A, B, Vocalization at PN7. There are no significant differences in the number of events (A) and total duration (B) among CON and KO groups (Mann–Whitney rank–sum test: A, U statistics = 344.5, p-value = 0.975; B, U statistics = 372, p = 0.640). C, D, Vocalization at PN14. KO demonstrated a significant decrease in the number of events (C) and total duration (D) among CON and KO groups (Mann–Whitney rank–sum test: C, U statistics = 142, *p-value = 0.042; D, U statistics = 154, *p = 0.013). PN7: n = 12 for KO, n = 57 for CON; PN14, n = 6 for KO, n = 31 for CON.