Sun bear

Etymology

The sun bear is named so for its characteristic orange to cream coloured, crescent-like chest patch. The generic name Helarctos comes from two Greek words: ήλιος (hēlios, 'related to the sun') and αρκτος (arctos, 'bear'). Another name is 'honey bear' (beruang madu in Malay), in reference to its habit of feeding on honey from honeycombs. 'Honey bear' can also refer to the kinkajou.

Taxonomy and phylogeny

The sun bear was first described in 1821 from Sumatra by British statesman Sir Thomas Stamford Bingley Raffles, who gave it the scientific name Ursus malayanus. In 1825, American naturalist Thomas Horsfield placed the species in a genus of its own, Helarctos. Two subspecies have been proposed on the basis of variations in size:

• Malayan sun bear (H. m. malayanus) Raffles, 1821: Occurs on the Asian mainland and Sumatra.
• Bornean sun bear (H. m. euryspilus) Horsfield, 1825: Occurs only in Borneo. Its skull is smaller than that of the Malayan sun bear.

H. anmamiticus, described by Pierre Marie Heude in 1901 from Annam, is not considered a distinct species, but is subordinated (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; however the Tibetan specimen was later found to be an Asian black bear (Ursus thibetanus). Genetic differences between the two subspecies are obscure. In 2002, Christopher Fitzgerald and Paul Krausman (of the American Society of Mammalogists) considered the sun bear monotypic.

The phylogenetic relationships among ursid species have remained ambiguous over the years. Noting the production of fertile hybrids between sun bears and sloth bears (Melursus ursinus), it was proposed that Helarctos be treated as a synonym of Melursus. However, studies differed on whether the two species were closely related. A 2007 phylogenetic study gives the relationships of the sun bear with other species of Ursidae based on complete mitochondrial DNA sequences as shown in the cladogram below. The brown bear/polar bear lineage was estimated to have diverged from the two black bears/sun bear lineage around 5.54 to 6.72 million years ago; the sun bear appears to have diverged from the two black bears 5.09–6.26 mya. However, the phylogenetic tree constructed by a nuclear gene sequencing analysis in 2008 swapped the positions of the sun bear and the sloth bear obtained in the previous study; moreover, all relationships other these two positions were well resolved. The researchers noted the need for further study to fully resolve the relationship.

Characteristics

The sun bear 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 100 and 140 centimetres (39 and 55 inches), and the shoulder height is nearly 70 cm (28 in). Adults weigh 25–65 kilograms (55–143 pounds). 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 their 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 may even lack the patch. Sun bears can expose the patch while standing on their hindfeet 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 whirls occur on the shoulders, from whence the hair radiates in all directions. A crest is seen on the sides of the neck and a whorl occurs 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 3–7 cm (1–3 in) long. The sympatric Asian black bear has cream-coloured chest markings of a similar shape as those of sun bears; a 2008 study discussed differences in claw markings of both bears as a means of identification.

During feeding, the sun bear can extend its exceptionally long tongue by 20–25 cm (8–10 in) to extract insects and honey. The teeth are very large, especially the canines, and the bite force 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 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—inward-turned front feet, flattened chest, powerful forelimbs with large claws—indicates adaptations for extensive climbing.

Ecology and behaviour

Sun bears lead the most arboreal (tree-living) lifestyle among all bears. They are mainly active during the day, though nocturnality might be more common in areas frequented by humans. The sun bear is an excellent climber; it sunbathes or sleeps in trees 2 to 7 metres (7 to 23 feet) 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. Sun bears are noted for their intelligence; a captive bear observed sugar being stored in a cupboard then locked by a key, and later used its own 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 some primates (such as gorillas and humans).

Sun bears are shy and reclusive animals, and 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 tamed often and kept as pets in the past. They are typically solitary but are sometimes seen in pairs (such as mothers and cubs). Sun bears stand on their hindfeet for a broader view of their surroundings or smell far-off objects; they try to intimidate their enemies by displaying the chest patch if threatened. Vocalisations include grunts and snuffles while foraging for insects, and roars similar to those of a male orangutan during the breeding season; less commonly they may give out short barks (like a rhinoceros) when they are surprised. Sun bears do not seem to hibernate, possibly because food resources are available the whole year throughout the range. They occupy home ranges of varying sizes in different areas, ranging from 7 to 27 square kilometres (2 ¹⁄₂ to 10 ¹⁄₂ square miles) in Borneo and peninsular Malaysia; a study in Ulu Segama Forest Reserve in Sabah (Malaysia) gave the sizes of ranges as 8.7–20.9 km² (3 ³⁄₈–8 ¹⁄₁₆ sq mi). Tigers are major predators; dholes and leopards have also been recorded preying on sun bears but cases are relatively fewer. A wild female sun bear was swallowed by a large reticulated python in East Kalimantan.

Diet

Sun bears are omnivores and feed on a broad variety of items such as ants, bees, beetles, honey, termites and plant material such as seeds and several kinds of fruits. Vertebrates such as birds, deer, eggs and reptiles may be eaten occasionally. They forage mostly at night. Sun bears tear open hollow trees with their long, sharp claws and teeth in search of wild bees and honey. They also break termite mounds and quickly lick and suck the contents, holding pieces of the broken mound with their front paws. They consume figs in large amounts and eat them whole. In a study in the forests of Kalimantan, fruits of Moraceae, Burseraceae and Myrtaceae species made up more than 50% of the fruit diet; in times of fruit scarcity, sun bears switched to a more insectivorous diet. A study in Central Borneo revealed that sun bears play an important role in the seed dispersal of Canarium pilosum (a tree in the family Burseraceae). Sun bears eat the centre of coconut palms, and crush oil-rich seeds such as acorns. Oil palms are nutritious but not enough for subsistence.

Reproduction

Sun bears are polyoestrous; births occur throughout the year. Oestrus lasts five to seven days. Sun bears become sexually mature at two to four years of age. Reported lengths for pregnancies vary from 95 to 240 days; pregnancy tends to be longer in zoos in temperate climate possibly due to delay in implantation or fertilisation. Births occur inside hollow tree cavities. A litter typically comprises one or two cubs weighing around 325 grams (11 ¹⁄₂ ounces) each. Cubs are born deaf with eyes closed. The eyes open at nearly 25 days but they remain blind till 50 days after birth; the sense of hearing improves over the first 50 days. Cubs younger than two months are dependent on external simulation for defecation. Cubs are kept on buttress roots at the base of trees until they learn how to walk and climb properly. Mothers protect their cubs aggressively. Offspring remain with their mother for nearly the first three years of their lives. Lifespan in captivity is generally over 20 years; one individual lived for nearly 31 years.

Distribution and habitat

Sun bears are found in the tropical forests of Southeast Asia; the range is bound by northeastern India to the north and extends south to southeast through Bangladesh, Cambodia, Myanmar, Laos, Thailand and Vietnam in mainland Asia to Brunei, Indonesia and Malaysia to the south. Their presence in China was confirmed after years in 2017 when they were sighted in Yingjiang County of Yunnan Province (China). Sun bears are 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 1,200 m (3,900 ft) in western Thailand and peninsular Malaysia. However, this varies widely throughout the range; in India larger numbers have been recorded at an elevation of up to 3,000 m (9,800 ft) 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 100 mm (4 in) for a long spell of three to seven months. In mountainous areas, Asian black bears are more common than sun bears, probably due to scarcity of invertebrates to feed on. The major habitats in southern Thailand and peninsular Malaysia are moist evergreen forests, with more or less non-varying 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.

Sun bears tend to avoid heavily logged forests and areas close to human settlement. However they have been seen in farmlands, plantations and orchards, where they may be considered vermin. A survey in Lower Kinabatagan (Malaysia) published in 2017 showed that sun bears were feared but were not common in oil palm plantations; bearded pigs, elephants and macaques were far more damaging to crops. Sun bears have been reported preying on poultry and livestock.

In the past sun bears ranged from Borneo and Sumatra in the north and Assam in the northwest to northeastern Vietnam in the northeast and at least Yunnan Province (China) in the east. Fossil remains suggest their occurrence farther north in the Pleistocene; sun bears may have occurred as far south as Java (Indonesia) in the middle to late Pleistocene. Today they have been eliminated from majority of their erstwhile range, especially in Thailand; populations are declining in most of the range countries. Sun bears disappeared from Singapore, possibly due to extensive deforestation, during the 1800s and 1900s. 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. Population densities vary from 4.3 and 5.9 individuals per 100 km² (39 sq mi) in Khao Yai National Park (Thailand) to 26 individuals per 100 km² (39 sq mi) in the Harapan Rainforest in southern Sumatra.

Threats

According to the IUCN Bear Specialist Group, sun bear populations have fallen by an estimated 35% in the last three decades. Numbers are especially low in Bangladesh and China, and populations in Vietnam are feared to decline severely by 50–80% in the next 30 years. Habitat fragmentation is on the rise particularly in Borneo, Sumatra and some areas of the mainland range. Heavy deforestation (due to agriculture, logging and forest fires) and hunting for wildlife trade are severe threats throughout the range; human-bear conflicts are a relatively minor threat. Compared to other continents, southeastern Asia has undergone severe depletion in forest cover over the past few decades (by almost 12% between 1990 and 2010); this has resulted in substantial habitat loss for forest-dependent species such as sun bears. A 2007 study in East Borneo recorded severe loss of habitat and food resources due to droughts and forest fires brought about by the El Niño.

During surveys in Kalimantan between 1994 and 1997, interviewees admitted to hunting sun bears and indicated that sun bear meat is eaten by indigenous people in several areas in Kalimantan. There was evidence of pet trade and sale of sun bear parts such as gall bladders in traditional Chinese medicine shops in Sabah and Sarawak. Sun bears were killed by shooting or administering poison to protect coconut and snakefruit plantations in East Kalimantan. A report published by TRAFFIC in 2011 showed that sun bears, along with Asian black bears and brown bears, are specifically targeted for the bear bile trade in southeastern Asia, and are kept in bear farms in Laos, Vietnam, and Myanmar. Poaching is common in several countries in the region. Hunting pressure is rising even in some protected areas; in the Nam Ha National Protected Area in Laos, hunter snares have been found that specifically target bears. A study in Nagaland (northeastern India) recorded a sparse distribution of sun bears in the Fakim and Ntangki National Parks, and reported extensive illegal hunting for food and trade in bear parts. Protective laws have shown little success in controlling these threats, especially due to poor execution and high potential for gains by the trade.

Conservation measures

The sun bear is listed as Vulnerable on the IUCN Red List, and is included in CITES Appendix I. With the exception of Sarawak (Malaysia) and Cambodia, the sun bear is legally protected from hunting in its whole range. A 2014 report documented rampant poaching and trade in sun bear parts in Sarawak, more than anywhere else in Malaysia; the researchers recommended stricter legislations in the state to protect local sun bears.

The Bornean Sun Bear Conservation Centre, founded by Wong Siew Te in Sabah (Malaysia) in 2008, aims to work for the welfare of sun bears rescued from poor conditions in captivity and spread awareness about their conservation. The Malayan sun bears are part of an international captive-breeding program and a Species Survival Plan under the Association of Zoos and Aquariums since late 1994. Since that same year, the European breed registry for sun bears is kept in the Cologne Zoological Garden, Germany.