Social dominance and reproductive success in pregnant and lactating golden hamsters (Mesocricetus auratus) under seminatural conditions.

Pairs of female hamsters were acclimated to seminatural enclosures and permitted to interact for brief periods on days 12-14 of gestation or on days 2-4 of lactation. In one experimental paradigm, food was provided in excess of the daily requirements while in a second, food rations were restricted. Control females were similarly housed and fed but were not exposed to another animal. Paired females readily established dominant-subordinate relationships. Dominant females successfully removed food from the subordinate females and, as a result, accumulated larger food hoards. Subordinate females gave birth to fewer pups than either dominant or subordinate animals when social interactions occurred late in pregnancy and maintained smaller litters when interactions occurred during lactation. Reductions in the fecundity of subordinate females were more pronounced when the food ration was restricted. Under ad lib feeding conditions dominant females also maintained fewer young than control animals, but when food was restricted they were more successful than the control group. Subordinate females successfully defended their burrows against intrusions by dominant animals; maternal cannibalism accounted for most reductions in litter size. These results suggest that a defensible burrow and the acquisition of a food hoard are essential for successful reproduction in this species.