Michael S. Reichert, Ph.D. - US grants

In many animals, aggressive signals, rather than overt physical fighting are used to resolve disputes. Despite intensive research into aggressive signaling, the means by which most animals assess their own status and that of competitors during contests remains unclear: for example, animals may use mutual assessment, in which persistence in a contest is based on assessing their fighting ability relative to that of their opponent, or they may use self-assessment, in which the decision to withdraw is based only on assessing their own accumulated costs, regardless of characteristics of their opponent. Recent theoretical work has provided a method to distinguish between possible means of assessment. This study will use these recent theoretical advances to determine whether male gray treefrogs, Hyla versicolor, use mutual or self assessment during aggressive vocal interactions. Measurements of the duration and level of escalation of staged aggressive encounters between calling males in size-equal and size-unequal pairings will be used to distinguish between these two possibilities. Under mutual assessment, contests are expected to be longer when individuals are more closely matched, regardless of their absolute size, while self-assessment predicts that contest duration is an increasing function of the absolute size of the smaller individual, regardless of size asymmetry.

This experiment will provide important new information on the significance of aggressive signaling that will be important for confirming the results of recent theoretical work. It will also continue the development of H. versicolor as a model for studies of aggressive signaling. Aggressive calling in frogs has been understudied in general, yet frogs offer many advantages to the study of communication. Finally, this project will provide important research experiences for several undergraduate students (including those from underrepresented groups), who will be given the opportunity to participate fully in the project's execution.