Chemical arms race between predator and prey: a test of predator digestive countermeasures against chemical labeling by dietary cues of prey

Abstract

Prey fishes use chemical cues in their predator's diet to cue the context and timing of antipredator behaviors that reduce the risk of predation. They also use dietary cues to learn to recognize and later detect the presence of a predator. Because dietary chemical information decreases hunting success of predators there should be selection on predators to mask or obliterate these cues through biochemical processes in their digestive tract. In this study, we compared response intensity of predator-naïve fathead minnows to the signature odors of two novel predators that had been fed either a minnow diet or a non-minnow diet. Unprocessed minnow mash and dechlorinated blank water were used as positive and negative controls, respectively. One predator was from a relatively ancestral fish group, the order esociformes, while the other predator was from a relatively derived group, the order perciformes. Naïve minnows were able to detect the presence of minnows in the diet of the ancestral and derived predators with equal efficiency and behavioral responses to minnow dietary cues were significantly different from non-minnow dietary treatments. We found no evidence that fish of relatively derived phylogeny have evolved counter-labeling strategies through enhanced biochemical processes during digestion.

Keywords:

• alarm cues
• dietary cues
• predator-prey
• fathead minnow
• mudminnow
• bluegill sunfish

Acknowledgements

Funding for this work was provided by a student research grant to RS and a faculty research grant to BDW, both from the College of Social and Natural Sciences, Minnesota State University Moorhead, MN. All procedures used for the housing of test subjects and collection of data were approved by the Minnesota State University Moorhead Institutional Animal Care and Use Committee under protocol 10-T-Biol-009-N-N-C/D.