Temporal refuges differ between anthropogenic and natural top down pressures in a subordinate carnivore

Abstract

Apex predators structure communities through consumptive and non-consumptive pathways. In the carnivore guild, this can result in a within-guild cascade through the suppression of mesocarnivores. As the top-down influences of apex predators wane due to human-driven declines, landscape level anthropogenic pressures are rising. Human impacts can be analogous to apex predators in that humans can drive increased mortality in both prey species and carnivores, and impact communities through indirect fear effects and food subsidies. Here, we evaluate whether anthropogenic top-down pressures can structure communities in a similar manner as apex predators in shaping the interactions of mesocarnivores. Specifically, we expect anthropogenic forces to induce comparable effects as occurrence of apex predators in driving spatiotemporal partitioning between two mesocarnivores. Using multiple camera-trap surveys, we compared the temporal response of a small carnivore, the raccoon (Procyon lotor), to the larger coyote (Canis latrans) at four sites across Michigan that represented opposing gradients of pressure from humans and apex predators. Contrary to our expectations, we found that raccoons shifted their activity pattern in response to coyotes at sites with higher anthropogenic pressures and exhibited no temporal response at sites with apex predators. Temporal shifts were characterized by raccoons being more diurnal in areas of high coyote activity. We conclude that despite superficial similarities, anthropogenic forces do not replace the function of native apex predators in structuring the mesocarnivore guild. As such, an intact and functioning native predator guild remains necessary to preserve spatiotemporal community structure, in natural and disturbed systems alike.