The Graduate Program in

David Hof

Photo of David Hof

PhD Candidate

B.S., University of Arizona, 2001

Advisor: Dissertation/thesis title:

Aggressive Signaling in New World Warblers

Research Interests

My main research interests center around the evolution of animal communication, and in particular the information contained in animal signals. To do this, I have focused thus far on how animals settle disputes through the use of communication. My research addresses two broad questions (i) is reliable information transferred during antagonistic interactions despite strong incentives for bluffing that would allow animals to gain resources they might otherwise lose through actual fighting (ii) if reliable information is transferred, what prevents animals from bluffing. I have been addressing these questions with respect to vocal communication in a group of migratory songbirds, the wood-warblers, focusing on one species, the black-throated blue warbler. Male warblers compete intensely over territorial resources and mates, and use song to mediate conflicts. In order to infer the information content of vocal signals used during disputes I am incorporating both observational and experimental approaches.

One type of information that might be transferred during antagonistic disputes is an animal’s intentions of behaving aggressively in the near future. Signals of aggressive intent thus signal information about future events, and it is not clear what prevents an animal from threatening to act aggressively and then not following through with aggressive actions. To determine if reliable information about aggressive intentions is transferred I have been conducting experiments that simulate intrusions on birds territories. I then record their vocal responses and present them with a male model that they can attack. This experiment can then determine if any features of vocal behavior can predict whether males will subsequently attack the model. Data thus far show that one surprising singing behavior, giving “soft” or “whispered” versions of songs, is a strong predictor of whether males will attack a conspecific model, suggesting that this signal contains reliable information about aggressive intent.