Responses of domestic chicks (Gallus gallus domesticus) to multimodal aposematic signals

This is the authors' abstract. We don't add key points for this paper.

Many aposematic prey combine their visual warning signals with additional signals. Together, these signals constitute a multi-modal or multicomponent warning display. The additional signals are thought to increase the effects of the visual signals on predators. Olfactory signals are much emphasized, but later studies have shown that also auditory signals like the buzzing of certain insects might have multimodal effects. The wasp displays typical visual aposematic signals, black and yellow stripes, but does also emit a characteristic buzzing. We wanted to test if, and in what way, the visual and acoustic display of the wasp has an aversive function on the predators. We therefore conducted a 12-trial discrimination-learning task on inexperienced chicks to study whether there are innate biases toward these signals and how they affect the speed of avoidance learning. We also performed three extinction-learning trials to study how memorable the signals were to the chicks. We show that the visual signals in the display of the wasp contribute to the protection from predators but in different ways; the yellow color had an aversive effect on inexperienced predators, while the striped pattern improved the aversion learning. The sound did not enhance the innate aversions but increased the aversion learning of stripes in green prey. Key words: aposematism, avoidance learning, chicks, innate biases, multimodal signals, sound, stripes. [Behav Ecol 17:392–398 (2006)] The theory of warning signals, or aposematism (Poulton,1890), describes the phenomenon that unpalatable prey may use conspicuous signals such as bright colors (Roper, 1990) or conspicuous patterns (Schuler and Hesse, 1985) to