The courtship song of voles: male ultrasound vocalizations modulate female receptivity in two vole species

Rodents use ultrasonic vocalization (USVs) during various social interactions. The research on the impact of USVs is predominantly focused on common laboratory species; however, their exact role in rodents' lives remains unknown. Within vole species, USVs are present during sexual encounters and are primarily emitted by males. Female voles, characterized as induced ovulators, require male stimuli for behavioural oestrus and ovulation. Ultrasounds occurring during male–female interactions may thus serve as external stimuli influencing female reproductive behaviour. In this study, using prerecorded male vocalization, we investigated the effects of male USVs on female proceptive and receptive behaviours towards males in two lab-bred wild-derived vole species: bank voles, Clethrionomys glareolus or Myodes glareolus and common voles, Microtus arvalis. The confrontation between males and females was performed after a significant delay following exposure to the vocalization, rather than immediately afterwards. This approach allowed us to investigate the delayed reactions of females. Our findings reveal that exposure to male USVs before behavioural tests significantly influenced the reproductive behaviour of females in both species. Specifically, we observed an increased frequency of lordosis positions and copulations after the ultrasound exposure, however with variations in the response timing between species. Furthermore, ultrasound exposure notably reduced the latency to the first copulation, suggesting changes in female physiology induced by the USVs. Taken together, this work underscores the significance of male USV as a potential stimulus capable of influencing female voles’ behaviour and potentially their physiology, resulting in enhanced receptivity.