Post by grrraaahhh on Sept 14, 2011 8:33:38 GMT -9
HELARCTOS MALAYNUS /SUN BEAR (PRELIMINARY PROFILE)
Helarctos malayanus (Raffles, 1821) Malayan Sun Bear
Ursus malayanus Raffles, 1821:254. Type locality ‘‘Sumatra.’’
Helarctos euryspilus Horsfield, 1825:221. Type locality ‘‘Borneo.’’
Helarctos malayanus Horsfield, 1825:234. First use of current name combination.
Helarctos anmamiticus Heude, 1901:1–2. Type locality ‘‘Annam, Vietnam.’’
Order Carnivora, family Ursidae, subfamily Ursinae, genus Helarctos. Helarctos has hybridized with Melursus
(Asakura 1969) and therefore may be a subgenus of Ursus. Helarctos and Melursus were proposed to be synonyms
(Van Gelder 1977).
Malayan Sun Bear (Helarctos malayanus). Details about this species are available only from observations made in zoological gardens. The fact is, however, that the Malayan sun bear is one of the rarest mammals in the tropical rainforest. During a four-month expedition through the Leuser Wildlife Reserve on northern Sumatra, I collected 202 observations of orangutans, 203 of the sam-bar, 79 relating to the serau, 156 concerning elephants, and no less than 75 relating to the extremely rare Sumatra rhinoceros. But I found only 22 signs the Malayan sun bear.
ECOLOGY & BEHAVIOR. The Sun Bear is generally nocturnal but is also seen during the day, often travelling in pairs. It inhabits dense forests of all elevations in this country; it is an excellent tree climber, and Medway (1969) says that it "can ascend the branchless trunk of a tall tree supported only by the claws, which leave characteristic gouged marks." The Sun Bear normally sleeps in a tree nest, probably built just before retiring. Fetherstonhaugh (1940) has described the nest-building procedure: "She would shin up a tree, climb out upon a limb until she reached a convenient fork where there were small leafy branches handy, and proceed to pull the twigs and leaves underneath her belly, lying upon them with her chin in the fork of the limb, her body along its length and all four legs hanging down. If overtaken by rain the procedure was the same and it was ludicrous to see her literally scuttle up the nearest tree and work against time to get a mat of leaves and twigs under her belly while leaving her back to the mercy of the elements; there she would stay with a look of patient misery on her face and not even hunger would get her down until the shower was over."
Breeding seems to be throughout the year; usually two cubs are born blind and hairless after a gestation of 95-96 days. The cubs stay with their mother until nearly grown. Dathe (1961) reports two successful full-term pregnancies in one year. The adult dentition is complete by the age of 18 months, and lifespan in captivity may be 20 years.
The gestation period is 7-8 months, and usually two cubs are born in a cave or hollow tree in early winter (in temperate regions; in Thailand?). The eyes of the cubs remain closed for about a week after birth; a short time after the eyes open, the young begin following the female as she forages, staying with her until they are nearly full grown or until the mother is in estrous again; females have been seen with 2 sets of cubs. Breeding begins at the age of about 3 years, and lifespan in captivity may be as much as 33 years.
PHYSICAL CHARACTERISTICS. The smallest of the world’s eight living bear species with length of head and body, 1,000–1,400 mm; length of tail, 30–70 mm; height at shoulder, ca. 700 mm; and mass, 25–65 kg (Dathe 1975). H. malayanus has a stocky build, short muzzle, large paws, strongly curved and pointed claws, and naked soles. Ears are small (40–60 mm) and round (Lekagul and McNeely 1977). Hind foot is 180–210 mm (Lekagul and McNeely 1977). Bornean sun bears seem to be the smallest and possibly subspecies status is warranted (H. malayanus eurispylus). On Borneo the sun bear weighs only about 35 to 65 kilograms (75 to 145 pounds), but bears in Sumatra and on mainland Southeast Asia weigh between 50-80 kg, although little data from the wild is available.
It has small rounded ears, a fleshy forehead that sometimes looks wrinkled, and an extremely long tongue (longest of all bear species). With feet turned slightly inward, large naked paws, and long curved claws, the sun bear is well adapted for climbing trees. Its feet are extraordinarily large compared to its body size, potentially assisting in digging and breaking into dead wood in search for insects. Paws are often peripherally brown or tan (Fetherstonhaugh 1948; Pocock 1932).
Fur is typically jet-black; adult coat has a very thick black undercoat with lighter guard hairs (Fetherstonhaugh 1940, 1948; Pocock 1932). Occasionally fur patterns will range from reddish brown to gray. Almost every sun bear has an individually distinct chest patch that is typically yellow, orange, or white, but may sometimes be speckled or spotted. The sun bear has a broad muzzle that is relatively short, and a large head that gives the bear a doglike appearance. Muzzle may be orange, gray, or silver (Fetherstonhaugh 1940). Shape of breast patch is variable but typically U-shaped and may be buff, cream colored, white, ochreous, yellow (Allen 1938; Fetherstonhaugh 1940, 1948; Pocock 1932), or entirely absent (Nowak 1991). Such contrasting color patches may be used to intimidate rivals by accentuating a bipedal threat posture (Ewer 1973; Searle 1968). A reddish bear lacking the chest mark occurred in southeastern Sabah, Borneo (Payne and Francis 1985).
Birth weight was 300 g for a captive-born cub (Dathe 1970) and ca. 325 g on average (Dathe 1975). Pelage of infants is grayblack with a dirty white U-shaped mark on the chest and a white or pale brown muzzle (Feng and Wang 1991). Pelage of young Ma-also observed throughout these areas (Duckworth et al. 1994). The status of H. malayanus in Cambodia is unknown, but illegal trafficking of Cambodian sun bears into Thailand has been documented (Mills 1991). No information was available on H. malayanus in Vietnam (Servheen 1990), but the species may inhabit that country (Servheen 1993).
DISTRIBUTION. The range of this species is not well documented, either historically or presently. However, the sun bear has been seen throughout Southeast Asia from the eastern edge of India, northern Burma to Laos, Cambodia, Vietnam, and Thailand, and farther south to peninsular Malaysia and on the islands of Sumatra and Borneo. There are historical records indicating that the sun bear was once present in eastern Tibet, Bangladesh, and portions of India and China and the island of Java. However, due to large scale habitat destruction and poaching, the sun bear’s range has been substantially reduced from its historic extent. The sun bear is believed to be extinct in Tibet and Bangladesh; it is likely that only very small numbers remain in southern China, if the sun bear is not actually extinct there as well.
DIET & FEEDING BEHAVIOR. Sun bears are omnivores with food habits similar to Selenarctos and primarily feed on termites, ants and beetle larvae, bee larvae and honey, and a large variety of fruits, when available. Occasionally certain flowers are eaten. Vegetation, like grasses or leaves, hardly feature in the diet. Near the forest edge in gardens they occasionally feed on the growing tips of palm trees, and occasionally small mammals and bird eggs. Their long sharp claws enable them to dig easily into the ground, break into logs, and their massive jaw muscles make it possible to bite through the bark of trees in search of insects and honey, and their long tongues help them to extract these foods from crevices. Sun Bears also eat the heart of coconut palms, and may do serious damage to coconut plantations, destroying numerous trees in a single night and returning to the plantation until all trees have been affected.
SKULL MORPHOLOGY. Zygomatic arch is wide, but jugal is slender (Allen 1938). A distinct sagittal crest occurs in adult animals. Paraoccipital process is large, blunt, and protrudes downward. Upper alveolar line may extend posteriorly and cut upper portion of glenoid cavity and upper edge of auditory meatus (Allen 1938). Rhinarium extends to upper lip, with its lateral portions extending beyond and concealing the septum when viewed laterally (Pocock 1917). Lips are protrusible (Pocock 1932), and tongue is long (Yin 1967). Both these features may be adaptations for extraction of honey and larvae from bees’ nests (Morris 1965). H. malayanus has the highest cephalization within Fissipedia (Ro¨hrs et al. 1989).
The shortened snout of H. malayanus may be related to contraction of upper toothrow and loss of P2 (Allen 1938). P3 abuts posterointernal base of canine, and their sockets are continuous. Canines are extremely stout and powerful and have a narrow compressed ridge on their posteroexternal border. M1 is nearly square, with its outer cusps higher than inner cusps. M2 is slightly longer than M1, with a contracted posterior heel (Allen 1938). H. malayanus often lacks some premolars; thus, dental formula is i 3/3, c 1/1, p 3–4/3, m 2/3, total 38–40 (Allen 1938; Lekagul and McNeely 1977). Tooth enamel of H. malayanus exhibits only undulating Hunter–Schreger bands (Stefen 2001).
Forelimbs of H. malayanus are bowed, and paws turn inward, a likely adaptation for arboreality (Pocock 1932). On the basis of multivariate analyses of the morphology of the shoulder girdle, H. malayanus may be closest to Ailuropoda melanoleuca with respect to its arboreal adaptations (Oxnard 1968). This includes the degree to which the shoulder can withstand tension.
A 27-year-old Malayan sun bear had mild to severe multifocal ballooning of myelin sheaths within dorsal and ventral lumbar intradural nerve rootlets (Anderson et al. 1993). Ursodeoxycholic acid of gall bladder bile averaged 8% for Helarctos compared with 17%, 19%, and 39% for Ursus maritimus, Ursus arctos, and Ursus americanus , respectively (Hagey et al. 1993).
FOSSIL RECORD. Although no fossils of H. malayanus are known, the species descended from Ursus minimus, a widespread Late Pliocene bear that was similar in size to H. malayanus (O’Brien 1993).
GENETICS. Helarctos malayanus has a diploid number of 74 chromosomes (Nash and O’Brien 1987). Chromosomes of H. malayanus differ from those of other ursines in having a paracentric inversion in chromosome 14, having a pericentric inversion in chromosome 18, lacking a negatively stained stalk with a light terminal satellite on chromosome 25, and having a reduced short arm of chromosome 34 (Nash and O’Brien 1987). The latter 2 chromosomal traits are shared by U. arctos. Nei’s genetic distance estimated between H. malayanus and U. arctos (0.026) was smaller than that between H. malayanus and U. thibetanus (0.037) and that between H. malayanus and M. ursinus (0.050—Goldman et al. 1989). Thus, morphological divergence of H. malayanus and M. ursinus is likely because of recent adaptive change ca. 5–7 million years ago (Goldman et al. 1989). Hybridization of H. malayanus and M. ursinus further illustrates the genetic proximity of these bears (Van Gelder 1977).
Helarctos malayanus may be the closest relative of U. americanus , as inferred from mitochondrial DNA sequences of D-loop region, cytochrome b, 12S rRNA, tRNA Pro, and tRNA (Zhang and Ryder 1994). Alternatively, the Malayan sun bear may be closest to the U. arctos–U. maritimus clade, the most recently derived ursines, on the basis of complete sequences of cytochrome b, tRNA Pro, and tRNA Thr Thr (Talbot and Shields 1996). U. americanus and U. thibetanus have been placed as sister taxa diverging from the ursine lineage ca. 6 million years ago, with H. malayanus diverging ca. 5 million years ago (Talbot and Shields 1996).
BEHAVIOR. Helarctos malayanus may attack humans, particularly when injured or when with young (Harrisson 1949; Medway 1969). H. malayanus in Thailand may charge without apparent warning or provocation (Lekagul and McNeely 1977); however, Malayan sun bears are inoffensive and timid if not bothered, and even a female with cubs will avoid a human if possible (Fetherstonhaugh 1940). Unprovoked H. malayanus attacks on humans may result from its poor vision, its timidity, or sudden confrontations, where flight appears impossible (Fetherstonhaugh 1940). H. malayanus often stands bipedally to get a better view of distant objects, when it encounters a threat (Lekagul and McNeely 1977), or to get a better scent of distant objects (Fetherstonhaugh 1940).
The Malayan sun bear in the wild may be solitary (Ortolani and Caro 1996). It is largely nocturnal (Lekagul and McNeely 1977; Medway 1969), but its activity may respond to human perturbations (Griffiths and van Schaik 1993). Malayan sun bears were largely diurnal (18%, n 5 28) in an unperturbed area and strictly nocturnal (100%, n 5 4) at a heavily traveled site on the basis of percentage of camera detections classified as nocturnal (Griffiths and van Schaik 1993).
Helarctos malayanus makes grunting and snuffling noises while searching for larvae and adult insects (Fetherstonhaugh 1948). Occasionally, it produces hoarse grunts or loud roars that may be confused with those of the adult male orangutan ( Pongo pygmaeus ). Rarely, Malayan sun bears give short barks like those of muntjac ( Muntiacus) or rhinoceros (Dicerorhinus sumatrensis— Payne and Francis 1985).
HABITAT. Tropical hardwood rainforests are the sun bear’s main habitat. These forests are highly valued by humans for timber production, and are being rapidly converted to second growth forest, cash-crop plantation agriculture and subsistence farming, grazing areas, and human settlements. Malaysia and Indonesia are the world’s leading exporters of tropical hardwoods, and most of these exports originate from the sun bear’s shrinking habitat. The specific impacts on sun bear distribution, population numbers and density, and food supply are unknown; but the consequences are certainly detrimental. These human activities replace important native lowland tropical forest with large expanses of land that cannot be used by bears. Necessary sun bear habitat is eliminated; and the plants, insects, and other foods the bears need also disappear. Deprived of their natural food resources, sun bears sometimes feed on cultivated crops – particularly palm hearts – and thereby destroy them. Such depredating bears are persecuted by landowners and are often killed.
In the wild, U. malayanus sometimes does considerable damage to coconut plantations and is said to be one of the most dangerous animals within its range (Lekagul and Mc-Neely 1977). Young individuals make interesting pets but become unruly within a few years. According to Mills (1993,1994,1995), sun bear cubs are highly popular as pets in the Orient, but when they reach adult size they commonly are sold for their parts, which are used in the medicinal trade. International commerce involving such utilization also is adversely affecting wild populations (see account of Ursus thibetanus). Servheen (1989) reported a general decline because of hunting for gallbladders and other body parts, lack of effective regulation, and logging and conversion of vast areas of forest to cropland and rubber plantations. U. malayanus may now have been extirpated in India and is very rare in Bangladesh and China. It is on appendix 1 of the CITES.
PREDATION THREATS. In terms of animal predation on sun bears, few published records exist. Kawanishi & Sunquist (2004) report on 3 tiger {Panthera tigris) scats containing sun bear remains from peninsular Malaysia. On one occasion, a large python successfully preyed on a female sun bear Fredrickson et. al 2005. Other predators on mainland Southeast Asia and Sumatra could potentially be the common leopard, and the clouded leopard (Neofelis nebulosa), which occur sympatrically with sun bears. The moon bear {Ursus thibethanus), also occurring sympatrically throughout parts of the sun bears range, being substantially larger than the sun bear, could potentially pose a risk to sun bears.
CONSERVATION STATUS. Malayan sun bear numbers are declining drastically because of habitat destruction and poaching for bear parts used in exotic foods, medicines, or aphrodisiacs (Mills and Servheen 1991). H. malayanus may be threatened by demand from Japan and Korea for bear gall bladders for medicinal uses (Payne and Andau 1991).
Helarctos malayanus is an Appendix I species of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES); thus, all international trade is prohibited (Mills and Servheen 1991). However, not all countries within the bear’s range accept CITES. H. malayanus is listed as Vulnerable according to the International Union on the Conservation of Nature and Natural Resources (Corbet and Hill 1992).
Throughout its range, wildlife law enforcement is limited or nonexistent (Mills and Servheen 1991). Malayan sun bears are protected in Laos (Mills and Servheen 1991). In peninsular Malaysia, capture of or trade in Malayan sun bears is prohibited under the Wildlife Act of 1972 (Mills and Servheen 1991). In Sabah, the Malayan sun bear is listed as a game species despite its Vulnerable status (Mills and Servheen 1991). The Wild Animals Reservation and Protection Act prohibits hunting, buying, selling, and consumption of Thailand’s native bears without the government’s permission. The same act allows every Thai to keep as pets 2 of any wild species (Mills and Servheen 1991), thus allowing a legal loophole for wildlife trafficking (Mills 1991; Mills and Servheen 1991). The Burma Wildlife Protection Act of 1936 protects all species within reserve forests; however, neither H. malayanus nor U. thibetanus was protected outside those reserves as of 1988. The Wildlife Protection Ordinance of 1931 prohibits hunting, capture, trade, transit, export, and possession of Malayan sun bears in Indonesia. In China, the Malayan sun bear is a Class I protected species under the Wildlife Protection Law and therefore is protected by the central government (Mills and Servheen 1991).
LITERATURE
To be continued....
Helarctos malayanus (Raffles, 1821) Malayan Sun Bear
Ursus malayanus Raffles, 1821:254. Type locality ‘‘Sumatra.’’
Helarctos euryspilus Horsfield, 1825:221. Type locality ‘‘Borneo.’’
Helarctos malayanus Horsfield, 1825:234. First use of current name combination.
Helarctos anmamiticus Heude, 1901:1–2. Type locality ‘‘Annam, Vietnam.’’
Order Carnivora, family Ursidae, subfamily Ursinae, genus Helarctos. Helarctos has hybridized with Melursus
(Asakura 1969) and therefore may be a subgenus of Ursus. Helarctos and Melursus were proposed to be synonyms
(Van Gelder 1977).
Malayan Sun Bear (Helarctos malayanus). Details about this species are available only from observations made in zoological gardens. The fact is, however, that the Malayan sun bear is one of the rarest mammals in the tropical rainforest. During a four-month expedition through the Leuser Wildlife Reserve on northern Sumatra, I collected 202 observations of orangutans, 203 of the sam-bar, 79 relating to the serau, 156 concerning elephants, and no less than 75 relating to the extremely rare Sumatra rhinoceros. But I found only 22 signs the Malayan sun bear.
ECOLOGY & BEHAVIOR. The Sun Bear is generally nocturnal but is also seen during the day, often travelling in pairs. It inhabits dense forests of all elevations in this country; it is an excellent tree climber, and Medway (1969) says that it "can ascend the branchless trunk of a tall tree supported only by the claws, which leave characteristic gouged marks." The Sun Bear normally sleeps in a tree nest, probably built just before retiring. Fetherstonhaugh (1940) has described the nest-building procedure: "She would shin up a tree, climb out upon a limb until she reached a convenient fork where there were small leafy branches handy, and proceed to pull the twigs and leaves underneath her belly, lying upon them with her chin in the fork of the limb, her body along its length and all four legs hanging down. If overtaken by rain the procedure was the same and it was ludicrous to see her literally scuttle up the nearest tree and work against time to get a mat of leaves and twigs under her belly while leaving her back to the mercy of the elements; there she would stay with a look of patient misery on her face and not even hunger would get her down until the shower was over."
Breeding seems to be throughout the year; usually two cubs are born blind and hairless after a gestation of 95-96 days. The cubs stay with their mother until nearly grown. Dathe (1961) reports two successful full-term pregnancies in one year. The adult dentition is complete by the age of 18 months, and lifespan in captivity may be 20 years.
The gestation period is 7-8 months, and usually two cubs are born in a cave or hollow tree in early winter (in temperate regions; in Thailand?). The eyes of the cubs remain closed for about a week after birth; a short time after the eyes open, the young begin following the female as she forages, staying with her until they are nearly full grown or until the mother is in estrous again; females have been seen with 2 sets of cubs. Breeding begins at the age of about 3 years, and lifespan in captivity may be as much as 33 years.
PHYSICAL CHARACTERISTICS. The smallest of the world’s eight living bear species with length of head and body, 1,000–1,400 mm; length of tail, 30–70 mm; height at shoulder, ca. 700 mm; and mass, 25–65 kg (Dathe 1975). H. malayanus has a stocky build, short muzzle, large paws, strongly curved and pointed claws, and naked soles. Ears are small (40–60 mm) and round (Lekagul and McNeely 1977). Hind foot is 180–210 mm (Lekagul and McNeely 1977). Bornean sun bears seem to be the smallest and possibly subspecies status is warranted (H. malayanus eurispylus). On Borneo the sun bear weighs only about 35 to 65 kilograms (75 to 145 pounds), but bears in Sumatra and on mainland Southeast Asia weigh between 50-80 kg, although little data from the wild is available.
It has small rounded ears, a fleshy forehead that sometimes looks wrinkled, and an extremely long tongue (longest of all bear species). With feet turned slightly inward, large naked paws, and long curved claws, the sun bear is well adapted for climbing trees. Its feet are extraordinarily large compared to its body size, potentially assisting in digging and breaking into dead wood in search for insects. Paws are often peripherally brown or tan (Fetherstonhaugh 1948; Pocock 1932).
Fur is typically jet-black; adult coat has a very thick black undercoat with lighter guard hairs (Fetherstonhaugh 1940, 1948; Pocock 1932). Occasionally fur patterns will range from reddish brown to gray. Almost every sun bear has an individually distinct chest patch that is typically yellow, orange, or white, but may sometimes be speckled or spotted. The sun bear has a broad muzzle that is relatively short, and a large head that gives the bear a doglike appearance. Muzzle may be orange, gray, or silver (Fetherstonhaugh 1940). Shape of breast patch is variable but typically U-shaped and may be buff, cream colored, white, ochreous, yellow (Allen 1938; Fetherstonhaugh 1940, 1948; Pocock 1932), or entirely absent (Nowak 1991). Such contrasting color patches may be used to intimidate rivals by accentuating a bipedal threat posture (Ewer 1973; Searle 1968). A reddish bear lacking the chest mark occurred in southeastern Sabah, Borneo (Payne and Francis 1985).
Birth weight was 300 g for a captive-born cub (Dathe 1970) and ca. 325 g on average (Dathe 1975). Pelage of infants is grayblack with a dirty white U-shaped mark on the chest and a white or pale brown muzzle (Feng and Wang 1991). Pelage of young Ma-also observed throughout these areas (Duckworth et al. 1994). The status of H. malayanus in Cambodia is unknown, but illegal trafficking of Cambodian sun bears into Thailand has been documented (Mills 1991). No information was available on H. malayanus in Vietnam (Servheen 1990), but the species may inhabit that country (Servheen 1993).
DISTRIBUTION. The range of this species is not well documented, either historically or presently. However, the sun bear has been seen throughout Southeast Asia from the eastern edge of India, northern Burma to Laos, Cambodia, Vietnam, and Thailand, and farther south to peninsular Malaysia and on the islands of Sumatra and Borneo. There are historical records indicating that the sun bear was once present in eastern Tibet, Bangladesh, and portions of India and China and the island of Java. However, due to large scale habitat destruction and poaching, the sun bear’s range has been substantially reduced from its historic extent. The sun bear is believed to be extinct in Tibet and Bangladesh; it is likely that only very small numbers remain in southern China, if the sun bear is not actually extinct there as well.
DIET & FEEDING BEHAVIOR. Sun bears are omnivores with food habits similar to Selenarctos and primarily feed on termites, ants and beetle larvae, bee larvae and honey, and a large variety of fruits, when available. Occasionally certain flowers are eaten. Vegetation, like grasses or leaves, hardly feature in the diet. Near the forest edge in gardens they occasionally feed on the growing tips of palm trees, and occasionally small mammals and bird eggs. Their long sharp claws enable them to dig easily into the ground, break into logs, and their massive jaw muscles make it possible to bite through the bark of trees in search of insects and honey, and their long tongues help them to extract these foods from crevices. Sun Bears also eat the heart of coconut palms, and may do serious damage to coconut plantations, destroying numerous trees in a single night and returning to the plantation until all trees have been affected.
SKULL MORPHOLOGY. Zygomatic arch is wide, but jugal is slender (Allen 1938). A distinct sagittal crest occurs in adult animals. Paraoccipital process is large, blunt, and protrudes downward. Upper alveolar line may extend posteriorly and cut upper portion of glenoid cavity and upper edge of auditory meatus (Allen 1938). Rhinarium extends to upper lip, with its lateral portions extending beyond and concealing the septum when viewed laterally (Pocock 1917). Lips are protrusible (Pocock 1932), and tongue is long (Yin 1967). Both these features may be adaptations for extraction of honey and larvae from bees’ nests (Morris 1965). H. malayanus has the highest cephalization within Fissipedia (Ro¨hrs et al. 1989).
The shortened snout of H. malayanus may be related to contraction of upper toothrow and loss of P2 (Allen 1938). P3 abuts posterointernal base of canine, and their sockets are continuous. Canines are extremely stout and powerful and have a narrow compressed ridge on their posteroexternal border. M1 is nearly square, with its outer cusps higher than inner cusps. M2 is slightly longer than M1, with a contracted posterior heel (Allen 1938). H. malayanus often lacks some premolars; thus, dental formula is i 3/3, c 1/1, p 3–4/3, m 2/3, total 38–40 (Allen 1938; Lekagul and McNeely 1977). Tooth enamel of H. malayanus exhibits only undulating Hunter–Schreger bands (Stefen 2001).
Forelimbs of H. malayanus are bowed, and paws turn inward, a likely adaptation for arboreality (Pocock 1932). On the basis of multivariate analyses of the morphology of the shoulder girdle, H. malayanus may be closest to Ailuropoda melanoleuca with respect to its arboreal adaptations (Oxnard 1968). This includes the degree to which the shoulder can withstand tension.
A 27-year-old Malayan sun bear had mild to severe multifocal ballooning of myelin sheaths within dorsal and ventral lumbar intradural nerve rootlets (Anderson et al. 1993). Ursodeoxycholic acid of gall bladder bile averaged 8% for Helarctos compared with 17%, 19%, and 39% for Ursus maritimus, Ursus arctos, and Ursus americanus , respectively (Hagey et al. 1993).
FOSSIL RECORD. Although no fossils of H. malayanus are known, the species descended from Ursus minimus, a widespread Late Pliocene bear that was similar in size to H. malayanus (O’Brien 1993).
GENETICS. Helarctos malayanus has a diploid number of 74 chromosomes (Nash and O’Brien 1987). Chromosomes of H. malayanus differ from those of other ursines in having a paracentric inversion in chromosome 14, having a pericentric inversion in chromosome 18, lacking a negatively stained stalk with a light terminal satellite on chromosome 25, and having a reduced short arm of chromosome 34 (Nash and O’Brien 1987). The latter 2 chromosomal traits are shared by U. arctos. Nei’s genetic distance estimated between H. malayanus and U. arctos (0.026) was smaller than that between H. malayanus and U. thibetanus (0.037) and that between H. malayanus and M. ursinus (0.050—Goldman et al. 1989). Thus, morphological divergence of H. malayanus and M. ursinus is likely because of recent adaptive change ca. 5–7 million years ago (Goldman et al. 1989). Hybridization of H. malayanus and M. ursinus further illustrates the genetic proximity of these bears (Van Gelder 1977).
Helarctos malayanus may be the closest relative of U. americanus , as inferred from mitochondrial DNA sequences of D-loop region, cytochrome b, 12S rRNA, tRNA Pro, and tRNA (Zhang and Ryder 1994). Alternatively, the Malayan sun bear may be closest to the U. arctos–U. maritimus clade, the most recently derived ursines, on the basis of complete sequences of cytochrome b, tRNA Pro, and tRNA Thr Thr (Talbot and Shields 1996). U. americanus and U. thibetanus have been placed as sister taxa diverging from the ursine lineage ca. 6 million years ago, with H. malayanus diverging ca. 5 million years ago (Talbot and Shields 1996).
BEHAVIOR. Helarctos malayanus may attack humans, particularly when injured or when with young (Harrisson 1949; Medway 1969). H. malayanus in Thailand may charge without apparent warning or provocation (Lekagul and McNeely 1977); however, Malayan sun bears are inoffensive and timid if not bothered, and even a female with cubs will avoid a human if possible (Fetherstonhaugh 1940). Unprovoked H. malayanus attacks on humans may result from its poor vision, its timidity, or sudden confrontations, where flight appears impossible (Fetherstonhaugh 1940). H. malayanus often stands bipedally to get a better view of distant objects, when it encounters a threat (Lekagul and McNeely 1977), or to get a better scent of distant objects (Fetherstonhaugh 1940).
The Malayan sun bear in the wild may be solitary (Ortolani and Caro 1996). It is largely nocturnal (Lekagul and McNeely 1977; Medway 1969), but its activity may respond to human perturbations (Griffiths and van Schaik 1993). Malayan sun bears were largely diurnal (18%, n 5 28) in an unperturbed area and strictly nocturnal (100%, n 5 4) at a heavily traveled site on the basis of percentage of camera detections classified as nocturnal (Griffiths and van Schaik 1993).
Helarctos malayanus makes grunting and snuffling noises while searching for larvae and adult insects (Fetherstonhaugh 1948). Occasionally, it produces hoarse grunts or loud roars that may be confused with those of the adult male orangutan ( Pongo pygmaeus ). Rarely, Malayan sun bears give short barks like those of muntjac ( Muntiacus) or rhinoceros (Dicerorhinus sumatrensis— Payne and Francis 1985).
HABITAT. Tropical hardwood rainforests are the sun bear’s main habitat. These forests are highly valued by humans for timber production, and are being rapidly converted to second growth forest, cash-crop plantation agriculture and subsistence farming, grazing areas, and human settlements. Malaysia and Indonesia are the world’s leading exporters of tropical hardwoods, and most of these exports originate from the sun bear’s shrinking habitat. The specific impacts on sun bear distribution, population numbers and density, and food supply are unknown; but the consequences are certainly detrimental. These human activities replace important native lowland tropical forest with large expanses of land that cannot be used by bears. Necessary sun bear habitat is eliminated; and the plants, insects, and other foods the bears need also disappear. Deprived of their natural food resources, sun bears sometimes feed on cultivated crops – particularly palm hearts – and thereby destroy them. Such depredating bears are persecuted by landowners and are often killed.
In the wild, U. malayanus sometimes does considerable damage to coconut plantations and is said to be one of the most dangerous animals within its range (Lekagul and Mc-Neely 1977). Young individuals make interesting pets but become unruly within a few years. According to Mills (1993,1994,1995), sun bear cubs are highly popular as pets in the Orient, but when they reach adult size they commonly are sold for their parts, which are used in the medicinal trade. International commerce involving such utilization also is adversely affecting wild populations (see account of Ursus thibetanus). Servheen (1989) reported a general decline because of hunting for gallbladders and other body parts, lack of effective regulation, and logging and conversion of vast areas of forest to cropland and rubber plantations. U. malayanus may now have been extirpated in India and is very rare in Bangladesh and China. It is on appendix 1 of the CITES.
PREDATION THREATS. In terms of animal predation on sun bears, few published records exist. Kawanishi & Sunquist (2004) report on 3 tiger {Panthera tigris) scats containing sun bear remains from peninsular Malaysia. On one occasion, a large python successfully preyed on a female sun bear Fredrickson et. al 2005. Other predators on mainland Southeast Asia and Sumatra could potentially be the common leopard, and the clouded leopard (Neofelis nebulosa), which occur sympatrically with sun bears. The moon bear {Ursus thibethanus), also occurring sympatrically throughout parts of the sun bears range, being substantially larger than the sun bear, could potentially pose a risk to sun bears.
CONSERVATION STATUS. Malayan sun bear numbers are declining drastically because of habitat destruction and poaching for bear parts used in exotic foods, medicines, or aphrodisiacs (Mills and Servheen 1991). H. malayanus may be threatened by demand from Japan and Korea for bear gall bladders for medicinal uses (Payne and Andau 1991).
Helarctos malayanus is an Appendix I species of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES); thus, all international trade is prohibited (Mills and Servheen 1991). However, not all countries within the bear’s range accept CITES. H. malayanus is listed as Vulnerable according to the International Union on the Conservation of Nature and Natural Resources (Corbet and Hill 1992).
Throughout its range, wildlife law enforcement is limited or nonexistent (Mills and Servheen 1991). Malayan sun bears are protected in Laos (Mills and Servheen 1991). In peninsular Malaysia, capture of or trade in Malayan sun bears is prohibited under the Wildlife Act of 1972 (Mills and Servheen 1991). In Sabah, the Malayan sun bear is listed as a game species despite its Vulnerable status (Mills and Servheen 1991). The Wild Animals Reservation and Protection Act prohibits hunting, buying, selling, and consumption of Thailand’s native bears without the government’s permission. The same act allows every Thai to keep as pets 2 of any wild species (Mills and Servheen 1991), thus allowing a legal loophole for wildlife trafficking (Mills 1991; Mills and Servheen 1991). The Burma Wildlife Protection Act of 1936 protects all species within reserve forests; however, neither H. malayanus nor U. thibetanus was protected outside those reserves as of 1988. The Wildlife Protection Ordinance of 1931 prohibits hunting, capture, trade, transit, export, and possession of Malayan sun bears in Indonesia. In China, the Malayan sun bear is a Class I protected species under the Wildlife Protection Law and therefore is protected by the central government (Mills and Servheen 1991).
LITERATURE
To be continued....