Variation in maternal care and individual differences in play, exploration, and grooming of juvenile Norway rat offspring.

Individual differences in two different forms of maternal licking, time in nest and nursing, were measured during the first 2 weeks after birth. Two treatments were imposed to reduce maternal anogenital licking (AGL): peripheral zinc sulfate to interfere with reception of pup chemosignals, and dietary saline to reduce appetite for pup urine. Both treatments reduced AGL but did not affect other maternal licking. Zinc sulfate was more effective than saline during the first week, but was somewhat less selective as it also increased time in nest. Selected behavioral patterns were measured in male and female juveniles and related by multiple regression to the behavior of their mothers. Independent of the method of manipulation, maternal AGL was a significant predictor of play and open-field defecation males and of some forms of activity in the open field in both sexes. The relationships between other maternal variables and juvenile behavior were more modest. These data demonstrate that intervening in the sensory regulation of maternal behavior can produce predictable changes in stimulation provided by the dam, thereby providing a useful means for investigating the effects of protracted differences in early stimulation in otherwise normal developmental contexts.