Populations of many large, wide-ranging carnivore species are threatened because of human pressures that come into conflict with their basic ecological needs. Despite three decades of substantial conservation efforts, tigers continue to suffer range contractions through continuing extirpation of local populations. A widely prevalent perception attributes this decline of tigers to illegal killing for trade in their body parts. However, using field studies of predation by Dr. Ulhas Karanth, Stith and Sunquist in 1995, 1999 and in 2000 developed a demographic model indicating that decline of tiger populations is primarily a consequence of prey depletion rather than direct killing because of their high reproductive potential in prey-rich habitats. This model is also supported by more recent data from field studies showing strong dependence of tiger density on prey abundance. Two key problems of animal population sampling are the inability to survey the entire area of interest and the inability to detect all individuals even within the surveyed area. Karanth in 1995 showed that ‘‘photographic captures’’ of tigers obtained from automated ‘‘camera traps’’ could be analyzed under a closed-population capture–recapture sampling framework. Tiger abundance or density obtained from a single location over multiple years can yield estimates of rates of population change. Photographic capture histories of individual animals over years also permit estimation of the vital rates (survival, recruitment, movement) that actually drive such changes in abundance.
Posted on: Fri, 05 Jul 2013 04:05:33 +0000
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