Abstract:

A satisfactory understanding of the process of mate choice by female frogs requires that we know how sensitive females are to the variation in males' calls under natural conditions and what is the time scale or ``window'' over which females compare males. In natural choruses, gray treefrog females may sit near calling males for many minutes before approaching a particular individual to mate, while in laboratory-based tests they may approach a speaker following less than 30 s of exposure to broadcast calls. Females prefer long to short calls. In order to estimate ``assessment time'' of females in nature, calls were broadcast from four pairs of 360-deg speakers surrounded by screen cages at a pond in Missouri. One speaker per pair presented calls of constant duration, while the other speaker shifted between calls longer or shorter than the constant duration call. The period over which this change in call duration occurred differed for each of the four pairs of speakers. The numbers of females captured at the speaker array over the breeding season indicated that the most likely assessment time was close to 2 min. This estimate is similar, but not identical, to that obtained from additional laboratory tests.