Dian’s tarsier  (Tarsius dentatus)

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

Weighing around just 100 grams, the six currently recognised tarsier species are amongst the smallest primates to exist (4), and demonstrate some of the most highly specialised features of the primate world. As an adaptation to their nocturnal lifestyle, these extraordinary animals possess the largest eyes relative to their body weight of any mammal (5). The huge chestnut-brown eyes cannot move, so the head has evolved the ability to turn 180 degrees, allowing a wide field of vision (6). Additionally, tarsiers possess specially-adapted, elongated tarsus bones, for which they earn their Latin and common name (6); their long hind limbs enabling these vertical-clingers-and-leapers to jump more than a remarkable 40 times their own length (5). The fingers are also long and slender and form a very effective cage to trap insects in the darkness of the forest night (5). Dian’s tarsier has a woolly, greyish-buff coat, whitish hairs on the upper lip, and a naked tail with a long, bushy tuft covering the latter half (2) (5) (6).

Dian’s tarsier is endemic to the island of Sulawesi, Indonesia’s fourth largest island (4).

Found amongst primary and secondary rainforest (5) between sea level and around 1500 meters above sea level (2).

Relatively little is known about the behaviour of Dian’s tarsier, which was first described as recently as 1991. Tarsiers on Sulawesi live in small groups of up to eight individuals, consisting of one adult male, one to three adult females and their offspring (4). In the morning, a conspicuous duet song is often performed by the male and females at or close to the sleeping site (5), serving both as a territorial advertisement and to strengthen group bonds (4). Dian’s tarsier’s reproductive biology is poorly understood, but tarsiers are known to give birth to single young, and pregnant females of this species have been observed year-round (4). Other tarsier species experience gestation periods of around 180 days, after which mothers have been seen carrying the infant either under their belly or in their mouth (2) (5).

This arboreal species sleeps in a group in tree cavities (as in strangling figs) and dense foliage during the day (4) (6), and forages in the undergrowth during the night (4). Like other tarsiers, Dian’s tarsier is exclusively insectivorous and carnivorous (5), feeding mainly on insects such as crickets, grasshoppers and moths (4).

Dian’s tarsier is still relatively abundant in central Sulawesi but population sizes are declining (4). Further more, the species is largely confined to the areas in and around the Lore Lindu National Park, and the park is considered essential for its continued survival (1). Thus, the species is classified on the IUCN Red List as Vulnerable (1). This tarsier is primarily threatened by loss, degradation and disturbance of its habitat. Although it appears that a limited amount of human disturbance can be tolerated, with the tarsier capable of adapting to traditional land uses such as small-scale agro-forestry, excessive disturbance seems to have a negative impact. In particular, logging activities pose the most serious danger, which not only clear potential sleeping sites but also open up the forest to other damaging forms of land use, such as cash-crop plantations, cattle farming or permanent human settlement. Unfortunately, growing human populations are placing enormous pressure on Sulawesi’s remaining forests, and pristine patches are becoming increasingly difficult to preserve (4).

Dian’s tarsier is protected within the Lore Lindu National Park, but there are currently no direct conservation measures targeting this species (1). It has been advocated that local governments and conservation groups should try to encourage landowners to use their land in less damaging ways, such as for small-scale agro-forestry, which Dian’s tarsier can inhabit. Since many farmers wrongly believe that tarsiers feed on cash-crops, an educational campaign should accompany this, promoting the species’ potential role as a natural predator of insects, and therefore a benefit to horticulturists. Minimising the use of chemical pesticides is also vital to the tarsier’s survival and relies on landowners’ cooperation. Other than this, it is important that efforts are made to maintain contiguous tracts of habitat and to safeguard potential sleeping sites if this tiny, mysterious primate is to remain in Sulawesi’s forests (4).

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

For more information on Dian’s tarsier see:

• Merker, S., Yustian, I. & Muehlenberg, M. (2005) Responding to forest degradation: altered habitat use by Dian’s tarsier Tarsius dianae in Sulawesi, Indonesia. Oryx, 39(2): 189 – 195.
• Niemitz, C., Nietsch, A., Warter, S. & Rumpler, Y. (1991) Tarsius dianae: a new primate species from central Sulawesi (Indonesia). Folia Primatologica, 56(2): 105 – 116.
• The Primata:
  www.theprimata.com/factsheets.html