Do animal size, seasons and vegetation type influence detection probability and density estimates of Serengeti ungulates?

Bukombe, J., Senzota, R. B., Fryxell, J. M., Kittle, A., Kija, H., Hopcraft, J. G. C. , Mduma, S. and Sinclair, A. R.E. (2016) Do animal size, seasons and vegetation type influence detection probability and density estimates of Serengeti ungulates? African Journal of Ecology, 54(1), pp. 29-38. (doi: 10.1111/aje.12255)

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Abstract

Accurate detection of individual animals and estimation of ungulate population density might be a function of vegetation cover, animal size, observation radius or season. We assessed the effect of these factors on estimates of detection probability and density using five ungulate species in Western Serengeti National Park, Tanzania. Estimates were derived from information collected using ground surveys involving line transects targeting three resident species (impala, topi and buffalo) and two migrants (wildebeest and zebra) and analysed using DISTANCE, MANOVA, t-test and Pearson correlation. Results showed that ground surveys that take observation radii of 100 m would appreciably estimate at least 80% of the available ungulates. Beyond 100 m radii, surveys would leave approximately 43% of individuals undetected, the reason being a substantial influence of animal size, vegetation cover and observation radius on the detection. Animal size and observation radius have interactive effects. On their own seasonal differences, they do not have any effect but in interaction with animal size have significant effects especially on the migrant species. As reliable estimates of detection and density are required for making reasonable inferences, we urge that surveys using DISTANCE approach should consider incorporating both ground and aerial survey methods and ensure adequate sample replication.

Item Type:Articles
Additional Information:This work was funded by the Canadian Natural Science sand Engineering Research Council grants to J.M. Fryxell and A.R.E. Sinclair. The authors thank COSTECH for providing some funds.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Hopcraft, Dr Grant
Authors: Bukombe, J., Senzota, R. B., Fryxell, J. M., Kittle, A., Kija, H., Hopcraft, J. G. C., Mduma, S., and Sinclair, A. R.E.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
Journal Name:African Journal of Ecology
Publisher:Wiley
ISSN:0141-6707
ISSN (Online):1365-2028
Published Online:20 November 2015

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