Meeting Abstract

95.1  Monday, Jan. 6 13:30  Assessment and communication in gray treefrog aggressive interactions REICHERT, M.S.; Humboldt University-Berlin; University of Missouri michael.s.reichert@hu-berlin.de

Aggressive behavior plays an important role in sexual selection and much research has been devoted to determining the characteristics that influence the outcome and level of escalation of animal contests. Nonetheless, a debate remains over the potential for contestants to assess one another in contests, and very little research has been done on this topic in anuran amphibians. I recently developed a method to stage aggressive interactions between male gray treefrogs, Hyla versicolor, that has allowed me to study their contest behavior in detail. Here, I synthesize the major findings of these experiments. Surprisingly, body size plays only a limited role in determining which individual wins or loses, and there was no evidence that individuals assess one another’s body sizes during contests. In contrast, acoustic signals are very important. Males modify the characteristics of both their advertisement and aggressive calls with increasing contest escalation. Males lower the pitch of their aggressive calls, which is a strong predictor of contest outcome. In a series of playback tests I obtained evidence for mutual assessment: males’ responses varied with the characteristics of the playback stimuli, and males with signals indicating a higher resource-holding potential were more likely to persist in a simulated competitive interaction. In sum, these results suggest that competitive communication interactions involving energetically-expensive signals are a critical component of aggressive behavior in this species. The methods developed to stage aggressive interactions can be applied to other anuran species, which in turn can be used to better understand the role of signals in the processes of assessment during animal contests.