Asian black bear
The Asian black bear (Ursus thibetanus, previously known as Selenarctos thibetanus) is also known as moon bear and white-chested bear. It is a medium-sized bear species and largely adapted to arboreal life.[2][3] It lives in the Himalayas, in the northern parts of the Indian subcontinent, Korea, northeastern China, the Russian Far East, the Honshū and Shikoku islands of Japan, and Taiwan. It is classified as vulnerable by the International Union for Conservation of Nature (IUCN), mostly because of deforestation and hunting for its body parts.[1]
The species is morphologically very similar to some prehistoric bears, and is thought by some scientists to be the ancestor of other extant bear species (aside from pandas and spectacled bears).[2] Though largely herbivorous, Asian black bears can be very aggressive toward humans, who frequently trap or kill them for traditional medicine.[4]
Characteristics
Asian black bears are black and have a light brown muzzle. They are white on the chin, and have a distinct white patch on the chest, which sometimes has the shape of a V.[5] Their ears are bell shaped, proportionately longer than those of other bears, and stick out sideways from the head. The tail is 11 cm (4.3 in) long.[4] Adults measure 70–100 cm (28–39 in) at the shoulder, and 120–190 cm (47–75 in) in length. Adult males weigh 60–200 kg (130–440 lb) with an average weight of about 135 kg (298 lb). Adult females weigh 40–125 kg (88–276 lb), and large ones up to 140 kg (310 lb).[4][6]
Asian black bears are similar in general appearance to brown bears, but are more lightly built and are more slender limbed. The lips and nose are larger and more mobile than those of brown bears. The skulls of Asian black bears are relatively small, but massive, particularly in the lower jaw. Adult males have skulls measuring 311.7 to 328 mm (12.27 to 12.91 in) in length and 199.5–228 mm (7.85–8.98 in) in width, while female skulls are 291.6–315 mm (11.48–12.40 in) long and 163–173 mm (6.4–6.8 in) wide. Compared to other bears of the genus Ursus, the projections of the skull are weakly developed; the sagittal crest is low and short, even in old specimens, and does not exceed more than 19–20% of the total length of the skull, unlike in brown bears, which have sagittal crests comprising up to 41% of the skull's length.[3]
Although mostly herbivorous, the jaw structure of Asian black bears is not as specialised for plant eating as that of pandas: Asian black bears have much narrower zygomatic arches, and the weight ratio of the two pterygoid muscles is also much smaller in Asian black bears. The lateral slips of the temporal muscles are thicker and stronger in black bears.[7]
A black bear with broken hind legs can still climb effectively. In contrast to polar bears, Asian black bears have powerful upper bodies for climbing trees, and relatively weak hind legs which are shorter than those in brown bears and American black bears.[3][4] They are the most bipedal of all bears, and have been known to walk upright for over a quarter mile.[8] The heel pads on the forefeet are larger than those of most other bear species. Their claws, which are primarily used for climbing and digging, are slightly longer on the fore foot (30–45 mm) than the back (18–36 mm),[9] and are larger and more hooked than those of the American black bear.[10]
On average, adult Asian black bears are slightly smaller than American black bears, though large males can exceed the size of several other bear species.[11]
The famed British sportsman known as the "Old Shekarry" wrote of how a black bear he shot in India probably weighed no less than 363 kg (800 lb) based on how many people it took to lift its body.[12] The largest Asian black bear on record allegedly weighed 200 kg (440 lb).[4] Zoo-kept specimens can weigh up to 225 kg (496 lb).[13] Although their senses are more acute than those of brown bears,[14] their eyesight is poor, and their hearing range is moderate, the upper limit being 30 kHz.[15]
Taxonomy[edit]
Ancestral and sister taxa[edit]
Biologically and morphologically, Asian black bears represent the beginning of the arboreal specialisations attained by sloth bears and sun bears.[3] Asian black bears have karyotypes nearly identical to those of the five other ursine bears, and, as is typical in the genus, they have 74 chromosomes.[16] From an evolutionary perspective, Asian black bears are the least changed of Old World bears, with certain scientists arguing that it is likely that all other lineages of ursine bear stem from this species.[2] Scientists have proposed that Asian black bears are either a surviving, albeit modified, form of Ursus etruscus, specifically the early, small variety of the middle Villafranchian (upper Pliocene to lower Pleistocene)[17] or a larger form of Ursus minimus, an extinct species that arose four million years ago. With the exception of the age of the bones, it is often difficult to distinguish the remains of Ursus minimus with those of modern Asian black bears.[2]
Asian black bears are close relatives to American black bears, with which they share a European common ancestor;[18] the two species are thought to have diverged 3 million years ago, though genetic evidence is inconclusive. Both American and Asiatic species are considered sister taxa, and are more closely related to each other than other species of bear.[19] The earliest American black bear fossils, which were located in Port Kennedy, Pennsylvania, greatly resemble the Asiatic species.[17] The first mtDNA study undertaken on Asian black bears suggested that the species arose after the American black bears, while a second study could not statistically resolve the branching order of sloth bears and the two black species, suggesting that these three species underwent a rapid radiation event. A third study suggested that American black bears and Asian black bears diverged as sister taxa after the sloth bear lineage and before the sun bear lineage.[16] Further investigations on the entire mitochondrial cytochrome b sequence indicate that the divergence of continental and Japanese black bear populations might have occurred when bears crossed the land bridge between the Korean peninsula and Japan 500,000 years ago, which is consistent with paleontological evidence.[20]
Behaviour:
Asian black bears are diurnal, though they become nocturnal near human habitations. They may live in family groups consisting of two adults and two successive litters of young. They will walk in a procession of largest to smallest. They are good climbers of rocks and trees, and will climb to feed, rest, sun, elude enemies and hibernate. Some older bears may become too heavy to climb.[28] Half of their life is spent in trees and they are one of the largest arboreal mammals.[16] In the Ussuri territory, black bears can spend up to 15% of their time in trees.[3] Asian black bears break branches and twigs to place under themselves when feeding on trees, thus causing many trees in their home ranges to have nest-like structures on their tops.[16] Asian black bears will rest for short periods in nests on trees standing fifteen feet or higher.[28] Asian black bears do not hibernate over most of their range. They may hibernate in their colder, northern ranges, though some bears will simply move to lower elevations. Nearly all pregnant sows hibernate. Black bears prepare their dens for hibernation in mid-October, and will sleep from November until March. Their dens can either be dug out hollow trees (sixty feet above ground), caves or holes in the ground, hollow logs, or steep, mountainous and sunny slopes.[28] They may also den in abandoned brown bear dens. Asiatic black bears tend to den at lower elevations and on less steep slopes than brown bears. Female black bears emerge from dens later than do males, and female black bears with cubs emerge later than barren females.[29] Asian black bears tend to be less mobile than brown bears. With sufficient food, Asian black bears can remain in an area of roughly 1–2 sq km, and sometimes even as little as 0.5–1 sq km.[28]
Asian black bears have a wide range of vocalisations, including grunts, whines, roars, slurping sounds (sometimes made when feeding) and "an appalling row" when wounded, alarmed or angry. They emit loud hisses when issuing warnings or threats, and scream when fighting. When approaching other bears, they produce "tut tut" sounds, thought to be produced by bears snapping their tongue against the roof of their mouth.[15] When courting, they emit clucking sounds.[28]
Feeding:
Asian black bears are omnivorous, and will feed on insects, beetle larvae, invertebrates, termites, grubs, carrion, bees, eggs, garbage, mushrooms, grasses, fruits, nuts, seeds, honey, herbs, acorns, cherries, dogwood, and grain.[28] Though herbivorous to a greater degree than brown bears,[3] and more carnivorous than American black bears,[8] Asian black bears are not as specialised in their diet as pandas are: while pandas depend on a constant supply of low calorie, yet abundant foodstuffs, black bears are more opportunistic and have opted for a nutritional boom-or-bust economy. They thus gorge themselves on a variety of seasonal high calorie foods, storing the excess calories as fat, and then hibernate during times of scarcity.[30] Black bears will eat pine nuts and acorns of the previous year in the April–May period. In times of scarcity, they enter river valleys to gain access to hazelnuts and insect larvae in rotting logs. From mid-May through late June, they will supplement their diet with green vegetation and fruit. Through July to September, they will climb trees to eat bird cherries, pine cones, vines and grapes. On rare occasions they will eat dead fish during the spawning season, though this constitutes a much lesser portion of their diet than in brown bears.[3] In the 1970s, black bears were reported to kill and eat Hanuman langurs in Nepal.[31] They appear to be more carnivorous than most other bears, including American black bears, and will kill ungulates with some regularity, including domestic livestock.[32] Wild ungulate prey can include muntjacs, serow, takin,[33] wild boar[34] and adult water buffaloes, which they kill by breaking their necks.[35]
Interspecific predatory relationships:
Asian black bears may be occasionally attacked by tigers and brown bears, although leopards,[36] and packs of wolves[3] and dholes[14] can also be threats. Eurasian lynxes are a potential predator of cubs.[3] Black bears usually dominate Amur leopards in physical confrontations in heavily vegetated areas, while leopards are uppermost in open areas, though the outcome of such encounters is largely dependent on the size of the individual animals.[37] Leopards have been known to prey on cubs younger than two years old.[36]
The Asian black bear's range overlaps with that of sloth bears in central and southern India, sun bears in Southeast Asia and brown bears in the southern part of the Russian Far East.[38] Ussuri brown bears may attack black bears,[29] though Himalayan brown bears seem to be intimidated by the black species in direct encounters.[39] They will eat the fruit dropped by black bears from trees, as they themselves are too large and cumbersome to climb.[39][40]
Tigers will occasionally prey on black bears. Russian hunters may occasionally find black bear carcasses showing evidence of tiger predation, and their remains may occur in tiger scats. If they manage to escape a tiger, black bears will attempt to rush up a tree and wait for the tiger to leave, though some tigers will pretend to leave, and wait for the bear to descend.[41] One Manchurian tiger was reported to have lured an Asiatic black bear by imitating the species' mating call.[28] Tigers regularly prey on young bears but adult bears are occasionally taken as well.[41] Black bears are usually safe from tiger attacks once they reach five years of age.[42] Although black bears prefer to avoid tigers, they can be extremely tenacious when attacked: Jim Corbett observed a fight between a tiger and the largest black bear he had ever seen, which resulted in the bear managing to chase off the tiger, despite having half its nose and scalp torn off.[43] However, black bears may be less vulnerable than brown bears to tiger predation, due to their habit of living in hollows or in close set rocks, thus making them harder to pursue.[36] At least one fatal attack on a juvenile bear has been recorded in Jigme Dorji National Park, as Bhutan's tiger populations have begun to colonise higher altitude areas.[42] Black bears may steal tiger kills: Jim Corbett twice saw black bears carry off tiger kills when the latter was absent.[42][43]
Distribution and habitat[edit]
Black bears typically inhabit deciduous forests, deserts, mixed forests and thornbrush forests. They rarely live in elevations of more than 12,000 feet (3,700 m). They usually inhabit elevations around 11,480 feet (3,500 m) in the Himalayas in the summer, and will climb down to 4,920 feet (1,500 m) in winter. They sometimes occur at sea level in Japan.[28]
The fossil record indicates that black bears once ranged as far west as Germany and France, though the species now occurs very patchily throughout its former range, which is now limited to the Asian continent. Black bears occupy a narrow band from southeastern Iran eastward through Afghanistan and Pakistan, across the foothills of the Himalayas in India, to Myanmar. With the exception of Malaysia, black bears occur in all countries in mainland Southeast Asia. They are absent from much of east-central China, though they have a patchy distribution in the southern and northeastern part of the country. Other population clusters exist in the southern Russian Far East and into North Korea. South Korea has a small remnant population. Black bears also occur in Japan's islands of Honshu and Shikoku and on Taiwan and Hainan.[38]
There is no definitive estimate as to the number of Asiatic black bears: Japan posed estimates of 8–14,000 bears living on Honshū, though the reliability of this is now doubted. Although their reliability is unclear, rangewide estimates of 5–6,000 bears have been presented by Russian biologists. In 2012, Japanese Ministry of the Environment estimated the population at 15–20,000.[44] Rough density estimates without corroborating methodology or data have been made in India and Pakistan, resulting in the estimates of 7–9,000 in India and 1,000 in Pakistan. Unsubstantiated estimates from China give varying estimates between 15–46,000, with a government estimate of 28,000.[38]
Bangladesh[edit]
Wildlife Trust of Bangladesh conducted an on field survey of bears in Bangladesh from 2008-2010 that included Asian black Bears. The survey was done in 87 different places mostly in north-central, north eastern and south eastern area of Bangladesh that had historical presence of bears. The survey result says that most of the areas still has some isolated small bear populations mainly the Asian black bears. According to the survey the most evidence found relating bears were of Asiastic black bears that included nests, footprints, local sighting etc. There are many reports on the presence of Asian black bears in central, north-central, north eastern and south eastern parts of Bangladesh.
Although Asian black bears still occurs in different parts of the country mainly in the Chittagong Hill Tracts, the population is very low in number. The survey also fears that Asian black bears will soon be extinct from Bangladesh if necessary steps are not taken in near future.[45]
China[edit]
Three subspecies of Asiatic black bear occur in China: the Tibet subspecies (U. thibetanus thibetanus), the Si Chuan subspecies (U. thibetanus mupinensis), and the northeast subspecies (U. thibetanus ussuricus), which is the only subspecies of bear in northeastern China. Asiatic black bears are mainly distributed in the conifer forests in the cold and temperate zones of northeast China, the main areas being Chang Bai, Zhang Guangcai, Lao Ye, and the Lesser Xingan Mountains. Within Liaoning province, there are about 100 black bears, which only inhabit the five counties of Xin Bin, Huan Ren, Ben Xi, Kuan Dian, and Fen Cheng. Within Jilin province, black bears occur mainly in the counties of Hunchun, Dun Hua, Wangqing, An Tu, Chang Bai, Fu Song, Jiao He, Hua Dian, Pan Shi, and Shu Lan. In Heilongjiang province, Asiatic black bears occur in the counties of Ning An, BaYan, Wu Chang, Tong He, Bao Qing, Fu Yuan, Yi Chun, Tao Shan, Lan Xi, Tie Li, Sun Wu, Ai Hui, De Du[citation needed], Bei An, and Nen Jiang. This population has a northern boundary of about 50° N and the southern boundary in Feng Cheng is about 40°30" N.[46]
Russia[edit]
In Russia, the black bear's northern range runs from Innokenti Bay on the coast of the Sea of Japan southwest to the elevated areas of Sikhote Alin crossing it at the sources of the Samarga River. At this point, the boundary directs itself to the north, through the middle course of the Khor, Anyui and Khungari rivers, and comes to the shore of the Amur, crossing the it at the level of the mouth of the Gorin. Along the Amur river, the species' presence has been noted as far as 51° N. Lat. From there, the territorial boundary runs southwest of the river's left bank, passing through the northern part of Lake Bolon and the juncture point of the Kur and Tunguska. Black bears are encountered in the Urmi's lower course. Within the Ussuri krai, the species is restricted to broad leaved Manchurian type forests.[3]
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