(A - B) Ultrasonic vocalization was measured at P6, P8 and P12 (WT n=14 pups, crmp2-/- n=13 pups). In crmp2-/- mice, there is a significant decrease in the rate and duration of calls at P8 (call rate, WT 352±58/5 min, crmp2-/- 164±41/5 min, p=0.015; call duration, WT 9.52±2 ms, crmp2-/- 3.36±1 ms, p=0.011) and P12 (call rate, WT 46±16/5 min crmp2-/- 1.54±1.24/5 min, p=0.002; call duration, WT 0.68±0.35 ms, crmp2-/- 0.007±0.006 ms, p=0.002). Mean ± SEM, *p<0.05, t-test (P6, P8), Mann-Whitney test (P12). (C) Representative sonograms of the P8 mice. 