Weaning in rats: I. Maternal behavior.

Maternal behavior during the weaning period (postpartum Days 14-35) was described from continuous timelapse videorecordings of Norway rat dams and their litters. Time spent nursing declined steadily after Day 20 but persisted until Day 34, about a week longer than suggested by reports of milk transfer. Most of the decline in nursing was due to progressively fewer nursing bouts per day; milk letdowns per day were consequently diminished. Although a private feeding chamber was available to the dams, they did not use this chamber to spend more time away from the pups as weaning progressed. Instead, the dams remained with the pups in the nesting chamber but devoted increasingly less time to nursing. Subtle, progressive changes in maternal behavior are closely orchestrated and coordinated with pup development.