Preliminary Data on the Behavior, Ecology, and Morphology of Pygmy Tarsiers (Tarsius pumilus)

Abstract

We here present the first behavioral, morphological, and ecological data on a living group of highland pygmy tarsiers, Tarsius pumilus, and compare them with the lowland tarsier species of Sulawesi. Pygmy tarsiers were previously known only from 3 museum specimens and had not been seen alive since the first specimens were collected in 1917 and 1930. As part of a 2-mo exploratory study, we recently located a group consisting of ≥4 pygmy tarsiers in the mossy cloud forest of Lore Lindu National Park, Central Sulawesi, Indonesia. We captured 1 adult female and 2 adult male group members. The tarsiers weighed a mean of 50 g, less than half the weight of adult lowland tarsiers. Our behavioral observations indicate that these tarsiers live in small groups that return to the same sleeping tree each morning. Though our data are preliminary, pygmy tarsier body proportions appear to differ from the lowland Sulawesian tarsier species, with relatively long hind limbs compared to total body length. We also observed differences in grouping and communication behaviors. Unlike lowland tarsiers, pygmy tarsiers possess multiple adult males per group and rarely vocalize or scentmark. These differences may correlate with variables unique to their high altitude habitat, especially a reduction in food and tree resources, given that tree density declined sharply along an altitudinal gradient. Our preliminary study identifies the importance of altitudinal ecological gradients to tarsier behavioral ecology in Central Sulawesi, providing questions and predictions for future research directions.