Concepts: Estimating Abundance of Prey Species Using Line Transect Sampling
The principal prey of tigers are typically large, diurnal ungulates and can be visually detected and counted by observers while walking, riding domesticated elephants, or in very open habitats from aircraft, moving along a straight line.
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Concepts: Estimating Abundance of Prey Species Using Line Transect Sampling Samantha Strindberg, N. Samba Kumar, Len Thomas, and Varun R. Goswami
6.1
Introduction
The principal prey of tigers are typically large, diurnal ungulates and can be visually detected and counted by observers while walking, riding domesticated elephants, or in very open habitats from aircraft, moving along a straight line. At the same time, the observers can also record distances to observed animals from this line. Therefore, line transect sampling is a method frequently used to estimate their density and abundance, as with many other wildlife species. It is a special case of a wider class of methods called distance sampling: in line transect surveys, data are collected along transect lines (as opposed to point transects, where data are collected from points). The basic distance sampling methods are described comprehensively in the book by Buckland et al. (2001), which is an update to a previous book by Buckland et al. (1993) and is predated by earlier work (e.g., Burnham et al. 1980). More advanced elements are described by Buckland et al. (2004) and recent
S. Strindberg () Wildlife Conservation Society (WCS), New York, NY, USA e-mail: [email protected]; http://www.wcs.org N.S. Kumar Wildlife Conservation Society, India Program, Bengaluru, India e-mail: [email protected] L. Thomas Centre for Research into Ecological and Environmental Modelling, University of St Andrews, Fife, UK e-mail: [email protected]; https://creem2.st-andrews.ac.uk/ V.R. Goswami Wildlife Conservation Society, India Program, Bengaluru, India Centre for Wildlife Studies, Bengaluru, India e-mail: [email protected]; http://wcsindia.org/home/; http://cwsindia.org/ © Springer Nature Singapore Pte Ltd. 2017 K.U. Karanth, J.D. Nichols (eds.), Methods For Monitoring Tiger And Prey Populations, DOI 10.1007/978-981-10-5436-5_6
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developments can be found in Buckland et al. (2015) and Kéry and Royle (2015). These references should be consulted to obtain an in-depth understanding of theory involved. Thomas and Karanth (2002) provided a concise summary of the line transect sampling method as applicable to tiger prey species earlier. The current chapter explains fundamental concepts of line transect sampling together with the summary of recent advances that are relevant for sampling tiger prey populations in forested habitats. Chapter 7 that follows describes field practices. In the line transect method, detections are made of individual animals (or groups of animals) of the target species; this requires habitat in which individual animals can be seen before they respond and move. Here we provide a basic introduction to line transect sampling focusing on visual detection of tiger prey species to estimate their density, abundance, and factors influencing their spatial distribution. Throughout, we assume that the target during any survey is one or several tiger prey species, such as gaur, Asiatic water buffalo, sambar, chital,
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