Effects of predation risk on parasite-host interactions and wildlife diseases

Abstract

Landscapes of fear can determine the dynamics of entire ecosystems. In response to perceived predation risk, prey can show physiological, behavioral, or morphological trait changes to avoid predation. This in turn can indirectly affect other species by modifying species interactions (e.g., altered feeding), with knock-on effects, such as trophic cascades, on the wider ecosystem. While such indirect effects stemming from the fear of predation have received extensive attention for herbivore-plant and predator-prey interactions, much less is known about how they alter parasite-host interactions and wildlife diseases. In this synthesis, we present a conceptual framework for how predation risk-as perceived by organisms that serve as hosts-can affect parasite-host interactions, with implications for infectious disease dynamics. By basing our approach on recent conceptual advances with respect to predation risk effects, we aim to expand this general framework to include parasite-host interactions and diseases. We further identify pathways through which parasite-host interactions can be affected, for example, through altered parasite avoidance behavior or tolerance of hosts to infections, and discuss the wider relevance of predation risk for parasite and host populations, including heuristic projections to population-level dynamics. Finally, we highlight the current unknowns, specifically the quantitative links from individual-level processes to population dynamics and community structure, and emphasize approaches to address these knowledge gaps.

Keywords: ecology of fear; nonconsumptive effects; parasitism; predation risk; trait‐mediated indirect effects.

FIGURE 1

Scope and concepts of current synthesis in the context of related topics and previous reviews. While consumptive effects of predators on parasite-host interactions have been covered by several previous reviews (a), a comprehensive synthesis of non-consumptive effects of predators on parasite-host interactions is missing to date (b). Similar to predators, parasites can also exert consumptive (c) and non-consumptive (d) effects on hosts, with repercussions for parasite-host interactions. Boxes include examples of trait- and density-mediated effects via the different mechanisms covered by previous in-depth reviews and references therein.

FIGURE 2

Different types of trait changes in prey in response to perceived predation risk by predators and host defenses against parasite infections. For details see text.

FIGURE 3

Conceptual framework of how the perception of predation risk by prey that serve as hosts to parasites can alter parasite-host interactions and have knock-on effects on the wider community (based on Peacor et al., 2020). All effects resulting from predation risk-induced trait change responses of prey (b) constitute trait-mediated indirect effects of predators. Potential changes in prey fitness (d) are considered to be non-consumptive predator effects on prey (orange) in the strict sense (sensu Peacor et al., 2020). Note that all pathways shown act on individual prey/hosts. Population-level effects, both for parasites and hosts, may result from some of these pathways but are treated in a separate section.

FIGURE 4

Framework for characterizing predation-risk effects on parasite-host interactions along four crucial steps in the life cycle of parasites where parasite-host interactions can be affected by predation risk-induced changes in traits of prey that also serve as host. For details see text.