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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.
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
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.
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
Karyotyping of this species by Niemitz et al. (1991) revealed that Tarsius dentatus has 46 chromosomes made of 5 pairs of acrocentric chromosomes and 17 meta- or submetacentric pairs, whereas T. syrichta has 80 chromosomes made of 7 meta- or submetacentric pairs and 33 acrocentric chromosomal pairs.
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 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
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
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.
Commensal/Parasitic Species:
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 )
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
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
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).[3] Dian's tarsier lives in rainforests.[3] It was formerly called T. dianae, but that has been shown to be a junior synonym.[1]
It is highly adapted to vertical clinging and leaping, like other tarsiers, and has a strict live animal diet, consisting mostly of insects.[4] Due to human intervention in the forest of South-east Asia, Dian's tarsier tends to adapt its ranging behavior based on the degree of human intervention. Slightly disturbed habitats have been shown to have little effect on the Dian's tarsier, but with larger disturbances, the habitat is less suitable.[4][2]
First claimed as a new species by Miller and Hollister in 1921.[5]
Dian's tarsier was named in 1991 in honor of the Roman goddess of hunting Diana and the late Dian Fossey.[6]
The weight of adult Dian's tarsier ranges from 100 to 150 grams.[7] This species is characterized by a greyish buff color to their wooly fur, a black spot is present on each side of the nose and white-colored fur appears on the middle lower lip and on both sides of the upper lip.[6]
Dian's tarsier is found in the primary rainforest[6] of the lower mountains of central Sulawesi.[8] It can also be found in habitat modified (disturbed) by humans such as secondary forests with logging, agroforestry or intensive agriculture.[8]
Groups can range from two to seven individuals. Each group is composed of one adult male paired with one to three adult females and their offspring, which can be male and female juveniles.[9]
Females of this species typically give birth to one child per year. Reproduction does not appear to vary by season. Dian's tarsiers use infant parking.[10]
This species is most active after dusk and before dawn. After dusk, Dian's tarsiers leave the sleeping sites they use during the day, traverse completely their home range, and go hunt for food in their home range at night where they will be more stationary during hunting and eating. Before dawn, duet vocalisation signals to other members of the group to return to the sleeping site.[4] Dian's tarsiers can travel more than 100 meters to reach their sleeping site in under 15 minutes before dawn.[7] They use forest undergrowth to move.[10]
Home ranges of mated males and females pairs overlap. There is slight overlap between the home ranges of different groups. The male home range is slightly larger than the female's in undisturbed habitat with average home ranges sizes of 1.77 hectares and 1.58 hectares respectively.[4]
This species shows sexually dimorphic morning duet vocalization. The majority of duet calls are started by the female. The female starts with a high pitched rapid series of notes. The pitch lowers towards the middle of the song where most commonly a trill will be made, other options include long notes. The pitch increases towards the end of the song. The male will sing at the same time as his mate. He sings a rapid series of notes that start with a low pitch and end in a high pitch. Songs have a median close to one minute in length. The end of the songs have more and irregularly spaced time between notes. These calls are specific to this species of tarsiers, as no other species of tarsiers responded to them.[7]
Strangler fig trees are the preferred sleeping site for Dian's tarsier. The individuals will sleep in crevices or opening in the tree. Although this species is also able to sleep in bamboo stands and dense shrubbery which are more common in degraded habitats. Members of the same group will sleep in the same site during the day. Typically, groups will return to the same sleeping site night after night,[9] though they can change site, particularly if the area was disturbed.[8] Some groups have been seen using two or more regular sites. Sleeping sites are typically located on the boundary of the home range, possibly to renew the sent of animals on their territory.[4]
Dian's tarsier eats most commonly crickets, grasshoppers and moths.[4]
Dian's tarsier species is in decline. The lowest population density found in 1998[11] was the highest population density found in 2000-2001.[8]
In Sulawesi, including in national parks such as the Lore Lindu National Park, old growth rainforest is being altered by humans. Logging of primary forest trees and illegal logging deteriorate the Dian's tarsier habitat. Other commercial avenues used on this land include: bamboo and rattan logging, and plantation of cash crops, such as cocoa and coffee, all plants that are not native to the area.[10] Between 2000 and 2017, the Dian's tarsier lost 10% of its total forest habitat and 4% of its protected forest habitat.[12]
Population density is the highest by far in undisturbed habitat at 57.1 groups/km2. All levels of disturbed habitat where Dian's tarsiers are found show similar population densities (32.9 groups/km2-38.0 groups/km2), with heavily disturbed habitats showing the lowest.[8]
Home ranges of females in low and moderate levels of human disturbed habitat are smaller than in undisturbed habitat. Home ranges in habitats heavily disturbed by humans are larger than in all other habitats. Researchers hypothesize that this is due to the increased number of insects in slightly disturbed habitat. This slightly disturbed habitat has more canopy openings which may attract more insects. The largest home ranges are in the most disturbed habitats, these also have the least insects, likely due to the use of pesticides in plantations.[4]
Nightly paths lengths are similar in males and females in undisturbed habitat. Female path length increases with increased human disturbance of the habitat.[4] Since nightly path length is related to energy expenditure, Dian's tarsiers expend more energy in more disturbed habitats.[10] Females typically cover more of their home range in one night in low and moderate levels of disturbance in their habitats.[4]
Maintaining forest habitat by stopping illegal logging, practicing agroforestry, protecting sleeping sites and preserving forest undergrowth would allow Dian's tarsier to live in a habitat with low levels of degradation. Better public knowledge that Dian's tarsier does not eat cash crops and instead eats insects, as well as reducing the use of chemical pesticides, would also help.[10]
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 highly adapted to vertical clinging and leaping, like other tarsiers, and has a strict live animal diet, consisting mostly of insects. Due to human intervention in the forest of South-east Asia, Dian's tarsier tends to adapt its ranging behavior based on the degree of human intervention. Slightly disturbed habitats have been shown to have little effect on the Dian's tarsier, but with larger disturbances, the habitat is less suitable.
First claimed as a new species by Miller and Hollister in 1921.
