New mothers display altered socioemotional behaviors, including increased caregiving and reduced anxiety, that are appropriate for the developmental needs of their offspring.  These behaviors are driven by hormones during pregnancy and are affected by the mother’s caregiving experience and the sensory qualities of the pups.  To examine if rat mothers’ caregiving and anxiety behaviors were driven more by her duration of postpartum maternal experience, the developmental stage of the pups she cares for, or an interaction between these factors we cross fostered litters among and between postpartum day 1 and postpartum day 8 dams.  This created four groups: early postpartum dams with young pups, early postpartum dams with older pups, late postpartum dams with young pups, and late postpartum dams with older pups.  We examined the dams’ maternal and anxiety-like behaviors starting 5 days later.  We found that early postpartum dams spent more time with pups than late postpartum dams, regardless of the litter’s age, while conversely dams interacting with older pups spent more time resting away from the nest regardless of their postpartum stage.  There were no main effects of postpartum stage or litter age on anxiety-like behaviors on the elevated plus maze, but there was an interaction between them; late postpartum dams with young pups entered the open arms less often than other groups, suggesting that inappropriately aged pups increased anxiety in dams who had sufficient experience with their own pups before cross fostering. These results indicate that maternal experience and developmental stage of the litter interact to affect postpartum maternal caregiving and anxiety behaviors.   Ongoing analyses will determine the associations between the dams’ dorsal raphe levels of tryptophan hydroxylase 2 (serotonin-synthesizing enzyme) and dams’ caregiving and anxiety.