Sun bear
The sun bear is a bear species in the family Ursidae found in the tropical forests of Southeast Asia. It is the only species in the genus Helarctos and the smallest bear species, standing nearly at the shoulder and weighing. It is stockily built, with large paws, strongly curved claws, small, rounded ears and a short snout. The fur is generally short and jet black, but can vary from grey to red. The sun bear gets its name from its characteristic orange to cream-coloured chest patch.
The sun bear's unique morphology with inward-turned front feet, flattened chest, powerful forelimbs with large claws suggests adaptations for climbing, and it is an excellent climber and the most arboreal of all bears. It sunbathes or sleeps in trees above the ground. It is mainly active during the day, though nocturnality might be more common in areas frequented by humans. It tends to remain solitary, but sometimes occur in pairs such as a mother and her cub. It does not hibernate, possibly because food resources are available the whole year throughout its range. It is an omnivore, and its diet includes ants, bees, beetles, honey, termites, and plant material such as seeds and several kinds of fruits; vertebrates such as birds and deer are also eaten occasionally. It breeds throughout the year; individuals become sexually mature at two to four years of age. Litters comprise one or two cubs that remain with their mother for around three years.
The range of the sun bear is bounded by Northeast India to the north then south to southeast through Bangladesh, mainland Southeast Asia, Brunei and Indonesia. These bears are threatened by heavy deforestation and poaching for food and the wildlife trade. They are also harmed in conflicts with humans when they enter farmlands, plantations, and orchards. The global population is estimated to have declined by 35% since the 1990s. It is listed as vulnerable on the IUCN Red List.
Etymology
The generic name Helarctos comes from two Greek words: ήλιος and αρκτος. Another name is "honey bear", beruang madu in Malay and Indonesian, in reference to its habit of feeding on honey from honeycombs.Taxonomy and phylogeny
The scientific name Ursus malayanus was proposed by Stamford Raffles in 1821 when he first described a sun bear from Sumatra. In 1825, Thomas Horsfield placed the species in a genus of its own, Helarctos, when describing a sun bear from Borneo.Subspecies and distribution
H. annamiticus, described by Pierre Marie Heude in 1901 from Annam, is not considered a distinct species, but is subordinated as a junior synonym to H. m. malayanus. In 1906, Richard Lydekker proposed another subspecies by the name H. m. wardii for a sun bear skull, noting its similarities to a skull from Tibet with a thicker coat, but the Tibetan specimen was later found to be an Asian black bear. Genetic differences between the two subspecies are obscure and some consider the species monotypic.Phylogeny
The phylogenetic relationships among ursid species have remained ambiguous over the years. Noting the production of fertile hybrids between sun bears and sloth bears, it was proposed that Helarctos be treated as a synonym of Melursus. However, studies differed on whether the two species were closely related. The brown bear/polar bear genetic lineage was estimated to have genetically diverged from the two black bears/sun bear lineage around ; the sun bear appears to have diverged from the two black bears between 6.26 and 5.09 mya. and 5.89–3.51 mya.Nuclear gene sequencing of bear species revealed that the sloth bear and the sun bear were the first Ursinae bears that radiated and are not included in the monophyletic Ursus group; moreover, all relationships between the bears were well resolved.
Characteristics
The sun bear is named so for its characteristic orange- to cream-coloured, crescent-like chest patch.It is the smallest of all bear species. It is stockily built, with large paws, strongly curved claws, small rounded ears and a short snout. The head-and-body length is between, and the shoulder height is nearly. Males tend to be larger than females by roughly 10-20%. Adults weigh. The snout is grey, silver, or orange. The fur is generally jet black, but can vary from grey to red. The hair is silky and fine, and is the shortest of all bear species, suiting its hot tropical habitat. The characteristic chest patch, typically U-shaped, but sometimes circular or spotlike, varies from orange or ochre-yellow to buff or cream, or even white. Some individuals lack this patch. Sun bears can expose the patch while standing on their hind feet as a threat display against enemies. Infants are greyish black with a pale brown or white snout and the chest patch is dirty white; the coat of older juveniles may be dark brown. The underfur is particularly thick and black in adults, while the guard hairs are lighter. Two whorls occur on the shoulders, from whence the hair radiates in all directions. It has a crest on the sides of the neck and a whorl in the centre of the breast patch. The edges of the paws are tan or brown, and the soles are fur-less, which possibly is an adaptation for climbing trees. The claws are sickle-shaped; the front claws are long and heavy. The tail is long. The sympatric Asian black bear has cream-coloured chest markings of a similar shape as those of sun bears and different claw markings.
During feeding, the sun bear can extend its exceptionally long tongue to extract insects and honey. The teeth are very large, especially the canines, and the bite force quotient is high relative to its body size for reasons not well understood; a possible explanation could be its frequent opening of tropical hardwood trees with its powerful jaws and claws in pursuit of insects, larvae, or honey. The bite force is high for its size: a sun bear weighing bites with a maximum force of 1907.3–2020.6 Newtons on the rear molar. The head is large, broad and heavy in proportion to the body, but the ears are proportionately smaller; the palate is wide in proportion to the skull. The overall unique morphology of this bear, such as its inward-turned front feet, flattened chest, and powerful fore limbs with large claws, indicates adaptations for extensive climbing.
Distribution and habitat
The sun bear is native to the tropical forests of Southeast Asia; its range is bound by northeastern India to the north and extends south to Bangladesh, Myanmar, Thailand, Cambodia, Laos, and Vietnam to Brunei, Indonesia, and Malaysia to the south. Its presence in China was confirmed in 2017 when it was sighted in Yingjiang County of Yunnan Province. It is extinct in Singapore.These bears dwell primarily in two main types of forests throughout their range - deciduous and seasonally evergreen forests to the north of the Isthmus of Kra, and non-seasonal evergreen forests in Indonesia and Malaysia. They are typically found at low altitudes, such as below in western Thailand and peninsular Malaysia, but this varies widely throughout the range; in India, larger numbers have been recorded at elevations up to than in low-lying areas, probably due to habitat loss at ground level. They occur in montane areas in northeast India, but may not extend farther north into the unfavourable and colder Himalayan region; their distribution might be restricted to the northwest due to competition with sloth bears. The sun bear is sympatric with the Asian black bear throughout the remaining areas in the mainland range featuring a mix of seasonal forest types, with monthly rainfall below for a long spell of 3–7 months. In mountainous areas, Asian black bears are more common than sun bears, probably due to scarcity of invertebrates on which to feed. The major habitats in southern Thailand and peninsular Malaysia are moist evergreen forests, with more or less unvarying climate and heavy rainfall throughout the year, and low-lying or montane dipterocarp forests. Mangroves may be inhabited, but usually only when they are close to preferred habitat types.
The sun bear tends to avoid heavily logged forests and areas close to human settlement. However, sun bears have been seen in farmlands, plantations and orchards, where they may be considered vermin. A survey in Lower Kinabatangan Segama Wetlands showed that sun bears were feared but were not common in oil palm plantations; Bornean bearded pigs, elephants and macaques were far more damaging to crops. Sun bears have been reported preying on poultry and livestock.
Fossil remains suggest its occurrence farther north during the Pleistocene; it may have occurred as far south as Java in the middle to Late Pleistocene. Fossils also known from the Middle Pleistocene of Thailand along with Stegodon, gaur, wild water buffalo, and other living and extinct mammals. Today, it is locally extinct in the majority of its erstwhile range, especially in Thailand; populations are declining in most of the range countries. It disappeared from Singapore during the 1800s and 1900s, possibly due to extensive deforestation. Sun bear populations appear to decrease in size northward from Sundaland, and numbers are especially low in the northern and western extremes of the range. This has possibly been the case since prehistoric times, and is not a result of human interference. The population density varies from in Khao Yai National Park to in the Harapan Rainforest in southern Sumatra.
Ecology and behaviour
The sun bear leads the most arboreal lifestyle among all bears.It is an excellent climber; it sunbathes or sleeps in trees above the ground. Bedding sites consist mainly of fallen hollow logs, but they also rest in standing trees with cavities, in cavities underneath fallen logs or tree roots, and in tree branches high above the ground. It is also an efficient swimmer.
The sun bear is solitary but is sometimes seen in pairs such as mothers and cubs. For a broad view of its surroundings or smell far-off objects, it stands on its hind feet; it tries to intimidate its enemies by displaying its chest patch if threatened. Its vocalisations includes grunts and snuffles while foraging for insects, and roars similar to those of a male orangutan during the breeding season; less commonly, it gives out short barks when surprised. It does not hibernate, possibly because food resources are available the whole year throughout the range.
The sun bear is mainly active during the day, although nocturnality might be more common in areas frequented by humans. It is noted for its intelligence; a captive bear observed sugar being stored in a cupboard locked by a key, and later used its claw to open the lock. A study published in 2019 described skillful mimicry of facial expressions by sun bears, with precision comparable to that seen in gorillas and humans.
The sun bear has home ranges of varying sizes in different areas, ranging from in Borneo and Peninsular Malaysia; and in Ulu Segama Forest Reserve in Sabah.
The tiger is its major predator; dholes and leopards have also been recorded preying on sun bears, but cases are relatively few. In one incident, a tiger-sun bear interaction resulted in a prolonged altercation and in the death of both animals. In another incident, a wild female sun bear was swallowed by a large reticulated python in East Kalimantan.
Sun bears usually do not attack humans unless provoked to do so, or if they are injured or with their cubs; their timid nature led these bears to be often tamed and kept as pets in the past. Sun bears are fierce when surprised in the forest.