Variation in call temporal properties and female preferences in Hyla intermedia

In anurans, long-range advertisement calls are known to convey information important for both species recognition and mate-quality assessment. To investigate how these kinds of information are encoded in mating calls, we carried out two-choice discrimination experiments on female Italian treefrogs, Hyla intermedia, and examined their patterns of call preferences in response to variation in fine-scale temporal properties. We analysed preferences for three fine-scale temporal properties: pulse rate, call duration, and call rise-time. Calls with the mean pulse rate were significantly preferred over alternatives with either higher-than-average or lower-than-average pulse rates. The mean rise-time call was preferred over alternatives with rise-times either close to or lower than the smallest values recorded in the study population. Unlike pulse rate and rise-time, females did not show significant preferences for calls of similar pulse rate, but different call duration. We compared female preference functions with the patterns of within-bout variation in call properties and used these results to illustrate the interactions between ultimate functions and proximate mechanisms of both call production and recognition in the co-evolutionary process of the treefrog communication system.