Vertical and horizontal vegetation cover synergistically shape prey behaviour

Abstract

An animal's perception of predation risk varies across a heterogeneous landscape. Animals rely on indirect cues in the environment, including availability of protective cover, openness of sightlines and distance to refuge to evaluate potential predation risk. Interactions between the indirect cues that influence an animal's perception of predation risk are poorly understood, especially for prey at risk of avian and terrestrial predation. We conducted a giving-up density (GUD) study to examine how interactions between terrestrial predator presence, ceiling (canopy) cover, wall (shrub/grass) cover and distance to nearest tree influence fox squirrel, Sciurus niger, risk perception. The GUD indicates an animal's perceived predation risk, such that increased GUD (decreased foraging) corresponds to greater perceived risk. We found that fox squirrels perceived cues of predation risk in response to a synergistic interaction between ceiling and wall cover. In open canopy areas, fox squirrels increased GUD where there was also increased wall cover. However, fox squirrels reduced GUD in closed canopy areas where there was also increased wall cover. We attribute the differential effects of wall cover depending on ceiling cover to the effectiveness of open sightlines in decreasing predation risk from avian or terrestrial predators. Our study shows that the effect of vegetation structure on prey risk perception and antipredator behaviour depends on the relative risk posed by avian and terrestrial predators that use different hunting strategies.