International Journal of Primatology

, Volume 29, Issue 5, pp 1175–1187

How Reliable are Density Estimates for Diurnal Primates?

  • Heather M. Hassel-Finnegan
  • Carola Borries
  • Eileen Larney
  • Mayuree Umponjan
  • Andreas Koenig
Article

DOI: 10.1007/s10764-008-9301-6

Cite this article as:
Hassel-Finnegan, H.M., Borries, C., Larney, E. et al. Int J Primatol (2008) 29: 1175. doi:10.1007/s10764-008-9301-6

Abstract

Primate population assessments provide the basis for comparative studies and are necessary prerequisites in determining conservation status. The most widely used assessment method is line transect sampling, which generates systematic data quickly and comparatively inexpensively. In contrast, the presumably most reliable method is long-term monitoring of known groups, which is both slow and costly. To assess the reliability of various analytical methods, we compared group and population densities for white-handed gibbons (Hylobates lar carpenteri) and Phayre’s leaf monkeys (Trachypithecus phayrei crepusculus) derived from transect walks with those from long-term group follows at Phu Khieo Wildlife Sanctuary, Thailand. Our assistants and we regularly walked a 4-km transect over 30 mo (480 km total), resulting in 155 gibbon sightings and 125 leaf monkey sightings. We then estimated densities via 1) DISTANCE and 2) the Kelker method based on perpendicular distances (PD) or animal-to-observer distances (AOD). We compared the 3 estimates to values based on known home ranges (95% kernels), accounting for home range overlap, combined with group size data. Analyses of line transect data consistently overestimated group densities for both species, while underestimating group size for leaf monkeys. Quality of results varied according to the group size and spread of each species. However, we found, in accordance with previous studies, that values derived via AOD (or its derivations) matched most closely with population estimates based on home range data.

Keywords

home range Hylobates lar carpenteri line transect Trachypithecus phayrei crepusculus 

Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  • Heather M. Hassel-Finnegan
    • 1
  • Carola Borries
    • 2
  • Eileen Larney
    • 1
  • Mayuree Umponjan
    • 3
    • 4
  • Andreas Koenig
    • 2
  1. 1.Interdepartmental Doctoral Program in Anthropological SciencesStony Brook UniversityStony BrookUSA
  2. 2.Department of AnthropologyStony Brook UniversityStony BrookUSA
  3. 3.Department of Forest BiologyKasetsart UniversityBangkokThailand
  4. 4.Wildlife Conservation Society (WCS)Thailand ProgramBangkokThailand

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