Maternally directed orienting behaviors of newborn rats

We observed an organized repertoire of behaviors performed by newborns of the laboratory rat when placed under suspended artificial surfaces simulating various properties of the awake dam's ventrum. Pups traveled and wriggled, turned on their sides and upside down, ventroflexed and probed into the surface while on side or upside down, and audibly barked, all in a state of heightened behavioral arousal. Within 48 to 72 hr after birth, these behaviors generally increased with the addition to the simulation of more maternal features, including the texture of the dam's ventral fur and odor, separately and in combination. In addition, the behaviors were intensified by 18 hours of maternal deprivation. The possible functional relations among the components of this repertoire, which we refer to as "maternally directed orienting and proximity-seeking behaviors," and between these behaviors and nipple attachment and suckling, are discussed.