Hostname: page-component-6bb9c88b65-x9fsb Total loading time: 0 Render date: 2025-07-26T07:11:38.288Z Has data issue: false hasContentIssue false
  • English
  • Français

Dramatic decline in orang-utan numbers in the Leuser Ecosystem, Northern Sumatra

Published online by Cambridge University Press:  24 April 2009

Carel P. van Schaik ,
Kathryn A. Monk  and
J. M. Yarrow Robertson
Kathryn A. Monk
Affiliation:
Research, Monitoring, and Information Division, Leuser Management Unit, JI. Dr Mansyur 68, Medan 20154, Indonesia
J. M. Yarrow Robertson
Affiliation:
Conservation Management Division, Leuser Management Unit, JI. Dr Mansyur 68, Medan 20154, Indonesia
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The Leuser Ecosystem, northern Sumatra, Indonesia, contains the world's largest orang-utan Pongo pygmaeus population. We examine the consequences of the recent wave of forest conversion, and legal and illegal logging, on orang-utan numbers in the Leuser Ecosystem. We review density variation inside the Leuser Ecosystem and its causes, and the consequences of selective logging, exhaustive logging and clear-felling for habitat conversion on orang-utan densities. The analysis of the orang-utan's decline is based on information on forest loss, logging intensity, and the delineation of logging concessions and legal changes in land use status. The results indicate a very rapid decline, by c. 45 per cent, from c.. 12,000 in early 1993, over a 6- to 7-year period. During 1998 and 1999, losses occurred at a rate of about 1000 orang-utans per year. At this rate, further losses in the near future are expected to put the survival of Leuser's orang-utans in serious doubt.

Keywords

Conversionfragmentationillegal loggingorang-utanplantationsselective loggingSumatra

Information

Type
Research Article
Information
Oryx , Volume 35 , Issue 1 , January 2001 , pp. 14 - 25
Copyright
Copyright © Fauna and Flora International 2001

References

Brown, J.H. & Lomolino, M.V. (1998) Biogeography (2nd edn). Sinauer Associates, Inc., Sunderland, MA.Google Scholar
Davies, A.G. & Payne, J.B. (1982) A Faunal Survey of Sabah. World Wildlife Fund, Kuala Lumpur, Malaysia.Google Scholar
Delgado, R. & van Schaik, C.P. (2000) The orang-utan (Pongo pygmaeus): behavioural ecology and conservation status: a tale of two islands. Evolutionary Anthropology, 9, 201–218.3.0.CO;2-Y>CrossRefGoogle Scholar
Djojosudharmo, S. & van Schaik, C.P. (1992) Why are orang utans so rare in the highlands? Altitudinal changes in a Sumatran forest. Tropical Biodiversity, 1, 11–22.Google Scholar
Hooijer, D.A. (1961) The orang-utan in Niah cave pre-history. Sarawak Museum Journal, 9, 408–421.Google Scholar
von Koenigswald, G.H.R. (1982) Distribution and evolution of the orang utan, Pongo pygmaeus (Hoppius). In The Orang Utan, its Biology and Conservation (ed. de Boer, L. E. M.), pp. 1–15. Dr W. Junk Publishers, The Hague.Google Scholar
Leighton, M., Seal, U.S., Soemarna, K. et al. (1995) Orang-utan life history and vortex analysis. In The Neglected Ape (eds Nadler, R. D., Galdikas, B. F. M., Sheeran, L. K. and Rosen, N.), pp. 97–107. Plenum Press, New York.CrossRefGoogle Scholar
MacKinnon, J. (1974) The behaviour and ecology of wild orangutans (Pongo pygmaeus). Animal Behaviour, 22, 3–74.CrossRefGoogle Scholar
MacKinnon, J. (1992) Species survival plan for the orang-utan. In Proceedings of the International Conference on Forest Biology and Conservation in Borneo (eds Ismail, G., Mohamed, M. and Omar, S.), pp. 209–219. Center for Borneo Studies, Kota Kinabalu.Google Scholar
Payne, J.B. (1987) Surveying orang-utan populations by counting nests from a helicopter: a pilot survey in Sabah. Primate Conservation, 8, 92–103.Google Scholar
Rao, M. & van Schaik, C.P. (1997) The behavioural ecology of Sumateran orang-utans in logged and unlogged forest. Tropical Biodiversity, 4, 173–185.Google Scholar
Rijksen, H.D. (1978) A Field Study on Sumatran Orang Utans (Pongo pygmaeus abelii Lesson 1827). H. Veenman & Zonen, B.V., Wageningen.Google Scholar
Rijksen, H.D. (1982) How to save the mysterious ‘man of the rain forest’? In The Orang Utan: Its Biology and Conservation (ed. de Boer, L. E. M.), pp. 317–341. Dr W. Junk Publishers, The Hague.Google Scholar
Rijksen, H.D. & Meijaard, E. (1999) Our Vanishing Relative: The Status of Wild Orang-Utans at the Close of the Twentieth Century. Tropenbos Publications, Wageningen.CrossRefGoogle Scholar
Robertson, J.M.Y. & van Schaik, C.P. (2001) Causal factors underlying the dramatic decline of the Sumatran orang-utan. Oryx, 35 (1), 26–38.CrossRefGoogle Scholar
van Schaik, C.P. (1996a) Does the orang-utan have a future? Population status in Gunung Leuser National Park. In Leuser: A Sumatran Sanctuary (eds van Schaik, C. P. and Supriatna, J.), pp. 249–258. YABSHI, Depok, Indonesia.Google Scholar
van Schaik, C.P. (1996b) Strangling figs: their role in the forest. In Leuser: A Sumatran Sanctuary (eds van Schaik, C. P. and Supriatna, J.), pp. 111–119. YABSHI, Depok, Indonesia.Google Scholar
van Schaik, C.P. (1999) The socioecology of fission-fusion sociality in orang-utans. Primates, 40, 73–90.CrossRefGoogle Scholar
van Schaik, C.P. & Mirmanto, E. (1985) Spatial variation in the structure and litterfall of a Sumatran rain forest. Biotropica, 17, 196–205.CrossRefGoogle Scholar
van Schaik, C.P. Azwar & Priatna, D. (1995a) Population estimates and habitat preferences of orang-utans based on line transects of nests. In The Neglected Ape (eds Nadler, R. D., Galdikas, B. F. M., Sheeran, L. K. and Rosen, N.), pp. 129–147. Plenum Press, New York.CrossRefGoogle Scholar
van Schaik, C.P., Poniran, S., Utami, S.S. et al. (1995b) Estimates of orang-utan distribution and status in Sumatra. In The Neglected Ape (eds Nadler, R. D., Galdikas, B. F. M., Sheeran, L. K. and Rosen, N.), pp. 109–116. Plenum Press, New York.CrossRefGoogle Scholar
van Schaik, C.P., Fox, E.A. & Sitompul, A.F. (1996) Manufacture and use of tools in wild Sumatran orang-utans. Naturwissenschaften, 83, 186–188.Google Scholar
van Schaik, C.P. & Knott, C. (in review) Geographic variation in tool use on Neesia fruits in orang-utans. American journal of Physical Anthropology.Google Scholar
Singleton, I.S. & van Schaik, C.P. (in press) Orang-utan homerange size and its determinants in a Sumatran swamp forest. International Journal of Primatology.Google Scholar
Sugardjito, J., te Boekhorst, I.J.A. & van Hooff, J.A.R.A.M. (1987) Ecological constraints on the grouping of wild orang-utans (Pongo pygmaeus) in the Gunung Leuser National Park, Sumatra, Indonesia. International Journal of Primatology, 8, 17–41.CrossRefGoogle Scholar
Utami, S.S. & Mitra Setia, T. (1995) Behavioural changes in wild male and female Sumatran orang-utans (Pongo pygmaeus abelii) during and following a resident male take-over. In The Neglected Ape (eds Nadler, R. D., Galdikas, B. F. M., Sheeran, L. K. and Rosen, N.), pp. 183–190. Plenum Press, New York.CrossRefGoogle Scholar
Wheatley, B.P. (1982) Energetics and foraging in Macaca fascicularis and Pongo pygmaeus and a selective advantage of large body size in the orang-utan. Primates, 23, 348–363.CrossRefGoogle Scholar