Pyrazine(s) in "Behavioral Ecology" OxfordUP

Warning signals made by unpalatable insects to potential predators commonly target more than one sense: such signals are "multimodal."

Pyrazines are odors produced by warningly colored insects when attacked, and have been shown to interact with food coloration, biasing avian predators against novel and typically aposematic food. However, at present it is not known whether this is an adaptation by prey to exploit a general feature of avian psychology, or an evolutionary response by birds to enhance their avoidance of unpalatable prey. Here we investigate the effect of other odors on the innate responses of naive domestic chicks (Gallus gallus domesticus) to food that is of novel color, or of a color that is associated with warning coloration, yellow. In the first experiment, we demonstrate that natural and artificial odors that have no association with aposematism in the wild can produce biases against both novel colored foods and yellow colored foods.

In a second experiment, we also show that odor novelty is vital for eliciting such effects. These results support the idea that warning odors have evolved in response to preexisting psychological biases against novel odors in predators, rather than predators evolving specific responses against odors associated with unpalatable prey.
http://beheco.oxfordjournals.org/cgi/content/full/12/2/134
Behavioral Ecology Vol. 12 No. 2: 134-139

© 2001 International Society for Behavioral Ecology


Non-warning odors trigger innate color aversions—as long as they are novel

Walter Jetz, Candy Rowe and Tim Guilford

These findings have considerable significance for the functional understanding of warning signals. Without the necessity to invoke aversion learning, multimodal warning signals can apparently exploit innate predispositions, similar to the way that startle displays are proposed to function (Sargent, 1990; Schlenoff, 1985). To date, the facilitation of avoidance learning has been the favored explanation of the adaptive significance of aposematic displays. Our findings advocate the additional prominent role of innate aversions.

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