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We investigate the potential flaws of estimating animal home range using indexes based on distance between captures as proposed by Püttker et al. (2012, Journal of Mammalogy 93:115-123). Through simulated capture distributions we demonstrated that distance indexes are inherently correlated with home-range estimates derived from the same data set. We also arrived at a similar conclusion using a real capture data set from the spiny rat (Thrichomys pachyurus). However, distance indexes were not correlated to home range based on radiotelemetry for the same individuals of T. pachyurus. Our results strongly support that the conclusions presented by Püttker et al. (2012) were due to statistical dependence between correlated measures and that these indexes might not represent the biological phenomenon of interest-the home range.
Key words: animal movement, ecological index, home range, index validation, spiny rat, Thrichomys pachyurus
© 2013 American Society of Mammalogists
DOI: 10.1644/12-MAMM-A-139.1
The size and shape of an animal's home range are of major importance to understanding how individuals interact with their resources, conspecifics, and other species in the bi- or tridimensional space (Powell 2000). Analytical approaches of ever-increasing sophistication have been proposed to estimate home-range size. However, most of them require many locations and make assumptions about the distribution or boundaries of the location coordinates (e.g., kernel, local convex hull [LoCoH], harmonic mean, alpha-hull, and mechanistic models [see Powell 2000; Moorcroft et al. 2006; Getz et al. 2007; Kie et al. 2010]).
In a recent study, Püttker et al. (2012) proposed the use of movement indexes as a home-range surrogate for small, rare, and short-lived species for which telemetry is unfeasible and information on movement usually depends on few recaptures. These considerations are warranted because researchers often face small sample sizes when trying to make conclusions regarding home-range patterns. However, small samples often prevent the use of modern and robust statistical methods. In some of these cases, movement indexes are a reasonable alternative for answering a variety of ecological questions. Püttker et al. (2012) attempt to validate the suitability of 3 movement indexes, previously used in other studies (Koeppl et al. 1977; Gaines and Johnson 1982; Slade and Swihart 1983; Swihart 1992; Slade and Russell 1998; Connor and Leopold 2001; Getz et al. 2005; Getz and McGuire 2008; for a detailed...