Sun bear

The sun bear (Helarctos malayanus) is a species in the family Ursidae occurring in the tropical forests of Southeast Asia. It is the smallest bear, standing nearly 70 centimetres (28 inches) at the shoulder and weighing 25–65 kilograms (55–143 pounds). It is stockily built, with large paws, strongly curved claws, small rounded ears and a short snout. The fur is generally jet-black, but can vary from grey to red. Sun bears get their name from the characteristic orange to cream coloured chest patch. Its unique morphology—inward-turned front feet, flattened chest, powerful forelimbs with large claws—suggests adaptations for climbing.

The most arboreal (tree-living) of all bears, the sun bear is an excellent climber and sunbathes or sleeps in trees 2 to 7 metres (7 to 23 feet) above the ground. It is mainly active during the day, though nocturnality might be more common in areas frequented by humans. Sun bears tend to remain solitary but sometimes occur in pairs (such as a mother and her cub). They do not seem to hibernate, possibly because food resources are available the whole year throughout the range. Being omnivores, sun bears have a broad diet including 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. They breed 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 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. These bears are threatened by heavy deforestation and illegal hunting 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% over the past three decades. The IUCN has listed this species as vulnerable.

The sun bear is named so for its characteristic orange to cream coloured, crescent-like chest patch.[4][5] The generic name Helarctos comes from two Greek words: ήλιος (hēlios, 'related to the sun') and αρκτος (arctos, 'bear').[3][6] Another name is 'honey bear' (beruang madu in Malay), in reference to its habit of feeding on honey from honeycombs.[7][8] 'Honey bear' can also refer to the kinkajou.[9]

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.[10] In 1825, American naturalist Thomas Horsfield placed the species in a genus of its own, Helarctos.[11] Two subspecies have been proposed on the basis of variations in size:[12][13]

  • Malayan sun bear (H. m. malayanus) Raffles, 1821: Occurs on the Asian mainland and Sumatra.[14]
  • Bornean sun bear (H. m. euryspilus) Horsfield, 1825: Occurs only in Borneo.[15] Its skull is smaller than that of the Malayan sun bear.[8]

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.[14] 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).[16][17] Genetic differences between the two subspecies are obscure.[18] In 2002, Christopher Fitzgerald and Paul Krausman (of the American Society of Mammalogists) considered the sun bear monotypic.[3]

The phylogenetic relationships among ursid species have remained ambiguous over the years.[19] 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.[20][21] However, studies differed on whether the two species were closely related.[22][23] 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.[24] 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.[25]

Ursidae
Ursinae

Polar bear (U. maritimus) Lossy-page1-2518px-Ursus maritimus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

Brown bear (Ursus arctos) Ursus arctos - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

American black bear (U. americanus) Ursus americanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

Asian black bear (U. thibetanus) Ursus thibetanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam -(white background).jpg

Sun bear (Helarctos malayanus) Ursus malayanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

Sloth bear (Melursus ursinus) Tremarctos ornatus 1824 (flipped).jpg

Spectacled bear (Tremarctos ornatus) Spectacled bear (1829).jpg

Giant panda (Ailuropoda melanoleuca) Recherches pour servir à l'histoire naturelle des mammifères (Pl. 50) (white background).jpg

Skull, showing short snout.

The sun bear is the smallest of all bear species.[3][8][26] 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.[3][27] 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.[3][26] Sun bears can expose the patch while standing on their hindfeet as a threat display against enemies.[8][3] 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.[3] 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.[28] The edges of the paws are tan or brown, and the soles are fur-less, which possibly is an adaptation for climbing trees.[3][26][29] The claws are sickle-shaped; the front claws are long and heavy. The tail is 3–7 cm (1–3 in) long.[30] 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.[4][31]

During feeding, the sun bear can extend its exceptionally long tongue by 20–25 cm (8–10 in) to extract insects and honey.[27][32] 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.[33] 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.[4][26] The overall unique morphology of this bear—inward-turned front feet, flattened chest, powerful forelimbs with large claws—indicates adaptations for extensive climbing.[26]

Sun bears are among the most arboreal of bears.

Sun bears lead the most arboreal (tree-living) lifestyle among all bears.[3][34] They are mainly active during the day, though nocturnality might be more common in areas frequented by humans.[8][35][36] 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.[8][37][38] It is also an efficient swimmer.[4] 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.[37] 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).[39][40]

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.[3][27] They are typically solitary but are sometimes seen in pairs (such as mothers and cubs).[8][37] 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.[3][8] 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.[3][8] Sun bears do not seem to hibernate, possibly because food resources are available the whole year throughout the range.[1] They occupy home ranges of varying sizes in different areas, ranging from 7 to 27 square kilometres (2 12 to 10 12 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 (3 388 116 sq mi).[1][41] Tigers are major predators; dholes and leopards have also been recorded preying on sun bears but cases are relatively fewer.[42] A wild female sun bear was swallowed by a large reticulated python in East Kalimantan.[43]

Diet

Sun bears have a broad omnivorous diet including plants.

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.[8][44] Vertebrates such as birds, deer, eggs and reptiles may be eaten occasionally.[45][46] 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.[8][37] They consume figs in large amounts and eat them whole.[47] 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.[48] 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).[49] Sun bears eat the centre of coconut palms, and crush oil-rich seeds such as acorns.[37] Oil palms are nutritious but not enough for subsistence.[50]

Reproduction

Sun bears are polyoestrous; births occur throughout the year.[51][52] Oestrus lasts five to seven days. Sun bears become sexually mature at two to four years of age.[3][34] 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.[34] Births occur inside hollow tree cavities.[1] A litter typically comprises one or two cubs weighing around 325 grams (11 12 ounces) each.[37] 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.[3][37]

Sun bear in the Bornean Sun Bear Conservation Centre (Malaysia)

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.[1][3] Their presence in China was confirmed after years in 2017 when they were sighted in Yingjiang County of Yunnan Province (China).[53] Sun bears are extinct in Singapore.[1]

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.[1][3]

Sun bears tend to avoid heavily logged forests and areas close to human settlement.[54][55][56] However they have been seen in farmlands, plantations and orchards, where they may be considered vermin.[57][58] 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.[50] Sun bears have been reported preying on poultry and livestock.[59]

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.[1][26] 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.[1] 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.[1][60]

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.[1][26] 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.[61][62] 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.[63]

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.[64] 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.[65] 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.[66] 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.[67] Protective laws have shown little success in controlling these threats, especially due to poor execution and high potential for gains by the trade.[65][68]

The sun bear is listed as Vulnerable on the IUCN Red List, and is included in CITES Appendix I.[1] 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.[69]

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.[70] 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.[71] Since that same year, the European breed registry for sun bears is kept in the Cologne Zoological Garden, Germany.[72]

  1. ^ a b c d e f g h i j k l m Scotson, L.; Fredriksson, G.; Augeri, D.; Cheah, C.; Ngoprasert, D. & Wai-Ming, W. (2017). "Helarctos malayanus (errata version published in 2018)". IUCN Red List of Threatened Species. 2017: e.T9760A123798233. Retrieved 30 May 2020.
  2. ^ Wozencraft, W.C. (2005). "Order Carnivora". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 587. ISBN 978-0-8018-8221-0. OCLC 62265494.
  3. ^ a b c d e f g h i j k l m n o p q Fitzgerald, C. S.; Krausman, P. R. (2002). "Helarctos malayanus". Mammalian Species. 696: 1–5. doi:10.1644/1545-1410(2002)696<0001:HM>2.0.CO;2.
  4. ^ a b c d Kemmerer, L. (2015). "Bear basics". In Kemmerer, L. (ed.). Bear Necessities: Rescue, Rehabilitation, Sanctuary, and Advocacy. Boston: Brill. pp. 17–34. ISBN 978-90-04-29309-0.
  5. ^ "Sun bear". National Geographic.
  6. ^ Liddell, H. G. & Scott, R. (1889). An Intermediate Greek–English Lexicon. Oxford: Clarendon Press. pp. 117, 350.
  7. ^ Lai, F.; Olesen, B. (2016). A Visual Celebration of Borneo's Wildlife. Singapore: Bjorn Olesen Wildlife Photography. p. 323. ISBN 978-0-7946-0787-6.
  8. ^ a b c d e f g h i j k Phillipps, Q. (2016). "Sun bear". Phillipps' Field guide to the Mammals of Borneo: Sabah, Sarawak, Brunei, and Kalimantan. Princeton: Princeton University Press. pp. 246–249. ISBN 978-0-691-16941-5.
  9. ^ de la Rosa, C. L.; Nocke, C. C. (2000). "Kinkajou Potos flavus". A Guide to the Carnivores of Central America: Natural History, Ecology, and Conservation. Texas: University of Texas Press. pp. 100–109. ISBN 0-292-71605-2.
  10. ^ Raffles, T. S. (1821). "XVII. Descriptive catalogue of a zoological collection, made on account of the honourable East India Company, in the island of Sumatra and its vicinity, under the direction of Sir Thomas Stamford Raffles, Lieutenant-Governor of Fort Marlborough; with additional notices illustrative of the natural history of those countries". Transactions of the Linnean Society of London. 13 (1): 239–274. doi:10.1111/j.1095-8339.1821.tb00064.x.
  11. ^ Horsfield, T. (1825). "Description of the Helarctos euryspilus exhibiting in the bear from the island of Borneo, the type of a subgenus of Ursus". Zoological Journal. 2: 221–234.
  12. ^ Santiapillai, A.; Santiapillai, C. (1988). "The status, distribution and conservation of the Malayan sun bear (Helarctos malayanus) in Indonesia". World Wildlife Federation (3769).
  13. ^ Chasen, F. N. (1940). "A handlist of Malaysian mammals: A systematic list of the mammals of the Malay Peninsula, Sumatra, Borneo and Java, including the adjacent small islands". Bulletin of the Raffles Museum. 15: 89–90.
  14. ^ a b Ellerman, J. R.; Morrison-Scott, T. C. S. (1966). "Genus Helarctos Horsfield, 1825". Checklist of Palaearctic and Indian mammals 1758 to 1946 (2nd ed.). London: British Museum of Natural History. p. 241.
  15. ^ Meijaard, E. (2004). "Craniometric differences among Malayan sun bears (Ursus malayanus); evolutionary and taxonomic implications" (PDF). Raffles Bulletin of Zoology. 52 (2): 665–672.
  16. ^ Lydekker, R. (1906). "On the occurrence of the bruang in the Tibetan Province". Proceedings of the Zoological Society of London. 66: 997–999.
  17. ^ Pocock, R. I. (1932). "The black and brown bears of Europe and Asia". Journal of the Bombay Natural History Society. 36: 101–138.
  18. ^ Zhang, Y.-P. (1996). "Genetic variability and conservation relevance of the sun bear as revealed by DNA sequences". Zoological Research. 17 (4): 459–468.
  19. ^ Waits, L.; Paetkau, D.; Strobeck, C. (1999). "Genetics of the bears of the world". In Servheen, C.; Herrero, S.; Peyton, B. (eds.). Bears: Status Survey and Conservation Action Plan. Gland: IUCN/SSC Bear and Polar Bear Specialist Groups. pp. 25–32. ISBN 2-8317-0462-6.
  20. ^ Asakura, S. (1969). "A note on a bear hybrid Melursus ursinus × Helarctos malayanus at Tama Zoo, Tokyo". International Zoo Yearbook. 9 (1): 88. doi:10.1111/j.1748-1090.1969.tb02631.x.
  21. ^ Van Gelder, R. G. (1977). "Mammalian hybrids and generic limits" (PDF). American Museum Novitates (2635): 1–25.
  22. ^ Goldman, D.; Giri, P. R.; O'Brien, S. J. (1989). "Molecular genetic-distance estimates among the Ursidae as indicated by one- and two-dimensional protein electrophoresis". Evolution. 43 (2): 282–295. doi:10.1111/j.1558-5646.1989.tb04228.x. JSTOR 2409208. PMID 28568545.
  23. ^ Bininda-Emonds, O. R. P.; Gittleman, J. L.; Purvis, A. (1999). "Building large trees by combining phylogenetic information: a complete phylogeny of the extant Carnivora (Mammalia)". Biological Reviews of the Cambridge Philosophical Society. 74 (2): 143–175. CiteSeerX 10.1.1.328.7194. doi:10.1017/s0006323199005307. PMID 10396181.
  24. ^ Yu, L.; Li, Y.-W.; Ryder, O. A.; Zhang, Y.-P. (2007). "Analysis of complete mitochondrial genome sequences increases phylogenetic resolution of bears (Ursidae), a mammalian family that experienced rapid speciation". BMC Evolutionary Biology. 7 (198): 198. doi:10.1186/1471-2148-7-198. PMC 2151078. PMID 17956639.
  25. ^ Pagès, M.; Calvignac, S.; Klein, C.; Paris, M.; Hughes, S.; Hänni, C. (2008). "Combined analysis of fourteen nuclear genes refines the Ursidae phylogeny". Molecular Phylogenetics and Evolution. 47 (1): 73–83. doi:10.1016/j.ympev.2007.10.019. PMID 18328735.
  26. ^ a b c d e f g Servheen, C. (1999). "Sun bear conservation action plan". In Servheen, C.; Herrero, S.; Peyton, B. (eds.). Bears: Status Survey and Conservation Action Plan. Gland: IUCN/SSC Bear and Polar Bear Specialist Groups. pp. 219–224. ISBN 2-8317-0462-6.
  27. ^ a b c Woods, J. G. (1885). "Sun bears". Animate Creation: Popular Edition of "Our Living World", a Natural History. 1. New York: Selmar Press. pp. 324–325.
  28. ^ Pocock, R. I. (1941). "Helarctos malayanus". The Fauna of British India, including Ceylon and Burma. Mammalia. 2. London: Taylor and Francis. pp. 224–232.
  29. ^ Servheen, C (1993). "The Sun Bear". In Stirling, I.; Kirshner, D.; Knight, F. (eds.). Bears, Majestic Creatures of the Wild. Pennsylvania: Rodale Press. p. 124.
  30. ^ Brown, G. (1996). Great Bear Almanac. The Lyons Press. p. 340. ISBN 978-1-55821-474-3.
  31. ^ Steinmetz, R.; Garshelis, D. L. (2008). "Distinguishing Asiatic black bears and sun bears by claw marks on climbed trees". Journal of Wildlife Management. 72 (3): 814–821. doi:10.2193/2007-098.
  32. ^ Meijaard, E. (1997). The Malayan sun bear on Borneo, with special emphasis on its conservation status in Kalimantan, Indonesia (Report). International Ministry of Forestry – Tropendos Kalimantan Project and World Society for the Protection of Animals, London. pp. 1–51.
  33. ^ Christiansen, P (2007). "Evolutionary implications of bite mechanics and feeding ecology in bears". Journal of Zoology. 272 (4): 423–443. doi:10.1111/j.1469-7998.2006.00286.x.
  34. ^ a b c Humphrey, S. R.; Bain, J. R. (1990). "Malayan sun bear". Endangered Animals of Thailand. Florida: Sandhill Crane Press. pp. 313–315. ISBN 1-877743-07-0.
  35. ^ Griffiths, M.; Schaik, C. P. (1993). "The impact of human traffic on the abundance and activity periods of Sumatran rain forest wildlife". Conservation Biology. 7 (3): 623–626. doi:10.1046/j.1523-1739.1993.07030623.x.
  36. ^ Guharajan, R.; Arnold, T. W.; Bolongon, G.; Dibden, G. H.; Abram, N. K.; Teoh, S. W.; Magguna, M. A.; Goossens, B.; Wong, S. T.; Nathan, S. K. S. S.; Garshelis, D. L. (2018). "Survival strategies of a frugivore, the sun bear, in a forest-oil palm landscape" (PDF). Biodiversity and Conservation. 27 (14): 3657–3677. doi:10.1007/s10531-018-1619-6.
  37. ^ a b c d e f g Nowak, R. M. (2005). "Ursus malayanus Malayan sun bear". Walker's Carnivores of the World. Baltimore: Johns Hopkins University Press. pp. 127-128. ISBN 0-8018-8032-7.
  38. ^ Wong, S. T.; Servheen, C. W.; Ambu, L. (2004). "Home range, movement and activity patterns, and bedding sites of Malayan sun bears Helarctos malayanus in the Rainforest of Borneo" (PDF). Biological Conservation. 119 (2): 169–181. doi:10.1016/j.biocon.2003.10.029. Archived from the original (PDF) on 11 May 2013. Retrieved 2013-02-07.
  39. ^ Taylor, D.; Hartmann, D.; Dezecache, G.; Te Wong, S.; Davila-Ross, M. (2019). "Facial complexity in sun bears: Exact facial mimicry and social sensitivity". Scientific Reports. 9 (1): 4961. doi:10.1038/s41598-019-39932-6. PMC 6428817. PMID 30899046.
  40. ^ Solly, M. (22 March 2019). "Sun bears mimic each other's facial expressions to communicate". Smithsonian Magazine.
  41. ^ Wong, S. T.; Servheen, C. W.; Ambu, L. (2004). "Home range, movement and activity patterns, and bedding sites of Malayan sun bears Helarctos malayanus in the Rainforest of Borneo" (PDF). Biological Conservation. 119 (2): 169–181. doi:10.1016/j.biocon.2003.10.029. Archived from the original (PDF) on 2013-05-11. Retrieved 2013-02-07.
  42. ^ Naing, H.; Htun, S.; Kamler, J. F.; Burnham, D.; Macdonald, D. W. (2020). "Large carnivores as potential predators of sun bears". Ursus. 2019 (30e4): 51. doi:10.2192/URSU-D-18-0022.2.
  43. ^ Fredriksson, G. M. (2005). "Predation on sun bears by reticulated python in East Kalimantan, Indonesian Borneo" (PDF). Raffles Bulletin of Zoology. 53 (1): 165–168. Archived from the original (PDF) on 2007-08-11.
  44. ^ Sethy, J.; Chauhan, N. P. S. (2018). "Dietary preference of Malayan sun bear Helarctos malayanus in Namdapha Tiger Reserve, Arunachal Pradesh, India". Wildlife Biology. 2018 (1). doi:10.2981/wlb.00351.
  45. ^ Wong, S. T.; Servheen C.; Ambu, L. (2002). "Food habits of Malayan Sun Bears in lowland tropical forests of Borneo" (PDF). Ursus. 13: 127–136.
  46. ^ Augeri, D. M. (2005). On the biogeographic ecology of the Malayan sun bear (PDF) (Thesis). Cambridge: Darwin College.
  47. ^ Wong, S. T.; Servheen C.; Ambu, L. (2002). "Food habits of Malayan sun bears in lowland tropical forests of Borneo" (PDF). Ursus. 13: 127–136.
  48. ^ Fredriksson, G. M.; Trisno, S. A. W. (2006). "Frugivory in sun bears (Helarctos malayanus) is linked to El Niño-related fluctuations in fruiting phenology, East Kalimantan, Indonesia". Biological Journal of the Linnean Society. 89 (3): 489–508. doi:10.1111/j.1095-8312.2006.00688.x.
  49. ^ McConkey, K.; Galetti, M. (1999). "Seed dispersal by the sun bear Helarctos malayanus in Central Borneo". Journal of Tropical Ecology. 15 (2): 237–241. doi:10.1017/S0266467499000784. hdl:11449/37442.
  50. ^ a b Guharajan, R.; Abram, N. K.; Magguna, M. A.; Goossens, B.; Wong, S. T.; Nathan, S. K. S. S.; Garshelis, D. L. (2017). "Does the vulnerable sun bear Helarctos malayanus damage crops and threaten people in oil palm plantations?" (PDF). Oryx. 53 (4): 611–619. doi:10.1017/S0030605317001089.
  51. ^ Frederick, C.; Hunt, K. E.; Kyes, R.; Collins, D.; Wasser, S. K. (2012). "Reproductive timing and aseasonality in the sun bear (Helarctos malayanus)". Journal of Mammalogy. 93 (2): 522–531. doi:10.1644/11-MAMM-A-108.1.
  52. ^ Schwarzenberger, F.; Fredriksson, G.; Schaller, K.; Kolter, L. (2004). "Fecal steroid analysis for monitoring reproduction in the sun bear (Helarctos malayanus)". Theriogenology. 62 (9): 1677–1692. CiteSeerX 10.1.1.556.2474. doi:10.1016/j.theriogenology.2004.03.007. PMID 15511554.
  53. ^ Li, F.; Zheng, X.; Jiang, X. L.; Chan, B. P. L. (2017). "Rediscovery of the sun bear (Helarctos malayanus) in Yingjiang County, Yunnan Province, China". Zoological Research. 38 (4): 206–207. doi:10.24272/j.issn.2095-8137.2017.044. PMC 5571478. PMID 28825452.
  54. ^ Nazeri, M.; Kumar, L.; Jusoff, K.; Bahaman, A. R. (2014). "Modeling the potential distribution of sun bear in Krau Wildlife Reserve, Malaysia". Ecological Informatics. 20: 27–32. doi:10.1016/j.ecoinf.2014.01.006.
  55. ^ Wong, W.-M.; Linkie, M. (2013). "Managing sun bears in a changing tropical landscape". Diversity and Distributions. 19 (7): 700–709. doi:10.1111/ddi.12020.
  56. ^ Nazeri, M.; Jusoff, K.; Madani, N.; Mahmud, A. R.; Bahman, A. R. (2012). "Predictive modeling and mapping of Malayan sun bear (Helarctos malayanus) distribution using maximum entropy". PLOS ONE. 7 (10): e48104. Bibcode:2012PLoSO...748104N. doi:10.1371/journal.pone.0048104. PMC 3480464. PMID 23110182.
  57. ^ Nomura, F.; Higashi, S.; Ambu, L.; Mohamed, M. (2004). "Notes on oil palm plantation use and seasonal spatial relationships of sun bears in Sabah, Malaysia". Ursus. 15 (2): 227–231. doi:10.2192/1537-6176(2004)015<0227:NOOPPU>2.0.CO;2. JSTOR 3872976.
  58. ^ Te Wong, S.; Servheen, C.; Ambu, L.; Norhayati, A. (2005). "Impacts of fruit production cycles on Malayan sun bears and bearded pigs in lowland tropical forest of Sabah, Malaysian Borneo". Journal of Tropical Ecology. 21 (6): 627–639. doi:10.1017/S0266467405002622.
  59. ^ Fredriksson, G. (2005). "Human-sun bear conflicts in East Kalimantan, Indonesian Borneo". Ursus. 16 (1): 130–137. doi:10.2192/1537-6176(2005)016[0130:HBCIEK]2.0.CO;2. JSTOR 3873066.
  60. ^ Ngoprasert, D.; Reed, D. H.; Steinmetz, R.; Gale, G. A. (2012). "Density estimation of Asian bears using photographic capture–recapture sampling based on chest marks". Ursus. 23 (2): 117–133. doi:10.2192/URSUS-D-11-00009.1.
  61. ^ Sodhi, N. S.; Koh, L. P.; Brook, B. W.; Ng, P. K.L. (2004). "Southeast Asian biodiversity: an impending disaster". Trends in Ecology & Evolution. 19 (12): 654–660. doi:10.1016/j.tree.2004.09.006. PMID 16701328.
  62. ^ Stibig, H.-J.; Achard, F.; Carboni, S.; Raši, R.; Miettinen, J. (2014). "Change in tropical forest cover of Southeast Asia from 1990 to 2010". Biogeosciences. 11 (2): 247–258. doi:10.5194/bg-11-247-2014.
  63. ^ Fredriksson, G. M.; Danielsen, L. S.; Swenson, J. E. (2006). "Impacts of El Niño related drought and forest fires on sun bear fruit resources in lowland dipterocarp forest of East Borneo". Biodiversity and Conservation. 16 (6): 1823–1838. doi:10.1007/s10531-006-9075-0.
  64. ^ Meijaard, E. (1999). "Human imposed threats to sun bears in Borneo" (PDF). Ursus. 11 (A Selection of Papers from the Eleventh International Conference on Bear Research and Management, Graz, Austria, September 1997, and Gatlinburg, Tennessee, April 1998): 185–192. JSTOR 3873000.
  65. ^ a b Foley, K. E.; Stengel, C. J.; Shepherd, C. R. (2011). Pills, powders, vials and flakes: the bear bile trade in Asia (PDF) (Report). TRAFFIC Southeast Asia, Petaling Jaya, Selangor, Malaysia. pp. 1–79.
  66. ^ Scotson, L.; Hunt, M. (2012). "Dismantling the "wall of death": emergency bear snare-line patrol in the Nam Kan National Protected Area, Lao PDR". International Bear News. 21 (4): 17–19.
  67. ^ Sethy, J.; Chauhan, N. P. S. (2012). "Conservation status of sun bear (Helarctos malayanus) in Nagaland state, north-east India" (PDF). Asian Journal of Conservation Biology. 1 (2): 103–109.
  68. ^ Asher, C. (1 August 2016). "Malayan sun bear: bile trade threatens the world's smallest bear". Mongabay. Retrieved 5 May 2020.
  69. ^ Krishnasamy, K.; Shepherd, C. R. (2014). "A review of the sun bear trade in Sarawak, Malysia" (PDF). TRAFFIC Bulletin. 26 (1): 37–40.
  70. ^ Li, T. C. (5 May 2014). "Sun bears: At home in the forest". The Star. Retrieved 5 May 2020.
  71. ^ Ball, J. (2000). Sun bear fact sheet (PDF) (Report). Association of Zoos and Aquariums. pp. 1–2. Archived from the original (PDF) on 27 August 2008.
  72. ^ Kok, J., ed. (2008). EAZA Bear TAG Annual Report 2007–2008 (Report). European Association of Zoos and Aquaria.