My research focuses on population monitoring and protection (e.g. ranger patrols) of threatened, landscape species in the tropics. Most recently, I have worked on projects involving jaguars (Panthera onca) and spectacled bears (Tremarctos ornatus) in Colombia and Sumatran tigers (Panthera tigris sumatrae) and their prey (Rusa unicolor, Sus scrofa, etc) in Indonesia.

Taking the case of the Sumatran tiger, for example, obtaining accurate estimates of this critically endangered species is extremely challenging because they occur at very low densities in even the best protected, most prey-rich habitats. It is therefore not surprising that the 3-4 month “snapshot” camera-trap surveys, which comprise most Sumatran tiger studies to date¹, result in very imprecise estimates. Cumulatively, these estimates do not paint a very clear picture of Sumatran tiger status. For example, the most recent island-wide estimate is 173-883 tigers², a wide range that varies by over 500%

Further convoluting the picture is the reality that tiger numbers naturally fluctuate in response to factors such as prey availability and intraspecific competition. Measuring changes in tiger numbers by comparing two distant points can be very misleading, particularly when differences in sampling methods are overlooked. Any inference from such an analysis is entirely dependent upon the stage of the tiger population cycle when the so-called baseline estimate was obtained. Starting from a peak and ending on a trough will create the illusion of a downward trend in tiger numbers. Start from a trough and end on a peak, an upward one. Multi-year surveys are clearly needed to inform more accurate estimation of Sumatran tiger numbers.

1. Including our 2006 survey in Batang Gadis National Park, North Sumatra. DOI: https://doi.org/10.1017/S003060530999055X ↩︎
2. IUCN estimate. https://www.iucnredlist.org/species/15955/214862019 ↩︎

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