Behavioral responses of infant rats to maternal licking: variations with age and sex.

Behavioral interactions of Norway rat pups and their dams during maternal anogenital licking (AGL) were observed. Regularities in posture and orientation that may facilitate AGL were noted, and age-related changes in the pup's postural adjustments that may contribute to the decline of AGL in the 3rd postpartum week were described. It was found that cutaneous stimulation of the perineum, such as that provided by AGL, stimulates a characteristic leg extension response from pups. It was concluded that this response, which includes immobility and extension of all limbs, may permit maternal licking to continue long enough to stimulate the pup to eliminate and to allow the dam to ingest the urine. Males and females were found to exhibit similar responses and similar age-related changes. However, the latency from onset of AGL to performance of the leg extension response was shorter in males.