Forget the audience: tadpoles release similar disturbance cues regardless of kinship or familiarity

Group-living prey rely on social information such as alarm signals and other social cues to avoid predation. By definition, “signals” imply that a message is voluntarily directed at receivers (i.e., the audience), whereas “cues” are released incidentally regardless of the audience composition. Thus, audience effects can be used to differentiate between signals and cues when communication is difficult to observe or quantify. In at least two fish species, chemical disturbance cues are released during a predator attack to signal to familiar audiences about predation risk. Here, we examined whether audience composition affects disturbance cue release in wood frog (Lithobates sylvaticus) tadpoles to better understand the function of disturbance cues across aquatic prey. Groups of tadpoles underwent simulated predator attacks to obtain disturbance cues. The groups were either familiar and related, unfamiliar and related, familiar and unrelated, or unfamiliar and unrelated. To assess the relative potency of each cue, we used a behavioral bioassay design involving activity changes in independent tadpole receivers (unfamiliar and unrelated to the donors). If tadpoles use disturbance cues to signal related and/or familiar individuals, we predicted increased fright responses in receivers to cues obtained from those groups. However, we detected no effect of audience composition, indicating that tadpoles release similar disturbance cues regardless of audience kinship or familiarity. Nevertheless, disturbance cues evoked a consistent antipredator response in receivers indicating that these chemicals still act as reliable risk cues. Further comparative studies using audience effects are necessary to understand how disturbance cues have evolved across aquatic prey.