Abstract
Females commonly exhibit directional preferences for males that produce more exaggerated, elaborate, or energetic signals. Key questions remain regarding individual variation in the expression of such preferences, particularly when performance related trade-offs in signaling occur in social environments (e.g., leks and choruses) where males dynamically compete for females. In this study of Cope’s gray treefrog ( Hyla chrysoscelis ), we investigated directional female preferences for longer calls and faster call rates, two performance-related traits that negatively covary. Subjects repeatedly chose between two simulated males with different call durations and call rates, but with equal overall calling efforts (pulses per unit time). In half of tests, call duration and rate were dynamically swapped between the two simulated males prior to females reaching a speaker. Females chose randomly with respect to differences in call duration and call rate and ignored dynamic shifts in calling behavior. The repeatability of female choice was not different from zero, and females were highly committed to choosing the simulated male they initially approached, even when stimuli differing in call duration and rate were dynamically swapped between speakers as she approached. There was no evidence that subpopulations of females differentially weighted call duration or rate in making their choices. Individual differences in body size, condition, and corticosterone levels had no effects on female responses. Together, these results support an inter-signal interaction hypothesis in showing that females choose mates by attending to the emergent signal property of calling effort instead of its constituent components of call duration and rate.