Dendrogale melanura

Geographic Range

Bornean smooth-tailed tree shrews are found exclusively on the island of Borneo. They are found in the mountainous northern part of the island including the mountains Kinabalu and Trus Madi in Sabah and the mountains of north-eastern Sarawak.

• Biogeographic Regions
• oriental oriental
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

Bornean smooth-tailed tree shrews are arboreal mammals that are endemic to the mountains of tropical northern Borneo. They are restricted to higher altitudes (above 900 m) at elevations averaging 1,524 m. At these elevations, Bornean smooth-tailed tree shrews have been observed in mossy, stunted jungles, though habitats could be more widespread, similar to the closely related northern smooth-tailed tree shrews which are found in evergreen and deciduous forests as well as bushes in rocky savannah. Northern smooth-tailed tree shrews also occasionally exploit undergrowth and understory forest tangles, which may also be true of Bornean smooth-tailed tree shrews.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• rainforest rainforest

Physical Description

Both members of the genus Dendrogale are distinguishable from other tree shrews due to their small body size, shortened rostrum, large ears, lack of shoulder stripes and tail covered by smooth, uniform hairs. Their morphological adaptations are suited to both an arboreal and a ground-dwelling life style. Some of their skeletal adaptations include thin ribs, an elongation of the lumbar region to allow flexion and extension of the vertebral column, a relatively short axis, and cervical vertebrae with wide inter-vertebral spaces to allow increased movement of the neck.

Bornean smooth-tailed tree shrews have a head and body length of 110 to 150 mm with a tail length of 90 to 140 mm and a body weight of approximately 42.5 g. They are distinguishable from the closely related northern smooth-tailed tree shrews by their dark body color, long claws, and lack of prominent facial striping. Bornean smooth-tailed tree shrews have a predominantly black dorsal surface with their ventral surface and the inner surface of their legs a light brownish yellow. They have faint brownish yellow facial stripes above and below the eyes. Based on skeletal morphology, it is likely there is no sexual dimorphism in this species. The dental formula is I 3/3 C 1/1 P 3/3 M 3/3 = 38.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

Nothing is known about the mating system of Bornean smooth-tailed tree shrews. Generally, tree shrew species are believed to be solitary or pair living. Certain species, such as common tree shrews , have also been described living in harems with one male and multiple females. However copulation outside of these groups is believed to occur. Promiscuity may also occur in Bornean smooth-tailed tree shrews. It has been suggested that the majority of mammals in northern Borneo breed over the summer months and likely pair formation occurs just prior to this period.

Nothing is known about reproduction in Bornean smooth-tailed tree shrews. Mammals in northern Borneo are believed to reproduce in the summer during which there is minimal precipitation. Generally, tree shrews tend to have 1 to 3 pairs of mammae and 1 to 3 young, the number varying among different species. The period of gestation in Scandentia ranges from 43 to 56 days. They reach their adult size at approximately three months of age and reach sexual maturity at approximately four months of age.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Details of parental investment in Bornean smooth-tailed tree shrews are not reported in the literature. However, females are likely invest in parental care through gestation and lactation.

• Parental Investment
• pre-fertilization
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female

Lifespan/Longevity

Lifespan of Bornean smooth-tailed tree shrews is not reported in the literature. It may be similar to that of other tree shrew species, approximately 10 years.

Behavior

Behavior of Bornean smooth-tailed tree shrews is not reported in the literature. Tree shrews are generally diurnal, live in pairs or are solitary, and are aggressive and territorial. Common tree shrews live in harems with one male and multiple females, suggesting another potential social structure for Bornean smooth-tailed tree shrews. Both members of the genus Dendrogale are recognized as mainly arboreal based on observations in the wild and skeletal morphology. The behavior of Bornean smooth-tailed tree shrews may be similar to the closely related northern smooth-tailed tree shrews , in which solitary individuals and pairs have been reported. Northern smooth-tailed tree shrews are active in the morning and afternoon and individuals show distress when they leave the cover of vegetation.

• Key Behaviors
• arboreal arboreal
• scansorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• solitary solitary
• territorial territorial

Home Range

Nothing is known about home range size of Bornean smooth-tailed tree shrews. They are believed to be territorial and use olfactory cues to mark the range of their territories. Males and females of common tree shrews have individual territories that precisely overlap and are known to defend these territories from the same sex. Territories held by Bornean smooth-tailed tree shrews could also be potentially sex-specific.

Communication and Perception

Nothing is known about vocalizations of Bornean smooth-tailed tree shrews. Northern smooth-tailed tree shrews emmit short-pitched calls, particularly when climbing. These calls were heard when the animals were at high density in an area during the morning and were not heard at all in the afternoon. The calls emitted consisted of a repetition of 4 to 9 short, high-pitched notes with the pitch rising for the first couple of notes and then remaining more consistent for the last third of the call. It is possible that Bornean smooth-tailed tree shrews emit similar types of calls.

Tree shrews are territorial and believed to use olfactory cues to mark specific spots along the edge of their territories to indicate their range. Tree shrews also emit species specific alarm calls to warn others of danger. Certain tree shrews such as common tree shrews emit chattering noises prior to copulation with females. All of these communication methods may be used by Bornean smooth-tailed tree shrews.

• Communication Channels
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Nothing is known about the diet of Bornean smooth-tailed tree shrews. Tree shrews generally consume a generalist omnivore diet and have a simple digestive system with a caecum. They have been observed, in captivity and in the wild consuming a variety of arthropods, fruits, and small vertebrates. Captive specimens of the closely related northern smooth-tailed tree shrews accept both small pieces of meat and fruit and one wild specimen was observed eating a butterfly.

• Primary Diet
• omnivore omnivore

• Animal Foods
• mammals
• amphibians
• insects

• Plant Foods
• seeds, grains, and nuts
• fruit

Predation

Predation on Bornean smooth-tailed tree shrews is not reported in the literature. Other species of tree shrews may be preyed on by a variety of mammalian, reptilian, and avian predators. Reptiles and birds of prey are thought to be the greatest threat. They avoid predation by avoiding detection by predators. This avoidance of detection is aided by their small body size and cryptic coloring. Tree shrews also produce species specific alarm calls. Likely predators on the island of Borneo are listed below.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

The ecosystem roles of Bornean smooth-tailed tree shrews are poorly understood. There is some evidence that other tree shrews may play an important role in seed dispersal due to the speed and the simplicity of their digestive systems. Bornean smooth-tailed tree shrews may also play a role in the population control of insects, a primary component of their diet. Tree shrews such as common tree shrews are also known to be hosts for a variety of nematode and cestode parasites, which may also be true for Bornean smooth-tailed tree shrews.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

There are no known positive effects of Bornean smooth-tailed tree shrews on humans.

Economic Importance for Humans: Negative

There are no known adverse effects of Bornean smooth-tailed tree shrews on humans.

Conservation Status

Bornean smooth-tailed tree shrews have not been observed since the early 1970s and several trapping efforts between 1989 and 1991 have proved unsuccessful. For this reason the species has been classified as Data Deficient by the IUCN. It is thought that the population is in decline, potentially due to habitat loss occurring at low elevations throughout Borneo caused by logging for agriculture expansion and establishment of non-tree plantations. With further data IUCN may change the classification of this species to Near Threatened or higher. Current conservation efforts for this species are taking place at Crocker Range National Park in Sabah, Borneo. CITES categorizes the entire tree shrew order Scandentia in Appendix II, which means that, while these species are not on the verge of extinction, their trade and use must be regulated to ensure their survival.

Additional Links

Encyclopedia of Life

Contributors

Madeline Bernuetz (author), University of Manitoba, Jane Waterman (editor), University of Manitoba, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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