Ranging patterns of hamadryas baboons: random walk analyses

Abstract

Random walks have long been used to characterize animal movement patterns; recently, this practice has received renewed impetus via the application of Lévy walk models. Whilst such models have produced encouraging results, the methods applied have been inconsistent and often problematic; furthermore, primates remain under-represented in such studies. This paper addresses both of these problems via the explanation of a novel and robust analytical method as applied to an extensive primate data set. In a study of a band of hamadryas baboons at the Filoha outpost of Awash National Park, Ethiopia from March 2005 to February 2006, the baboons’ location was mapped every 15 min during all-day follows using a handheld GPS unit, yielding over 3000 step lengths and waiting times documented across 105 complete follows. Both power law and exponential models were fitted to the step length and waiting time data via maximum likelihood procedures within a model selection paradigm facilitated by the use of an information criterion to distinguish between models. Results show that the step lengths were exponentially distributed, and thus consistent with a random distribution of resources in space. Waiting times, however, were power law distributed, and thus consistent with a power law distribution of patch sizes. We evaluate these results within a discussion of the extent to which random search algorithms are applicable to animals with extensive knowledge of their habitats.