Impact of forest disturbance on the Buton tarsier

Buton Tarsier

Tarsiers represent one of the oldest extant lineages of primates. Photo taken by Dr Nancy Priston

A study into tarsiers on Buton Island, Sulawesi, shows that, counter-intuitively, they favour disturbed habitats over areas that have been least affected by human impact, particularly when choosing their sleeping sites.

Southeast Asia, and specifically Sulawesi, houses a highly diverse number of endemic small mammal species. Cataloguing mammals is challenging, as cryptic and elusive species such as tarsiers (Tarsius spp) are often overlooked. Tarsiers are small (100-150g) nocturnal protosimians. They represent one of the oldest extant lineages of primates; the oldest fossil has been dated to the Eocene period. Tarsiers were once widespread across Africa and Asia, but are now restricted to just a few islands in Southeast Asia.

Tarsiers showed a preference for more disturbed habitats

Like owls, tarsiers have an acute auditory ability that allows them to detect prey. They call frequently as they travel to and from their roost sites, making them easy for researchers to locate!

Sulawesi has been geographically isolated for millennia, resulting in high levels of endemism. Increases in the local human population have resulted in forest destruction, as subsistence farming encroaches on pristine forest. My study took place on Buton Island, where it has been estimated that 10% of the lowland forest is being lost annually. I studied the Buton tarsier’s habitat choices and particularly the selection of sleeping sites.

Habitats

Buton tarsier

Buton tarsier photographed by Dr Nancy Priston

Three forest areas were surveyed for tarsier roost sites and habitat surveys were conducted around these sites. Study sites were selected to represent a gradient of human impacts on the forest. Most tarsiers were seen in the most disturbed areas and fewest tarsiers were seen in the least disturbed areas.

Microhabitat analyses revealed that tarsiers were choosing areas with large circumference vines and strangler fig trees, small trees and large logs. Lianas are very useful for arboreal species such as tarsiers; they link trees together making movement through the canopy easier. They also provide platforms for the prey of the tarsier (arthropods).

Counter-intuitively, perhaps, tarsiers showed a preference for more disturbed habitats. However, as these areas allow them the greatest freedom of movement and access to their preferred prey, the tarsiers are clearly choosing sensibly.

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