Pygmy tarsiers inhabit montane cloud forests at elevations between 1800 and 2200 m in the central Sulawesi mountains. At elevations between 1900 and 2000 m, moss-covered conifer forest predominates. Above this elevation, the canopy is only 10 to 20 m high, leaves are small, tree trunks are not buttressed, large woody vines are absent, and species diversity of trees and shrubs is lower than in lowland tropical rainforest. Pygmy tarsiers often reside in the lower canopy, among sapling trunks, and on the forest floor. Upper montane forests are characterized by the presence of dense mist. Humidity in these regions is 85 to 100%, creating a clammy, cold, and wet environment. (Grow and Gursky-Doyen, 2010; Jablonski, 2003; Musser and Dagosto, 1987)
Like other tarsiers, pygmy tarsiers are small-bodied haplorhine primates whose appearance is dominated by large round eyes, large bare ears, long hind limbs with elongated ankles, elongated digits, and a long slender tail.
Pygmy tarsiers are easily distinguished from other tarsiers by their small body size, which averages approximately 50 g, less than half the size of lowland tarsier species. Their head and body length, which ranges from 80 to 111 mm is approximately 75% that of other tarsiers. Pygmy tarsiers do not express sexual dimorphism.
Pygmy tarsiers are similiar in overall appearance to spectral tarsiers, of which they were once considered a subspecies. The pelage of pygmy tarsiers is silky and is longer and denser than that of spectral tarsiers. They are red-brown in color, although pygmy tarsiers occasionally lack the buff colored post-auricular spot common among spectral tarsiers. The underbelly of pygmy tarsiers is buff, grayish, or slate colored. Hair on the face is usually shorter than hair on the rest of the body.
Pygmy tarsiers have a rounded head with a short snout. Their ears are relatively smaller than those of other tarsiers, and the degree of orbital enlargement is smaller than other species. Their eyes are approximately 16 mm in diameter.
Members of this species have a long slender tail. Approximately one third of the ventral surface of the tail is scaly, which is attributed to its function in body posture. The tail is heavily haired and is dark brown or black in color. The tip of the tail bears a tuft of hair.
Pygmy tarsiers, like, spectral tarsiers, have short fore limbs and small hands, suggesting that these animals use their hands more for locomotion than for immobilizing prey, as do other tarsier species. Pygmy tarsiers have several distinctive morphological characteristics that may stem from their unique highland habitat. Their body proportions differ considerably from lowland tarsiers. Pygmy tarsiers have a longer tail relative to head-body length and longer thighs relative to overall hind limb length, Despite their smaller overall size, absolute thigh length is still comparable to that of other Sulawesian tarsiers. These qualities are advantageous for leaping great distances between trees in thin forest cover. The small size of pygmy tarsiers may be an adaptation to the cooler, less productive highland environment. Although most tarsiers have low basal metabolic rates, pygmy tarsiers may have increased metabolic rates due to their small size and cold habitat.
Although most tarsiers have reduced nails that do not extend past the digital pads, pygmy tarsiers have nails on all five digits of the hand, including the hallux, and on the two lateral digits of the foot. These nails extend beyond the edge of the digital pads, are laterally compressed, and are sharply pointed at the tips, resembling claws. The digital pads on both their hands and feet are reduced in size. Both their claw-like nails and reduced pads are thought to provide a better grasp on the mossy substrate to which they cling during feeding and locomotion. (Groves and Shekelle, 2010; Grow and Gursky-Doyen, 2010; Musser and Dagosto, 1987; Niemitz, 1984; Nowak, 1999; Schwartz, 2003)
Because they are infrequently observed and until recently were considered a subspecies of spectral tarsiers (Tarsius tarsier), little is known regarding the mating systems of pygmy tarsiers. Spectral tarsiers, their closest geographic neighbor and a member of the genus, are typically monogamous, although some social groups consistently exhibit polygyny. (Grow and Gursky-Doyen, 2010; Gursky-Doyen, 2010)
Although little is known regarding the reproductive behavior of pygmy tarsiers, it likely resembles that of other tarsiers. Spectral tarsiers have two breeding seasons annually, spaced 6 months apart. One breeding season occurs at the beginning of the rainy season, and the other occurs at the end of the rainy season. Births in spectral tarsiers occur in May and from November to December.
Pygmy tarsiers likely have a long gestation period of around 6 months and produce only one offspring per year. Gestation of Philippine tarsiers lasts 178 days, after which time a fully furred, well-developed offspring is born. Young cling to the mother's ventrum or are carried in the mouth. Philippine tarsiers are precocial, and offspring are soon able to follow their kin. They can leap at about 1 month of age and can capture prey at approximately 42 days of age. Weaning is thought to occur shortly afterward. Prenatal development is incredibly slow in western tarsiers, and, as such, neonates are born with approximately 60 to 70% of the brain mass and 20% of the body mass of an adult. Newborn spectral tarsiers have similarly high infant-to-adult weight ratios of 20 to 33%. Female western tarsiers can first conceive around 2 years of age in captivity. (Fitch-Snyder, 2003; Grow and Gursky-Doyen, 2010; Gursky, 2000; Musser and Dagosto, 1987; Nowak, 1999; Schwartz, 2003)
Little is known regarding parental investment of pygmy tarsiers. In closely related spectral tarsiers, parental care is primarily maternal. Some allocare is exhibited by subadult females, and much less so by adult and subadult males, but this is extremely limited compared to that displayed by some platyrrhine primates. Philippine tarsiers are born well-developed, and young cling to their mother's belly. Mothers nurse their young and may also carry young in their mouth. Young spectral tarsiers mature quickly; they can travel in groups 23 days after birth and are able to hunt alone after 42 days. Young females remain with their parents until adulthood, whereas young males leave their natal group as juveniles. (Gursky, 2000; Musser and Dagosto, 1987; Nowak, 1999)
Little information is available regarding longevity of pygmy tarsiers. The oldest wild-caught tarsier continued to live in captivity until 12 years, 5 months of age (a male Tarsius syrichta). Record lifespans of captive-bred tarsiers are 11 years, 10 months (a male Tarsius syrichta) and over 13 years (a female Tarsius bancanus).
Tarsiers are nocturnal or crepuscular and mainly arboreal. In the dense vegetation of their habitat, pygmy tarsiers spend most of the day sleeping on vertical branches or possibly in hollow trees. When clinging to a vertical branch, they often use their tail to brace themselves against the vertical support and to support their body. The head of pygmy tarsiers tends to drop downward between the shoulders when sleeping. If disturbed while resting, these animals may move up and down the vertical support with the face presented towards the threat, mouth open, and teeth bared. When waking, pygmy tarsiers continuously furl or crinkle their ears.
Tarsiers spend much of their time scanning for prey from low positions on tree trunks. Although they do not build nests, they may return to the same tree to sleep. Preferred sleeping trees are large, and scarcity of large trees at high altitudes may restrict the number of possible sleeping sites for this species.
Pygmy tarsiers have a wide field of vision and can rotate their head nearly 360 degrees. They can leap several meters from tree to tree, and their leaps tend to be froglike. On a flat surface, they can leap from 1.2 to 1.7 m long and up to 0.6 m high. When leaping, their tail is arched over their back. When walking on all fours, however, the tail hangs down.
Only one group of pygmy tarsiers has been observed in the wild. This group consisted of 1 adult female and 2 adult males, which is unusual for Tarsius. Lowland Sulawesian tarsiers usually live in family groups of 1 adult male, 1 to 2 adult females, and offspring, though group size varies with resource availability and other ecological factors. Social group composition of pygmy tarsiers may be a result of ecological constraints unique to their high-altitude habitat, which alters the dynamics of group living. The population density of pygmy tarsiers also appears to be much lower than that of other tarsiers, as indicated by the historical difficulty in finding individuals to confirm the continued existence of the species. A 3-month survey found only 3 individuals in 60 nights of attempted trapping, whereas in another 3-month survey, 100 spectral tarsiers were recorded.
Spectral tarsiers, and possibly pygmy tarsiers, are territorial. Spectral tarsiers actively chase others out of their home range and mark their core areas by rubbing the branches with urine and epigastric glands. (Groves and Shekelle, 2010; Jablonski, 2003; Musser and Dagosto, 1987; Nowak, 1999)
Little is known regarding the home range of pygmy tarsiers. Female pygmy tarsiers have a home range of at least 1.2 ha. Males and females exhibit different patterns of travel, and males are difficult to track. (Groves and Shekelle, 2010)
Tarsiers commonly communicate through vocalizations and urine scent marking. However, each of these is observed much less frequently among pygmy tarsiers than other species. The infrequency of observed scent marking in this species, however, may be due to difficulty in monitoring canopy habitat and high rainfall quickly washing away urine.
The auditory bullae of pygmy tarsiers are more enlarged than those of other tarsiers, perhaps because the heavy fog and thick moss cover common in their habitat tend to reduce sound travel. However, vocal communication is markedly reduced in pygmy tarsiers. They rarely perform the male-female vocal duets or family choruses typical of lowland species. Because these vocalizations are associated with territory maintenance, this could indicate that pygmy tarsiers are less territorial than lowland species, or that they make use other means of communication to communication the same information.
The eye of tarsiers is unique among primates and is largely responsible for tarsier survival. Lacking a tapetum lucidum, the eyes of tarsiers are greatly enlarged to allow night vision. The average volume of their eyes is equal to the average tarsier cranial capacity. Because their eyes are immobile within the orbits, tarsiers adjust their vision by moving their head, which can rotate through nearly 180 degrees in either direction. The extent to which tarsiers use visual signals, such as postures and displays, is not known
In all primate species tactile communication is important between mothers and their offspring, as well as between mates. (Groves and Shekelle, 2010; Grow and Gursky-Doyen, 2010; Musser and Dagosto, 1987; Nowak, 1999; Schwartz, 2003)
Tarsiers are the only primates that are totally carnivorous. Pygmy tarsiers are insectivorous and eat primarily arthropods with heavily keratinized exoskeletons. Larger arthropods are less abundant at higher altitudes. Pygmy tarsiers also commonly prey upon small vertebrates.
Tarsiers hunt by leaping from tree trunks and pouncing on terrestrial prey. They kill prey by biting down with the anterior teeth, and they chew with a side to side motion. Tarsiers typically take large prey for their body size and consume the entire prey, which can result in large fluctuations in body weight. Pygmy tarsiers drink water by lapping. (Grow and Gursky-Doyen, 2010; Musser and Dagosto, 1987; Nowak, 1999; Schwartz, 2003)
Despite the rarity of alarm calls, predation is a considerable threat to pygmy tarsiers. Most common predators are diurnal raptors, the main birds of prey in Sulawesi. The open canopy cover of the highland montane forests makes this species especially vulnerable to raptor attacks. (Grow and Gursky-Doyen, 2010; Musser and Dagosto, 1987)
Pygmy tarsiers consume a large variety of arthropods and small vertebrates, and they are preyed upon by diurnal raptors. Tarsiers also act as hosts to a number of ecto- and endoparasites. (Brack and Niemitz, 1984; Grow and Gursky-Doyen, 2010; Jablonski, 2003)
There are no known adverse effects of pygmy tarsiers on humans.
Because they are only known from a few museum specimens and one wild group, the IUCN lists pygmy tarsiers as "Data Deficient." However, populations are small, fragmented and declining, and this species could easily become endangered. Deforestation is a threat, although their remote habitat, which has thus far seen only small-scale human expansion, may place this species at lesser risk.
The CITES treaty on the international trade in wildlife includes all tarsiers in Appendix II, limiting international trade. (Grow and Gursky-Doyen, 2010; Musser and Dagosto, 1987; Nowak, 1999; Shekelle and Salim, 2008; Wright, 2003)
Trevor Ford (author), Yale University, Eric Sargis (editor), Yale University, Gail McCormick (editor), Animal Diversity Web Staff.
uses sound to communicate
Referring to an animal that lives in trees; tree-climbing.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species
active at dawn and dusk
to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
union of egg and spermatozoan
An animal that eats mainly insects or spiders.
animals that live only on an island or set of islands.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
parental care is carried out by males
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
found in the oriental region of the world. In other words, India and southeast Asia.
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
specialized for leaping or bounding locomotion; jumps or hops.
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
young are relatively well-developed when born
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Niemitz, C. 1984. Taxonomy and distribution of the genus Tarsius Storr, 1780. Pp. 1-16 in Biology of Tarsiers. New York: Gustav Fischer Verlag.
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Schwartz, J. 2003. How Close Are the Similarities between Tarsiers and Other Primates?. Pp. 50-96 in P Wright, E Simons, S Gursky, eds. Tarsier: Past, Present, and Future. New Brunswick: Rutgers University Press.
Shekelle, M., A. Salim. 2008. "Tarsius pumilus" (On-line). In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. Accessed May 08, 2011 at http://www.iucnredlist.org/apps/redlist/details/21490/0.
Wright, P. 2003. Are Tarsiers Silently Leaping into Extinction?. Pp. 296-308 in P Wright, E Simons, S Gursky, eds. Tarsiers: Past, Present, and Future. New Brunswick: Rutgers University Press.