Litter deficits of socially stressed and low status hamster dams

The effects of maternal social stress, induced by pairing pregnant females, and social status, measured by agonistic behavior within pairs, on pup development was investigated in hamsters. Using litters from untreated first pregnancies as a control, 40 dams were housed either alone or paired with another dam during their second pregnancy. Within a pair, the dam with more aggressive and fewer defensive responses than the other was considered dominant. Compared to their first unpaired litters, second litters of paired dams were smaller in number. Comparisons among second litters showed that paired dams, especially submissive dams, had fewer pups than unpaired dams. It was concluded that both maternal social stress and low status increase intrauterine mortality.