CHEMICAL ALARM SIGNALING IN AQUATIC PREDATOR-PREY SYSTEMS - A REVIEW AND PROSPECTUS

The importance of chemical cues in predator-prey interactions has rece ntly received increasing attention from ecologists. The sources of che micals to which prey species respond often originate as cues released by the predator (reviewed by Kats and Dill, this issue). Alternatively , cues may be released by other prey animals when they detect or are a ttacked by a predator. Such cues, known as chemical alarm signals, are particularly common in aquatic systems. These signals provide the bas is of our current review. Short-term behavioural responses of prey ani mals to alarm signals have received the most attention. Behavioural re sponses of prey resemble those exhibited to known predators, and are t herefore likely to make receivers less vulnerable to predation. More r ecently, studies have shown that benefits to alarm signal receivers ex tend beyond the immediate behavioural response of nearby conspecifics over a few minutes. For example, alarm signals are important in mediat ing the learning of unknown predators and dangerous habitats. Furtherm ore, alarm signals have been implicated in induced morphological defen ces, and defences that involve shifts in life history characteristics. In some systems, predators may have ways to counteract alarm signals used by their prey. We suggest that researchers must consider alarm si gnalling and associated learning phenomena when formulating hypotheses and designing future experiments.