The central importance of information in studies of animal communication

The concept of information plays a central role in studies of animal communication. Animals’ responses to the calls of different individuals, to food calls, alarm calls, and to signals that predict behaviour, all suggest that recipients acquire information from signals and that this information affects their response. Some scientists, however, want to replace the concept of information with one based on the ‘manipulation’ of recipients by signallers through the induction of nervous-system responses. Here we review both theory and data that argue against hypotheses based exclusively on manipulation or on a fixed, obligatory link between a signal’s physical features and the responses it elicits. Results from dozens of studies indicate that calls with ‘arousing’ or ‘aversive’ features may also contain information that affects receivers’ responses; that acoustically similar calls can elicit different responses; acoustically different calls can elicit similar responses; and ‘eavesdropping’ animals respond to the relationship instantiated by signal sequences. Animal signals encode a surprisingly rich amount of information. The content of this information can be studied scientifically.