Differential temporal structures in mouse ultrasonic vocalizations relay sex and age information about the producer

Abstract

Mice produce a variety of ultrasonic vocalizations (USVs) during social interactions among conspecifics. However, it remains unclear which features of these calls mice utilize to distinguish one type of USV from another. In this study, we examine male courtship USVs, neonatal isolation USVs, and female social contact USVs, and find that the temporal structure of the calls alone is sufficient for a high level of discriminability. Specifically, we found that males produce temporally distinct short and long duration USVs with resulting short and long duration call intervals, while females produce nearly exclusively short USVs with short call durations. Young pups were found to produce medium duration USVs with long call intervals only. Interestingly, as the pups aged, their USV durations and call intervals decreased and approached values observed in juvenile male courtship USVs. Therefore, the gross USV rhythmic structure carries a high degree of information about both sex and age of the producer, and may be utilized by mice during call discrimination. These findings are reminiscent to some pinniped species, who face similar challenges in the transmission of their calls (i.e., a high density of calling conspecifics), who also use gross temporal features to distinguish call types.