Movement-based analysis of interactions in African lions

Abstract

Spatial interactions can reveal the influence animals have on each other. In this context, ‘interaction’ refers to the joint occurrence in space (static interaction) or in both space and time (dynamic interaction). Most studies have focused on static interactions, estimated in terms of home range (HR) overlap. The few studies that have addressed dynamic interactions, corresponding to mutual attraction or avoidance within shared sections of animals' HRs, used statistical tests that assume independent relocations. Thus, although serial correlation in relocations provides invaluable information on space use dynamics, it has often been considered a statistical impairment. We developed a permutation test that explicitly takes serial correlation into account to test adequately whether two animals tend to move independently of each other, or show mutual attraction or avoidance, when moving in shared HR sections. We applied this novel method to 55 GPS-collared free-ranging lions, Panthera leo, in Hwange National Park (Zimbabwe), for which we also investigated static interactions by computing activity-weighted (i.e. using utilization distribution) HR overlap. Overlapping HRs were not at all uncommon for lions from different social groups. Within shared HR sections, individuals that tended to move jointly were often related. We found only one case of avoidance, involving two males, suggesting that when male lions, even unrelated ones, moved within a shared HR section, they generally did so independently of each other. Potentially competing males usually appeared to show avoidance by establishing HRs sufficiently far apart to allow for only marginal overlap, with only males tolerant of each other sharing sections of their HRs. Our results show that the simultaneous study of static and dynamic interactions can provide a comprehensive view of how space/time sharing with conspecifics influences animal movements and space use.