Spectral tarsier  (Tarsius tarsier)

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (3).

Like all tarsiers, the spectral tarsier is most notable for its huge eyes, which are the largest, relative to body weight, of any mammal. The head is rounded, with a short neck and small muzzle, and bears thin, membranous, naked ears, which are highly mobile and in constant motion. The soft, silky coat is grey to grey-buff in colour, lighter on the underparts, and the tail is long, with scale-like skin for most of its length, and a long, bushy tuft towards the end. As in all tarsiers, the forelimbs are short, but the hindlimbs are greatly elongated, measuring about twice the length of the head and body, a feature which gives rise to the genus name, Tarsius, referring to the elongated tarsal or ankle region. The digits are long and slender, and are tipped with rounded pads, which aid grip. All the digits bear flattened nails, except the second and third toes, which are equipped with a ‘toilet claw’, used in grooming (2) (4) (5).

The spectral tarsier is found in Sulawesi, Indonesia, and on some of the small surrounding islands (1) (2) (4) (5) (6), but the population is thought to potentially constitute a number of distinct species, and is likely to be subdivided in the future (1).

This species occurs in a range of habitats, including both primary and secondary forest, as well as mangrove forest, scrub, bamboo, plantations, and even urban gardens (1) (2) (4) (7). The main habitat requirements appear to be adequate cover, a year-round abundance of insects, and the availability of suitable sleeping sites, such as dense thickets, vine tangles, tree holes, or the complex aerial roots of strangler figs (7).

Tarsiers are agile acrobats, capable of impressive leaps of up to five or six metres (4) (7). The spectral tarsier is most active at night, the huge eyes giving good night vision, despite lacking the reflective layer, or ‘tapetum’, typical of most other nocturnal primates (2). In addition, the eyes are forward-facing, allowing the tarsier to accurately judge distances (2), and the head is able to rotate nearly 360°, giving an extremely wide field of vision (4) (5). Unusually for a primate, tarsiers feed exclusively on live prey, mainly taking insects, but also occasionally small vertebrates such as lizards (1) (2) (4) (5) (8). Prey may be taken in the trees or from the ground (7).

The spectral tarsier lives in small family groups consisting of a male, one or two breeding females, and young (2) (5) (7) (9). The group scent-marks and defends a small territory of around one hectare (2) (4) (5) (7) (10), and shares a sleeping site during the day (4) (7) (11). Group members also regularly interact during the night (11) (12) and come together again at the sleeping site at dawn. The group often perform a vocal chorus, and the male and female may also perform a duet, in which each has a distinct part (2) (4) (7). Breeding occurs twice a year, from April to May and November to December (2) (4) (7), the female giving birth to a single young, after a gestation period of around 190 days (2). Remarkably, the newborn is up to a third of the female’s weight, a larger proportion than any other mammal (2) (13). Well developed at birth, the young spectral tarsier is able to climb at just a day old and hunt alone by 26 days (2) (4) (5) (7). For the first few weeks, the infant may be carried in the female’s mouth or ‘parked’ on a branch while the group hunts (2) (5) (7) (14), with group members regularly returning to ‘babysit’, groom, feed or play with it (7) (13) (14).

Although it may show some tolerance of forest conversion, the main threat to the spectral tarsier is believed to be habitat loss due to clearance for agriculture and illegal logging. It is also under threat from mining, the use of agricultural pesticides (which may affect its insect prey), predation by domestic dogs and cats, and capture for the pet trade (1) (4). Although still relatively abundant in some areas (9), and apparently one of the least threatened of the tarsiers (1), future taxonomic study may well reveal the spectral tarsier to constitute more than one distinct species, in which case some populations are likely to be more threatened than others (1).

The spectral tarsier is protected by law in Indonesia (1) (6), and international trade in the species should be carefully regulated under its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES) (3). The spectral tarsier occurs in a number of protected areas, including Tangkoko Batuangus Nature Reserve on Sulawesi (1) (6) (9), although improved management may be needed in some (1). Tarsiers are likely to be beneficial to farmers by feeding on insect pests such as grasshoppers, but there is a common misconception that tarsiers are themselves crop pests, and public education programmes would be helpful in correcting this. Finally, urgent study is needed to clarify the taxonomic and conservation status of different spectral tarsier populations, to ensure that any distinct forms, or indeed any undescribed species, receive adequate protection (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about tarsiers and about primate conservation see:

• Primate Info Net:
  http://pin.primate.wisc.edu/factsheets/entry/tarsier/taxon
• Nocturnal Primate Research Group:
  http://www.nprg.org/home.shtml
• Wright, P.C., Simons, E.L. and Gursky, S. (2003) Tarsiers: Past, Present, and Future. Rutgers University Press, Piscataway, New Jersey.
• IUCN/SSC Primate Specialist Group:
  http://www.primate-sg.org/