Predator olfactory cues generate a foraging-predation trade-off through prey apprehension

Abstract

Most animals are faced with the challenge of securing food under the risk of predation. This frequently generates a trade-off whereby animals respond to predator cues with reduced movement to avoid predation at the direct cost of reduced foraging success. However, predators may also cause prey to be apprehensive in their foraging activities, which would generate an indirect 'apprehension cost'. Apprehension arises when a forager redirects attention from foraging tasks to predator detection and incurs a cost from such multi-tasking, because the forager ends up making more mistakes in its foraging tasks as a result. Here, we test this apprehension cost hypothesis and show that damselflies miss a greater proportion of their prey during foraging bouts in response to both olfactory cues produced by conspecifics that have only viewed a fish predator and olfactory cues produced directly by fish. This reduced feeding efficiency is in addition to the stereotypical anti-predator response of reduced activity, which we also observed. These results show that costs associated with anti-predator responses not only arise through behavioural alterations that reduce the risk of predation, but also from the indirect costs of apprehension and multi-tasking that can reduce feeding efficiency under the threat of predation.

Keywords: cues; non-consumptive; olfaction; predation risk; predators; prey.

Figure 1.

Damselflies reduce activity and become less efficient predators in the presence of predator olfactory cues. Shown are boxplots (line is the median, box is interquartile distance (IQD) and the whiskers denote ±1.58IQD) of the difference in a given damselfly behaviour before and after the application of predator cue treatments (n=20 individuals per treatment). Statistically significant differences (p<0.05) between treatments are denoted by the absence of shared letters. Image credit: CSIRO Australian National Insect Collection. Data from the experiment are deposited in the Dryad Digital Repository [19].