Effects of age, sex, and odours from conspecific adult males on ultrasonic vocalizations of infant CS1 mice.

Young CS1 mice aged 2, 4, 6, 8 and 10 days were each sequentially exposed to odours of urine from strange adult infanticidal and non-infanticidal males and the number of ultrasonic vocalizations monitored. There was a clear age effect, with pups 6-8 days calling the most. For pups of 2 and 6 days of age there were significant positive correlations between body weight and number of calls but for 10-day-old pups a negative correlation was found. Female pups called more than males, particularly when exposed to odours but this was not due to body weight. Overall, more calls were produced when odours from infanticidal rather than non-infanticidal males were presented and individual pups altered their ultrasonic output as the odours were changed.