ULTRASONIC VOCALISATIONS IN C57BL/6J MICE: AGE AND SEX DIFFERENCES ACROSS DIFFERENT SOCIAL CONTEXTS

Mice communicate using ultrasonic vocalisations (USVs) above the human hearing range (>20 kHz). USVs provide a sensitive measure of affective state, inform pharmacological evaluations, and reveal communication patterns in mouse models with social or communicative impairments. USVs can also provide insight into the motor control processes involved in producing vocalisations. To compare communication patterns across development and sexes, we characterised USVs of pups, young adults, and older C57BL/6J mice across multiple behavioural paradigms.
USVs were recorded from twelve males and twelve females during same- and opposite-sex interactions, and from seven male and seven female pups following separation from the dam and litter. Only one animal was recorded at a time.
Pups produced 34 ± 29 USVs/min. Adult males produced 29 ± 49 USVs/min with females, but only 2 ± 1 USVs/min with other males, and females paired with females produced 2 ± 1 USVs/min. Both principal and peak frequencies were significantly higher in pups than in males interacting with males, and the mean power (dB/Hz) of pup USVs was significantly greater than that of females interacting with females, indicating louder vocalisations in pups. In adults, females produced fewer and shorter USVs than males when paired with females. Furthermore, the data showed that females produced more complex call types than males during same-sex interactions.
These results identify robust paradigms for eliciting USVs and reveal sex-dependent differences in vocal behaviour that change longitudinally. This dataset provides a framework for studying vocal repertoires in mouse models with social or communicative impairments.