The Waiting Game: Elk avoid predator encounters at fine spatial scales

Abstract

Ungulates are known to avoid predation by grouping up, increasing vigilance, and reducing residency time among preferred habitats. Similarly, shifting return rates may represent a means of pre-emptively minimizing exposure to risk by being less predictable on the landscape to predators. We hypothesized that across seasons elk (Cervus canadensis) would be attracted to areas with high forage resulting in shorter revisit times, whereas revisit times would be longer to sites where perceived (indirect) predation risk was high, or where predators were observed on the cameras (direct risk) between elk events. With data from remote cameras (n = 44) distributed across the Ya Ha Tinda ranch in Alberta, Canada (2017–2018), we used Cox proportional hazards models to examine what influenced herd-level variation in elk revisit times during both winter and summer. After controlling for seasonal shifts in movements and/or distribution with data from GPS-collared resident elk, we assessed whether elk stayed away from sites recently visited by predators and how interactions between site characteristics (e.g. landcover types, edge density, distance to human infrastructure) and elk group size might further influence revisit times. Best supported winter models revealed sites were revisited by elk 61% sooner when surrounded by a high proportion of grasslands and revisited 68% longer when wolves (Canis lupus) occurred between elk, but this delay was consistently less among sites predominantly surrounded by grassland. During summer, elk revisit times among sites surrounded by higher edge densities were 12% longer, where as revisit times of elk to a site where a predator had previously occurred increased by 57% when the predator was a wolf, 40% when it was a bear (Ursus arctos), and 66% when it was a cougar (Puma concolor). Measuring fine-scale temporal dynamics in elk use across a risky landscape may help us better understanding how they avoid predator encounters altogether when coping with frequent changes in predation risk.