International Journal of Primatology

, Volume 31, Issue 3, pp 485–499 | Cite as

Line Transect Sampling of Primates: Can Animal-to-Observer Distance Methods Work?

  • Stephen T. BucklandEmail author
  • Andrew J. Plumptre
  • Len Thomas
  • Eric A. Rexstad


Line transect sampling is widely used for estimating abundance of primate populations. Researchers commonly use animal-to-observer distances (AODs) in analysis, in preference to perpendicular distances from the line, which is in marked contrast with standard practice for other applications of line transect sampling. We formalize the mathematical shortcomings of approaches based on AODs, and show that they are likely to give strongly biased estimates of density. We review papers that claim good performance for the method, and explore this performance through simulations. These confirm strong bias in estimates of density using AODs. We conclude that AOD methods are conceptually flawed, and that they cannot in general provide valid estimates of density.


animal-to-observer distances distance sampling estimating primate density Kelker strip modified Kelker method primate surveys 



We thank Anne Savage, the editor, and 2 reviewers for their constructive comments on earlier drafts.


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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Stephen T. Buckland
    • 1
    Email author
  • Andrew J. Plumptre
    • 2
  • Len Thomas
    • 1
  • Eric A. Rexstad
    • 1
  1. 1.Centre for Research into Ecological and Environmental ModellingUniversity of St. Andrews, The ObservatorySt. AndrewsUK
  2. 2.Wildlife Conservation SocietyKampalaUganda

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