Spectral tarsiers, (Wright, et al., 2003), are endemic to the Indonesian islands of Southeast Asia including Sulawesi, Pulau Peleng, and Pulau Selajar. The greatest densities of this species are found in the northern peninsula of Sulawesi Island.
Spectral tarsiers are found in primary and secondary rainforests, though they prefer secondary growth forests. This is likely due to the greater abundance of food items in secondary growth forests. Their habitat ranges from the lowland evergreen rainforest near sea level to the lower montane rainforest up to 1500 m. Spectral tarsiers have also been found in mangroves and scrub forest. (Wright, et al., 2003)
Spectral tarsiers have a small, round body covered in soft, velvety fur. Their pelage ranges from gray to buff-gray in color. They have long scaly tails with tufts of fur only present on the distal third of the tail. Spectral tarsiers exhibit sexual dimorphism: females weigh 102 to 114 g while males weight 118 to 130 g.
Members of the genus Tarsius possess long, slender hands, feet, and digits. Their hands are thought to be the longest of any living primate relative to body size. These extremely elongated hands are designed for clinging and gripping despite the lack of opposable thumbs. The third finger of T. tarsier is extremely long and slender and is only 15% shorter than the humerus. This trait is not symmetrically reproduced from the anterior to the posterior, as the fourth digit is the longest of the hindlimb digits. The second and third digits of the hindlimb are equipped with specialized toilet claws. Spectral tarsiers are thought to be the most primitive tarsiers, as they lack disks on the ends of their fingers.
Tarsiers are among the smallest known primates. Their head-body length ranges from 9.5 to 14 cm and tail length ranges from 20 to 26 cm. Total length ranges from 29.5 to 40 cm. Spectral tarsiers have long legs that are specialized for their saltatory form of locomotion; they can jump more than 40 times the length of their body. The tibia and fibula are fused together and act as a shock absorber when the animal jumps from tree to tree. The hindlimbs of tarsiers are twice as long as their head-body length. The femur, the bones of the lower leg (the fused tibia and fibula), and the bones of the foot are each roughly equal in length. (MacDonald, 2006; MacKinnon and MacKinnon, 1980; McNab and Wright, 1987; Napier and Napier, 1985; Rosenberger, 2010; Wright, et al., 2003)
Tarsiers have the biggest eyes of any mammal relative to their body weight. In fact, their eyes are larger than their brain. Interestingly, tarsiers lack a tapetum lucidum, a highly reflective layer behind the retina that is characteristic of most nocturnal mammals. Instead tarsiers have extremely large eyes and a well-developed fovea to maximize light-gathering capacity and to allow the development of highly resolved pin-sharp vision. These adaptations have bestowed tarsiers with the most acute night vision of all primates. The eyes of spectral tarsiers are immobile due to their large size, but this is compensated for by the ability to rotate the head 180 degrees.
The ears of spectral tarsiers are thin and membranous and are able to move independently. Tarsiers possess sharp, heterodont teeth and quadrate molars. The dental formula of tarsiers is: I2/1, C1/1, P3/3, M3/3 = 34. Spectral tarsiers have a low basal metabolic rate and a low body temperature. They do not exhibit torpor, yet brown adipose tissue can be found in adults within the interscapular area; this is likely a retained paedomorphic trait. (MacDonald, 2006; MacKinnon and MacKinnon, 1980; McNab and Wright, 1987; Napier and Napier, 1985; Rosenberger, 2010; Wright, et al., 2003)
The majority of tarsiers are monogamous; however, spectral tarsiers may practice facultative monogamy or polygyny. Monogamy appears to be the prevalent mating system in this species due to limited numbers of high-quality sleeping sites. Each individual female requires a high-quality sleeping site for herself and her young. Fig trees with large diameters are preferred but rare, which generally leads males and females to share sleeping sites and thus to form monogamous pairs.
Polygynous groups occur 19% of the time. Monogamous groups often consist of two or three females with one reproducing female and one territorial male, while polygynous groups consist of six or more individuals with multiple reproducing females and a single male. The presence of large testes in T. tarsier suggests that polygyny is fairly common, as large testes have been related to promiscuous mating systems. (Gursky-Doyen, 2010; MacDonald, 2006)
Spectral tarsiers breed twice a year, and copulation occurs during either May or November. The gestation period is approximately 6 months, and births also usually occur during May or November. Females give birth to a single offspring, which is born fully furred and with its eyes open. Newborns are precocial and are able to climb at just one day of age. Among mammals, tarsier offspring are the largest relative to the mother's body mass. Newborns weigh on average 23.7 g, nearly 22% of the mother's body mass. A large proportion their weight is invested in the brain mass, eyes, and cranium.
Lactation generally lasts up to 80 days. Weaning occurs between 4 and 10 weeks of age, and independence occurs directly after weaning as offspring are capable of hunting on their own. Spectral tarsiers reach sexual maturity at 17 months of age. Females possess a bicornuate uterus and haemochorial placenta. (Gursky, 2002; Gursky-Doyen, 2010; Napier and Napier, 1985; Roberts, 1994)
Young spectral tarsiers are precocial and receive only maternal care. Mothers pick up and carry their infants by mouth for the first 3 weeks and cache them trees while they forage. Offspring are left alone for an average of 27 minutes at a time, and then they are moved to new locations. Mothers generally remain within 4 m of their young when foraging. Caching young in trees reduces the energetic cost of foraging, as carrying offspring is costly and offspring can weigh up to one third of the mother’s weight. Mothers sling offspring older than 3 weeks of age under their bellies while leaping and moving from tree to tree. (Gursky, 2010; Gursky-Doyen, 2010; Napier and Napier, 1985)
One spectral tarsier was 10 years and 9 months of age at the conclusion of a mark and re-capture study, and the only signs of aging in this individual were gray/light hair on the face. Therefore, this probably does not represent the longest lifespan of spectral tarsiers in the wild.
A female tarsier greater than 5 years of age currently resides at the Singapore zoo. A closely related species, Tarsius bancanus has a lifespan of 17 years and 7 months in captivity. It is likely that T. tarsier has a similar lifespan in captivity. (Shekelle and Nietsch, 2008)
Spectral tarsiers are both crepuscular and nocturnal and are very active throughout the night. At dusk, they travel for about 30 minutes until they find a forage site. During this time, they frequently stop to groom themselves by licking and scratching their fur with their toilet claws. If a heavy rain occurs, tarsiers find a dry area and remain inactive. They move through the trees and can leap more than 40 times the length of their body. As morning approaches, spectral tarsiers "sing" as they return to their sleeping sites, either as a duet with their mate or in a family chorus. These songs signal to neighboring groups that a territory is occupied. Spectral tarsiers are extremely territorial and engage in disputes with neighboring groups that venture into their boundaries. They mark their territories with urine and glandular secretions.
Spectral tarsiers usually live in pairs or small family groups. They are highly social animals. When two adult group members are in physical contact, they spend all of their time resting and socializing. When less than 10 m apart, they forage and, when they are 50 to 100 m apart, they spend most of their time traveling. Spectral tarsiers also engage in play behavior, snuggling, allogrooming, and food sharing. Competition for food results in increased time foraging. Individuals appear to benefit from group living, particularly when predation pressure is high, when females are sexually receptive, and when there is high likelihood of encountering a potentially infanticidal male. (Gron, 2010; Gursky, 2002; Gursky-Doyen, 2011; MacKinnon and MacKinnon, 1980)
The average home range of spectral tarsiers is 3 ha for males and 2 ha for females. They have high site fidelity, remaining at the same sleeping site for multiple years, usually with a mate. Females often establish a territory adjacent to their parental territory, while males disperse twice as far as females. Spectral tarsiers scent-mark their territories with urine and secretions from their epigastric glands. (Gursky, 2010)
Species-specific vocalizations of spectral tarsiers include trills and twitters, alarm calls, duet songs, and family choruses. Twitters and trills are used to converse or to make their location known to other group members while foraging. Alarms calls serve as a warning system to others when a predator is spotted and also encourage predator mobbing. Duet songs and family choruses convey territoriality and function as a mate guarding mechanism. As morning approaches, the female of the duet pair initiates a song once she has returned to the family’s sleeping site. The male and female sing very different but equally high-pitched songs, which can be heard up to 100 m away. Species-specific vocal acoustics are used in conjunction with morphogenetics to assess classification of tarsiers.
Spectral tarsiers use their urine as well as secretions from the epigastric gland, ano-genital gland, and circum-oral gland to mark the boundaries of their territory. Males scent mark twice as frequently as females.
Physical contact appears to contribute to tarsier sociality, and members of the same group often rest and socialize while touching. Spectral tarsiers sit next to one another and intertwine tails and are know to snuggle.
Visual communication appears to be most effective when group members are in close contact with one another. They communicate by changes in facial musculature and body posture. Folded ears seem to convey uneasiness, and a crouched posture is taken when defensive. When aggressive, a tarsier stands on its hind feet with its mouth open. (Burton and Nietsch, 2010; Gron, 2010; Gursky, 2002; Gursky-Doyen and Supriatna, 2010; MacKinnon and MacKinnon, 1980)
Spectral tarsiers feeds exclusively on live animals. They primarily prey on flying insects such as moths, locusts, beetles and cicadas. They occasionally eat small vertebrates, such as lizards or bats. Spectral tarsiers listen with their independently moving ears to locate potential prey. Once a prey item is targeted, a tarsier ambushes its prey with a sudden lunge, grasps it with its long, slender fingers, and bites to kill it. The tarsier then returns to its perch to consume its prey. This form of ambush hunting requires excellent hand-eye coordination. Spectral tarsiers can collect their prey out of the air, on the ground, or off leaves and branches. Tarsiers can eat 10% of their own body weight every 24 hours, and they drink water several times throughout the night.
Spectral tarsiers appear to take advantage of the moonlight when foraging. This is an unusual behavior, as most small, nocturnal mammals exhibit lunar phobia as a predator avoidance mechanism. Tarsiers cope with this increased risk of predation by foraging in groups. (Gron, 2010; Gursky, 2002; MacDonald, 2006; MacKinnon and MacKinnon, 1980; Shekelle and Salim, 2008)
Potential predators of spectral tarsiers include arboreal snakes, civets, monitor lizards, owls and other raptors, and feral cats. If a predator, particularly a snake, is identified, they emit an alarm call. This initiates mobbing behavior, in which numerous tarsiers gather and approach the predator as a group, screaming, lunging, and even biting. Mob groups usually consist of adult males from neighboring groups, which is interesting as most spectral tarsier social groups only contain one territorial adult male. This grouping by neighboring males suggests some form of cooperation among males during predator mobbing. If spectral tarsiers spot a bird of prey such as an owl, they sound an alarm call and participate in avoidance mechanisms such as moving further away from the predator and increasing cryptic behaviors. (Gursky, 2005; MacKinnon and MacKinnon, 1980)
Spectral tarsiers may influence populations of their insect prey. They host intestinal parasites such as hookworms and tapeworms. A related species, Tarsius bacanus, hosts various species of intestinal worms such as Moniliformes tarsii and Moniliformes echinoseroxi; spectral tarsiers may be susceptible to these parasites. (Roberts, 1994)
Tarsius tarsier is important to evolutionary biologists and taxonomists as it is thought to be the most primitive of the tarsiers; therefore it can be studied to better understand primate evolution.
Spectral tarsiers are primarily insectivorous, and may aid in the mitigation of insect pest populations. Tarsiers also draw tourists to the Indonesian islands and are beneficial to humans financially as a form of ecotourism. Tarsiers are occasionally kept as pets, though they do not survive well. (MacKinnon and MacKinnon, 1980)
Spectral tarsiers kept as pets frequently host parasites, such as intestinal worms, that can be transmitted to humans. Tarsiers do not survive well as pets due to their high energetic diet requirements. (MacDonald, 2006)
Spectral tarsiers are currently abundant on the island of Sulawesi, particularly among the northern peninsula with a density ranging from 156 to 800 individuals per square kilometer. However, this species is still considered vulnerable due to habitat destruction caused by logging. Logging reduces tarsier densities through the destruction of preferred sleeping sites such as strangler fig trees. Strangler figs are removed from human-utilized forests because they are seen as a threat to other commercially valuable trees. (Gron, 2010; Shekelle and Salim, 2008)
Tarsiers have recently moved from the suborder Prosimii to the suborder Haplorrhinii, although their classification is still under debate. Tarsius spectrum (Pallus, 1778) is a junior synonym for Tarsius tarsier (Erxleben, 1777).
Fossil relatives of tarsiers have been found in Asia, Europe, North America, and Africa, however modern tarsiers are restricted to a few islands in Southeast Asia. They have likely occupied this region for more than 40 million years.
Tarsiers get their name from their elongated tarsal region. In the past, tarsiers were used as a totem animal of the head-hunting Iban people of Borneo. (MacDonald, 2006; Napier and Napier, 1985; Shekelle and Salim, 2008)
Kenzie Mogk (author), University of Manitoba, Jane Waterman (editor), University of Manitoba, 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
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
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
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).
Having one mate at a time.
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.
the business of buying and selling animals for people to keep in their homes as pets.
having more than one female as a mate at one time
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
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
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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