melanoleuca as endangered.
Several brown bear subspecies are listed as endangered under the United States Endangered Species Act: Mexican grizzly bears, Ursus arctos nelsoni, European brown bears, U. arctos arctos, and Tibetan brown bears or horse bears, U. arctos pruinosus. Baluchistan bears, Ursus thibetanus gedrosianus, are also considered endangered.
The following species are on Appendix I of CITES: Ailuropoda melanoleuca, Helarctos malayanus, Melursus ursinus, Tremarctos ornatus, Ursus thibetanus, and populations of Ursus arctos in Bhutan, China, Mexico and Mongolia. All other populations of U. arctos are included in Appendix II.
Convention on the International Trade in Endangered Species of Wild Flora and Fauna, 2005. "CITES Appendices I, II, and III" (On-line). Convention on International Trade in Endangered Species of Wild Flora and Fauna. Accessed July 13, 2005 at http://www.cites.org/eng/app/appendices.shtml.
IUCN Species Survival Commission, 2004. "The 2004 IUCN Red List of Threatened Species" (On-line). International Union for the Conservation of Nature. Accessed July 13, 2005 at http://www.redlist.org/.
U.S. Fish and Wildlife Service, 2005. "U.S. Fish and Wildlife Service Endangered Species Program" (On-line). Accessed July 13, 2005 at http://www.fws.gov/endangered/.
Bears are a small group of mostly large mammals, with 8 species in 5 genera (Ursus, Tremarctos, Melursus, Helarctos, and Ailuropoda). Although Ursidae is not diverse, species in this family are widespread and culturally significant to human populations throughout their range.
Flynn, J., J. Finarelli, S. Zehr, J. Hsu, M. Nedbal. 2005. Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships. Systematic Biology, 54: 317-337.
Nowak, R. 1991. Walker's Mammals of the World, Fifth Edition. Baltimore: The Johns Hopkins University Press.
Vaughan, T., J. Ryan, N. Czaplewski. 2000. Mammalogy, 4th edition. New York: Saunders College Publishing.
Bears are often implicated in predation on livestock, although their impact on livestock populations is most often vastly over-stated. This is particularly true of Tremarctos ornatus, which is persecuted for livestock predation despite its primarily frugivorous lifestyle. Bears regularly attack and kill humans when they feel threatened. Females accompanied by their young may be especially aggresssive and unpredictable. Bear attacks that seem at first to be unprovoked, often prove to be inadvertently provoked when investigated. Bears that live near humans, or have become habituated to humans, cause damage by breaking into homes, food stores, and garbage. Some bear species damage crops, such as manioc and corn.
Negative Impacts: injures humans (bites or stings); crop pest
Bears are important members of healthy ecosystems and are sometimes used as indicator species of habitat health and wildness. Bears have also been hunted by humans throughout history for their meat, fat, and fur. Other body parts are used in traditional Chinese pharmacopias, although their usefulness in curing ailments has never been demonstrated. Research on the metabolic pathways black bears use during their winter torpor may help in the development of treatments for kidney failure, gallstones, severe burns, and other illnesses.
Positive Impacts: body parts are source of valuable material; research and education
Bears are found on all continents except Antarctica and Australia, but are primarily found throughout the northern hemisphere, historically occurring as far south as the Atlas Mountains of northwestern Africa, the Andes of South America, and the Sunda shelf region. This range has been reduced in historical times as a result of human persecution and habitat destruction. For example, brown bear (Ursus arctos) populations in the Atlas Mountains are thought to be extinct and their range has been significantly altered in North America and Europe.
Common characteristics of modern bears include large bodies with stocky legs, long snouts, shaggy hair, plantigrade paws with five nonretractile claws, and short tails. While the polar bear is mostly carnivorous, and the giant panda feeds almost entirely on bamboo, the remaining six species are omnivorous with varied diets.
With the exception of courting individuals and mothers with their young, bears are typically solitary animals. They are generally diurnal, but may be active during the night (nocturnal) or twilight (crepuscular), particularly around humans. Bears possess an excellent sense of smell and, despite their heavy build and awkward gait, are adept runners, climbers, and swimmers. In autumn, some bear species forage large amounts of fermented fruits, which affects their behaviour. Bears use shelters, such as caves and burrows, as their dens; most species occupy their dens during the winter for a long period (up to 100 days) of sleep similar to hibernation.
Bears have been hunted since prehistoric times for their meat and fur. With their tremendous physical presence and charisma, they play a prominent role in the arts, mythology, and other cultural aspects of various human societies. In modern times, the bears' existence has been pressured through the encroachment on their habitats and the illegal trade of bears and bear parts, including the Asianbile 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.
The English word "bear" comes from Old Englishbera and belongs to a family of names for the bear in Germanic languages that originate from an adjective meaning "brown". In Scandinavia, the word for bear is björn (or bjørn), and is a relatively common given name for males. The use of this name is ancient and has been found mentioned in several runestone inscriptions.
The Proto-Indo-European (PIE) word for bear, *h₂ŕ̥tḱos seems to have been subject to taboo deformation or replacement in some languages (as was the word for wolf, wlkwos), resulting in the use of numerous unrelated words with meanings like "brown one" (English bruin) and "honey-eater" (Slavic medved). Thus, some Indo-European language groups do not share the same PIE root.
"Bear" was originally a euphemism for the creature, and was said by superstitious peasants who believed saying the actual term for "bear" would summon it. Because peasants avoided saying the original name, it has been lost to history and "bear" has replaced it.[unreliable source?]
The earliest members of Ursidae belong to the extinct subfamily Amphicynodontinae, including Parictis (late Eocene to early middle Miocene, 38–18 Mya) and the slightly younger Allocyon (early Oligocene, 34–30 Mya), both from North America. These animals looked very different from today's bears, being small and raccoon-like in overall appearance, and diets perhaps more similar to that of a badger. Parictis does not appear in Eurasia and Africa until the Miocene. It is unclear whether late-Eocene ursids were also present in Eurasia, although faunal exchange across the Bering land bridge may have been possible during a major sea level low stand as early as the late Eocene (about 37 Mya) and continuing into the early Oligocene. European genera morphologically are very similar to Allocyon, and also the much younger American Kolponomos (about 18 Mya), are known from the Oligocene, including Amphicticeps and Amphicynodon.
Plithocyon armagnacensis skull
The raccoon-sized, dog-like Cephalogale is the oldest-known member of the subfamily Hemicyoninae, which first appeared during the middle Oligocene in Eurasia about 30 Mya ago. The subfamily also includes the younger genera Phoberocyon (20–15 Mya), and Plithocyon (15–7 Mya).
A Cephalogale-like species gave rise to the genus Ursavus during the early Oligocene (30–28 Mya); this genus proliferated into many species in Asia and is ancestral to all living bears. Species of Ursavus subsequently entered North America, together with Amphicynodon and Cephalogale, during the early Miocene (21–18 Mya).
Members of the living lineages of bears diverged from Ursavus around 20 Mya ago, likely via the species Ursavus elmensis. Based on genetic and morphological data, the Ailuropodinae (pandas) were the first to diverge from other living bears about 19 Mya ago, although no fossils of this group have been found before about 5 Mya.
The subfamily Ursinae experienced a dramatic proliferation of taxa about 5.3–4.5 Mya ago coincident with major environmental changes, with the first members of the genus Ursus also appearing 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 ago, the species Ursus minimus appears in the fossil record of Europe; apart from its size, it was nearly identical to today's Asiatic 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 Asiatic black bear, and the American black bear); and the brown bears (which includes the polar bear). Modern brown bears evolved from U. minimus via Ursus etruscus, which itself is ancestral to both the extinct Pleistocenecave bear and today's brown and polar bears. Species of Ursinae have migrated repeatedly into North America from Eurasia as early as 4 Mya during the early Pliocene.
The fossil record of bears is exceptionally good. Direct ancestor-descendent relationships between individual species are often fairly well established, with sufficient intermediate forms known to make the precise cut-off between an ancestral and its daughter species subjective.
The giant panda's taxonomy (subfamily Ailuropodinae) has long been debated. Its original classification by Armand David in 1869 was within the bear genus Ursus, but in 1870, it was reclassified by Alphonse Milne-Edwards to the raccoon family. In recent studies, the majority of DNA analyses suggest the giant panda has a much closer relationship to other bears and should be considered a member of the family Ursidae. Estimates of divergence dates place the giant panda as the most ancient offshoot among living taxa within Ursidae, having split from other bears 17.9 to 22.1 Mya. The red panda was included within Ursidae in the past. However, more recent research does not support such a conclusion, and instead places it in its own family Ailuridae, in superfamily Musteloidea along with Mustelidae, Procyonidae, and Mephitidae. Multiple similarities between the two pandas, including the presence of false thumbs, are thus thought to represent an example of convergent evolution for feeding primarily on bamboo.
Unlike their neighbors elsewhere, the brown bears of Alaska's ABC Islands evidently are more closely related to polar bears than to other brown bears in the world. Researchers Gerald Shields and Sandra Talbot of the University of Alaska Fairbanks Institute of Arctic Biology studied the DNA of several samples of the species and found their DNA is different from that of other brown bears. The discovery has shown, while all other brown bears share a brown bear as their closest relative, those of Alaska's ABC Islands differ and share their closest relation with the polar bear. Also, the very rare Tibetan blue bear is a type of brown bear. This animal has never been photographed.
Koalas are often referred to as bears due to their appearance; they are not bears, however, but are marsupials.
The genera Melursus and Helarctos are sometimes also included in Ursus. The Asiatic black bear and the polar bear used to be placed in their own genera, Selenarctos and Thalarctos; these names have since been reduced in rank to subgeneric rank.
A number of hybrids have been bred between American black, brown, and polar bears.
Despite being quadrupeds, bears can stand and sit similarly to humans.
Unlike most other Carnivora, bears have plantigrade feet
Bears are generally bulky and robust animals with relatively short legs. They are sexually dimorphic with regard to size, with the males being larger. Larger species tend to show increased levels of sexual dimorphism in comparison to smaller species, and where a species varies in size across its distribution, individuals from larger-sized areas tend also to vary more. Bears are the most massive terrestrial members of the order Carnivora. Some exceptional polar bears and Kodiak bears (a brown bear subspecies) have been weighed at over 750 kg (1,650 lb). As to which species is the largest depends on whether the assessment is based on which species has the largest individuals (brown bears) or on the largest average size (polar bears), as some races of brown bears are much smaller than polar bears. Adult male Kodiak bears average 480 to 533 kg (1,058 to 1,175 lb) compared to an average of 386 to 408 kg (851 to 899 lb) in adult male polar bears, per the Guinness Book of World Records. The smallest bears are the sun bears of Asia, which weigh an average of 65 kg (143 lb) for the males and 45 kg (99 lb) for the females, though the smallest mature females can weigh only 20 kg (44 lb). All "medium"-sized bear species (which include the other five extant species) are around the same average weight, with males averaging around 100 to 120 kg (220 to 260 lb) and females averaging around 60 to 85 kg (132 to 187 lb), although it is not uncommon for male American black bears to considerably exceed "average" weights. Head-and-body length can range from 120 cm (47 in) in sun bears to 300 cm (120 in) in large polar and brown bears and shoulder height can range from 60 cm (24 in) to over 160 cm (63 in) in the same species, respectively. The tails of bears are often considered a vestigal feature and can range from 3 to 22 cm (1.2 to 8.7 in).
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 still quite fast, with the brown bear reaching 48 km/h (30 mph), although they are still slower than felines and canines. Bears can stand on their hind feet and sit up straight with remarkable balance. Bears' nonretractable claws are used for digging, climbing, tearing, and catching prey. Their ears are rounded.
Bears have an excellent sense of smell, better than the dogs (Canidae), or possibly any other mammal. This sense of smell is used for signalling between bears (either to warn off rivals or detect mates) and for finding food. Smell is the principal sense used by bears to find most of their food.
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. The canine teeth are large, and the molar teeth flat and crushing. Considerable variation occurs in dental formula even within a given species. This may indicate bears are still in the process of evolving from carnivorous to predominantly herbivorous diets. Polar bears appear to have secondarily re-evolved fully functional carnassials, as their diets have switched back towards carnivory. The dental formula for living bears is: 3.1.2-22.214.171.124-4.3
Bears are primarily found in the Northern Hemisphere, and with one exception, only in Asia, North America and Europe. The single exception is the spectacled bear (Tremarctos ornatus); native to South America it inhabits the Andean region. The Atlas bear, a subspecies of the brown bear, was the only bear native to Africa. It was distributed in North Africa from Morocco to Libya, but has been extinct since around the 1870s. 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 Sea. All the remaining species are Asian.
With the exception of the polar bear, bears are mostly forest species. Some species, particularly the brown bear, may inhabit or seasonally use other areas, such as alpine scrub or tundra.
While many people think bears are nocturnal, they are, in fact, generally diurnal, active for the most part during the day. The belief they are nocturnal apparently comes from the habits of bears that live near humans, which engage in some nocturnal activities, such as raiding trash cans or crops while avoiding humans. The sloth bear of Asia is the most nocturnal of the bears, but this varies by individual, and females with cubs are often diurnal to avoid competition with males and nocturnal predators. Bears are overwhelmingly solitary and are considered to be the most asocial of all the Carnivora. Liaisons between breeding bears are brief, and the only times bears are encountered in small groups are mothers with young or occasional seasonal bounties of rich food (such as salmon runs).
Brown bears make use of infrequent but predictable salmon runs in order to feed
Their carnivorous reputation not withstanding, most bears have adopted diets of more plant than animal matter and are completely opportunistic omnivores. Some bears will climb trees to obtain mast (edible vegatative or reproductive parts such as acorns); smaller species that are more able to climb include a greater amount of this in their diets. 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. One exception is the polar bear, which has adopted a diet mainly of marine mammals to survive in the Arctic. The other exception is the giant panda, which has adopted a diet mainly of bamboo. Stable isotope analysis of the extinct giant short-faced bear (Arctodus simus) shows it was also an exclusive meat-eater, probably a scavenger. The sloth bear, though not as specialized as the previous two species, 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 they favour. At certain times of the year, these insects can make up 90% of their diets. All bears will feed on any food source that becomes available, the nature of which varies seasonally. A study of Asiatic black bears in Taiwan found they would consume large numbers of acorns when they were most common, and switch to ungulates at other times of the year.
When taking warm-blooded animals, bears will typically take small or young animals, as they are easier to catch. However, both species of black bears and the brown bear can sometimes take large prey, such as ungulates. Often, bears will feed on other large animals when they encounter a carcass, whether or not the carcass is claimed by, or is the kill of, another predator. This competition is the main source of interspecies conflict. Bears are typically the apex predators in their ranges due to their size and power, and can defend a carcass against nearly all comers. Mother bears also can usually defend their cubs against other predators. The tiger is the only predator known to regularly prey on adult bears, including sloth bears, Asiatic black bears, giant pandas, sun bears and small brown bears.
The age at which bears reach sexual maturity is highly variable, both between and within species. Sexual maturity is dependent on body condition, which is in turn dependent upon the food supply available to the growing individual. The females of smaller species may have young in as little as two years, whereas the larger species may not rear young until they are four or even 9 years old. First breeding may be even later in males, where competition for mates may leave younger males without access to females.
American black bears mating
The bear's courtship period is very brief. Bears in northern climates reproduce seasonally, usually after a period of inactivity similar to hibernation, although tropical species breed all year round. Cubs are born toothless, blind, and bald. The cubs of brown bears, usually born in litters of one to three, will typically stay with the mother for two full seasons. They feed on their mother's milk through the duration of their relationship with their mother, although as the cubs continue to grow, nursing becomes less frequent and cubs learn to begin hunting with the mother. They will remain with the mother for about three years, until she enters the next cycle of estrus and drives the cubs off. Bears will reach sexual maturity in five to seven years. Male bears, especially polar and brown bears, will kill and sometimes devour cubs born to another father to induce a female to breed again. Female bears are often successful in driving off males in protection of their cubs, despite being rather smaller.
Many bears of northern regions are assumed[by whom?] to hibernate in the winter, a belief supported by a number of scientific studies. While many bear species do go into a physiological state often colloquially called "hibernation" or "winter sleep", it is not true hibernation. In true hibernators, body temperatures drop to near ambient and heart rates slow drastically, but the animals periodically rouse themselves to urinate or defecate and to eat from stored food. The body temperature of bears, on the other hand, drops only a few degrees from normal, and the heart rate slows from a normal value of 55 to just 9 beats per minute. They normally do not wake during this "hibernation", so do not eat, drink, urinate, or defecate the entire period. Higher body heat and being easily roused may be adaptations, because females give birth to their cubs during this winter sleep.
Some species, such as the polar bear, American black bear, sloth bear, and brown bear, are dangerous to humans, especially in areas where they have become used to people. All bears are physically powerful and are likely capable of fatally attacking a person, but they, for the most part, are shy, are easily frightened and will avoid humans. Injuries caused by bears are rare, but are often widely reported. The danger that bears pose is often vastly exaggerated, in part by the human imagination. However, when a mother feels her cubs are threatened, she will behave ferociously. It is recommended to give all bears a wide berth because they are behaviorally unpredictable.
Where bears raid crops or attack livestock, they may come into conflict with humans. These problems may be the work of only a few bears, but they create a climate of conflict, as farmers and ranchers may perceive all losses as due to bears and advocate the preventive removal of all bears. Mitigation methods may be used to reduce bear damage to crops, and reduce local antipathy towards bears.
Laws have been passed in many areas of the world to protect bears from habitat destruction. Public perception of bears is often very positive, as people identify with bears due to their omnivorous diets, ability to stand on two legs, and symbolic importance, and support for bear protection is widespread, at least in more affluent societies. In more rural and poorer regions, attitudes may be more shaped by the dangers posed by bears and the economic costs they cause to farmers and ranchers. Some populated areas with bear populations have also outlawed the feeding of bears, including allowing them access to garbage or other food waste. Bears in captivity have been trained to dance, box, or ride bicycles; however, this use of the animals became controversial in the late 20th century. Bears were kept for baiting in Europe at least since the 16th century.
The female first name "Ursula", originally derived from a Christian saint's name and common in English- and German-speaking countries, means "little she-bear" (diminutive of Latinursa). In Switzerland, the male first name "Urs" is especially popular, while the name of the canton and city of Bern is derived from Bär, German for bear.
In Scandinavia, the male personal names Björn (Sweden, Iceland) and Bjørn (Norway, Denmark), meaning "bear", are relatively common. In Finland, the male personal name Otso is an old poetic name for bear, similar to Kontio.
The Irish family name "McMahon" means "Son of Bear" in Irish.
In East European Jewish communities, the name Ber (בער)—Yiddish cognate of "Bear"—has been attested as a common male first name, at least since the 18th century, and was, among others, the name of several prominent rabbis. The Yiddish Ber is still in use among Orthodox Jewish communities in Israel, the US, and other countries. With the transition from Yiddish to Hebrew under the influence of zionism, the Hebrew word for "bear", dov (דב), was taken up in contemporary Israel and is at present among the commonly used male first names in that country.
"Ten Bears" (Paruasemana) was the name of a well-known 19th century chieftain among the Comanche. Also among other Native American tribes, bear-related names are attested.
There is evidence of prehistoric bear worship. Anthropologists such as Joseph Campbell have regarded this as a common feature in most of the fishing and hunting-tribes. The prehistoric Finns, along with most Siberian peoples, considered the bear as the spirit of one's forefathers. This is why the bear (karhu) was a greatly respected animal, with several euphemistic names (such as otso, mesikämmen and kontio). The bear is the national animal of Finland.
This kind of attitude is reflected in the traditional Russianfairy tale "Morozko", whose arrogant protagonist Ivan tries to kill a mother bear and her cubs—and is punished and humbled by having his own head turned magically into a bear's head and being subsequently shunned by human society.
Evidence of bear worship has been found in early Chinese and Ainu cultures, as well (see Iomante). Korean people in their mythology identify the bear as their ancestor and symbolic animal. According to the Korean legend, a god imposed a difficult test on a she-bear; when she passed it, the god turned her into a woman and married her.
Legends of saints taming bears are common in the Alpine zone. In the arms of the bishopric of Freising, the bear is the dangerous totem animal tamed by St. Corbinian and made to carry his civilised baggage over the mountains. A bear also features prominently in the legend of St. Romedius, who is also said to have tamed one of these animals and had the same bear carry him from his hermitage in the mountains to the city of Trento.
This recurrent motif was used by the Church as a symbol of the victory of Christianity over paganism. In the Norse settlements of northern England during the 10th century, a type of "hogback" grave cover of a long narrow block of stone, with a shaped apex like the roof beam of a long house, is carved with a muzzled, thus Christianised, bear clasping each gable end. Though the best collection of these is in the church at Brompton, North Yorkshire, their distribution ranges across northern England and southern Scotland, with a scattered few in the north Midlands and single survivals in Wales, Cornwall, and Ireland; a late group is found in the Orkney Islands.
Smokey Bear has become a part of American culture since his introduction in 1944. Known to almost all Americans, he and his message, "Only you can prevent forest fires" (updated in 2001 to "Only you can prevent wildfires"), have been a symbol of preserving woodlands. Smokey wears a hat similar to one worn by U.S. Forest Service rangers; state police officers in some states wear a similar style, giving rise to the CB slang "bear" or "Smokey" for the highway patrol.
The physical attributes and behaviours of bears are commonly used in figures of speech in English.
In the stock market, a bear market is a period of declining prices. Pessimistic forecasting or negative activity is said to be bearish (due to the stereotypical posture of bears looking downwards), and one who expresses bearish sentiment is a bear. Its opposite is a bull market, and bullish sentiment from bulls.
In gay slang, the term "bear" refers to male individuals who possess physical attributes much like a bear, such as a heavy build, abundant body hair, and commonly facial hair.
A bear hug is typically a tight hug that involves wrapping one's arms around another person, often leaving that person's arms immobile.
Bear tracking – in the old Western states of the U.S. and, to this day, in the former Dakota Territory, the expression "you ain't just a bear trackin'" is used to mean "you ain't lying" or "that's for sure". This expression evolved as an outgrowth of the experience pioneer hunters and mountainmen had when tracking bear. Bears often lay down false tracks and are notorious for doubling back on anything tracking them. If you are not following bear tracks, you are not following false trails or leads in your thoughts, words or deeds.
In Korean culture a person is referred to as being "like a bear" when they are stubborn or not sensitive to what is happening around their surroundings. Used as a phrase to call a person "stubborn bear".
The Bible compares King David's "bitter warriors", who fight with such fury that they could overcome many times their number of opponents, with "a bear robbed of her whelps in the field" (2 Samuel 17:8 s:Bible (King James)/2 Samuel#Chapter 17). The phrase "a bereaved bear" (דב שכול), derived from this Biblical source, is still used in the literary Hebrew of contemporary Israel.
Other organizations exist to further wild bear education and conservation. Bear Trust International works for wild bears and other wildlife through four core program initiatives: 1) Conservation Education, 2) Wild Bear Research, 3) Wild Bear Management, and, 4) Habitat Conservation. Speciality organizations for each of the eight species of bears worldwide include:
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Bears are large, robustly built animals. The smallest species, Helarctos malayanus ranges in size from 25 to 65 kg, the largest individuals can weigh up to 800 kg (Ursus maritimus). Males are larger than females, sometimes more than twice their size. Bears have small, rounded ears, small eyes, and very short tails. Most species have long, rough fur, and the hairs that make it up are generally unicolored (rather than being agouti, the common pattern among mammals). Sun bears have a smooth coat. Most bears are brown, black, or white; some have striking white marks on the chest or face. Giant pandas are well-known for their distinctive bands of black and white fur. Bear skulls are massive, with unspecialized incisors, elongate canines, reduced premolars, and bunodont cheek teeth. All bear species possess robust, recurved, non-retractile claws that they use for digging and ripping. The feet of bears are plantigrade, and most have hairy soles, although tree climbing bears, such as Helarctos, have naked soles. There are five digits on each foot. Giant pandas (Ailuropoda melanoleuca) have an additional, opposable feature of the forepaws, sometimes called a panda's "thumb". It is not a true digit but a pad-covered enlargement of the radial sesamoid bone. Pandas use this opposable structure to manipulate bamboo.