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. Buckland
  • Andrew J. Plumptre
  • Len Thomas
  • Eric A. Rexstad
Article

Abstract

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.

Keywords

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

Notes

Acknowledgments

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

References

  1. Brugiere, D., & Fleury, M.-C. (2000). Estimating primate densities using home range and line transect methods: a comparative test with the black colobus monkey Colobus satanus. Primates, 41, 373–382.CrossRefGoogle Scholar
  2. Buckland, S. T., Anderson, D. R., Burnham, K. P., Laake, J. L., Borchers, D. L., & Thomas, L. (2001). Introduction to distance sampling. Oxford: Oxford University Press.Google Scholar
  3. Buckland, S. T., Anderson, D. R., Burnham, K. P., Laake, J. L., Borchers, D. L., & Thomas, L. (Eds.). (2004). Advanced distance sampling. Oxford: Oxford University Press.Google Scholar
  4. Buckland, S. T., Plumptre, A. J., Thomas, L., & Rexstad, E. A. (2010). Design and analysis of line transect surveys for primates. In Press.Google Scholar
  5. Chapman, C., Fedigan, L. M., & Fedigan, L. (1988). A comparison of transect methods of estimating population densities of Costa Rican primates. Brenesia, 30, 67–80.Google Scholar
  6. Defler, T. R., & Pintor, D. (1985). Censusing primates by transect in a forest of known primate density. International Journal of Primatology, 6, 243–259.CrossRefGoogle Scholar
  7. Fashing, P. J., & Cords, M. (2000). Diurnal primate densities and biomass in the Kakamega Forest: an evaluation of census methods and a comparison with other forests. American Journal of Primatology, 50, 139–152.CrossRefPubMedGoogle Scholar
  8. Hassel-Finnegan, H. M., Borries, C., Larney, E., Umponjan, M., & Koenig, A. (2008). How reliable are density estimates for diurnal primates? International Journal of Primatology, 29, 1175–1187.CrossRefGoogle Scholar
  9. Hayes, R. J., & Buckland, S. T. (1983). Radial distance models for the line transect method. Biometrics, 39, 29–42.CrossRefGoogle Scholar
  10. Hayne, D. W. (1949). An examination of the strip census method for estimating animal populations. Journal of Wildlife Management, 13, 145–157.CrossRefGoogle Scholar
  11. Hurlbert, S. H. (1984). Pseudoreplication and the design of ecological field experiments. Ecological Monographs, 54, 187–211.CrossRefGoogle Scholar
  12. Johnson, E. G., & Routledge, R. D. (1985). The line transect method: a nonparametric estimator based on shape restrictions. Biometrics, 41, 669–679.CrossRefGoogle Scholar
  13. Kelker, G. H. (1945). Measurement and interpretation of forces that determine populations of managed deer. PhD thesis, University of Michigan.Google Scholar
  14. Marques, T. A., Thomas, L., Fancy, S. G., & Buckland, S. T. (2007). Improving estimates of bird density using multiple covariate distance sampling. The Auk, 124, 1229–1243.CrossRefGoogle Scholar
  15. Marshall, A. R., Lovett, J. C., & White, P. C. L. (2008). Selection of line-transect methods for estimating the density of group-living animals: lessons from the primates. American Journal of Primatology, 70, 1–11.CrossRefGoogle Scholar
  16. Mitani, J. C., Struhsaker, T. T., & Lwanga, J. S. (2000). Primate community dynamics in old growth forest over 23.5 years at Ngogo, Kibale National Park, Uganda: implications for conservation and census methods. International Journal of Primatology, 21, 269–286.CrossRefGoogle Scholar
  17. Olupot, W., & Waser, P. M. (2005). Patterns of male residency and intergroup transfer in gray-cheeked mangabeys (Lophocebus albigena). American Journal of Primatology, 66, 331–349.CrossRefPubMedGoogle Scholar
  18. Plumptre, A. J., & Cox, D. (2006). Counting primates for conservation: primate surveys in Uganda. Primates, 47, 65–73.CrossRefPubMedGoogle Scholar
  19. Struhsaker, T. T. (1975). The red colobus monkey. Chicago: University of Chicago Press.Google Scholar
  20. Struhsaker, T. T. (1981). Census methods for estimating densities. In National Research Council, Techniques for the study of primate population ecology (pp. 36–80). Washington, DC: National Academy Press.Google Scholar
  21. Thomas, L., Buckland, S. T., Rexstad, E. R., Laake, J. L., Strindberg, S., Hedley, S. L., et al. (2010). Distance software: design and analysis of distance sampling surveys for estimating population size. Journal of Applied Ecology, 47, 5–14.Google Scholar
  22. Whitesides, G. H., Oates, J. F., Green, S. M., & Kluberdanz, R. P. (1988). Estimating primate densities from transects in a west African rain forest: a comparison of techniques. Journal of Animal Ecology, 57, 345–367.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Stephen T. Buckland
    • 1
  • 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

Personalised recommendations