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How Sampling-Based Overdispersion Undermines India's Tiger Monitoring Orthodoxy

By Arjun M. Gopalaswamy, K. Ullas Karanth, Mohan Delampady, Nils Christian Stenseth

Posted 19 Jul 2019
bioRxiv DOI: 10.1101/708628

Conservation agencies entrusted with recovery of iconic mammals may exaggerate population trends without adequate scientific evidence. Recently, such populations were termed as "political populations" in the conservation literature. We surmise that political populations emerge when agencies are pressured to report abundances at large spatial scales for species that are difficult to survey. Indian tiger conservation agencies use an experimental approach called double-sampling using index-calibration models. A recent, mathematical, study demonstrated the unreliability of this approach in the context of India's tigers. Yet, this approach continues to be applied and even promoted by global tiger conservation agencies in other tiger range countries. In this article, we aim to: (1) discuss the ecological oddities emerging from results of India's national tiger surveys, (2) demystify the mathematics underlying the problems of this survey methodology and (3) confront these findings with results from India's recent national tiger survey of 2014. Our analyses show that the predictions of tiger abundance using sign-based indices reported in the 2014 survey in fact vary greatly and can be severely misleading and confirming the presence of high sampling-based overdispersion and parameter covariance. We call for species conservation initiatives to implement monitoring methods that are designed to clearly answer, a priori, scientific or management objectives instead of potentially implementing them as reactions to extraneous, social or fund raising pressures.

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