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Hormones, neurological areas of the brain, as well as experience have been seen to play a role in the onset and maintenance of maternal behavior (Elwood, 1983; Kendrick et al., 1997; Kinsley et al., 1999; Lonstein et al., 1999) . Many of the studies done have involved rats and mice with few performed on human and non-human primates. In this paper I will examine the influence of hormones, the brain, and experience on maternal behavior in mammals.
ENDOCRINE/NEUROPEPTIDE INFLUENCES .
Hormones are seen to affect the onset and maintenance of maternal behavior. Several factors support this idea. The first form of evidence that hormones play a role in maternal behavior was exhibited in an experiment by Rosenbalt et al. (1973, as seen in Reite et al., 1985). In it they found that females displayed maternal behavior to fostered pups hours before parturition. Secondly, in pregnancy termination experiments, latency of maternal behavior was related to the time of termination, the closer to parturition the termination was the shorter the latency in maternal behavior (Lott et al., 1969, as seen in Reite et al, 1985). Thirdly, in an experiment conducted by Terkel et al. (1969, as seen in Reite et al., 1985) where the blood of a postpartum rat was transfused into that of a virgin rat, it was found that when the blood transfusion took place 30 min after parturition latencies for pup retrieval were much shorter than in those virgin females that did not receive a transfusion. .
Among the many hormones involved in regulating maternal behavior prolactin, placental lactogen, oxytocin, b-endorphin, as well as the ovarian hormones estrogen and progesterone have been shown to play an important role in maternal care. Several of these hormones regulate the release of the others therefore, they are dependent on each other for proper expression. Hormones act to synchronize maternal care with parturition. A complete expression of maternal behavior is seen immediately following parturition in both altrical and precocial mammals (Pryce et al.