ESR 6:231-237 (2009)  -  doi:10.3354/esr00166

Reconstructing the observation process to correct for changing detection probability of a critically endangered species

A. J. McConville1, Iu. A. Grachev2, A. Keane1,3, T. Coulson3, A. B. Bekenov2, E. J. Milner-Gulland1,3,*

1Centre for Environmental Policy, Imperial College London, Exhibition Road, London SW7 2AZ, UK
2Laboratory of Theriology, Institute of Zoology, Ministry of Education and Science, Akademgorodok, Almaty 480032, Kazakhstan
3Department of Life Sciences and Centre for Population Biology, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, UK
*Corresponding author. Email:

ABSTRACT: Effective conservation decision-making requires robust estimates of population trends. It is often assumed that, as long as monitoring methods remain consistent over time, trends in relative abundance are valid proxies for actual abundance. However, if the bias and uncertainty of relative abundance estimates change over time, this can have a serious impact on the validity of monitoring programmes. We developed a simple model for the retrospective assessment of the likely error and bias in abundance estimates from aerial surveys of the saiga antelope. Due to dramatic reductions in group size and density, current estimates of abundance are probably substantially lower than the true population size, and the level of uncertainty surrounding these estimates precludes their use for monitoring trends. This has implications for the Government of Kazakhstan’s ability to monitor progress towards their agreed conservation goals. The method is potentially widely applicable to species for which historical data on relative abundance and group size are available.


KEY WORDS: Monitoring · Saiga tatarica · Antelope · Aerial survey · Kazakhstan · Distance · Population trend · Ungulate · Relative abundance


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Cite this article as: McConville AJ, Grachev IuA, Keane A, Coulson T, Bekenov AB, Milner-Gulland EJ (2009) Reconstructing the observation process to correct for changing detection probability of a critically endangered species. Endang Species Res 6:231-237

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