Contrasting risks from different predators change the overall nonlethal effects of predation risk

Abstract

Prey are often at risk from multiple predator species with differing hunting modes, but the resulting response to the spatial variation in predation risk (the landscape of fear) has rarely been considered in predator prey models. We tested whether attack frequency and hunting success along a habitat gradient (distance from an estuarine shoreline) differed between 2 predators hunting a single prey species, so affecting the optimal antipredation position along this gradient. Sparrowhawks ambushed redshanks most frequently from the predator-concealing cover of the shoreline, and their capture success rate was twice as high as when hunting far from the shoreline (>50 m). In contrast, pursuit-hunting peregrines attacked redshanks most frequently far from the shoreline, though their capture success rate was unaffected by distance. Thus, the relative occurrence and success of both predators varied so that avoidance of one predator led to increased predation risk from the other, generating 2 broad conclusions. First, the equilibrium distribution of prey in the presence of multiple predators is likely to reflect the attack frequency and attack success rate of both predators combined across relevant environmental gradients. Second, predation-risk avoidance gradients may be less steep, or less tightly linked to any single habitat feature, than might be predicted if a single predator is considered.