A simple alternative to line transects of nests for estimating orangutan densities (original) (raw)

Abstract

We conducted a validation of the line transect technique to estimate densities of orangutan (Pongo pygmaeus) nests in a Bornean swamp forest, and compared these results with density estimates based on nest counts in plots and on female home ranges. First, we examined the accuracy of the line transect method. We found that the densities based on a pass in both directions of two experienced pairs of observers was 27% below a combined sample based on transect walks by eight pairs of observers, suggesting that regular line-transect densities may seriously underestimate true densities. Second, we compared these results with those obtained by nest counts in 0.2-ha plots. This method produced an estimated 15.24 nests/ha, as compared to 10.0 and 10.9, respectively, by two experienced pairs of observers who walked a line transect in both directions. Third, we estimated orangutan densities based on female home range size and overlap and the proportion of females in the population, which produced a density of 4.25–4.5 individuals/km2 . Converting nest densities into orangutan densities, using locally estimated parameters for nest production rate and proportion of nest builders in the population, we found that density estimates based on the line transect results of the most experienced pairs on a double pass were 2.82 and 3.08 orangutans/km2, based on the combined line transect data are 4.04, and based on plot counts are 4.30. In this swamp forest, plot counts therefore give more accurate estimates than do line transects. We recommend that this new method be evaluated in other forest types as well.

Access this article

Log in via an institution

Subscribe and save

• Starting from 10 chapters or articles per month
• Access and download chapters and articles from more than 300k books and 2,500 journals
• Cancel anytime View plans

Buy Now

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1

Similar content being viewed by others

References

• Ancrenaz M, Gimenez O, Ambu L, Ancrenaz K, Andau P, Goossens B, Payne J, Sawang A, Tuuga A, Lackman-Ancrenaz I (2005) Aerial surveys give new estimates for orangutans in Sabah, Malaysia. PLoSBiology 3(1,e3):1–8
  Google Scholar
• Buckland ST, Anderson DR, Burnham KP, Laake JL (1993) Distance sampling: estimating abundance of biological populations. Chapman and Hall, London
  Google Scholar
• Buij R, Wich SA, Lubis AH, Sterck EHM (2002) Seasonal movements in the Sumatran orangutan (Pongo pygmaeus abelii) and consequences for conservation. Biol Cons 107:83–87
  Article Google Scholar
• Buij R, Singleton I, Krakauer E, van Schaik CP (2003) Rapid assessment of orangutan density. Biol Cons 114:103–113
  Article Google Scholar
• Cowlishaw G, Dunbar R (2000) Primate conservation biology. University of Chicago Press, Chicago
  Google Scholar
• Ghiglieri MP (1984) The chimpanzees of Kibale forest. Columbia University Press, N.Y.
  Google Scholar
• Hashimoto C (1995) Population census of the chimpanzees in the Kalinzu forest, Uganda: comparison between methods with nest counts. Primates 36:477–488
  Google Scholar
• Johnson AE, Knott CD, Pamungkas B, Pasaribu M, Marshall AJ (2005) A survey of the orangutan (Pongo pygmaeus pygmaeus) population in and around Gunung Palung National Park, West Kalimantan, Indonesia based on nest counts. Biol Cons (in press)
• Morrogh-Bernard H, Husson S, Page SE, Rieley JO (2003) Population status of the Bornean orang-utan (Pongo pygmaeus) in the Sebangau peat swamp forest, Central Kalimantan, Indonesia. Biol Cons 110:141–152
  Article Google Scholar
• Rijksen HR, Meijaard E (1999) Our vanishing relative: The status of wild orang-utans at the close of the twentieth century. Kluwer, Boston
  Google Scholar
• Russon AE, Erman A, Dennis R (2001) The population and distribution of orang-utans (Pongo pygmaeus pygmaeus) in and around the Danau Sentarum Wildlife Reserve, West Kalimantan, Indonesia. Biol Cons 97:21–28
  Article Google Scholar
• van Schaik CP, Azwar, Priatna D (1995) Population estimates and habitat preferences of orangutans based on line transects of nests. In: Nadler RD, Galdikas BMF, Sheeran LK, Rosen N (eds) The neglected ape. Plenum Press, N.Y., pp129–147
  Google Scholar
• van Schaik CP, Monk KA, Robertson JMY (2001) Dramatic decline in orang-utan numbers in the Leuser ecosystem, Northern Sumatra. Oryx 35:14–25
  Article Google Scholar
• Singleton IS (2000) Ranging behaviour and seaasonal movements of sumatran orangutans (Pongo pygmaeus abelii) in Swamp Forests. PhD dissertation, University of Kent
• Singleton IS, van Schaik CP (2002) The social organization of a population of Sumatran orangutans. Folia Primatol 73:1-20
  Article PubMed Google Scholar
• Thomas L, Laake JL, Strindberg S, Marques FFC, Borchers DL, Buckland ST, Anderson DR, Burnham KP, Hedley SL, Pollard JH (2001) Distance 4.0. Beta 3. Research unit for wildlife population assessment. University of St. Andrews, UK
• Wich SA, Singleton I, Utami-Atmoko SS, Geurts ML, Rijksen HD, van Schaik CP (2003) The status of the sumatran orangutan Pongo abelii: an update. Oryx 37:49–54
  Article Google Scholar

Download references

Acknowledgements

We thank the BOS-Foundation for permission to work at Mawas, and its staff for the great support of all activities; the staff and students from Universitas Nasional, Jakarta (Tatang Mitra Setia, Imran Said L. Tobing, Didik Prasetyo, Dwi Mulyawati, Tirza Yohana, Lili Aries Sadikin, Adi Hadinata, Ari Meididit, Fikty Apirlinayati, Fitriah Basalamah, and Ika Mian Karlina) for participating in the line transect experiment; the Indonesian Institute of Sciences (LIPI) for permission to work in Indonesia; the L.S.B. Leakey Foundation for financial support of the Tuanan Orangutan Project; the Netherlands Organisation for Scientific Research for financially supporting S.A. Wich, and Meredith Bastian and Maria van Noordwijk for comments on the MS.

Author information

Authors and Affiliations

1. Anthropologisches Institut und Museum, Universität Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
   Carel P. van Schaik
2. Department of Behavioural Biology, Utrecht University, PO Box 80086, 3508TB, Utrecht, The Netherlands
   Serge A. Wich
3. Fakultas Biologi, Universitas Nasional, Jl Sawo Manila, Pejaten, Pasar Minggu, Jakarta, Indonesia
   Sri Suci Utami
4. Kantor Mawas, Jl Yos Sudarso 1A, Palangkaraya, 73112, Kalimantan Tengah, Indonesia
   Kisar Odom

Authors

1. Carel P. van Schaik
2. Serge A. Wich
3. Sri Suci Utami
4. Kisar Odom

Corresponding author

Correspondence toCarel P. van Schaik.

Rights and permissions

About this article

Cite this article

van Schaik, C.P., Wich, S.A., Utami, S.S. et al. A simple alternative to line transects of nests for estimating orangutan densities.Primates 46, 249–254 (2005). https://doi.org/10.1007/s10329-005-0134-z

Download citation

• Received: 29 September 2003
• Accepted: 29 March 2005
• Published: 28 June 2005
• Issue date: October 2005
• DOI: https://doi.org/10.1007/s10329-005-0134-z

Keywords