Tarsiidae

Diversity

There are 7 extant species of tarsiers, all in the genus Tarsius . Tarsier species are all similar in size, morphology, and ecology. They are all small, nocturnal, predaceous primates specialized for leaping and clinging. Tarsiers are the most "primitive" of the haplorrhine primates , with fossils dating to the Eocene. They were once widely distributed, fossils are known from North America, Europe, North Africa, and Asia.

Geographic Range

Tarsiers are found only in archipelagos in southeast Asia, including Sumatra, Borneo, Sulawesi, and parts of the Philippine Islands.

• Biogeographic Regions
• oriental oriental
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

Tarsier species are all highly arboreal and are found primarily in tropical, forested habitats with dense vertical growth. They use leaping between vertical tree trunks or other vertical supports extensively to get around and this is an important component of their habitats. They may venture into non-forested habitats if there are sufficient vertical surfaces for clinging and leaping. They will jump to the ground to move around as well, but will only remain on the ground momentarily. Sleeping roosts in trees, hollows, and clusters of vines are also important components of their habitats. Most of their foraging time is spent below 1 m in the vertical structure of a forest. Sleeping roosts are mainly at 2 to 5 meters above the ground.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest

• Other Habitat Features
• riparian riparian

Physical Description

Tarsiers are small primates, weighing 80 to 150 g. Their fur is velvety or silky and buff, grayish brown, or dark brown on the back and grayish or buffy on the underside, generally resembling the color of dead leaves or bark. Species from higher altitudes sometimes have curly hair. Their most distinctive features are their round heads, remarkably large eyes that are directed forward, and their medium to large, hairless, and very mobile ears. Their eyes are so large that one of them weighs nearly as much as their brain. The skin in relatively naked areas of the body are often colored by glandular secretions. Males of some species have orange on the skin near their testicles and other species have dark brown spots on their ears. Their muzzle is short, and they seem to have almost no neck (although they are capable of turning their head over 180 degrees!). Tarsiers have long, slender bodies, but tend to look round because of their habit of crouching while clinging to a branch. Body lengths are up to 10 cm. Like all haplorrhines , tarsiers have hairs on their nose pads. There is little to no sexual dimorphism, although males may be slightly larger.

Tarsier forelimbs are short and their hindlimbs elongated, the hindlimbs are longer in proportion to body length than in any other mammal. They are unique among mammals in that the elongation of their hindlimbs is the result of lengthening of the tarsals (especially the calcaneum and navicular) rather than the metatarsals . By elongating the tarsals, tarsiers can lengthen the limbs without sacrificing dexterity of the hands, often a result of metatarsal elongation. The elongation of their tarsals gives their names "Tarsiidae" or " Tarsius ". The digits are extraordinarily long and tipped with soft, rounded toe pads that help them grip and cling to surfaces. The pollex is not opposable, but the hallux is. All digits have flattened nails except the second and third hind toes, which have claw-like nails used for grooming (sometimes called "toilet claws"). The tail is naked except for tufts of hairs at the tip and is thin and long, from 20 to 25 cm. Tarsier species have ridges of skin on the ventral surfaces of their tail that help them to stabilize themselves against tree trunks when clinging.

The skulls of tarsiers are unmistakeable due to the huge, forward-directed orbits . These have expanded rims and are separated by a thin interorbital septum . The dental formula is 2/1, 1/1, 3/3, 3/3 = 34. The upper medial incisors are large and pointed; the upper canines are small; and the upper molars are tritubercular .

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

• Sexual Dimorphism
• sexes alike
• male larger

Reproduction

In species for which information is available, male tarsiers generally have larger home ranges that overlap with those of several females. Males may also rest during the day in the company of one or several females. Some evidence also suggests that a portion of males are not reproductively active and may represent "spare" males that cannot compete with dominant, reproductively active males. Social group members may help to care for offspring.

• Mating System
• polygynous polygynous
• cooperative breeder cooperative breeder

Most tarsier species seem to reproduce seasonally. Some species may reproduce throughout the year, but most births are concentrated seasonally. Tarsiers give birth to a single young after a gestation period of about 6 months. Tarsier young weigh 25 to 30% of their mother's body weight, the largest young relative to maternal body mass in mammals. There is little information on reproduction in some tarsier species. In the few species for which there is information, births peak or occur at the end of the rainy season (generally between February and July, varying regionally).

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

Females invest heavily in their single offspring through gestation and lactation. Young are born at a precocial stage, able to cling and climb on the day of their birth. In some species the young are cared for by their mother as well as the dominant male of the group and subadult or secondary females. Information on parental investment in most species is lacking. Young may associate with their parents for a period of time after weaning.

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

Lifespan/Longevity

Tarsiers can live up to 16 years, although there is little data on wild lifespan for most species.

Behavior

All tarsier species are nocturnal or crepuscular. Most species live in small social groups, sometimes of just a single male and female but often consisting of a single, dominant male, several females, and their dependent young. Western tarsiers ( Tarsius bancanus ) seem to be more solitary. Tarsiers are mainly seen alone during their active, nocturnal phase, but often sleep with other individuals during the day, although some species rest alone as well. Social groups and individuals defend territories with scent marking and vocalizations. Scent marks can be quite consistent in some species, indicating very stable home ranges. Males generally have larger home ranges that overlap with those of several females. When social groups get together, they may spend time grooming each other.

Tarsiers are extremely specialized for vertical clinging and leaping. Their rigid tails with ventral ridges help them to cling to vertical supports. Their extremely elongated hindlimbs, well-developed leg muscles (thigh muscles may represent 12% of total body mass), and long fingers with gripping tips enable them to make impressive leaps of up to 45 times their body length. They are especially adept at backward leaping, propelling themselves backwards, rotating in the air, and landing with their feet. They also use quadrupedal locomotion, small hops, and can run on their hindlimbs on the ground.

• Key Behaviors
• arboreal arboreal
• scansorial
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• sedentary sedentary
• territorial territorial
• social social
• dominance hierarchies dominance hierarchies

Communication and Perception

Tarsiers use scent marking and vocalizations to mark and defend territories and to confirm group membership. Scent marking is through urine and gland secretions deposited onto objects in their environment. Glands are on their lips, chest, and anogenital region. Individuals may vocalize, often at dawn and dusk, but duetting or chorusing is also common among members of social groups. Vocalizations at dawn and dusk may represent times when individuals are departing from or arriving at communal resting areas. The majority of their nocturnal foraging time may be spent alone. Some species are relatively silent except for inter-individual contact calls.

• Communication Channels
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• duets duets
• choruses choruses
• scent marks scent marks

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

Food Habits

Tarsier species eat only animal prey. They use their exceptional vision and hearing at night to detect prey and their agile, rapid leaps to grab prey up to their own size. Their primary prey are arthropods, especially moths and butterflies , orthopterans , ants , and beetles , but they also eat birds, lizards, and snakes. In most species, foraging occurs most at less than 1.5 meters from the ground. In Tarsius spectrum the majority of prey are caught on branches or leaves (~60%) or in the air (~25%). Only about 5% of prey are caught on the ground.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods

Predation

Tarsiers may fall prey to any number of arboreal, nocturnal predators that share their tropical, forested habitats. They have been observed mobbing and being captured by snakes and a slow loris ( Nycticebus ). Their nocturnal habits, exceptionally keen vision and hearing, and their agility protect them from predation to some extent. Their habit of clinging to vertical surfaces makes it more difficult for most animals to capture them.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Tarsier species are important predators of arthropod prey and other animals in their tropical forest habitats. They show remarkable convergences with owls and effectively occupy a similar niche. Over 30 convergences have been noted between owls and tarsiers, including external morphology, characteristics of their inner ears, and their ecology. They are host to a diverse fauna of endoparasites.

Economic Importance for Humans: Positive

Tarsiers are generally too small to be hunted for food. They are fascinating primates, providing perspectives on the evolution of their unique locomotion style and life histories. Their nocturnal habits make them difficult to observe, so ecotourism opportunities are limited. However, tarsiers are efficient predators of large arthropods, many of which are crop pests, so help to control their populations.

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

There are no adverse effects of tarsiers on humans.

Conservation Status

The IUCN recognizes 8 species of tarsiers, including the newly named Lariang tarsier ( Tarsius lariang , 2006). Two species are considered endangered, three are considered vulnerable, 1 is near threatened, and 2 are data deficient. All tarsier species are considered threatened by habitat destruction of 30% or more throughout their range and continued taxonomic uncertainty makes assessing risks difficult. In appropriate, primary forest habitat tarsier species can be common, but they become more rare in degraded habitat. They may be negatively impacted by human use of insecticides in some areas.

Other Comments

The oldest fossil tarsiiform primate is from 50 mya from Eocene sediments and was found in China.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (author), Animal Diversity Web.

Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.

References

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IUCN, 2009. "IUCN Redlist of Threatened Species" (On-line). Accessed July 27, 2009 at http://www.iucnredlist.org/ .

Niemitz, C. 2003. Tarsiers ( Tarsiidae ). Pp. 91-100 in Grzimek Animal Life Encyclopedia , Vol. 14, 2nd Edition. Detroit: Gale Group.

Nowak, R., J. Paradiso. 1983. Walker's Mammals of the World, Fourth edition . Baltimore, London: John Hopkins University Press.

Szalay, F., E. Delson. 1979. Evolutionary History of the Primates . New York: Academic Press.

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Vaughan, T. 1986. Mammalogy, 3rd Edition . Philadelphia: Saunders College Publishing.

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