Study of social behaviour and communication of the Philippine tarsier (Tarsius syrichta) using radio-telemetry and bioacoustic methods

Introduction

Tarsiers are small nocturnal primates living in Asia. Only one species – the Philippine tarsier (Tarsius syrichta) is found in the Philippines¹.

Sociality

As nocturnal and cryptic primates tarsier have been long time considered asocial. However, numerous studies of Indonesian primate species revealed great variability in social systems of these primates. Tarsius spectrum sleeping in family groups and foraging in proximity of other individuals seem to be the most social. Also alloparenting has been described in this species. His social system is characterized from monogamous pairs to polygynous groups ^7,9,10. Similar system has been described in Tarsius dianae ¹¹. On the contrary other Indonesian species Tarsius bancanus is solitarily during nightly foraging and daily rest. Its social systems is characterized as monogamous or noyau, where male home-ranges overlap several female home-ranges ^14,19.

The Philippine tarsier (Tarsius syrichta) is regarded as solitary species. Individuals were observed sleeping strictly solitarily, home-ranges of males overlap those of more than one female ^2,3,13. However, only few studies have dealt with sociality of the Philippine tarsiers. The classifications are made on the basis of sleeping animals or overlap of the home-ranges. It must by emphasized that tarsiers are one of the most difficult nocturnal primates to observe in their natural habitat because of its rapid mode of locomotion and the lack of tapetum lucidum in their eyes and also incorrect methodology are responsible for lack of data about social behaviour of these primates ^4,9.

Communication

Vocalizations and scent marking were recognized as main modes of communication between tarsiers. The most conspicuous acoustic signals in tarsiers are loud calls emitted regularly on dusk and dawn. The loud calls were studied in Indonesian species. Their spectrograms, inter-sex and also geographical variability which can help to describe new species were analysed ^{6,10,12,13,15,16}. In many primate species individual differences in loud calls have been revealed ^17,18. They enable individual recognition and can influence mate choice. In tarsiers where acoustic communication is so important the individual differences have not been studied so far.

No aspect of acoustic communication has been studied in the Philippine tarsiers.

Ontogenetical development and maternal care

Tarsiers give birth to one extremely large offspring once in a year. Tarsier infants weigh one quarter to one third of adult weight at birth. Thus, mother parks the infant and forages nearby ^5,8,10,13.

There has been increase in numbers of researchers and studies dealing with tarsier during last decade. However, most of them focused on Indonesian tarsier species and detailed information about the Philippine tarsiers is lacking. Our long term study of social behaviour and home-ranges will help to characterize their social and mating system. Bioacoustic methods can help us to understand communication between individuals more deeply. Our study will contribute to the current knowledge about the Philippine tarsier and will provide broad basis for future comparison within as well as between tarsier species. The results of our study will be important for improving conservation strategies as well.

Goals

Our project is the first long term study conducted on the Philippine tarsier (Tarsius syrichta). We focus on study of sociality and communication in the population of Tarsius syrichta fraterculus) living on Bohol. This main goal of the study will be achieved using three different approaches described below.

1. Study of home-ranges

We will collect data about home-range area of several animals and its seasonal changes by focal observing of radio-collared animals during three years.
We will focus on:
a) sociality – if they are strictly solitary or are found in proximity to other individuals at least in some part of the year.
b) mating system – if there are polygynous, have noyau system or pair bonds.

2. Study of communication

We will collect data about:
a) social interactions
b) vocal communication – we will focus on acoustic repertoire and analysis of loud calls – their characteristic, seasonal changes and variability between sexes or idividuals.

3. Study of onotgenetical development and maternal care

We will collect basic data about reproduction of the Philippine tarsiers, development of youngs and maternal care.

Methods

Data collecting and analyses

For observation of the animals we use radio-telemetry. During the first year we radio-collared five animals (males and females) that were followed for several months. In following years we plan to radio-collar up to ten individuals. Animals are followed daily from dusk to dawn if possible and we monitor their movements and behaviour.

At the same time we record data for study of acoustic communication.

Youngs cannot be radio-collared so they are be observed in proximity of their radio-collared mother and we record their development and interactions.

Animals are radio-collared with collars TW-4 (Biotrack Limited (UK)). For recording of vocalization we use directional microphone Sennheiser ME 66, digital recorder Olympus LS-10.

Data will be analysed using ArcView a Ranges VI(Kenward) softwares, bioacoustic data using Avisoft software (Avisoft-SASLab Pro Software).

Schedule and locality

Schedule and locality is described in Project section.

Research team

You will find information about our research team in the section About us.

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. 1997. A preliminary study of the Philippine tarsier (Tarsius syrichta) in Leyte. American journal of physical anthropology 73.
³ Dagosto, M., Gebo, D.L. & Dolino, C. 2001. Positional behavior and social organization of the Philippine tarsier (Tarsius syrichta). Primates 42, 233-243.
⁴ Fleagle, J. 1998. Primate adaptation and evolution. New York: Academic Press.
⁵ Gursky, S. 1994. Infant care in the spectral tarsier, Tarsius spectrum: a prliminary analysis. International Journal of Primatology 15, 843-853.
⁶ Gursky, S. 2000. Sociality in the spectral tarsier, Tarsius spectrum. American Journal of Primatology 51, 89-101.
⁷ Gursky, S. 2002. Determinants of gregariousness in the spectral tarsier (Prosimian: Tarsius spectrum). Journal of Zoology 256, 401-410.
⁸ Gursky, S. 2002. The behavioral ecology of the spectral tarsier, Tarsius spectrum. Evolutionary Anthropology 11, 226-234.
⁹ Gursky, S. 2005. Associations between adult spectral tarsiers. American Journal of Physical Anthropology 128, 74-83.
¹⁰ MacKinnon, J.R. & MacKinnon, K.S. 1980. The behaviour of wild spectral tarsier. International Journal of Primatology 1, 361-379.
¹¹ Merker, S. 2006. Habitat-specific ranging patterns of Dian´s tarsiers (Tarsius dianae) as revealed by radiotracking. American Journal of Primatology 68, 111-125.
¹² Merker, S. & Groves, C.P. 2006. Tarsius lariang: a new primate species from western central Sulawesi. International Journal of Primatology 27, 465-485.
¹³ 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.
¹⁴ Niemitz, C. 1984. The biology of tarsiers. Stuttgart: Gustav Fischer.
¹⁵ Niemitz, C., Nietsch, A., Warter, S. & Rumpler, Y. 1991. Tarsius dianae – a new primate species from central Sulawesi (Indonesia). Folia Primatologica 56, 105-&.
¹⁶ Nietsch, A. 1999. Duet Vocalizations among different populations of Sulawesi tarsiers. International Journal of Primatology 20, 567-583.
¹⁷ Snowdon, C.T. & Cleveland, J. 1980. Individual recognition of contact calls by pygmy marmosets. Animal Behaviour 28, 717-727.
¹⁸ Wich, S.A., Koski, S., De Vries, H. & Van Schaik, C.P. 2003. Individual and contextual variation in Thomas langur male loud calls. Ethology 109, 1-13.
¹⁹ Yustian, I. 2007. Ecology and conservation status of Tarsius bancanus saltator on belitung. Göttingen: Cuvillier Verlag.