Differential genetic background control state-dependent courtship ultrasonic vocalizations in mice

In male mice, courtship behaviors encompass distinct appetitive and consummatory phases, accompanied by ultrasonic vocalizations (USV) that vary with courtship progression and exhibit strain-specific patterns. Despite these differences, how genetics contribute to state- and strain-dependent USV variations remain unclear. We examined USV syllable patterns during courtship in inbred C57BL/6J (B6) and 129S4/SvJae (129) mouse strains, along with their mixed-background F2 offspring. During appetitive behaviors, such as body and anogenital sniffing, B6 and 129 males produced distinct USV. F2 males emitted USV reflecting combinations of B6 and 129 patterns, correlative with the continuous similarity to each strain. In contrast, all groups emitted strikingly similar USV during mounting. These findings suggest that appetitive and consummatory phases are governed by distinct genetic mechanisms, shaped by evolutionary pressures for vocalization diversity during appetitive behaviors and conservation during consummatory behaviors, supporting adaptation to selection pressures that favor flexibility in mate attraction while ensuring consistency in mating success.