Ultrasonic vocalizations in mice: Effects of sex, age, and environmental conditions.

Ultrasonic vocalizations (USVs) are key communicative signals in rodents, reflecting developmental stage, sex, and social context. Most studies on female mice USVs focus on their effects on male behavior or pup interactions, while few address vocalizations unrelated to reproduction or maternal care. The present study aimed to fill this gap by characterizing USVs in C57BL/6 mice of both sexes at different developmental stages and under distinct contexts. Neonatal (PND 3-4), postnatal (PND 13-14), adolescent (PND 30-45), and adult (PND 90) mice were evaluated in various contexts. Our results reveal a dynamic transitional pattern in USV production. Neonates of both sexes emitted a high number of calls, which markedly declined after the postnatal period, indicating a behavioral shift in communication. Sexual dimorphism emerged in adulthood, as females partially recovered vocalization rates, whereas males maintained low emission levels after adolescence. Although no significant differences in USVs were detected between stressed and non-stressed adolescents, some stressed individuals completely ceased vocalizing, suggesting a strong individual variability in response to acute stress, independently of sex. In adulthood, males and females exhibited distinct vocal strategies depending on the social or non-social context. Overall, these findings highlight the importance of USVs as sensitive markers of developmental, sex-dependent, and context-specific communicative behaviors, providing valuable insights for refining animal models in behavioral neuroscience.