Philippine tarsier (Tarsius syrichta)

This interesting animal is often described as the smallest monkey of the world. But it is neither monkey nor the smallest.

Morphology

With their body size they really belong to smallest primates of the world (average weight is 110 – 140 gram) ^2,4. They got their English, Latin and also Czech name according to elongated tarsus. Elongated and clubbed fingers serve for better adhesion to substrate. The whole body except the tail is covered with very soft fur. They have extremely big head in comparisons with body. Their enormously huge eyes are fixed in the skull and weight together more than brain of this animals. Such big eyes are necessary for their nocturnal life. Perfect vision is extremely important for them. In contrast to most of nocturnal primates tarsiers lack tapeum lucidum (light reflecting area). A special adaptation of the back bone allows rotating head up to 180 degrees without moving the body.

Ecology and behaviour

Tarsiers are nocturnal insectivorous primates. They are the only strictly carnivorous primates. Tarsiers prey mainly on insects, but may feed also on spiders, crustaceans, small vertebrates, e.g. lizards. To the main predators except humans belong feral cats, civets, raptors or snakes.

Tarsiers are active from dusk to dawn. During day they rest covered in the trees 1-2 m from the ground. Tarsiers are arboreal clingers and leapers. Social system of tarsier is quite variable from monogamous pairs to family group with alloparenting. Because of nocturnal life style the olfactory and acoustic communication are the most important. Tarsiers scent mark their home-ranges regularly and regularly vocalize at dusk and dawn. Social system and acoustic communication are the main topics of our research. Tarsiers live in various habitat types – primary and secondary forest, mangroves include tropical rainforest with dense vegetation and trees that offer it protection like tall grasses, bushes and bamboo shoots. They are lacking in areas with high human density and intense agriculture ^2,4, so their occurrence becomes rarer.

Systematics

Tarsiers form their own lineage between prosimians and monkeys. To date nine species living in Southeast Asia – Sulawesi, Sundaes a Philippines have been described. Eight species are found in Indonesia – Tarsius bancanus (Horsfield 1821), Tarsius dianae (Niemitz et al. 1991), Tarsius pelengensis (Sody 1949), Tarsius pumilus (Miller & Hollister 1921), Tarsius sangirensis (Meyer 1897), Tarsius spectrum (Erxleben 1777), Tarsius lariang (Merker & Groves 2006) and recently described Tarsius tumpara (Shekelle et al. 2008).

Only one species Tarsius syrichta (Linnaeus 1758) is found in the Philippines. Three subspecies of Tarsius syrichtahave been described. All these subspecies are found on islands that belonged to former large Pleistocene island of Greater Mindanao. Tarsius syrichta syrichta (Linnaeus 1758) lives on Samar and Leyte, Tarsius syrichta carbonarius (Heude 1899) on Mindanao, Tarsius syrichta fraterculus (Miller 1910) on Bohol. Other populations were found on Dinagat, Siargo and Basilan (Brandon-Jones et al. 2004) and they could be regarded as different subspecies ¹.

Population status and conservation

Tarsiers and the Philippines remaining biodiversity and the ecosystems are under tremendous threats. Logging and mining have destroyed most of the forests. Except of the degradation of their habitat tarsiers are threatened directly by humans. Tarsiers are killed as pests while hunting for insects on the field and they are hunted for illegal wildlife pet trade or used as tourist attractions. These animals are often kept in small cages with unsuitable conditions. As tourism increased, a rising number of tarsiers were taken from the wild. You can see tarsiers under such condition in Loboc, one of the greatest Bohol’s tourist destinations. Holders offer the tarsiers show in order to attract visitors for boat trip. Tarsiers are own by local people thathave received permit for holding several specimens. Stressed animals are kept in absolutely unsuitable conditions, in small cages, visitors are allowed to feed, touch and hold them – all during the day, which is very stressful for nocturnal animals. In these circumstances tarsiers don not survive more than few weeks or months. Conservation centre of The Philipine Tarsier Foundation in Corella on Bohol island offers totally different conditions to both tarsiers and visitors.

According to the IUCN Red book ³ this species has been transferred from “Data Deficient” category to the „Near Threatened“ category. Population of the Philippine tarsier is decreasing. Habitat loss and illegal pet trade are the main threats. Monitoring in the Corella locality (B. Aure, C. Escabi, and V. Cerna) has been conducted recently. After the Presidential Proclamation from 1997 the Philippine tarsier (Tarsius syrichta) is specially protected faunal species of the Philippines. His future depends on conservation activities and education of local people. Detailed research that will help to gain lacking information about this species is necessary.

Because of they nocturnal life, rapid locomotion and lacking tapetum lucidum tarsiers are one of the most difficult nocturnal primates to observe in their natural habitat. Only few studies have focused on the Philippine tarsiers (T. syrichta)and informations about their behaviour and also distribution are very incomplete.

References

¹ Brandon-Jones, D., Eudey, A.A., Geissmann, T., Groves, C.P., Melnick, D.J., Morales, J.C., Shekelle, M. & Stewart, C.B. 2004. Asian primate classification. International Journal of Primatology 25, 97-164
² Dagosto, M., Gebo, D.L. & Dolino, C. 2001. Positional behavior and social organization of the Philippine tarsier (Tarsius syrichta). Primates 42, 233-243.
³ Arboleda, I. 2008. Tarsius syrichta. In: IUCN 2008. 2008 IUCN Red List of Threatened Species.
⁴ Neri-Arboleda, I., Stott, P. & Arboleda, N.P. 2002. Home ranges, spatial movements and habitat associations of the Philippine tarsier (Tarsius syrichta) in Corella, Bohol. Journal of Zoology 257, 387-402.