Rates of female mouse ultrasonic vocalizations are low and are not modulated by estrous state during interactions with muted males

Abstract

Vocalizations produced during courtship can communicate signaler attributes and facilitate mating success. Adult male mice produce high rates of ultrasonic vocalizations (USVs) during courtship interactions with females. For many decades, it was thought that only males produced courtship USVs, but recent studies using microphone arrays to assign USVs to individual signalers report that female mice produce a portion (5-18%) of total courtship USVs. The factors that regulate courtship USV production by female mice are poorly understood. In this study, we tested the idea that female courtship USV production is regulated by estrous state. To facilitate the detection of female USVs, we paired female subjects with males that were muted for USV production via ablation of midbrain neurons that are required for USV production but not for male sexual motivation. We report that total USVs recorded during interactions between group-housed B6 background female mice and muted males are low and are not modulated by female estrous state. Similar results were obtained for single-housed B6 background females and for single-housed outbred wild-derived female mice paired with muted males. These findings suggest either that female mice produce substantial rates of courtship USVs only when interacting with vocal male partners or that prior studies have overestimated female courtship USV production. Studies employing methods that can unambiguously assign USVs to individual signalers, regardless of inter-mouse distances, are needed to distinguish between these possibilities.