Auditory and distance cues interact to modulate female gray treefrog preferences for male advertisement calls

Abstract

Social interactions of animals depend on a complex interplay of signals, receivers, and internal and external information available to the participants. Mate choice decisions in breeding aggregations, in particular, represent some of the most consequential such interactions. As a measure of female mate preferences, we examined the strength of phonotaxis toward male advertisement calls that is shown by female gray treefrogs (Hyla versicolor). We varied two temporal features of the call stimuli (pulse number and intercall interval (ICI)) and observed the response of females from a distance of 6.4\xa0m. Response strength was doubled or more, compared to control trials from 1\xa0m. However, earlier described preferences for higher pulse number calls were not observed. Our design did uncover significant effects of the ICI on response strength, with stronger responses as the ICI increased. Latency of females to depart from the origin toward sound stimuli was also increased at greater distances, compared to tests from 1\xa0m, suggesting changes in sampling behavior by females. Lastly, prior experience of female treefrogs with the more distant stimuli significantly influenced later trials, depending on rest periods outside the arena and the ICI of the prior stimuli. Overall, female gray treefrog phonotaxis responses from greater distances, more typical of field conditions, reveal different patterns of preference for stimulus temporal features. These differences may at least partially account for poor correspondence between field and lab female gray treefrog mate choices. Selection of mates based on their individual characteristics drives sexual selection processes. However, the strength of this selection can be reduced or enhanced by interaction of female preferences for male characteristics and a female’s internal and external circumstances. We tested the strength of female gray treefrog (Hyla versicolor) preferences by measuring the speed with which females approached particular synthetic male advertisement call stimuli. Our design was unique for its use of larger distances between females and male stimuli and for our use of a very broad range of stimuli. This approach provided new insight into constraints on female preference and choice based on distance, sampling behavior, and prior experience.