Uncertain foraging opportunities and predation risk exert additive effects on induced neophobia in cichlids

Abstract

Neophobia is defined as the avoidance of novel or unknown stimuli, including unknown predators, and can be induced by exposure to uncertain ecological conditions. In addition to uncertainty related to predation risk, uncertainty may also arise from increased foraging competition. Prey forced to spend time and energy competing for limited resources may not have enough time available to devote to predator identification and hence benefit from increased neophobia. Here, we tested the potential interaction of reduced foraging opportunities and elevated predation risk on the strength of neophobia (the antipredator response towards a novel chemical cue). In our first experiment, shoals of juvenile convict cichlids, Amatitlania nigrofasciata , were exposed to high (10% total body weight/day) or low (1% total body weight/day) relative food abundance for 7 days. During the final 3 days, we exposed the shoals to high versus low background predation risk, resulting in a 2 × 2 design. We found that while low food abundance alone and risk alone induced a weak neophobic response to a novel cue (versus water control), cichlids pre-exposed to high risk and low food abundance exhibited significantly a stronger neophobic response, in an additive pattern. In our second experiment, we exposed shoals of cichlids to a fixed amount of food distributed on a single (high competition) patch or across five (low competition) patches for 7 days, with the same risk manipulation as above for the final 3 days. As in experiment 1, we found that high competition alone and risk alone elicited a weak neophobic response to novel cues and that high risk and high competition had additive effects on the strength of induced neophobia among juvenile cichlids. Together, our results indicate that uncertainty of risk and of foraging opportunities exert additive effects on the phenotypically plastic neophobia among prey populations. • Neophobia should reduce costs of bad decisions under uncertain conditions. • Increased competition should increase uncertainty of foraging opportunities. • We exposed cichlids to high vs low predation risk under high vs low competition. • Neophobic responses were stronger under high competition. • Uncertain risk and foraging opportunities exert additive effects on neophobia.