Development of Pup USVs

Rat pups produce ultrasonic vocalizations (USVs) when separated from their mother, providing an early form of communication that signals distress and elicits maternal care. In this extensive study, we tracked the development of isolation-induced USVs in male and female rat pups between postnatal days 2 and 14, and examined how early-life stress affects this process. We found that USVs undergo rapid developmental changes, with increasing acoustic complexity and the emergence of distinct high-frequency call types around postnatal days 8 to 11. Maternal separation selectively reduced the number and duration of low-frequency calls and disrupted the temporal organization of vocalizations, while the emergence of high-frequency call types was largely preserved. Together, these findings reveal a critical period of vocal development in rat pups and show that early-life stress can selectively alter specific components of this developmental trajectory.