Meeting Abstract
Variation in circulating levels of adrenal glucocorticoids can alter the expression of male sexual signals. However, whether variation in circulating glucocorticoid levels among courting males affects the probability of attracting females remains poorly understood. Here, we address this issue in the green treefrog, Hyla cinerea. Males of this species engage in aggressive vocal interactions that increase circulating levels of corticosterone (CORT) in rival male contest losers. We previously showed that CORT administration to calling males, simulating CORT production in vocal contest losers, decreases call duration and vocal effort, suggesting that elevated CORT compromises the attractiveness of male vocalizations. Using dual speaker playback experiments, we examined whether females show a preference for vocalizations characteristic of males with low versus high circulating CORT levels. Results from a total of 30 phonotaxis trials revealed that 24 females showed phonotaxis towards the speaker broadcasting calls characteristic of males with low CORT levels while only 6 females showed phonotaxis towards the calls characteristic of males with high CORT levels. These results indicate that females show a strong preference for the acoustic courtship signals of males with low CORT levels, suggesting that elevations in circulating glucocorticoids during male contests can diminish the probability of attracting females.
