Body length: 100 to 150 cm; smallest of all the bear species
Average weight: 30 to 90 kg
Lifespan: Unknown in the wild; 36 years in captivity [1]
Distribution: Southeast Asia
Status: Vulnerable (IUCN), Appendix I (CITES)
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Ursidae
Genus: Helarctos
Species: Helarctoc malayanus
English: Sun bear, Malayan sun bear
French: Ours malais, Ours des cocotiers
Spanish: Oso de Sol, Oso Malayo
Indonesian: Beruang madu (honey bear)
Helarctos malayanus malayanus (mainland SE Asia and Sumatra)
Helarctos malayanus eurispylus (Borneo; Raffles, 1821)
Adult sun bears weigh between 30 and 90 kg, with males being about one third larger than females. The Bornean sub-species H. m. eurispylus is on the lower end of this spectrum, weighing around 40% less than its mainland and Sumatran counterpart. While sun bears are the smallest of the eight living bear species, they have many disproportionately large physical features, which give them phenomenal strength relative to their body size. The skull is wider than for other bear species, with a short snout [2]. The canines are large and also wide in cross-section. The structure of the jaw and surrounding muscles and teeth give sun bears a powerful bite force for their size [3]. Sun bears also have the longest tongue of any bear species, reaching to up to 46 cm. Their claws are long and sharp, and they’re comparable in size to the claws of a brown bear (Ursus arctos). Their paws are large with naked soles, and the front legs are bowed with the paws angled inwards [4]. Their ears are small and round. Sun bears often have abundant skin on their head and neck, creating rolls of fat around the forehead. Their coat is shiny black, short, and sleek. (In very rare cases, they may be reddish-brown, possibly as a result of malnutrition.) The muzzle is covered with beige hairs that often reach to above the eyes. Sun bears usually have a bright chest patch that is deep yellow to orange in colour although varying in size, shape, and colour, but it may sometimes be completely absent. The chest patch stays the same for the life of a bear and is unique to the individual.
| Body length | Tail length | Body mass |
|---|---|---|
| 100 - 150a | 3 - 7a | 30 - 90a |
Length measurements in cm and mass in kg.
Sexual dimorphism: Males are around one-third larger than females.
Sun bears are well adapted to living in tropical forests. They are expert climbers; their large naked paws, long curved claws, and small muscular bodies allow them to spend many hours clinging to the side of trees while breaking into bees’ nests. Sun bears have large feet and massive claws that help them dig into the ground and break into dead wood to search for food. Their relatively small body size and adaptable diet may allow sun bears some resilience in times of extreme food scarcity. They are mostly diurnal and crepuscular, but they can be active at night, adjusting their activity patterns to avoid humans [6–9]. When not foraging, sun bears like to sleep on fallen logs, on the branches of tall trees, or hidden in the crevices of hollow trunks. Their choice of sleeping site and body position while resting is important in helping sun bears stay cool in a hot climate [10].
Sun bears are normally solitary, except when with cubs, although they’re sometimes seen in pairs. Reportedly, several bears may be found at the same site when feeding from large fruiting trees (personal communication, G. Fredriksson and S.T. Wong). Sun bear cubs have been observed at any month of the year in the wild in Kalimantan (Indonesian Borneo), and studies of zoo-kept bears suggest that sun bears can breed at any time of the year [11, 12]. Pregnancy lasts between 96 and 110 days, usually producing a single cub. Sun bears give birth within the cavities of hollow trees and are not known to hibernate [11–14]. Although sun bears and Asiatic black bears overlap in many areas only one known sun bear – Asiatic black bear hybrid has been documented in Cambodia [15].
| Gestation (days) | Maximum litter size | Adult lifespan (years) | Maximum age (years) |
|---|---|---|---|
| 96 - 110 | 2a | Unknownb | 36 (captivity) |
a usually 1; [5]. b probably between 10 and 24 years in the wild, like other bear species.
Mating system: Polygynous
Breeding interval: Polyestrous
Breeding season: All year
Like many tropical species, sun bear populations are difficult to monitor because they live in densely forested areas (note that they can live in some partially forested areas), are very secretive, and avoid humans. Their presence remains undocumented for large parts of their potential range, especially in northwestern Myanmar and parts of the eastern mainland of Southeast Asia. In short, we have no reliable population estimates for sun bears.
To monitor populations, scientists use bear sign transects, camera traps, and rural interview surveys. Bear sign surveys collect signs of bears, left by climbing and foraging, within small fixed size survey blocks (i.e., transects). The number of bear signs within a transect is thought to be relative (not absolute) to the actual number of bears within an area (i.e., more sign = higher bear density). Sign transects are useful for monitoring local changes in bear populations over time.
Sign surveys in mainland Southeast Asia yielded the highest sign densities in areas of northern Thailand and Lao PDR (Thung Yai Wildlife Sanctuary, Thailand; Nam Et Phou Louey National Protected Area, Lao PDR) and relatively low sign densities in southern mainland Asia, Cambodia, Vietnam, and southern Lao PDR [16].
Camera trap studies have generated information on population density and trend in a few sites in Thailand and Sumatra. In Thailand camera trap catch rates of sun bears indicated that bear populations declined during 1999–2007 in Kao Yai National Park, while remaining stable over the same period in Kuiburi National Park and Thung Yai Naresuan Wildlife Sanctuary [17, 18]. A mark-recapture study was conducted in Kao Yai National Park in 2010 that individually identified bears by their chest marks via cameras set in groups of three with a bait hanging in the middle. This study gave estimated population densities of 4.3 (95% CI 1.6– 11.6) and 5.9 (95% CI 2.3–15.4) bears per 100 km2 in areas of the park [19]. A different technique was used in southern Sumatra, which is an aseasonal ecosystem in which sun bears do not co-exist with Asiatic black bears (see Habitat section). Researchers did not individually identify bears, and they estimated a much higher density of sun bears, equaling 26 bears per 100 km2 (D. Lee, unpublished data). Further research is needed to determine whether these results are comparable and whether sun bears densities really are lower in the mainland (where they overlap with Asiatic black bears) compared with the insular region (where they do not).
Interview surveys in Thailand, Lao PDR, and Vietnam have recorded widespread declines of sun bears. In Thung Yai Naresuan Wildlife Sanctuary, Thailand, locals reported that hunting had caused sun bear numbers to decline by more than 40% within a 20-year period between 1984 and 2004 [20]. In Lao PDR and Vietnam interview surveys documented widespread declines of sun bear numbers with local extirpations in some areas, caused by hunting [16, 21]. The World Conservation Union (IUCN) Bear Specialist Group (BSG) Sun Bear Expert Team interviewed experts from 10 out of 11 sun bear range countries excluding Brunei. Results indicated a range-wide decline of more than 30% in the last 30 years and that sun bears in Bangladesh and China are close to local extinction [22].
Global sun bear range extends across much of Southeast Asia, northward to Yunnan Province, China, and southwards throughout the islands of Borneo and Sumatra. In historic times, this whole region would have been largely under contiguous forest cover. Sun bear populations are geographically limited in the northeast by the Red River in Vietnam and in the northwest, in Assam, India, by the Brahmaputra River [23–25]. Some unconfirmed records suggest that sun bear range may have once extended further north, into China’s Sichuan Province and Eastern Tibet [26]. Range is presumably limited there by the colder climates of the Himalayan sub-region and by competition with the sloth bear (Melurus ursinus) [27]. Fossil records from the Pleistocene period have been found much farther north in China and further south in Java [23].
In the present day, sun bear distribution is patchy and much reduced, with the range contracting as a result of human activities. Sun bears have disappeared from many areas where forest habitat has disappeared, with populations fairing the worst at the edges of range in China, northeast India, Bangladesh, and Vietnam. Sun bears are extirpated in Singapore [28–31]. They are thought to be more abundant in the southernmost parts of their range, in insular Southeast Asia, and occur in increasingly lower densities further north [27]. Naturally lower densities throughout all of sun bear range north of the Isthmus of Kra, in southern Thailand, may be influenced by co-existence with the Asiatic black bear [27].
Green = Extant, Yellow = Possibly Extant. Map data courtesy of IUCN Redlist.
Sun bear range can be divided into two ecologically distinct regions: mainland Southeast Asia and insular Southeast Asia. A major shift in climate, forest type, and faunal composition occurs at the Isthmus of Kra, in southern Thailand. North of the Isthmus of Kra, sun bear habitat is seasonal evergreen forest, which has a cold dry season and a hot wet season. These forest types are a mixture of semi-evergreen, various deciduous, dry dipterocarp, and montane evergreen [32, 33]. Here, sun bears co-exist with Asiatic black bears, and the species compete for resources [34, 35]. South of the Isthmus of Kra, where Asiatic black bears do not occur, the climate is aseasonal, tropical, and generally constant across the insular region, which receives high annual rainfall that is relatively evenly distributed throughout the year. Sun bear habitat in the insular region is made up of a mixture of hill dipterocarp forest, peat swamp, freshwater swamp, limestone/karst hills, lower- to sub-montane forest, and mangrove swamps [36–40].
Sun bears prefer to live in areas of undisturbed forest with plentiful food resources. They tend to avoid areas of high human activity where they suffer higher mortality rates [8, 36, 37, 40–43]. Sun bears use a wide range of elevations, preferring productive lowland areas in much of mainland Southeast Asia and peninsular Malaysia, but they are also found at higher elevations [25, 27, 31, 34, 43–46]. While they avoid humans, they do use habitats disturbed by humans, such as logged forests, and can venture into human use areas close to the forest edge [7, 42, 47]. Sun bears venture into plantations adjacent to forest, agricultural lands, and orchards to forage on certain crops [6, 8, 48–52]. In Brunei, where poaching of sun bears is seemingly low, sun bears have been recorded near urban areas, in city parks, and crossing major highways [53]. While human crops may be an important food source for them in times of food scarcity, sun bears are forest dependent, feeding only from human crops that are situated near natural forest [6, 38, 48].
Radio tracking studies in Peninsular Malaysia and Borneo recorded female home ranges of 5.8–8.1 km2 [9] and male home ranges of 4–49.7 km2 [6, 7] whereas daily movements ranged from 1.5 to 4.6 km [9]. Sun bear home range is similar to that recorded for sloth bears in Nepal and Sri Lanka [54, 55]. Sun bear home range sizes north of the Isthmus of Kra are unknown.
| Region | Males | Females |
|---|---|---|
| Tabin, Sabah, Borneo | 4 – 5.1 | 1.2 – 1.3 |
| Danum, Sabah, Borneo | 14.8 (+/– 6.1) | N/A |
| Sungai Wain, East Kalimantan, Borneo | N/A | 5.8 – 8.1 |
| Krau, Peninsular Malaysia | 17.4 – 49.7 | N/A |
Sources: [6, 7, 9, 48].
Sun bears are generalist omnivores. The Indonesian name for sun bears translates to “honey bear.” Their diet includes honey and insects such as bees, bee larvae, termites, ants, and beetle larvae. Their long, sharp claws enable them to dig easily into the ground and break into rotting logs [37] and to cling to trees for long periods of time, ripping open tree trunks to access the nests and honey of stingless bees. They use their long tongues to extract the insects and larvae from crevices.
Sun bears are also frugivorous, feeding on a large variety of fruits. Figs (Ficus spp.) are an especially important nutritional resource and available throughout the year [32, 37, 38, 41]. Sun bears also feed on growth shoots of palms and occasionally eat flowers [32]. In Bornean forests, fruits of plants in the families Moraceae (fig/ mulberry), Burseraceae (torchwood), and Myrtaceae (myrtle) make up more than 50% of sun bears’ fruit diet [32] whereas in western Thailand fruits of plants in the Lauraceae (laurel), Fagaceae (beech), Fabaceae (legume/pea/bean), Lamiaceae (mint), and Sapindaceae (soapberry) are the most commonly consumed [27, 34].
Sun bears living near forest edges are also known to feed on plantations of sugar palm, oil palm, and pineapple; crops of sweet corn, cucumber, pumpkin, sesame, and maize; orchards of coconut, apple, durian, banana, jackfruit, and snake fruit; and, very rarely, livestock such as goats and chickens [8, 56].
| Food habit | Main food items |
|---|---|
| Omnivorous (30% plants/70% animals) | Termites, ants, beetle larvae, bee larvae, honey, palms, flowers, figs (Ficus spp.), and fruits from plants in the families Moraceae, Burseraceae, Myrtaceae, Lauraceae, Fagaceae, Fabaceae, Lamiaceae, and Sapindaceae |
Dietary proportions may vary by region and by the time of year. Animal products are largely invertebrates [32, 37, 38, 41].
The IUCN Red List of Threatened Species classifies sun bears as Vulnerable, estimating that populations have declined globally by more than 30% in the last 30 years [22]. Domestic and international laws protect sun bears from hunting and trade in most places [57]. Sun bears have been listed as Appendix I by the Convention on Trade in Endangered Species (CITES) since 1979, which prohibits cross-border trade.
Once known as the world’s least-known bear, slow advances in scientific knowledge of sun bears is strengthening understanding of their population status. Sun bears would benefit from further focused scientific studies, especially in poorly represented regions (such as northeastern Myanmar) to document presence, determine the status of populations, and identify management/conservation priorities. Monitoring populations by way of sign density on transects is one of the most practical field methods available for surveying bears over large areas. Camera trap surveys are another useful monitoring tool, and bycatch data from studies of other species may be a valuable source of information. Interviews within rural human communities living close to bear habitat are helpful when collecting data in the forest is not possible as in many areas of Cambodia, Lao PDR, and Vietnam where the prevalence of unexploded ordnance in historic war zones and proximity to unstable international borders make field conditions too dangerous for field research.
Local and international capacity to protect sun bears is limited by lack of political will and administrative capacity [58]. With the current rates of deforestation and range fragmentation, it may be impossible to restore range-wide sun bear population connectivity in the future. Future management actions might involve active management of genetically isolated populations.
Threats to sun bears include habitat loss, alteration, and fragmentation; illegal hunting and commercial trade; and mortalities related to human–bear conflict. The contribution of these threats to population declines is difficult to measure and likely varies by region. Loss of habitat can be somewhat quantified by loss of tree cover within sun bear range, which has undergone a higher rate of forest loss in the last 30 years than any other region [59]. In insular Southeast Asia most forest has been lost to plantations (e.g., oil palm, rubber) and unsustainable and/or illegal logging [39, 40, 60]. Protected areas are not exempt: in Indonesia 40% of the forest lost during 2000–2012 occurred within national parks and protected forests [61]. Likewise, in Kalimantan, Borneo, 56% of protected lowland forests were cleared between 1985 and 2001 [62]. Human-caused fires throughout the insular region are also diminishing habitat quality for sun bears, especially in Malaysia and Indonesia. Fires are most extensive during El Niño-related droughts.
Forest loss leads to fragmentation of sun bear range and has likely caused the isolation of many populations. Isolated populations may be prone to higher rates of mortality because of a variety of inter-related factors that reduce access to resources and increase risk of mortality [63, 64]. Bear populations at very low densities or within small patches of habitat have to rely on the ability to move between patches for access to food and mates [63, 65], and sun bear tolerance to moving through degraded habitat is poorly understood. The bears’ ability to travel long distances may be extremely important during periods of low food availability when they may have to travel further to meet food requirements, as can happen in insular Southeast Asia during periods of prolonged drought related to El Niño weather events [32, 56].
Illegal hunting and commercial trade in sun bears and their parts causes an unknown but potentially severe impact on sun bear populations [58, 66, 67]. Commercial poaching of sun bears is considered a moderate to major threat in all range countries except Brunei [22, 53]. Recent country-level studies cite poaching as a major driver of population declines in Thailand, Northeast India, Lao PDR, and Vietnam [31, 68, 69, Steinmetz and Ngopraserth, unpublished data]. Poaching with wire snares is common throughout most of sun bear range. In northeastern Lao PDR, hunters use a snaring method that specifically targets bears and threatens to wipe out local populations. Farmers affected by wildlife crop damage set snares around the perimeter of crop fields and in some instances catch bears [70]. In Peninsular Malaysia camera traps frequently recorded bears with missing paws, and in one of the few radio collaring studies focusing on sun bears three out of five captured bears had missing paws [6]. Enforcement of domestic and international wildlife laws is severely lacking in most areas and fails to deter illegal bear trade [58, 67]. The value of bile and paws on the illegal wildlife market has increased steadily over the past two decades [71]. In areas of high poverty, hunters stand to earn far more than their annual salary gained from agricultural yield by trading bears and their parts [50].
Aside from commercial trade, motivations for killing sun bears include protecting crops and livestock [7, 8, 50], subsistence use, consumption of wild meat [72], and fear of bears near villages. Bears live close to humans throughout much of their range, and human-caused habitat fragmentation typically means humans have increased accessibility to sun bear habitat, leading to increased hunting as well as further human development (i.e., roads, hunting, agriculture, logging) and a higher likelihood of bears coming into conflict with humans [73]. Incidences of sun bears attacking humans are low and usually happen as an act of self-defense—under normal circumstances the bears choose to avoid humans.
Lorraine Scotson – PhD, University of Minnesota
Gabriella Fredriksson – PhD, University of Amsterdam
IUCN Redlist: https://www.iucnredlist.org/species/9760/123798233
Free the Bears: https://freethebears.org/
Bornean Sun Bear Conservation Center: http://www.bsbcc.org.my/
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