Chemical cues and reducing the risk of predation

Abstract

The use of chemical cues to recognize elevated risk of predation is widespread in crustaceans and the responses to chemical cues can decrease the risk of predation. There are multiple sources of such cues: odors from damaged conspecifics, damaged heterospecifics, conspecifics digested by predators, predator odors, and odors associated with predation risk by learning. The most common responses to such odors are behaviors such as decreased movement or movement away from the source of cues, but in small planktonic species development of defensive morphologies such as spines also occurs. When faced with combinations of chemical cues, such as danger cues and food cues, most crustaceans respond primarily to the danger cue. Starvation can eliminate the dominance of danger cues over food cues. In the crab Heterozius rotundifrons, there is no response to chemical cues indicating increased predation risk unless tactile cues are also detected. Learned associations can result in crustaceans showing responses to cues that in themselves may be weak indicators of elevated predation risk. More field work is needed to document the extent to which patterns reported from the laboratory are important in nature.