Androgen-dependent male vocal performance influences female preference in Neotropical singing mice

Vocalizations used in aggressive and mating contexts often convey reliable information about signaller condition when physical or physiological limitations constrain signal expression. In vertebrates, androgens modulate the expression of vocal signals and provide a proximate link between male condition and signal form. In many songbirds, assessment of males is based on production of trills that are constrained by a performance trade-off between how fast notes are repeated and the frequency bandwidth of each note. In this study, we first recorded trills of male Neotropical singing mice (Scotinomys) to examine whether they show a similar performance trade-off, and then manipulated androgen levels to assess their role in modulating vocal performance. Lastly, we broadcast experimentally manipulated trills to females to determine whether they preferred versions resembling those of androgen-treated males. Singing mice showed a vocal performance trade-off similar to that of birds. Males treated with androgens maintained vocal performance, but castrated mice that were administered empty implants produced trills with lower performance. Females approached high-performance trills more rapidly and spent more time near corresponding speakers. Together, our results demonstrate that androgens modulate the production of physically challenging vocalizations, and the resulting signal variation influences female receiver response.