Movement ecology in a captive environment: the effects of ground substrate on movement paths of captive rhesus macaques, Macaca mulatta

摘要

Movement ecology is a growing field, and an important component of movement ecology is investigating how environmental factors influence animal movements. The structure of food resources, such as density and distribution, has been shown to influence the speed, distance and tortuosity of animal paths. We investigated the influence of the type of ground substrate on the movement paths of groups of captive rhesus macaques. Grass substrate provides supplementary food resources (e.g. insects, blades of grass) having more random and unpredictable distribution and higher density relative to gravel substrate, which is more depauperate in supplemental foods. Adult females in four grass enclosures travelled along more tortuous paths, as measured by higher frequency of changes in direction and stops and a smaller straightness index compared to adult females in two gravel enclosures. These results were largely replicated in a group that was moved from an enclosure with gravel to one with grass. Dominance rank further influenced tortuosity within enclosures with gravel substrate: higher-ranking animals showed less tortuous paths and shorter total distances than lower-ranking animals. Additionally, movement bouts in which the apparent goal was feeding on monkey chow were faster (regardless of substrate) and longer (in enclosures with grass substrate) compared to movement bouts in which the apparent goal was foraging for supplemental foods. Captive macaques, like free-ranging animals, move along more tortuous paths and at slower speeds when their food resources are randomly distributed and high in density.