This section contains a description of the follow on work from the 1999 discovery by the Operation Wallacea teams of a possible new species of tarsier on Buton Island. This project is designed to assess the status of this new tarsier (15.2). A second study has examined the effect of habitat on the density and distribution of the Buton tarsier (15.3)

Introduction

The tarsier is a small, nocturnal primate found in Indonesia and the Philippines. It is widely distributed and relatively common in Sulawesi, due to its broad insectivorous niche and lack of significant predators (only snakes, civets and owls). However the conservation status of individual species within Sulawesi is still not well known, the IUCN Red List (1996) classifies all Sulawesi tarsier species as "Data deficient".

At present three species of tarsier are known from Sulawesi mainland, Tarsius spectrum (northern peninsular, < 1500m a.s.l., Mackinnon and MacKinnon 1980), Tarsius dianae (< 600m a.s.l., Central Sulawesi, Niemitz et al. 1991) and Tarsius pumilus (montane forest habitats >2000m a.s.l., Central Sulawesi, Musser and Dagosto 1987). Further forms such as those on the Togian Islands (Nietsch 1993), Sangihe Islands (Feiler 1990) and Selayar Island (Groves 1998) have been shown to have a distinct duet call/morphology from the above species.

The tarsier has a distinct duet call between mated pairs, produced at dawn and dusk close to their habitual sleeping site. These have been shown to vary significantly between the described species (Nietsch 1999; Nietsch & Kopp 1998; Nietsch & Theile 1998). These duet calls are a pattern of notes clearly different from contact or alarm calls, which are produced throughout their active period. Experiments on the function of duet behaviour strongly suggested that it serves functions in territory defense or advertising as well as in mate recognition (Nietsch and Theile 1998). Playback experiments revealed that tarsier males and females do not recognize the calls of a different species as calls of conspecific animals (Nietsch and Kopp 1999). Duet calls in Sulawesi tarsiers may thus serve as a pre-mating isolating mechanism.

To identify variations in the duet call of tarsiers from locations within Sulawesi Tenggara, indicated by sonogram analysis and tarsiers’ response to playback of different duet calls.

The main study location is Buton Island, the largest of the islands found to the south-east of mainland Sulawesi. Fieldwork is being carried out in the centre of the island, in the Kakinauwe Nature Reserve (810ha, 20-296m a.s.l.) north and east of the village of Labundo Bundo (S05011.115’, E122054.288’). The forest has been selectively logged up until 1987, the western end was burned in 1992, leaving patchy vegetation types with relatively high abundance of saplings (average 2-3m tall) and fig trees. The western end of the Reserve was selected for this study due to suitable habitat and accessibility, with altitude from 70-150m a.s.l..

Other locations have been selected for short visits, these include: Rawa Aopa Watumohai National Park; Puwarto, Kendari; Tanjung Peropa Suaga Margasatua, Pulau Kabaena.

The study in 1999 by Operation Wallacea yielded the first record of tarsiers on Buton Islands. Preliminary analysis of the duet calls of this insular population done by A. Nietsch suggested that its duet pattern might be unique when compared with the duet patterns of the mainland tarsiers, including T. spectrum and T. dianae. This strongly suggest that the Buton tarsiers are a distinct species.

Initially tarsier duet calls were recorded from the Buton Island site using a Marantz Professional Walkman and directional microphone. In order to assess the degree of intra-population variability in call pattern duet recordings have been made from at least 5 groups. Other data recorded includes: call start time, call description and number of animals calling. Recordings if duet calls are now being made from other locations during short trips, for comparative analysis.

Playback experiments, to identify any recognition of different species’ duet calls by Buton individuals, have been tested in Labundo Bundo. Duet calls of the Buton tarsier (as a control) and other Sulawesi tarsier species (as the experiment) (provided by A. Nietsch) have been played back to three groups, at various times of day. The playback used two Marantz recorders, when available, and Sony 1.5 Watt speakers placed 3-5m from the sleeping location. A response to the Buton call playback indicates the study pair’s recognition of the recorded calls, while response to the other tarsier species calls indicates if they recognise these species calls, i.e. if they can communicate with them. No response by the study animal suggests no recognition of the playback call; a duet call response may show recognition of the playback call; and an alarm call could indicate recognition of a distinct, but similar call.

Mist netting of tarsiers is being carried out to increase the size of data set of morphological data recorded in 1999. The choice of morphological measurements to be taken is based on work by Niemtz et.al. (1991) on T. dianae, and Nietsch (1993) on T. spectrum. Additionally external characteristics are recorded and photographic records of each individual caught are made.

DNA hair samples are being collected from each specimen netted and preserved in DMSO (Dimethyle Suphoxide) with salt solution, and also dry tubes. The location for the analysis is being presently organised, possibly with M. Shekelle from Washington University, USA.

To date sufficient duet calls have been recorded from at least 5 groups of tarsiers on Buton Island, to allow statistical analysis, following sonogram analysis. Calls have also been recorded from 2 locations on the mainland and these appear to be significantly different from those of all other tarsiers. The sonogram analysis will be carried out in collaboration with A. Nietsch on return to Europe.

The playback experiments only produced a response (vocal or observed) to the control (Buton duet call) at dawn and dusk, when tarsiers are known to be active. During the day no vocal response was recorded, and animals could not be observed. Responses recorded at dawn and dusk may be of limited significance as there is no control to be sure the response is induced by the playback and not another nearby animal calling. However on two occasions (with the control playback) a positive behavioural response was observed prior to the vocal duet call response, suggesting the latter was induced by the playback call. This indicates that the playback control is recognised by the study group, but that other tarsier species calls were not recognised. On one of these occasions after a positive response to the control playback, an alarm call was induced by the T. spectrum duet call playback, indicating some recognition.

One tarsier specimen was caught on 5^th September at Labundo Bundo, morphological data and DNA samples collected. Duet playback experiments were carried out on this animal, but no vocal response was produced, though a change in behaviour was observed during and shortly after the playback.

This research is a further development from the initial work carried out in 1999, and has set a solid background to develop future systematic and ecological studies in following years. This work will continue until October 2000, contributing to understanding the conservation requirements of tarsiers throughout Sulawesi, by increasing the knowledge on the distribution of vocally distinct groups within Sulawesi Tenggara.

A paper entitled Description of a possible new tarsier species from Buton Island, SE Sulawesi will be produced by March 2001 by James Burton from the University of Edinburgh.

A paper entitled Duet call variation in tarsiers from South and South East Sulawesi will be produced by J. Burton, A. Nietsch & M.L. Kopp.

The program for genetic analysis of tarsier hair samples is presently being discussed and may result in the publication of a genetics paper.

Given the possible new species status of the Buton tarsiers it is important to obtain data on the distribution and abundance of this animal in a range of habitats to assess the population densities and habitat preferences. The habitat changes occurring on Buton Island may affect the long term chances of survival for the species which is confined to this single island and how the tarsier population density is affected by forest disturbance is a key issue.

Abundance of tarsier groups at the Labundo Bundo site, Buton Island, was estimated by locating and mapping the sleeping sites of the ten nearest groups to a fixed point at four sites in the forest. Their locations were selected to reflect the variation in secondary habitat present on Buton Island. Sites were visited for ten days each, at dawn and dusk, to listen for tarsier duet calls and trace the tarsiers back to their sleeping trees. Once tarsiers were sighted at their sleeping sites, the location of these trees was mapped and various parameters measured such as height and DBH of tree, tree species etc. The positions of the ten nearest sleeping trees to the first tree found were mapped as a basis for calculating density of tarsiers in the area. In each site fifty 10m x 10m quadrats were placed systematically along transect lines in a 1 hectare area, and quantitative habitat data was recorded for analysis and correlation with tarsier density. Parameters included number of trees of various size categories, ground cover of small vegetation, and numbers of horizontal resting point such as lianas and fallen trees and were chosen to reflect suitability of the habitat for locomotor activity of tarsiers.

Initial results show a high abundance of tarsiers in the seriously disturbed primary forest site. The study will allow comparison of tarsier abundances between the tarsier form on Buton and T. dianae, previously studied in Sulawesi Tengah. Density and abundance data will be correlated with habitat data. A Geographical Information Systems package will be used to analyse data spatially, with the distances between sleeping trees considered to calculate exact density. The relative positions of the sleeping sites to habitat variations will also be considered.

Dissertations entitled A morphological and behavioural study of tarsiers and An abundance and habitat study of the unknown Tarsius spp. on Buton were produced in April 2001 by Tara Richardson from the University of Derby.  Copies of these dissertations which were both awarded Firsts, are available at the Labundo field centre and from the UK offices.   Aaron White from the University of Durham produced a dissertation entitled A comparison of the density and abundance of tarsiers in two different habitat types in May 2001