Tupaia

Diversity

The genus Tupaia is one of four genera within the family Tupaiidae (order Scandentia ). There are currently 20 recognized species of treeshrews across the four genera, with 15 of the species belonging to Tupaia . The diversification of treeshrews is still not well understood. New genetic data suggests that the genus Urogale should be subsumed under Tupaia due to high genetic relatedness This would increase the species included under Tupaia from 15 to 16 species.

Geographic Range

Members of Tupaia are native to regions in Southeast Asia. Treeshrews inhabit a large range of regions because of their extensive species diversity. The majority of species inhabit the Indo-Malaysian region, but treeshrews can be found across India, China, Indonesia, Malaysia, Thailand, Bangladesh, Burma, Borneo, Singapore, Nepal, Bali, the Philippines, and surrounding islands.

• Biogeographic Regions
• oriental oriental
  • native native

Habitat

Species in the genus Tupaia are mainly considered semi-terrestrial. Most species are scansorial and live in both the trees and on the ground of rainforests and other dense forests. These forests are almost exclusively under an elevation of 1,000 m. The only species commonly found higher than 1,000 m above sea level is Tupaia montana , which has a habitat range in mountains between 1,000 m to 3,400 m. The majority of species in Tupaia are found on the forest floor and utilize the fallen logs, branches, tree roots, and other vegetation as foraging sites, pathways, and refuges. During the drier months when vegetation is less dense, treeshrews may be seen more frequently in trees than on the ground. Of the 15 species of treeshrew in Tupaia , only Tupaia minor is primarily arboreal. T. minor lives in the dense canopies above the forest floor year-round. It is difficult to observe treeshrews due to their small stature and habitat with dense vegetation, so the exact amount of time species spend on the forest floor versus in the trees is unknown.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest
• mountains mountains

Systematic and Taxonomic History

The taxonomic classification of treeshrews has been widely misunderstood throughout history. Despite its name, treeshrews are not related to any family of shrews ( order Eulipotyphla ). Treeshrews were also once thought to be grouped with squirrels ( order Rodentia ), culogos ( order Dermoptera ), or primates due to their morphological similarities. Eventually, treeshrews were placed in the now-abandoned order Insectivora .

Data from extensive DNA and morphological analysis has suggested that treeshrews should be classified in their own group, order Scandentia . Initially, Scandentia had one family ( family Tupaiidae ) and two subfamilies ( Tupaiinae and Ptilocerinae ). However, the current classification acknowledges two families: Tupaiidae and Ptiloceridae . Within Ptiloceridae , there is one genus: Ptilocercus . Within Tupaiidae , there are 4 genera: Anathana , Dendrogale , Tupaia , and Urogale . Dendrogale has been recognized as the sister group of the other three genera, but the relationships among Anathana , Tupaia , and Urogale are still undetermined. There have been some efforts to combine Urogale with Tupaia , but this has largely gone unsupported. The order Scandentia is considered monophyletic, although there is a notable lack of systematic reviews for treeshrews. Without understanding the relationship of all the genera, it is difficult to accurately describe the species diversity and taxonomic history within Tupaia .

There have been 120 species of treeshrew proposed, but currently, there are only 20 recognized species. Among these species, 15 belong to Tupaia . The 15 species include: northern treeshrew ( Tupaia belangeri ), golden-bellied treeshrew ( Tupaia chrysogaster ), striped treeshrew ( Tupaia dorsalis ), common treeshrew ( Tupaia glis ), slender treeshrew ( Tupaia gracilis ), Javan treeshrew ( Tupaia javanica ), pygmy/lesser treeshrew ( Tupaia minor ), Bornean treeshrew ( Tupaia longipes ), mountain treeshrew ( Tupaia montana ), Nicobar treeshrew ( Tupaia nicobarica ), painted treeshrew ( Tupaia picta ), Palawan treeshrew ( Tupaia palawanensis ), ruddy treeshrew ( Tupaia splendidula ), Chinese tree shrew ( Tupaia belangeri chinensis ), and large tree shrew ( Tupaia tana ). Most recent taxonomic reviews of Tupaia consider the genus to be monophyletic.

Physical Description

Treeshrews are small mammals with body lengths that range from 12 cm to 21 cm. The tail length is approximately the same or slightly larger than the body size, with a range of 14 cm to 20 cm. There is a large range in body mass, with species weighing from 46 g to 210 g. Treeshrews are monomorphic, as there is no difference in size between males and females. Treeshrews are considered to have a relatively short life expectancy, but the actual lifespan is unknown. Because Tupaia includes many species and because the taxonomic history is still not well-understood, there is some variation in the physical characteristics between species.

All members of Tupaia are described as squirrel-like, with dense, olive-brown fur and lighter coloration on their ventral side. Some species also have white stripes on the shoulders, while others have a black stripe running down the chest or tail. Treeshrews have long bushy tails, hands and feet with multiple digits, and rotating ankle joints that assist in climbing. They are also distinguished by their hairless ears, large eyes, elongated rostrums, and curved claws. Slight modifications to the skeleton can be seen between species. Arboreal treeshrews have wider hind feet than primarily terrestrial species. All members of Tupaia have long snouts, but insectivorous treeshrews have relatively longer rostrums than primarily frugivorous ones. Species that dig have longer, more curved claws than species who are not observed frequently digging. The morphology of treeshrews is representative of their respective diets and habitat preferences. There has been no recorded change in physical appearance during different times of the year.

The dental formula for treeshrews in Tupaia is I 2/3, C 1/1, PM 3/3, M 3/3. They have tribosphenic teeth and dilambdodont molars that occlude with the premolars. The canines are enlarged and curved for stabbing and holding food. The incisors form a tooth comb for self-grooming.

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

• Sexual Dimorphism
• sexes alike

Reproduction

The mating system in Tupaia is generally considered a solitary ranging pair system. In most species, one female and one male form a monogamous pair. The male attracts the female by using vocal calls, and if the female accepts, she responds with the same call. Using scent markings, the pair overlaps their home ranges to form and defend a territory together. Breeding pairs do not spend their time together after reproduction. Both the male and female forage in and defend the same territory range, but act independent of one another. In general, males defend the territory against other males, while females become aggressive towards other females. The pairs nest separately, although some data suggests that the males stay near the female’s nest until the young are fully independent. Within Tupaia , only species T. minor and T. nicobarica have strongly bonded monogamous pairs that forage, nest, and defend together. Some observations have also suggested the presence of a polygynous mating system in select species. Evidence of polygyny is shown when one male has an overlapping range with multiple females, although this system is significantly less common than monogamy. Due to their solitary nature, treeshrews have no observed social hierarchy.

• Mating System
• monogamous monogamous
• polygynous polygynous

Species in Tupaia have two breeding seasons per year. Mating occurs from March to May, then again from August to November. Seasonal breeding seasons can be largely impacted by food availability. Some species stop mating as soon as September, while infrequent breeding events have also been observed from November to February. On average, there are 2 offspring per litter, although there can be between 1 to 4 offspring birthed at a time. During delivery, the mother marks the offspring with her scent to identify them as her own. If delivery occurs while the mother is under stress, the offspring are not scent-marked and will later be consumed by the mother. Offspring are birthed and weaned in a separate nest than either the mother’s or father’s nests. Newborn treeshrews are altricial and weaning occurs immediately after birth. The fat-rich milk from the mother encourages quick development and only lasts between 25 to 33 days. During weaning, young sleep for up to 40 hours at a time, only briefly waking up to clean themselves and the nest. After weaning, the young leave the nest and stay with the mother for 2 to 3 more weeks before becoming fully independent and solitary. Treeshrews in captivity reached sexual maturity at around 3 months, while treeshrews in the wild reached maturity closer to 1 year.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• viviparous viviparous

Parental investment in Tupaia is considered absentee parental care. Both the mother and father have limited investment in the offspring. Before birth, both the mother and father maintain trails and defend the territory. After birth, the father remains in the area and continues to defend the territory until the offspring are independent but provides no direct care. Maternal care is direct, although still limited. The mother births the offspring in a separate nest away from her own and returns to nurse the young approximately every other day. During these alternate visits, the mother spends less than 5 minutes at a time before leaving again. Neither parent provides any grooming or direct protection to the young. The majority of investment comes from the mother’s milk, which is extremely rich in fat and allows the young to develop rapidly. After 25 to 33 days, the young are developed enough to leave their own nest and travel, forage, and nest with the mother. The mother cares for offspring for up to 22 days after they've left the nest, after which the young become fully independent and solitary until reaching sexual maturity.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-hatching/birth
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • female

Lifespan/Longevity

The lifespan of Tupaia has not been formally reported in the literature. Analysis of older treeshrews shows significant tooth wear, but it is unknown whether or not this influences lifespan. More research needs to be done to determine the longevity of treeshrews in the wild and in captivity.

Behavior

Treeshrews are solitary mammals. Social interactions between treeshrews occur primarily between bonded pairs or between a mother and non-independent offspring. Interactions among pairs are limited, lasting between 8 to 20 minutes at a time. Species in Tupaia are both arboreal and terrestrial, although most species spend the majority of their time on the ground foraging and clearing pathways. In order to avoid predation, treeshrews alternate what pathways they use to get between nests and common foraging sites, so a significant amount of time is spent maintaining pathways. Treeshrews are diurnal and most active in the early mornings and evenings of the day. Weather has a significant effect on behavioral patterns. During bad weather, resting times increase and time spent away from the nest is much shorter. On average, over 60% of time is allocated to foraging, 12% spent resting, and the rest of the day being spent grooming, scent-marking, mating, or defending territory. Scent-marking occurs among both males and females. Territories are marked using urine or excretions from the ano-genital region. During mating, both females and females rub against each other to mark their scents on the other. Males will also urinate on females after mating to mark their scent.

• Key Behaviors
• arboreal arboreal
• scansorial
• cursorial
• terricolous
• diurnal diurnal
• motile motile
• solitary solitary
• territorial territorial

Communication and Perception

Treeshrews communicate using vocal calls and scent-marking. Scent-marking is used to claim territory, identify a mate, and identify offspring. Scent-marking via urination is used for short-term markings, while marking using excretions from the ano-genital region can last up to a few days. Within Tupaia , different species have different vocal calls depending on the volume, frequency, and duration of the call. Species can be identified based solely on the sound of their alarm call. Beyond alarm calls, different vocalizations are used to communicate depending on the circumstance. Up to 8 variations in vocal calls have been identified, but there is suspected to be more variation than has been studied so far.

When searching for a mate, males vocalize a type of ‘chattering’ call. If the female is interested in mating, she will mimic the same vocalization to accept the male. Bonded pairs use intermittent high-pitched ‘whistling’ calls to find one another after being separated. Upon finding each other, a lower chattering call is used for further communication. Female treeshrews utilize a similar chattering call when telling newly-weaned young to follow her out of the nest. Offspring that are still weaning were not observed to make any vocal calls at all. Treeshrews also give off loud ‘shrieks’ as warnings during territory disputes or other aggressive behaviors. These warnings occurred among treeshrews, as well as between treeshrews and birds.

• 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

Treeshrews in Tupaia are both insectivorous and frugivorous. Some species have a more diverse diet than others. T. glis eats a wide variety of insects, other small invertebrates, and fruits, while T. gracilis only eats a small variety of insects and fruits, and T. minor eats insects, fruits, and even seeds. There is little information on the exact invertebrate species eaten by treeshrews due to difficulty collecting observational data and limitations on analyzing stomach and fecal samples. Of the 33 fruit species that have been identified, 7 of them belonged to fig trees ( Ficus ). One species, T. montana , also feeds on the exudate produced by pitcher plants ( Nepenthes lowii ).

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
• herbivore herbivore
  • frugivore frugivore
• omnivore omnivore

Predation

Treeshrews prevent predation by employing a variety of strategies to avoid being seen. They are small, fast, quiet, and difficult to spot, making them difficult targets. Their cryptic coloration allows them to blend into vegetation while on the ground and in the trees. Treeshrews maintain multiple pathways throughout dense forests, allowing them to quickly escape predators. They also change their routes frequently to avoid being tracked by their scents. When traveling to their offspring’s nest, females wait multiple days in between visits to keep the young from being found. If spotted by a predator from above, treeshrews can escape into the forest floor. If spotted by a predator from below, treeshrews can escape into the canopies of the trees. Treeshrews will also vocalize a warning call if a potential predator gets too close.

There is limited information on what species predate on treeshrews due to difficulty with collecting observational data. Primary predators include small mammalian carnivores and large birds of prey. Due to the morphology and behavioral patterns of carnivores in the area, most likely predators include mongooses, civets, yellow-throated martens ( Martes flavigula ), Malay weasels ( Mustela nudipes ), marbled cats ( Pardofelis marmorata ), leopard cats ( Prionailurus bengalensis ), and clouded leopards ( Neofelis nebulosa ).

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Treeshrews are important components of the ecosystem due to their role in seed dispersal. The diet of treeshrews in Tupaia consists of insects, fruit, and some seeds. Upon eating the fruit, treeshrews pass the food within 13 to 38 minutes after ingestion. This allows nutrients and energy from the fruit to be gained without digesting the plant seeds. The seeds are then spread with the treeshrew droppings, which maintains plant abundance and diversity within the ecosystem. This creates a mutualistic relationship between the treeshrews and the plants. A commensal relationship can be seen with T. montana and pitcher plants ( Nepenthes lowii ). T. montana feeds on the exudate produced by the plant, which neither harms nor helps the pitcher plant. All species of treeshrew serve as a prey item for other mammalian carnivores as well as some bird species. Treeshrews also contribute to the development of niche spaces and refuges through the creation of foraging pathways. These spaces provide further habitat for species and supports the biodiversity of the ecosystem.

• Ecosystem Impact
• disperses seeds
• creates habitat

Economic Importance for Humans: Positive

The role of Tupaia as seed dispersers is important for maintaining forest ecosystems in and around Asia, which is crucial for supplying humans with natural resources. Insectivorous treeshrews also help control insect pest populations. Treeshrews are extremely important in infectious disease research. Species within Tupaia have been found to have a similar genotype to humans. Treeshrew immune response to human viruses also follows a similar pattern to that of a human immune response. The value of treeshrews as a research model for the testing of bacterial, viral, and genetic conditions is one of the most notable effects of Tupaia on humans.

• Positive Impacts
• research and education
• controls pest population

Economic Importance for Humans: Negative

Treeshrews may be considered a pest in some areas due to their omnivorous, diverse diets which could potentially interfere with farming. However, there is minimal evidence to support this statement. Otherwise, there are no known adverse effects of Tupaia on humans.

• Negative Impacts
• crop pest

Conservation Status

The conservation status for the majority of species in Tupaia is either unknown or decreasing. Only species T. belangeri and T. palawanensis have stable populations. Species T. chrysogaster and T. montana have an unknown population status. All other species in Tupaia have decreasing populations. There is a notable lack of recent population assessments for treeshrews. Confusion with the taxonomic classification of treeshrew species also makes it difficult to determine their conservation status.

There are little to no conservation efforts for Tupaia . Minimal conservation efforts include regulating the trade of wild specimens, although the majority of species do not have any specific legal protection.

Additional Links

Encyclopedia of Life

Contributors

Emma Fike (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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