Tarsiers

(Tarsiidae)

Class Mammalia

Order Primates

Family Tarsiidae

Thumbnail description
Very small nocturnal primates with huge eyes, extremely long hind limbs, and a long and thin more or less sparsely haired tail; all species are brownish or grayish ochre in color

Size
11–16.4 in (28–42 cm); 3.1–5.1 oz (90–145 g)

Number of genera, species
1 genus; 6 or more species

Habitat
Secondary and primary rainforest, scrub, agroforestry plantations, grass, mangroves

Conservation status
Lower Risk/Near Threatened: 1 species; Lower Risk/Conservation Dependent: 1 species; Data Deficient: 4 species

Distribution
Parts of the Southeast Asian archipelagos including Sumatra, Borneo, Sulawesi, and some of the Philippine Islands

Evolution and systematics

Although bearing many derived modern features, the extant tarsiers are the most ancestral haplorhine (tarsiers, monkeys, apes, and humans) living primates. The undisputed oldest fossil representative of tarsiers, Xanthorhysis tabrumi, is not less than 50 million years old, and was unearthed by Beard and colleagues in Eocene sediments in China. Once, the tarsiiform primates were widely distributed, fossil remains being found, for example, in Egypt, Germany, France, Thailand, and North America (Wyoming, New Mexico). The extinct tarsiiform family of Omomyidae shares quite a number of traits with the extant Tarsius, such as the olfactory bulb lying above the interorbital septum. But at present, the mosaic of shared and less similar characters does not allow a definitive decision about the probable direct ancestors of the present day tarsiers.

Like all other haplorhine primates, the tarsiers are very probably derived from diurnal ancestors, as they have lost the tapetum lucidum in their eyes, a reflecting layer that maximizes light-gathering capacity. By contrast, this reflecting tapetum is characteristic of all nocturnal strepsirhine (prosimian) primates. Sharing a central fovea in the retina of their eyes, a fused frontal bone, and a posteriorly closed orbit with anthropoid primates, as well as many other features, the tarsiers are recognized, today, as a sister group of the anthropoid primates. Their closest living relatives are South American platyrrhine monkeys. This is also supported by recent findings in molecular genetics.

Therefore, anthropoid primates and tarsiers, together, have to be united in the suborder Haplorhini. As Groves found in 1998, the term prosimian is no longer appropriate in a formal taxonomic sense, but belongs in the realm of folk taxonomy. To include tarsiers within the prosimians, i.e. together with the lemurs, galagos, etc., however, is somewhat misleading, as it groups these higher, haplorhine primates falsely with the less closely related Strepsirhini.

At present, the single extant family, Tarsiidae, includes only one genus, Tarsius, although the validity of a second genus Rabienus was seriously discussed by Groves in 1998. Until 1984 only three tarsier species were recognized, but currently six

species are recognized. Two or three more species may be added within the coming years.

Physical characteristics

Tarsiers are very small nocturnal and crepuscular primates. They possess a short-snouted, round head, ranging between 1.4 and 1.7 in (3.5–4.4 cm) in length, and middle-sized to very large, skinny, mobile ears. Their eyes are huge, with one eye weighing nearly as much as the whole brain. The eyes do not fit into the cranial orbit, but protrude from their sockets like an egg in an egg cup. The owl-like appearance of tarsiers is a consequence of many common features in the biology of both these nocturnal predators. More than 30 such convergences of tarsiers with owls have been described, such as the same pelage color in both sexes, similarities in the anatomy of the eyes, the semicircular canals in the inner ear, and the sensory biology for prey location. The dental formula for tarsiers is (I2/2 C1/1 P3/3 M3/3) 2 36.

The fur of all species shows the colors of dead leaves, i.e., the tarsiers are sand-colored to ochre or grayish buff, with a considerable variation towards reddish or brownish. The Philippine species (Tarsius syrichta) tends to be lighter than the western tarsier (T. bancanus) and the Sulawesi species (T. spectrum). The fur is velvet-like but sometimes somewhat curly. A curly pelage seems to be more frequent in tarsiers from higher altitudes. All sparsely haired or naked parts of

the skin are pigmented ranging from a more sandy color, e.g. in the Philippine species, to a rich dark brown, e.g., in Dian's tarsier (T. dianae). Orange skin color at the testicles or dark brown patches in the ears, however, are caused by secretions from skin glands.

The slender body, reaching up to about 4 in (10 cm) in length, often appears round in the clinging or sitting animals. The hands are equipped with long or even extraordinarily long, very prehensile fingers for clinging and climbing, but especially for catching prey. Their tips have round discs of finger pads for an enhanced grip when clinging to vertical stems. The thumb is opposable to the palm and the fifth digit through movements in its basal joint. As an extreme adaptation to leaping between vertical supports, the hind limbs are longer in relation to body size than in any other mammal, reaching 2.3 times the length of the precaudal spine. As a portion of the hind extremity, the foot is proportionately longer than the thigh and the lower leg, which is mainly due to the strongly elongated calcaneal and navicular bones. There is a strong, opposable great toe. Except for toilet claws on the second and third toes, all toes and fingers have nails.

The tail of all species is long and rodlike. Except for the pygmy tarsier (T. pumilus), where it is certainly shorter, the tail measures between 7.8 and 9.8 in (20–25 cm), which is about 2.5 times the trunk length. In the Sulawesi tarsiers, the tail retains scaly skin structures, a most ancestral and, therefore, most spectacular feature, which is not found in any other primate. The tails of all species appear to be naked, at least partially. This is most obvious in the Philippine tarsier, which possesses only a thin, roughly 2.4 in (6 cm) long, sparsely haired tuft, the length of the single hair being only about 0.1 in (3 mm) long. In the western tarsier, the tuft hair is about 0.3 in (7 mm) long, whereas in the Sulawesi species the single hairs may measure 0.2–0.5 in (5–12 mm). Although far from being bushy, more than half of the distal part of the tail of the Sulawesi tarsiers is hairy.

There is a sensitive skin area on the ventral side of the tail of all tarsier species. Being endowed with papillary skin ridges, this is friction skin that is used as a support area. Tarsiers spare much of their energy budget by sitting on their tails when resting on a vertical support, much like woodpeckers do.

Distribution

Tarsiers are found from southeastern Sumatra in the west to the Philippine island of Mindanao in the east, and from the Philippine island of Samar in the north to the Indonesian island of Selayar in the south. Thus their range extends from 102°E to 127°E and from 13°N to 7°S—about 1,700 mi (2,750 km) longitudinal range and about 1,300 mi (2,100 km) latitudinal range.

Habitat

All tarsiers are predominantly arboreal and are considerably adapted to more or less vertical supports.

Western tarsiers strongly prefer vertical supports of 0.4–1.6 in (1–4 cm) in diameter. Leaping between vertical tree trunks, they use only a very thin layer of the space of their habitat, foraging more than 80% of the time below 3 ft (1 m) above the ground. Soil contacts make up roughly 5% of all leaps, but they consume only about 1% of the time budget. Sleeping sites of the western tarsier (for single individuals) are often found between 6.6 and 16.4 ft (2–5 m) above the ground.

Spectral tarsiers (T. spectrum) sleep in small groups, often in hollow trees or densely growing vines, mostly between 3 ft (1 m) and roughly 60 ft (20 m) above the ground.

Also, some tarsiers may venture into other neighboring habitats like mangrove areas, grassland, or diverse forms of plantations, provided that both suitable supports for clinging and leaping are present and prey animals are found in sufficient numbers. Habitat choice above the ground between vertical supports must be a very efficient mechanism for predator avoidance, as tarsiers produce very few offspring.

Behavior

Although they are social primates, as demonstrated, for example, by their territorial scent marking behavior, tarsiers are not or not very gregarious during their activity phase. Scent marking behavior includes the deposition of urine and secretions from skin glands within their lips, on their chest, and in their anogenital region. Group or duetting vocalizations near or at the sleeping site, known from all Sulawesi forms, may be an expression of pair or group coherence. The Philippine and the western tarsiers are not silent, but territorial group vocalizations or duetting have never been reported.

Tarsiers are nocturnal animals, but at least some of the species also show high crepuscular activity. Vocalizations near sleeping sites in the Sulawesi species and subspecies may mark the temporal transition from non-gregarious nocturnalism and diurnal gregarious primates in each of the species concerned.

Tarsiers are vertical clingers and leapers. They are world champions in backward leaping, catapulting themselves backward from a vertical support, turning around in mid-leap, and landing forward on the next tree sapling. With one leap they may cover the distance of 45 times their body length.

Feeding ecology and diet

All tarsiers eat animal food exclusively; no field or captive studies have documented any plant food in their diet. Tarsiers locate their prey by sound or by sight, their closest competitors

being insectivorous bats and small owls. They catch and relish all sorts of arthropods. Birds up to their own body weight have been observed to be caught in mid-flight and killed on the ground, their head, brain, and beak being completely eaten. Lizards and even poisonous snakes can be killed and eaten. Their unselective menu may be a kind of life insurance, as they may, in times of seasonal scarcity, just switch to a different kind of prey.

Tarsiers prefer to eat during vertical clinging. Although this behavior seems to be the best predator prevention, when the animal is distracted and chewing noisily, the sympatric slow loris may catch a tarsier. Also, a constricting snake was observed killing a tarsier, in spite of being heavily mobbed by other tarsiers.

Thus far, only the western tarsier has been studied for parasites. Without exception, all individuals investigated were infested by endoparasites. According to a yet unpublished feces analysis, the same seems to be true also for spectral tarsiers.

Reproductive biology

Tarsiers give birth to a single offspring and never have twins. This is due to the fact that at birth an infant tarsier weighs almost one-quarter of its mother's weight, an accomplishment that is unique among the primates and probably among mammals as well. About 100 years ago Hubrecht investigated some 600 pregnant uteri, finding only one pair of twins at a very early stage (one of which could have easily been resorped at a later stage). Tarsiers have an ovarian cycle of about 28 days. Through 2003, seasonal births had been observed in three tarsier species.

Although there are indications of pair bonding (e.g., snuggling behavior at a shared common sleeping site), the greater home rages of males and the presence of sexual dimorphism (though weaker than in many other primates) indicate a certain degree of polygamy in the tarsiers' reproductive system.

Conservation status

Although tarsiers do not appear to be rare in many areas, they are very sensitive to changes in their environment. For example, Merker found the population density of Dian's tarsier to be 268 individuals per 0.04 mi² (1 km²) in undisturbed primary forest, 130–190 in slightly or medium disturbed areas, and 45 in plantations outside natural forest. Neri-Arboleda found 16 males and 41 females of the Philippine tarsier per 0.04 mi² (1 km²), mainly in early mid-succession forest. All authors agree that rapid habitat destruction is the major threat to the tarsiers. The spectral tarsier is listed by the IUCN as

Lower Risk/Near Threatened; Dian's tarsier as Lower Risk/Conservation Dependent; and the Philippine, pygmy, western, and Sangihe tarsiers are listed as Data Deficient.

Significance to humans

Tarsiers are too small to be hunted. With only one young per year they do not have the potential to be pests. Since they eat many harmful insects including grasshoppers, moths, and caterpillars, they may play an unquantified role as pest control agents in agroforestry. However, tarsiers are at risk, if insecticides are applied by humans. With their huge eyes tarsiers appear in very different kinds of art, from an edging of the famous "Vienna School" to the cover of a science fiction novel. Also, the famous extraterrestrial movie creature E.T. undoubtedly shows the features of a tarsier.

Species accounts

List of Species

Philippine tarsier

Tarsius syrichta

taxonomy

Tarsius syrichta Linnaeus, 1758, southern Philippine Islands.

other common names

French: Tarsier des Philippines; German: Philippinenkoboldmaki.

physical characteristics

11.5–15.9 in (29.–40.2 cm); 3.9–5 oz (110–142 g); light buff or sand-colored, more gray than the other species; tail tuft very sparse and short.

distribution

Southeastern Philippine islands of Samar, Marippi, Biliran, Leyte, Dinagat, Siargao, Bohol, and Mindanao.

habitat

Secondary lowland rainforest in early mid-succession, rarely shrubs or bamboo, not in grassland or plantations.

behavior

Family groups with one male and one or two females with their offspring. The home ranges of males and their (first) female overlap to about 40%. Males and females sleep separately. Nocturnal and crepuscular; generally silent, but make contact calls.

feeding ecology and diet

Hunting for small invertebrates and vertebrates, mostly 3–6 ft (1–2 m) above the ground, leaping to about 85% between vertical stems.

reproductive biology

Likely polygamous. One offspring is born, in most cases by the end of the rainy season between April and July. Gestation lasts approximately six months.

conservation status

Data Deficient.

significance to humans

None known.

Western tarsier

Tarsius bancanus

taxonomy

Tarsius bancanus Horsfield, 1821, eastern Sumatra, Borneo, and adjacent island.

other common names

English: Horsfield's tarsier; French: Tarsier occidental; German: Sundakoboldmaki.

physical characteristics

12.6–14.6 in (32–37 cm); 3.8–4.8 oz (107–135 g); buff, sometimes sand-colored; tail tuft short, but well developed. Biggest eyes in relation to head size in any mammal.

distribution

Southeastern Sumatra and Borneo, and the islands of Bangka, Belitung, Karimata, and Serasan.

habitat

Secondary and primary rainforest, shrubs, plantations.

behavior

Scent marking is very traditional, indicating very stable home ranges. Males and females sleep separately. Rather silent, nocturnal and crepuscular.

feeding ecology and diet

Western tarsiers eat anything that moves and does not defend itself too effectively, from ants and beetles to bats and birds, even animals up to the tarsier's own body weight. On one occasion, a western tarsier was observed catching and eating a poisonous snake.

reproductive biology

Different field studies suggest pair bonds or polygynous social organization. Births occur throughout the year, with a conspicuous increase in frequency by the end of the rainy season between February and June. The giant baby, weighing about one quarter of its mother's weight, is able to climb on the first day of its life. Some skeletally adult males have small testes, suggesting the existence of a social category of reproductively inactive "spare males."

conservation status

Data Deficient.

significance to humans

This tarsier was considered an omen animal by the formerly head-hunting Iban people in Sarawak, Borneo. Since their extremely flexible cervical spine allows head rotations of at least 360°, their head was considered to be loose. If a head hunter encountered a tarsier, he was obliged to turn around immediately, because otherwise, the spell of the spirits might hit him and his community.

Spectral tarsier

Tarsius spectrum

taxonomy

Tarsius spectrum Pallas, 1778, northern Sulawesi.

other common names

English: Eastern tarsier, Sulawesi tarsier; French: Tarsier spectral, tarsier des Célèbes; German: Minahassakoboldmaki.

physical characteristics

About 13.8 in (35 cm); 3.3–5.1 oz (94–154 g); buff, but generally darker and more gray than the western tarsier; tail tuft bushy and long, tail scaly; big skinny ears.

distribution

At least on Minahassa Peninsula of northern Sulawesi.

habitat

Spectral tarsiers inhabit secondary and primary forest, large grasslands, and, less often, plantations. They sleep, however, in hollow trees, crowns of coconut palms, or in thick vines.

behavior

Not very gregarious. On the average, one intergroup encounter and 1–4 intragroup encounters per night. Group members were found to forage mostly between 66 ft (20 m) and 180 ft (55 m) apart from each other, depending from prey availability. During intragroup encounters, allogrooming or copulations may occur. Sleeping group associations consist mostly of an adult pair with or without offspring. Gursky found that 12% of the sleeping groups had a second adult female. Snuggling occurs more often at the sleep tree, while scent marking or play can be observed at the sleeping site or elsewhere at similar frequencies. Female home ranges are about 5.7 acres (2.3 ha), those of males 7.7 acres (3.1 ha). During the day spectral tarsiers may sleep for about nine hours and use slightly more than two additional hours of the day for social interactions. Duet songs usually last longer than 2 minutes and consist of repeated short phrases, the average duration of which is 11 sec. Average single calls last 190 msec in females and 140 msec in males.

feeding ecology and diet

About 60% of the predominantly insect prey is caught on leaves or branches, about 5% on the ground, and the remaining third is caught in the air. Moths and butterflies, including many caterpillars, form the greatest percentage of the insect prey (32%) followed by orthopterans (grasshoppers, cockroaches, etc., 24%), ants (13%), and beetles (11%). These averages vary between the dry and wet seasons.

reproductive biology

Polygamous. There is one birth per year; the gestation period is around 190 days. The main birth season is April and May at the end of the monsoon rainy period. The young are weaned after 2.5 months. The adult male of the group and subadult females care for the young more than the subadult males.

conservation status

Lower Risk/Near Threatened.

significance to humans

None known.

Dian's tarsier

Tarsius dianae

taxonomy

Tarsius dianae Niemitz Nietsch, Warter and Rumpler, 1991.

other common names

French: Tarsier de Dian; German: Dianakoboldmaki.

physical characteristics

13–13.8 in (33–34.9 cm); 3.4–3.9 oz (95–110g); fur somewhat curly, buff-tinged gray, bright hairs on upper lip; tail tuft long and bushy; finger and toe nails dark brown and keeled.

distribution

Central montane areas of Sulawesi.

habitat

Seems to be most abundant in primary rainforest, about 270 individuals per 0.04 mi² (1 km²). In secondary forest density was about 190 individuals per 0.04 mi² (1 km²). Compared with primary forest, only half the density was found in agro-forestry patches. In areas with stronger disturbance, density was still lower.

behavior

Like the spectral tarsier, Dian's tarsier spends about 50% of its time below 5 ft (1.5 m) above the ground. But in contrast, Dian's tarsier spends about 23% of its time above 10 ft (3.1 m). Also, this species uses horizontal supports more than the spectral tarsier and the western tarsier. An average duet song lasts about 45 sec and is not divided into phrases. Average singe calls last about 80 msec in both sexes.

feeding ecology and diet

Moths, crickets, and lizards have been observed to be eaten.

reproductive biology

Nothing is known.

conservation status

Lower Risk/Conservation Dependent.

significance to humans

None known.

Sangihe tarsier

Tarsius sangirensis

taxonomy

Tarsius sangirensis Meyer, 1897.

other common names

French: Tarsier de Sangihe; German: Sangihekoboldmaki.

physical characteristics

Less woolly than the neighboring spectral tarsier with a poorly marked postauricular spot (this spot is conspicuous and almost white in the spectral tarsier); large, broad skull with long tooth rows and short lateral incisors and canines.

distribution

Islands of Sangihe and Siau (between Sulawesi and Mindanao).

habitat

Nothing is known.

behavior

Nothing is known.

feeding ecology and diet

Nothing is known.

reproductive biology

Nothing is known.

conservation status

Data Deficient.

significance to humans

None known.

Pygmy tarsier

Tarsius pumilus

taxonomy

Tarsius pumilus Miller and Hollister, 1921, central Sulawesi. Treated as a spectral tarsier subspecies for many decades, it regained species level by Niemitz in 1985, which was confirmed later by several authors.

other common names

English: Lesser spectral tarsier, mountain tarsier; French: Tarsier naïn; German: Zwergkoboldmaki; Spanish: Tarsero piemeno.

physical characteristics

Head and body length, 3.8–4.1 in (9.5–10.5 cm); Fur color similar to spectral tarsier, but more curly. Considerably smaller than any other tarsier species.

distribution

Central Sulawesi montane regions (e.g., about 2,625 ft [800 m] above sea level).

habitat

Montane foggy rainforests.

behavior

Nocturnal and crepuscular. Duetting vocalizations, long high-pitched whistling notes by the female, and a series of calls by the males (about 3 calls/sec).

feeding ecology and diet

Nothing is known.

reproductive biology

Nothing is known.

conservation status

Data Deficient.

significance to humans

None known.

Resources

Books

Fleagle, John G. Primate Adaptation and Evolution. 2nd ed. San Diego: Academic Press, 1999.

Jouffroy, Françoise-K., Ch. Berge, and C. Niemitz. "Comparative Study of the Lower Extremity in the Genus Tarsius." In Biology of Tarsiers, edited by Carsten Niemitz. Stuttgart: Gustav Fischer, 1984.

Merker, St. Vom Aussterben bedroht oder anpassungfähig?—Der Koboldmaki Tarsius dianae in den Regenwäldern Sulawesis. PhD Thesis. Göttingen, Germany, Georg-August-University, 2003.

Neri-Arboleda, Irene. Ecology and Behaviour of Tarsius syrichta in Bohol, Philippines: Implications for Conservation. PhD Thesis. Adelaide, South Australia, University of Adelaide, 2001.

Niemitz, Carsten, ed. Biology of Tarsiers. Stuttgart: Gustav Fischer, 1984.

——. "Synecological Relationships and Feeding Behaviour of the Genus Tarsius." In Biology of Tarsiers, edited by Carsten Niemitz. Stuttgart: Gustav Fischer, 1984.

——. "Tarsiers." In The New Encyclopedia of Mammals, edited by David Macdonald. Oxford: Oxford University Press, 2001.

——. Zur Funktionsmorphologie der Gattung Tarsius Storr, 1780 (Mammalia, Primates, Tarsiidae). Courier Forschungsinstitut Senckenberg, Vol. 25. Frankfurt: Senckenberg, 1977.

Ross, C. "The Craniofacial Evidence for Anthropoid and Tarsier Relationships." In Anthropoid Origins, edited by John G. Fleagle and Richard F. Kay. New York: Plenum Press, 1994.

Periodicals

Beard, K. Christopher. "A New Genus of Tarsiidae (Mammalia: Primates) from the Middle Eocene of Shanxi Province, China, with Notes on the Historical Biogeography of Tarsiers." Bulletin of the Carnegie Museum of Natural History 34 (1998): 260–277.

Beard, K. Christopher, Q. Tao, M. R. Dawson, B. Wang, and L. Chuanhuei. "A Diverse New Primate Fauna from Middle Eocene Fissure-Fillings in Southeastern China." Nature 368 (1994): 604–609.

Dagosto, M., D. L. Gebo, and C. Dolino. "Positional Behavior and Social Organization of the Philippine Tarsier (Tarsius syrichta)." Primates 42 (2001): 233–243.

Feiler, A. "Über die Säugetiere der Sangihe-und Talaud-Inseln-der Beitrag A. B. Meyers für ihre Erforschung." Zoologische Abhandlungen Staatliches Museum für Tierkunde Dresden 46 (1990): 75–94.

Groves, C. "Systematics of Tarsiers and Lorises." Primates 39 (1998): 13–27.

Gursky, S. "The Conservation Status of Two Sulawesian Tarsier Species: Tarsius spectrum and Tarsius dianae." Primate Conservation 18 (1998): 88–91.

——. "Sociality in the Spectral Tarsier, Tarsius spectrum." American Journal of Primatology 51 (2000): 89–101.

——. "Allocare in a Nocturnal Primate: Data on the Spectral Tarsier, Tarsius spectrum." Folia Primatologica 71 (2000): 39–54.

——. "Effect of Seasonality on the Behavior of an Insectivorous Primate, Tarsius spectrum." International Journal of Primatology 21 (2000): 477–495.

——. "Predation on a Wild Spectral Tarsier (Tarsius spectrum) by a Snake." Folia Primatologica 73 (2002): 60–62.

——. "Determinants of Gregariousness in the Spectral Tarsier (Prosimian: Tarsius spectrum)." Journal of the Zoological Society of London 256 (2002): 401–410.

Merker, St., I. Yustian, and M. Mühlenberg. "Loosing Ground But Yet Doing Well—Tarsius dianae in Man-Altered Rainforests of Central Sulawesi, Indonesia." (in press).

Niemitz, C. "Can a Primate Be an Owl? Convergences in the Same Ecological Niche." Fortschritte der Zoologie 30 (1985): 666–670.

——. "Der Koboldmaki. Evolutionsforschung an einem Primaten." Naturwissenschaftliche Rundschau 38 (1985): 43–49.

——. "Risiken und Krankheiten als Evolutionsfaktoren— Eine Untersuchung am Beispiel von Tarsius." Zoologischer Garten N.F. 59 (1989): 1–12.

Niemitz, C., et al. "Tarsius dianae: A New Primate Species from Central Sulawesi." Folia Primatologica 56 (1991): 105–116.

Schmitz, J., M. Ohme, and H. Zischler. "SINE Insertions in Cladistic Analyses and the Phylogenetic Affiliations of Tarsius bancanus to Other Primates." Genetics 157 (2001): 777–784.

Carsten Niemitz, PhD