Tarsiidae is the only family in the genus Tarsius. There are 7 extant species of tarsiers, all similar in size, morphology, and ecology. They are all small, nocturnal, carnivorous primates specialized for leaping and clinging. Tarsiers are the most "primitive" of the haplorhine primates, with fossils dating to the Eocene. They were once widely distributed, fossils are known from North America, Europe, North Africa, and Asia (Niemitz, 2003). Tarsier species are all highly arboreal and are found primarily in tropical, forested habitats with dense vertical growth. They use “vertical clinging and leaping” between tree trunks or other vertical supports extensively while locomoting (Niemitz, 2003). 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. 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 (Feldhamer et al., 1999; Groves, 1989; Niemitz, 2003).
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.
Tarsiers are found only in archipelagos in southeast Asia, including Sumatra, Borneo, Sulawesi, and parts of the Philippine Islands.
Biogeographic Regions: oriental (Native )
Other Geographic Terms: island endemic
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 ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike; male larger
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 ; terrestrial
Terrestrial Biomes: forest ; rainforest
Other Habitat Features: riparian
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 tarsier 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 (Insectivore , Eats non-insect arthropods)
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.
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.
- slow lorises (Nycticebus)
- snakes (Serpentes)
Anti-predator Adaptations: cryptic
Life History and Behavior
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 ; chemical
Other Communication Modes: duets ; choruses ; scent marks
Perception Channels: visual ; tactile ; acoustic ; chemical
Tarsiers can live up to 16 years, although there is little data on wild lifespan for most species.
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 ; 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 ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; 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 ; 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)
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimens with Sequences:7
Specimens with Barcodes:4
Species With Barcodes:2
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.
Relevance to Humans and Ecosystems
There are no adverse effects of tarsiers on humans.
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
Tarsiers are haplorrhine primates of the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes. Although the group was once more widespread, all the species living today are found in the islands of Southeast Asia.
Fossils of tarsiiform primates are found in Asia, Europe, and North America, with disputed fossils from Africa, but extant tarsiers are restricted to several Southeast Asian islands, including the Philippines, Sulawesi, Borneo, and Sumatra. The fossil record indicates that their dentition has not changed much, except in size, in the past 45 million years.
Within the family Tarsiidae, there are two extinct genera, Xanthorhysis and Afrotarsius. However, the placement of Afrotarsius is not certain, and it is sometimes listed in its own family, Afrotarsiidae, within the infraorder Tarsiiformes, or considered an anthropoid primate.
So far, three fossil species of the genus Tarsius are known from the fossil record:
- Tarsius eocaenus is known from the Middle Eocene in China.
- Tarsius thailandicus lived during the Early Miocene in northwestern Thailand.
- Tarsius sirindhornae lived during the Middle Miocene in northern Thailand.
The genus Tarsius has a longer fossil record than any other primate genus, but the assignment of the Eocene and Miocene fossils to the genus is questionable.
The phylogenetic position of extant tarsiers within the order Primates has been debated for much of the past century, and tarsiers have alternately been classified with strepsirrhine primates in the suborder Prosimii, or as the sister group to the simians (=Anthropoidea) in the infraorder Haplorrhini. Analysis of SINE insertions, a type of macromutation to the DNA, is argued to offer very persuasive evidence for the monophyly of Haplorrhini, where other lines of evidence, such as DNA sequence data, remain ambiguous. Thus, some systematists argue the debate is conclusively settled in favor of a monophyletic Haplorrhini. In common with simians, tarsiers have a mutation in the L-gulonolactone oxidase (GULO) gene, which confers the need for vitamin C in the diet. Since the strepsirrhines do not have this mutation and have retained the ability to make vitamin C, the genetic trait that confers the need for it in the diet would tend to place tarsiers with haplorrhines.
At a lower phylogenetic level, the tarsiers have, until recently, all been placed in the genus Tarsius, while it was debated whether the species should be placed in two (a Sulawesi and a Philippine-western group) or three separate genera (Sulawesi, Philippine and western groups). Species level taxonomy is complex, with morphology often being of limited use compared to vocalizations. Further confusion existed over the validity of certain names. Among others, the widely used T. dianae has been shown to be a junior synonym of T. dentatus, and comparably, T. spectrum is now considered a junior synonym of T. tarsier.
In 2010, Colin Groves and Myron Shekelle suggested splitting the genus Tarsius into three genera, the Philippine tarsiers (genus Carlito), the western tarsiers (genus Cephalopachus), and the eastern tarsiers (genus Tarsius). This was based on differences in dentition, eye size, limb and hand length, tail tufts, tail sitting pads, the number of mammae, chromosome count, socioecology, vocalizations, and distribution. The senior taxon of the species, T. tarsier was restricted to the population of a Selayar island, which then required the resurrection of the defunct taxon T. fuscus. Their classification, which includes several newly described species, is as follows:
- Infraorder Tarsiiformes
- Family Tarsiidae: tarsiers
- Genus Carlito
- Philippine tarsier, Carlito syrichta
- C. s. syrichta
- C. s. fraterculus
- C. s. carbonarius
- Philippine tarsier, Carlito syrichta
- Genus Cephalopachus
- Horsfield's tarsier, Cephalopachus bancanus
- C. b. bancanus
- C. b. natunensis
- C. b. boreanus
- C. b. saltator
- Horsfield's tarsier, Cephalopachus bancanus
- Genus Tarsius
- Genus Carlito
- Family Tarsiidae: tarsiers
Anatomy and physiology
Tarsiers are small animals with enormous eyes; each eyeball is approximately 16 mm in diameter and is as large as its entire brain. The unique cranial anatomy of the tarsier results from the need to balance their large eyes and heavy head so they are able to wait silently for nutritious prey. Tarsiers have an incredibly strong auditory sense because their auditory cortex is very distinct. Tarsiers also have very long hind limbs, due mostly to the extremely elongated tarsus bones of the feet, from which the animals get their name. The combination of their elongated tarsi and fused tibiofibulae makes them morphologically specialized for vertical clinging and leaping. The head and body range from 10 to 15 cm in length, but the hind limbs are about twice this long (including the feet), and they also have a slender tail from 20 to 25 cm long. Their fingers are also elongated, with the third finger being about the same length as the upper arm. Most of the digits have nails, but the second and third toes of the hind feet bear claws instead, which are used for grooming. Tarsiers have very soft, velvety fur, which is generally buff, beige, or ochre in color.
The tarsier's brain is different from other primates in terms of the arrangement of the connections between the two eyes and the lateral geniculate nucleus, which is the main region of the thalamus that receives visual information. The sequence of cellular layers receiving information from the ipsilateral (same side of the head) and contralateral (opposite side of the head) eyes in the lateral geniculate nucleus distinguishes tarsiers from lemurs, lorises, and monkeys, which are all similar in this respect. Some neuroscientists suggested that "this apparent difference distinguishes tarsiers from all other primates, reinforcing the view that they arose in an early, independent line of primate evolution."
Tarsiers are the only extant entirely carnivorous primates: they are primarily insectivorous, and catch insects by jumping at them. They are also known to prey on birds, snakes, lizards, and bats.
Pygmy tarsiers differ from other species in terms of their morphology, communication, and behavior. The differences in morphology that distinguish pygmy tarsiers from other species are likely based on their high altitude environment.
All tarsier species are nocturnal in their habits, but like many nocturnal organisms, some individuals may show more or less activity during the daytime. Based on the anatomy of all tarsiers, they are all adapted for leaping even though they all vary based on their species.
Ecological variation is responsible for differences in morphology and behavior in tarsiers because different species become adapted to local conditions based on the level of altitude. For example, the colder climate at higher elevations can influence cranial morphology.
Gestation takes about six months, and tarsiers give birth to single offspring. Young tarsiers are born furred, and with open eyes, and are able to climb within a day of birth. They reach sexual maturity by the end of their second year. Sociality and mating system varies, with tarsiers from Sulawesi living in small family groups, while Philippine and western tarsiers are reported to sleep and forage alone.
Tarsiers tend to be extremely shy animals.
A sanctuary near the town of Corella, on the Philippine island of Bohol, is having some success restoring tarsier populations. The Philippines Tarsier Foundation (PTFI) has developed a large, semi-wild enclosure known as the Tarsier Research and Development Center. Carlito Pizarras, also known as the "Tarsier man", founded this sanctuary where visitors can observe tarsiers in the wild. As of 2011, the sanctuary was maintained by him and his brother. The trees in the sanctuary are populated with nocturnal insects that make up the tarsier's diet.
The conservation status of all tarsiers is vulnerable to extinction. Tarsiers are a conservation dependent species meaning that they need to have more and improved management of protected habitats or they will definitely become extinct in the future.
The 2008-described Siau Island tarsier is regarded as Critically Endangered and was listed among The World's 25 Most Endangered Primates by Conservation International and the IUCN/SCC Primate Specialist Group in 2008. The Malaysian government protects tarsiers by listing them in the Totally Protected Animals of Sarawak, the Malaysian state in Borneo where they are commonly found.
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- General references
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