Associations between sympatric apex predators across a diverse landscape

Abstract

Coexistence between sympatric predators is achieved through a variety of behaviors that reduce competitive interactions. We examined fine-scale co-occurrence between sympatric apex predators across a large and highly variable landscape characterized by anthropogenic presence and related mortality in Idaho, USA. We analyzed data from 201 camera traps across 130,000 km2 to examine spatiotemporal associations between four apex predators: humans (Homo sapiens), wolves (Canis lupus), black bears (Ursus americanus), and cougars (Puma concolor). We hypothesized that the dominant competitors in our system would be associated with reduced detections of subordinate competitors (i.e., humans > wolves > black bears > cougars). Such a hierarchy proved true only when examining spatial associations between humans and wolves. We found a positive spatial association between black bear and cougars, suggesting that cougar kills may provide scavenging opportunities for bears. Although we found a slight positive spatial association between black bears and wolves, we found strong differences in temporal activity patterns between them. Mesic forest yielded higher detections of all predators (except humans) compared to xeric habitat. Cougars in particular appeared to be better predicted by habitat than presence of sympatric predators with more detections in mesic compared to mountain and xeric habitats. Understanding the co-occurrence of apex predators in a system is not a simple measure of their relative dominance cascading from one level to the next.