Broadening the ecology of fear: non-lethal effects arise from diverse responses to predation and parasitism

Research on the 'ecology of fear' posits that defensive prey responses to avoid predation can cause non-lethal effects across ecological scales. Parasites also elicit defensive responses in hosts with associated non-lethal effects, which raises the longstanding, yet unresolved question of how non-lethal effects of parasites compare with those of predators. We developed a framework for systematically answering this question for all types of predator-prey and host-parasite systems. Our framework reveals likely differences in non-lethal effects not only between predators and parasites, but also between different types of predators and parasites. Trait responses should be strongest towards predators, parasitoids and parasitic castrators, but more numerous and perhaps more frequent for parasites than for predators. In a case study of larval amphibians, whose trait responses to both predators and parasites have been relatively well studied, existing data indicate that individuals generally respond more strongly and proactively to short-term predation risks than to parasitism. Apart from studies using amphibians, there have been few direct comparisons of responses to predation and parasitism, and none have incorporated responses to micropredators, parasitoids or parasitic castrators, or examined their long-term consequences. Addressing these and other data gaps highlighted by our framework can advance the field towards understanding how non-lethal effects impact prey/host population dynamics and shape food webs that contain multiple predator and parasite species.

Automated summary

Research on the 'ecology of fear' investigates how prey and hosts defend themselves against predators and parasites, respectively, and the different non-lethal effects that may result. This study suggests that trait responses may be stronger towards predators, parasitoids, and parasitic castrators, but more numerous and frequent for parasites than predators. Existing data on larval amphibians indicate that individuals respond more strongly to short-term predation risks than to parasitism. Further research is needed to directly compare responses to predation and parasitism, including the effects of micropredators, parasitoids, and parasitic castrators, and their long-term consequences.