Sensory biases in response to novel complex acoustic signals in male and female grey treefrogs, Hyla chrysoscelis.

Abstract

The sensory bias hypothesis proposes that female preferences for male sexual signalling traits evolved in contexts other than mating. Individuals of both sexes may experience similar selection pressures in these contexts; thus males may have similar biases to females for variation in signal traits. We tested this prediction in the grey treefrog, Hyla chrysoscelis, in which males produce simple advertisement calls, but females are more attracted to certain novel complex stimuli. We recorded males' responses to playbacks of both simple advertisement calls and complex calls consisting of the advertisement call with an acoustic appendage (filtered noise, or heterospecific call pulses) either leading or following the call. We tested females' preferences for the same stimuli in phonotaxis tests. We found evidence for a sensory bias in both sexes: males gave more aggressive calls in response to complex stimuli and females sometimes preferred complex over simple calls. These biases were not universal and depended on both temporal order and appendage characteristics, but how these effects manifested differed between the sexes. Ultimately, our approach of studying biases of both sexes in response to novel mating signals will shed light on the origin of mating preferences, and the mechanisms by which sensory biases operate.