Ursus thibetanus

Geographic Range

Ursus thibetanus is widely distributed. Asiatic black bears can be found north of Pakistan, south of Afghanistan, east of the Himalayans, north of Vietnam, south of China, and in Thailand.

• Biogeographic Regions
• palearctic palearctic
  • native native
• oriental oriental
  • native native

Habitat

Asiatic black bears live in moist forests, on steep mountains, and in areas where the vegetation is thick. They live at higher elevations in the summer, and descend during the winter. Occasionally, they come out of the forests to forage on plains.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest

Physical Description

The size differs between males and females. Males typically weigh 110 to 150 kg, while females weigh 65 to 90 kg. The head and body measure 120 to 180 cm in length, while the tail is an additional 6.5 to 10.6 cm. The head is large and rounded, and the eyes are small. The ears are large and are set farther apart than on an American black bear. The body is heavy, the legs are thick and strong, and the paws are broad. The stance is plantigrade. The tail is short and is barely visible under a long, coarse coat. The black pelage has a light beige to white “V” shape on the chest area, a small beige to white colored crescent across the throat, and a small spot of white on the chin. The white fur on the muzzle seldom reaches the orbits of the bear.

The skull of U. thibetanus is typical of the Suborder Caniformia , bearing a long rostrum. However, the orbits are typically smaller than those of most caniforms. The width of the mastoid rarely exceeds the length of the palate. The auditory bullae are flat. The muzzle is long and narrow, and does not extend very far over the canines. The dental formula is usually 3/3, 1/1, 4/4, 2/3 = 42. However, the premolars can sometimes be lost as the bear ages. The postcarnassial teeth are enlarged, and occlusal surfaces are adapted to crushing. Normally, there is a diastema between the premolars. The upper carnassial of U. thibetanus is triangular.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Little is known about Asiatic black bears in the wild; most of what is known about their social and reproductive behavior has been collected by observing the bears in zoos and environments other than their natural habitat.

In captive environments, the mating pattern of Asiatic black bears is classified as promiscuous. Females enter periods of estrus and non-estrus at irregular intervals, and undergo mating for 12 to 35 days. For males above the age of 6 years, larger bears spend more days mating than smaller males. There is a social hierarchy related to the age and body weight of male bears and only larger males mate with the females. Those of small size (those weighing less than 80 kg) have reduced chances of mating.

In the wild, Asiatic black bears typically forage alone. However, during breeding season, pairs can be seen hunting and gathering together.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

The reproductive patterns vary widely in the different populations of U. thibetanus . In Siberia, mating takes place in June or July, with the births occurring in February, typically. In Pakistan, mating occurs in October, and births occur in February. Across the species, breeding usually begins when U. thibetanus is 3 to 4 years old. The pregnancy lasts from 7 to 8 months, and cubs are born in a cave or hollow tree in early winter. There are usually 2 cubs per litter, and the cubs typically weigh about 8 to 10.5 ounces. Asiatic black bears are thought to have delayed implantation where the embryo floats freely in the womb before it implants in the uterine lining, though this is not known definitively. Studies conducted on pregnant and nonpregnant bears show that concentrations of serum progesterone (P4) and prolactin (PRL) might be connected with the process of delayed implantation in U. thibetanus . Lower concentrations of both P4 and PRL are found in nonpregnant bears. Increased concentrations of these cause the activation of the corpus luteum, which prepares the uterus for implantation. Rising levels of both P4 and PRL are found to occur approximately two months after copulation. Therefore the duration of the delayed implantation in U. thibetanus is around two months. It is not yet known whether delayed implantation occurs all of the time in U. thibetanus , or only under certain circumstances. It is also not yet known what causes the levels of the particular hormones under study to change, though it may be due to environmental cues or in response to other hormones circulating in the body.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• viviparous viviparous
• delayed implantation delayed implantation

The cubs of U. thibetanus cannot open their eyes until 1 week has passed, and they are not fully weaned until just over 3 months. The cubs live with their mother until they are 2 to 3 years old. Not much is known about the type of care that parents provide in the wild, due to the lack of studies of behavior outside of captive environments.

• Parental Investment
• altricial altricial
• pre-weaning/fledging
  • provisioning
    • female

Lifespan/Longevity

Little is known about lifespan in U. thibetanus , especially out in the wild. There are few resources available for information on lifespan in the wild or in captivity.

Behavior

Asiatic black bears are primarily nocturnal feeders and sleep in a tree hole or in a cave during the daytime, but they do sometimes forage diurnally. During the autumn, their nocturnal activity increases. They shift their ranges in early autumn in order to obtain native broadleaved food species (mast crops) at lower elevations. They are powerful swimmers, and their short (2 inches, or 5.08 cm) claws make them adept tree climbers. They are plantigrade, and typically walk on four feet, but when they fight, they stand up on their two hind feet and slap their enemy with their forepaws. Asiatic black bears usually avoid man and only attack when they are wounded or trying to protect their young, but unprovoked attacks have been documented many times throughout history.

Not all Asiatic black bears hibernate, though many do. They store fat during the late summer to use during the winter months of hibernation. Some may sleep the entire winter period, while others may only hibernate for the worst periods of winter weather. Asiatic black bears behave as other bears during hibernation; they do not excrete urea or solid fecal material, instead converting the waste material to proteins. During periods of hibernation, the heartbeat drops from 40 to 70 beats per minute to 8 to 12 beats per minute, and the metabolic rate decreases by 50%. The body temperature decreases by only 3 to 7 degrees Centigrade. Due to the fact that the body temperature of U. thibetanus , as well as many other bears, does not substantially drop and the bear can be easily awakened, some ecophysiologists do not consider the bear's period of inactivity to be true hibernation. Others argue that it is true hibernation, due to the fact that the pulse rate drops by 50%.

• Key Behaviors
• arboreal arboreal
• scansorial
• terricolous
• nocturnal nocturnal
• motile motile
• migratory migratory
• hibernation hibernation
• daily torpor
• solitary solitary
• territorial territorial

Home Range

The territory of U. thibetanus can vary greatly, from around 6.4 or 9.7 square kiliometers to around 16.4 or 36.5 square kilometers, depending on the availability of food. The denser the available food supply is, the smaller the range.

Communication and Perception

Exceptional sight, hearing, and smell are characteristics of U. thibetanus . No studies are available as to the exact form of communication between Asiatic black bears. However, extensive research has been conducted on other members of the family Ursidae that have senses similar to those of the Asiatic black bear. Using evidence from these studies, it can be inferred that Asiatic black bears communicate vocally and use their heightened sense of hearing to aid in listening to these vocalizations. For example, when bear cubs are separated from their mothers, they make crying calls. Low guttural noises can be indications of a bear being apprehensive, and clicking the teeth together is an indication of aggressiveness.

Bears often communicate visually with each other by the way in which they move or behave in the presence of other bears; for example, the behavior of a bear can convey either dominant or subordinate status to another. To indicate subordinate status, a bear moves away, or sits or lies down. To convey dominance, a bear walks or runs towards a rival.

Bears use their acute sense of smell in order to communicate with other members of their species; they do so by urinating, defecating, and by rubbing against trees to leave their scent for other bears to detect.

• Communication Channels
• visual visual
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Asiatic black bears most often feed diurnally. However, their nocturnal activity increases through autumn. This occurs because the bears must increase their food intake in order to store body fat for insulation and caloric needs for use during harsh winters and hibernation. Asiatic black bears seem to be able to shift their circadian rhythm in order to obtain desired foods; for example, when raiding crops, they are more likely to do so at night in order to avoid contact with humans. Asiatic black bears posses an acute sense of smell that lets them locate grubs and other insects up to 3 feet (approximately 1 meter) below the ground. Asiatic black bears are omnivorous, though they are primarily vegetarians. A recent study showed that nuts from Fagaceae trees occupied the highest proportion of autumn foods. When food production and availability is poor, Asiatic black bears have been known to strip the bark off of trees in order to supplement their deficient diet with nutrients. Their normal diet consists of fruits, roots and tubers, as well as small invertebrates and vertebrates, and carrion. However, cases in which they eat buffalo by breaking the neck have been documented. They also eat other prey they find that tigers have killed.

Asiatic black bears have been known to eat any available food source, including the livestock and produce of farms. Their proclivity for domestic animals and crops has made humans target them, and Asiatic black bears are often killed while trying to feed.

• Primary Diet
• omnivore omnivore

• Animal Foods
• mammals
• carrion carrion
• insects
• terrestrial worms

• Plant Foods
• roots and tubers
• wood, bark, or stems
• fruit

Predation

The main predator of U. thibetanus is the Siberian tiger ( Panthera tigris ). The fact that tiger kills are a favorite food of U. thibetanus leaves it susceptible to tiger attacks when the tiger returns to its kill and finds the bear feeding on the carrion.

Ecosystem Roles

Asiatic black bears are the prey of Siberian Tigers. Asiatic black bears feed upon the carrion that the tigers kill, and if the bears are caught while feeding, they are killed and eaten by the tigers.

Asiatic black bears feed upon grubs and insects, placing them on the third trophic level. As omnivores, they are secondary consumers.

Studies conducted in various locations in Japan show that there are a few typical parasites of Asiatic black bears, occurring in the esophageal and tracheal connective tissue, lungs, and ventral body hair.

Three common nematode parasites found in the esophageal and tracheal connective tissue of Asiatic black bears are Baylisascaris transfuga , Cercopithifilaria japonica , and the filarial nematode Dirofilaria ursi . The biting louse Trichodectes pinguis is found in the ventral body hairs, as well as numerous species of the hard tick Haemaphysalis megaspinosa . There has been one instance in which Hepatozoon canis was found in the lungs of an Asiatic black bear. This was the first time this parasite has been found in any species of bear.

Economic Importance for Humans: Positive

The bile and gallbladders of Asiatic black bears are harvested for medical use in some oriental countries. These organs are thought to reduce inflammation and reduce fevers.

Asiatic black bears are also hunted for their paws, skin, and meat.

• Positive Impacts
• body parts are source of valuable material
• source of medicine or drug source of medicine or drug

Economic Importance for Humans: Negative

There have been documented cases of unprovoked attacks by Asiatic black bears on humans, as well as cases of provoked attacks on humans when a bear felt endangered. Most attacks on humans take place in the late summer, around the time of the mating season.

Asiatic black bears sometimes prey on livestock and crops, thus making themselves susceptible to being killed by humans when caught.

• Negative Impacts
• injures humans
  • bites or stings
• crop pest

Conservation Status

The habitat of U. thibetanus is threatened by uncontrolled harvesting and deforestation. There is no special effort being put forth to help the continuing decline in numbers of Asiatic black bears. Diversity of habitats and food is important in providing alternative foods when one food source fails. As a result of deforestation and other human activities, however, the diversity of habitats is being destroyed. Even in the protected areas, there is not enough variety to fully support the Asiatic black bears. As a result, each population of Asiatic black bears is becoming increasingly isolated.

Population studies in 2001 in Japan found that different populations of Asiatic black bears were becoming genetically isolated from each other. Even between the two closest populations, there was a low but significant amount of genetic differentiation. In the individual populations, genetic diversity was decreasing. Since each population was changing and evolving separately, genetic isolation between the populations is a problem that needs to be addressed, and conservation efforts must be initiated.

Additional Links

Encyclopedia of Life

Contributors

Matthew Wund (editor), University of Michigan-Ann Arbor.

Tracie Goodness (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

References

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