Sun bear
The sun bear, Helarctos malayanus, wears a pale crescent across its chest, and that bright mark gave the animal its name. It is the smallest bear in the world. It lives in the tropical forests of Southeast Asia, far from the snowfields and salmon rivers most people picture when they think of bears. Almost everything about this animal runs against the usual bear story. What kind of body does a bear need to live among branches instead of on open ground? Why does it spend so much effort tearing into old timber and termite mounds? And why is a species so well matched to its forest losing that forest so quickly?
The genus name Helarctos joins two Greek words, hēlios, which relates to the sun, and arctos, which means bear. Across Malay and Indonesian the animal has a second name, beruang madu. It translates as honey bear, a nod to its appetite for honeycombs.
Science first met the animal through Stamford Raffles, who described a sun bear from Sumatra in 1821 and called it Ursus malayanus. Four years later Thomas Horsfield studied a sun bear from Borneo and gave the species a genus of its own, Helarctos.
Later names did not last. In 1901 Pierre Marie Heude described H. annamiticus from Annam, but it is now treated as a junior synonym of the Malayan form. In 1906 Richard Lydekker proposed a subspecies, H. m. wardii, from a single skull. He noticed its resemblance to a thick-coated skull from Tibet. That Tibetan specimen turned out to belong to an Asian black bear, Ursus thibetanus.
Today two subspecies are usually recognised. The Malayan sun bear, H. m. malayanus, occurs in mainland Southeast Asia, Bangladesh and Sumatra. The Bornean sun bear, H. m. euryspilus, lives only on Borneo and has a smaller skull. Genetic differences between them are obscure enough that some researchers call the species monotypic.
The bear's place among its relatives has been just as unsettled. Sun bears and sloth bears, Melursus ursinus, can produce fertile hybrids. That led to a proposal to fold Helarctos into Melursus, though studies disagreed on how close the two really are. Nuclear gene sequencing later showed that the sloth bear and the sun bear were the first of the Ursinae bears to branch off, and that neither belongs to the Ursus group. The brown bear and polar bear lineage had split away from the line leading to the two black bears and the sun bear even earlier. Within that line, one estimate puts the sun bear's split from the two black bears between 6.26 and 5.09 million years ago. Another gives 5.89-3.51 million years ago.
Head and body together measure 100 to 140 cm, and males tend to run roughly 10-20% larger than females. The coat is usually jet black, though it can shade from grey to red. The hair is silky and fine, and it is the shortest of any bear, a sensible choice for a hot climate. Underfur on adults is thick and black, while the guard hairs are lighter. Two whorls on the shoulders send the hair radiating outward, and a third whorl sits in the middle of the chest patch.
No two chest patches are alike. Most are U-shaped, but some are circular or reduced to a spot. Colours run from orange or ochre-yellow to buff, cream or even white, and some individuals have no patch at all. A threatened sun bear can rise onto its hind feet and show the patch to its enemy. Cubs start out greyish black with a pale brown or white snout and a dirty white patch. Older juveniles may be dark brown. Adults have a snout that is grey, silver or orange. The Asian black bear, which shares part of the range, has cream chest markings of a similar shape, though its claw markings differ.
The feet explain how this bear moves through trees. The front feet turn inward, the chest is flattened, and the forelimbs are powerful. The soles have no fur, and the paw edges are tan or brown. The claws are sickle-shaped, with the front ones long and heavy. The tail is a stub of only 3 to 7 cm. Together these features make the sun bear the most arboreal of all bears. It sunbathes or sleeps in trees 2 to 7 m above the ground. It also beds down in fallen hollow logs, in standing trees with cavities, under fallen logs or roots, and on high branches. It swims efficiently as well.
The head is large, broad and heavy, with proportionally small ears and a wide palate. The tongue is exceptionally long, which helps it reach insects and honey. A sun bear weighing 50 kg bites with a maximum force of 1907.3-2020.6 Newtons on the rear molar. That is high for its size, and the reason is not well understood. One possible explanation is its habit of breaking into tropical hardwood trees with jaws and claws.
One captive sun bear watched a keeper store sugar in a cupboard locked with a key. Later the bear used a claw to open that lock. The species is noted for this kind of intelligence. A study published in 2019 described skilful mimicry of facial expressions in sun bears, with a precision comparable to that seen in gorillas and humans.
Socially, the sun bear keeps to itself. It is solitary, though a mother and cub are sometimes seen together. To get a wider view or catch a faraway scent, it stands on its hind feet. Its voice has range. It grunts and snuffles while hunting insects, and it gives short barks when startled. During the breeding season it roars in a way that resembles a male orangutan.
Most activity happens in daylight, although bears living near people may be more nocturnal. There is no winter sleep for this animal, possibly because food stays available all year across its range. Home ranges vary by place. They span 7 to 27 km2 in Borneo and Peninsular Malaysia, and 8.7 to 20.9 km2 in the Ulu Segama Forest Reserve in Sabah.
Sun bears usually avoid trouble with people. They tend to attack only when provoked, injured or guarding cubs, though they can be fierce when surprised in the forest. That timid streak is why people in the past often tamed them and kept them as pets.
In the forests of Kalimantan, fruits from the Moraceae, Burseraceae and Myrtaceae families made up more than 50% of the sun bear's fruit diet. When fruit ran short, the bears turned more heavily to insects. Their menu is broad, taking in ants, bees, beetles, termites, seeds and many kinds of fruit. Birds and deer are eaten only occasionally.
Scat collected in the Ulu Segama Forest Reserve in Sabah shows how wide the range can be. It contained the remains of turtles and other reptiles, as well as figs and other fruits.
The bear's technique matters as much as its menu. For termites, it breaks a mound apart, holds the chunks in its front paws, and quickly licks and sucks out the contents. For honey and wild bees, it tears into hollow trees. It also eats the heart of coconut palms and crushes oil-rich seeds such as acorns. Oil palms are nutritious but cannot sustain a sun bear alone. Foraging itself happens mostly at night.
The bear gives something back to the forest it eats from. A study in Central Borneo found that sun bears play an important part in dispersing the seeds of Canarium pilosum.
A newborn sun bear weighs around 325 g, and it arrives deaf with its eyes closed. Births take place inside hollow tree cavities, and a litter usually holds one or two cubs. Eyes open at nearly 25 days, yet the cub remains blind until about 50 days. Hearing improves across those same first 50 days. For the first two months a cub cannot defecate without external stimulation. Once the cubs are strong enough, mothers keep them on buttress roots at the base of trees. There they stay until they can walk and climb properly.
Breeding is not tied to a season. The species is polyoestrous, oestrus lasts five to seven days, and births happen throughout the year. Sexual maturity arrives at two to four years of age. Reported gestation runs from 95 to 240 days. It tends to be longer in zoos in temperate climates, possibly because of delayed implantation or fertilisation. Mothers defend their young aggressively and keep them close for nearly the first three years. In captivity the lifespan is generally over 20 years, and one individual lived to 34.
Mothers have reason to be fierce. The tiger is the main predator of sun bears, while dholes and leopards have been recorded preying on them less often. In one incident a tiger and a sun bear fought a prolonged battle that killed both animals. In East Kalimantan, a large reticulated python swallowed a wild female sun bear.
On Borneo, pythons were found to strike at the bears' most vulnerable moments. They use the night, when a sun bear is asleep or nursing a cub. Elsewhere in Southeast Asia, a male leopard was photographed holding a sun bear cub by the throat.
In 2017 a sun bear was sighted in Yingjiang County in Yunnan Province, which confirmed that the species reaches China. Its range stretches from northeastern India through Bangladesh, Myanmar, Thailand, Cambodia, Laos and Vietnam. It continues south into Brunei, Indonesia and Malaysia. It has vanished from Singapore, disappearing during the 1800s and 1900s, possibly because of extensive deforestation.
North of the Isthmus of Kra, sun bears live in deciduous and seasonally evergreen forests. In Indonesia and Malaysia they favour non-seasonal evergreen forests. In southern Thailand and peninsular Malaysia the main habitats are moist evergreen forests with heavy rain all year, along with lowland and montane dipterocarp forests. Mangroves may hold bears too, but usually only near preferred forest.
Altitude varies widely. In western Thailand and peninsular Malaysia, bears are typically found below 1200 m. In India, more have been recorded at elevations up to 3000 m than in the lowlands, probably because lowland habitat has been lost. The colder Himalayan region may be unsuitable for them. Competition with sloth bears might limit the range to the northwest.
The sun bear shares much of its mainland range with the Asian black bear, in forests where monthly rainfall stays below 100 mm for 3 to 7 months. In the mountains the black bear is more common, probably because invertebrate food is scarce there.
Sun bears avoid heavily logged forest and land near settlements. Even so, they have turned up in farmlands, plantations and orchards, where they may be treated as vermin. A survey in the Lower Kinabatangan Segama Wetlands found that the bears were feared but uncommon in oil palm plantations. Bornean bearded pigs, elephants and macaques did far more damage to crops. Sun bears have also been reported preying on poultry and livestock.
Fossils show a longer story. In the Pleistocene the species lived farther north, and it may have reached as far south as Java in the middle to late part of that epoch. Middle Pleistocene fossils from Thailand sit alongside Stegodon, gaur and wild water buffalo. Numbers fall off northward from Sundaland, and they are especially low at the northern and western edges. This pattern may go back to prehistoric times and is not necessarily the result of human interference. Density ranges from 4.3 and 5.9 per km2 in Khao Yai National Park to 26 per km2 in the Harapan Rainforest in southern Sumatra.
The IUCN Bear Specialist Group estimates that sun bear numbers have dropped by 35% since the 1990s. Populations are especially low in Bangladesh and China. In Vietnam, the feared decline is 50-80% over the next 30 years. Forest cover in Southeast Asia shrank by almost 12% between 1990 and 2010. Agriculture, logging and forest fires drive much of that loss, and fragmentation is rising in Borneo, Sumatra and parts of the mainland. A 2007 study in East Borneo recorded severe loss of habitat and food after droughts and fires linked to El Niño.
Direct killing adds to the pressure. In 2018 and 2019, researchers surveyed 128 traditional Chinese medicine outlets in 24 locations across Sabah and Sarawak. Bear parts or derivatives were on sale in 25% of them, including gall bladders, and many likely came from local sun bears. In east Kalimantan, bears were shot or poisoned to protect coconut and snakefruit plantations. A TRAFFIC report in 2011 found that sun bears, Asian black bears and brown bears are specifically targeted for the bear bile trade. They are kept on bear farms in Laos, Vietnam and Myanmar.
Protected areas do not guarantee safety. In the Nam Ha National Protected Area in Laos, hunters have set snares aimed specifically at bears. A study in Nagaland, in northeastern India, found sun bears sparse in Fakim and Ntangki National Parks, with extensive illegal hunting for food and bear parts. Laws have done little to slow the trade, largely because of poor enforcement and the profits on offer.
On paper, the protection is strong. The sun bear is listed as vulnerable on the IUCN Red List and is included in CITES Appendix I. It is legally protected from hunting across its range, except in Sarawak and Cambodia. A 2014 report documented rampant poaching and trade in Sarawak, more than anywhere else in Malaysia, and urged stricter state laws.
Captive efforts run alongside. The Malayan sun bear has been part of an international captive-breeding program and an Association of Zoos and Aquariums Species Survival Plan since late 1994. In that same year, the Cologne Zoological Garden in Germany began keeping the European breed registry. The Bornean Sun Bear Conservation Centre, founded in 2008, cares for sun bears rescued from poor conditions in captivity. Several sanctuaries across Southeast Asia work against the illegal trade, and a conservation action plan was published in 2019.
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Common questions
Why is it called the sun bear?
It is named for the orange to cream-coloured crescent on its chest. The genus name Helarctos combines the Greek words for sun and bear.
Where do sun bears live?
They live in the tropical forests of Southeast Asia, from northeastern India and Bangladesh through the mainland to Brunei, Indonesia and Malaysia. A sighting in Yunnan Province, China, in 2017 confirmed their presence there.
What do sun bears eat?
They are omnivores that eat ants, bees, beetles, honey, termites, seeds and many fruits. Birds and deer are eaten only occasionally.
How big are sun bears?
Adults weigh 25-65 kg and stand nearly 70 cm at the shoulder. Males tend to be roughly 10-20% larger than females.
How many cubs does a sun bear have?
A litter usually has one or two cubs, which weigh around 325 g each at birth. They stay with their mother for nearly the first three years.
Are sun bears endangered?
The IUCN Red List lists the species as vulnerable. Its population is estimated to have fallen by 35% since the 1990s, mainly from deforestation and hunting for the wildlife trade.
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