Hormonal and behavioral aspects of maternal care in the hamster: a review.

This review covers a description of the maternal behavior cycle in the hamster and relationships between the endocrine system and prepartum changes in activity, aggression, sexual receptivity, and maternal care. Postpartum maternal behavior consists of the mother's "normal" cannibalism of some portion of her litter, the formation of a bond between mother and her young, the development of behavioral synchrony between the mother and her pups, and maternal aggression toward conspecifics. The maternal responses of virgin female, male, and juvenile animals are described and methodological considerations in the testing of both virgin and parturient animals are presented. Finally, a theoretical framework for considering the regulation of maternal care in the hamster is presented. Two main phases of regulation are proposed; an onset phase that that originates prepartum and depends on the physiological conditions of pregnancy and a maintenance phase which provides for the continuation of maternal care during lactation and is based on both endogenous maternal factors and external litter-related stimuli. A transition period beginning at parturition facilitates the shift between the onset and maintenance phases.