Tarsius dentatus (Dian's tarsier) from the northern part of Sulawesi, Indonesia was originally described as a new species in 1921 by Miller and Hollister. In 1991, Niemitz and coworkers characterized a purported new species named Tarsius dentatus. However, in 1997, Shekelle and coworkers proposed that T. dianae was a synonym of T. dentatus. Further analysis is required to determine whether they are the same species. Dian's tarsiers occur predominantly in central Sulawesi, an island of Indonesia. Their presence is largely determined by their vocalizations (Nietsch and Kopp, 1998). Gursky (1998, 2007) states that most members of the species live in the Morowali Nature Reserve and Lore Lindu National Park.
Biogeographic Regions: oriental (Native )
Other Geographic Terms: island endemic
Tarsiers are easily distinguished by their size, large orbits, and elongated tarsal bones. The head of tarsiers is round with a reduced muzzle and short neck. Tarsius dentatus is larger than T. pumilus but similar in size to T. tarsius. The coat color of Dian's tarsiers is grayish-buff and the tail is naked except for some hair at the end. Tarsius dentatus can be identified by the presence of short, white hairs flanking the upper lip and in the middle of the lower lip. It can be distinguished from T. tarsier by the lack of brown pelage at the hip, thigh, or knee and darker pigmentation on the tail, fingers, toes, and nails. Tarsius dentatus also has a more conspicuous black line of fur surrounding the eyes than does T. tarsier. The ears of T. dentatus are shorter and wider than those of T. tarsier and there is a hairless patch at the base of each ear. The fur of subadults is slightly more gray and woolly than those of T. tarsier. The digits are padded to allow gripping with grasping hands and feet. The finger nails of T. dentatus are curved, pointed, and dark. Females have two pairs of mammary glands.
Because this species is nocturnal and lacks a tapetum lucidum, its eyes are enlarged to a diameter of approximately 16 mm. The eyes appear asymmetrical and not fully opened compared to those of T. tarsier. Tarsius dentatus is able to rotate its head 180 degrees. The nasal region is covered with short hair except for an area of naked skin around the nostrils. Tarsius dentatus has well-developed, laterally folded nostrils. It also has large ears, but they are short compared to those of T. tarsier.
Tarsius dentatus has a more delicate mandible than that of T. tarsier. The dental formula of this species is 2/1:1:3:3, and it has large, pointed upper and lower incisors. The upper canines are small.
Tarsiers are small and nocturnal. They do not exhibit torpor, a state of dormancy during food shortages.
Range mass: 95 to 110 g.
Average mass: 100 g.
Range length: 115 to 121 mm.
Average length: 120 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
This tarsier species lives both in primary and secondary lowland rainforests in central Sulawesi. Field studies reveal that the population density of T. dentatus varies from 129 to 136 individuals per square kilometer (Gursky, 2007). At an altitude of 500 to 1000 meters, population density is estimated to be 180 individuals, while at 1000 to 1500 meters, only 57 individuals per square kilometer were observed. The population was also approximately ten times more dense in secondary forests than primary forests.
Range elevation: 1500 (high) m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: rainforest
Habitat and Ecology
Tarsiers are primarily insectivores that hunt by visual predation and feed on crickets (Gryllidae), grasshoppers (Orthoptera), and moths (Lepidoptera). They also eat small lizards and crustaceans, such as shrimps, in captivity. Tarsiers capture prey by carefully watching prey movements and leaping forward suddenly to capture prey in both hands. The food is chewed with a side-to-side motion of the jaw while the tarsier sits on its hind limbs grasping a tree branch. Tarsiers also ingest water by lapping, or take in liquid using the tongue. However, the specific eating habits of Tarsius dentatus remain to be studied.
Animal Foods: reptiles; insects
Primary Diet: carnivore (Insectivore )
Tarsiers capture and eat live animal prey at night. Hence, their role in the ecosystem has been compared to that of an owl. Tarsiers prefer to prey on insects active at night that experience less dramatic seasonal fluctuations in population. Tarsier predation minimizes competition because other insectivores such as bats and birds cannot easily maneuver through the dense understory of the forest at night. Tarsius dentatus also serves as a host for many common parasites. Through fecal analysis, Niemitz et al. (1991) found intestinal parasites including Entamoeba and two Digenea trematode species, none of which are present in T. tarsier.
- Digenea trematode
Predators of tarsiers are not well studied, but Gursky (2007) suggests that they include birds of prey (Falconiformes), civets (Viverra), and snakes (Serpentes). In the Merker etal. (2005) field study of Tarsius dentatus no predation was observed.
Life History and Behavior
Males and females communicate with a special call known as the "male-female duet" in which females and males emit differently pitched sounds for 45 seconds at a sleeping site before dawn. There is regional variation in duet calls. The female begins calling by lowering the frequency pitch 16 to 9 kHz, continues her call at 7 or 8 to 1 kHz, and concludes by bringing the pitch back up to 9 to 16 kHz with a range of 1 to 9 kHz. Similarly, the male's pitch falls from 10 kHz to 5 kHz at the beginning and steadily rises to 14 kHz until the end. It is thought that the duets serve to prevent conflict by warning potential intruders of the claimed territory and of already paired individuals.
The species also identifies scent marks made from secreted urine and other substances from the epigastric glands.
Communication Channels: visual ; tactile ; acoustic ; chemical
Other Communication Modes: duets ; scent marks
Perception Channels: visual ; tactile ; acoustic ; chemical
Tarsius dentatus has never been kept in captivity, but in general tarsiers in captivity live an average of 5 years with a maximum of 12 years.
Although tarsiers were believed to be monogamous, studies have shown that Sulawesi tarsiers actually exhibit facultative polygyny and form strong pair bonds. Males are more territorial than females and have a greater home range. The mating system of Tarsius dentatus remains to be studied.
The mating behavior of Tarsius dentatus has not been studied. Before the onset of female ovulation, both male and female tarsiers groom themselves and mark their environment more frequently with urine and feces. Males have been observed to chase after estrous females while chirping like a bird, and they examine female genitals by sniffing. Vocalizations by both sexes also increase in frequency, and include a "piercing-twittering 'chit-chit'".
The reproductive behavior of Tarsius dentatus has not been studied. In general, tarsier females give birth to one offspring per year with a long gestation period. The rate of fetal and postnatal development of tarsiers is among the slowest of all mammals. Tarsier infants are also proportionally the largest of all non-anthropoid primate infants. Most of their mass is composed of brain mass, eyes, and cranium. The dedication of resources to the brain leads to the rapid development of foraging and locomotor behaviors.
Pregnancy is often very costly for female tarsiers. Pregnant females have low mobility, impaired foraging abilities, and maintain smaller home ranges than their non-pregnant counterparts. Furthermore, postpartum females cannot lactate and transport infants at the same time due to energy restrictions. They often "park" their offspring on a secure branch. Pregnant females were observed in a year-round study, and there appears to be no seasonal variation in mating.
Studies on T. tarsier have revealed that young tarsier females stay with their parents until adulthood, whereas young males leave as juveniles.
Breeding interval: Interbirth intervals have not been documented in Tarsius dentatus.
Breeding season: Female tarsiers have been observed pregnant year round.
Average number of offspring: 1.
Average gestation period: 6 months.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Pairs of female and male tarsiers stay together to form close bonds for at least 15 months. Tarsier infants can cling to a vertical surface. Female progeny stay with their parents until adulthood, whereas young males leave during youth. Tarsier mothers and young have been reported to exhibit reciprocal sniffing after birth as a way of recognition.
Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); extended period of juvenile learning
Tarsius dentatus is categorized as low risk on multiple conservation lists because of their nocturnal habits, ability to adjust to disturbed habitats, and because they reside in large, protected parks such as Lora Lindi (also Lora Lindu). Despite efforts to preserve these parks, the species is still threatened by habitat destruction and hunting by humans. Lore Lindi National Park is surrounded by many agrarian communities that hunt within the park and use timber and rattan as a source of income. Similarly, Morowali Nature Reserve also protects a group of endemic slash-and-burn horticulturalists, Wana, who hunt tarsiers with dogs and blowguns and burn the land for dry rice agriculture.
US Federal List: no special status
CITES: appendix ii
State of Michigan List: no special status
IUCN Red List of Threatened Species: vulnerable
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1996Data Deficient
- 1994Indeterminate(Groombridge 1994)
Relevance to Humans and Ecosystems
There are no known adverse effects of Tarsius dentatus on humans.
Spectral tarsiers have been a popular tourist attraction in Tangkoko, northern Sulawewsi (Fitch-Snyder, 2003). In the future, when Tarsius dentatus is better studied and more popular, Morowali Nature Reserve and Lore Lindu National Park might serve as sites for economic tourism.
Tarsiers are an ancient line of primates existing for at least forty million years. They occupy a unique primate niche and have many morphological and behavioral specializations. Tarsius dentatus is invaluable to the scientific and education communities for understanding the origin and evolution of haplorhine primates.
Positive Impacts: ecotourism ; research and education
Dian's tarsier (Tarsius dentatus), also known as the Diana tarsier, is a nocturnal primate endemic to central Sulawesi, Indonesia. Its head-body length is 11.5–12 centimetres (4.5–4.7 in) and it has a tail of 22 centimetres (8.7 in). Dian's tarsier lives in rainforests. It was formerly called T. dianae, but that has been shown to be a junior synonym.
It is found in primary, secondary, and mangrove forests. It is nocturnal and lives in small groups of two to seven members. It is highly adapted to vertical clinging and leaping, like other tarsiers, and has a strict live animal diet, mostly insects with some small vertebrates.
- Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. p. 127. OCLC 62265494. ISBN 0-801-88221-4.
- Shekelle, M. & Merker, S. (2008). Tarsius dentatus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 1 January 2009.
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