Males of many species produce spectacular courtship displays to attract females to mate. Females may prefer males with elaborate displays because these displays act as signals, conveying information about the male's "quality" as a mate. Males produce these signals, but the signals must transmit through the environment to reach the female. The environment can affect signals during transmission: for example, sound carries better in some environments than others and ambient light can affect how colors appear. Therefore, the signal that reaches the female depends both on what is sent by the male and the environment through which it is transmitted. This may select for males that choose display locations with good transmission properties (e.g. good lighting or good acoustics) to increase the attractiveness of their display. In this research project, greater sage grouse (Centrocercus urophasianus) will be used as a model system to examine the importance of the acoustic environment in influencing both male display behaviors and male success in convincing females to mate. During the breeding season, male sage grouse aggregate on display grounds called "leks" and compete to establish display territories. On their territories, males produce spectacular vocalizations, which females assess when choosing their mates. The "acoustic quality" of male display territories is variable across the lek, and this variation will impact the pitch and loudness of vocalizations perceived by females; for this reason, the acoustic quality of a territory may affect the mating success of the resident male. An Acoustic Localization System (ALS) will be used to create detailed maps of male territories and the locations of favored display sites. ALS is a technique whereby a sound is recorded on multiple microphones, and the difference in the time at which the sound reaches each microphone is used to reconstruct the location of sound source. This ALS data will be combined with measurements of male mating success and the acoustic quality of male display sites to test two hypotheses: 1) that the acoustic quality of a territory impacts the attractiveness of the resident male, and 2) that within their territories, males preferentially display from locations that improve signal transmission. The results of this project will contribute to our understanding of how the environment affects acoustic communication and courtship in animals. This project will involve the development and refinement of methods for studying acoustic communication and territorial behaviors that can be used by many other researchers. In the process, this research will provide research and training opportunities to undergraduates, graduate students and postdoctoral researchers at the University of California, Davis. Finally, greater sage grouse are federally recognized as a "species of concern", and both the loss of sage-grouse habitat and the increase in human-produced noise are likely causes of their declining numbers. Results from this work will increase our understanding of how different habitat characteristics affect reproduction in sage grouse; this information will inform future decisions about the suitability of habitat for sage grouse. In addition, results from this project will increase our understanding of how sound propagates through the sage-grouse habitat, and will inform the debate on how human-produced noise impacts acoustic communication and reproduction on the lek.
