Courtship vocalizations of wild house mice show highly dynamic changes and correlate with male copulatory success

Abstract

Courtship vocalizations can influence mate choice and reproductive success and thus evolve through sexual selection. House mice, Mus musculus, are intensively studied; however, little is known about their vocalizations emitted during courtship sequences and whether and/or how they influence male copulatory success. To address these questions, we recorded the behaviour and vocalizations of pairs of wild house mice across distinct phases of courtship and mating. Over 53 000 vocalizations were detected and classified, and of these ca. 90% were ultrasonic (USV) and 10% were broadband (BBV) vocalizations, presumably emitted by males and females, respectively. Mice altered their vocal rate, composition and repertoire at each stage of courtship and mating. They increased the emissions of all simple USVs while reducing other calls upon contact with a potential mate. Then, once males began mounting and engaging in other sexual interactions, the pairs emitted more complex calls, especially harmonic USVs and BBVs with spectral nonlinearities. Vocalizations were closely associated with male mating behaviour and peaked in rates and complexity just before males approached the female to mount. USV bouts began earlier and contained more complex syllables when mounting attempts ended in copulation. As courtship progressed, the timing of USV and BBV emissions became tightly synchronized, as with duetting of songbirds. We observed several differences in the vocal repertoire and spectral features of calls between mice that successfully copulated with ejaculation and those that did not. USV emission was positively correlated with male sexual behaviours, especially among copulating mice, suggesting that the effect of USV emission on male mating success depends on their sexual behaviour, and vice versa. Our results show that the courtship vocalizations of wild house mice are more complex and dynamic than those previously reported and provide the first evidence for vocalizations that correlate with and predict male copulatory success.