INFLUENCE OF LITTER GENDER COMPOSITION ON SUBSEQUENT MATERNAL-BEHAVIOR AND MATERNAL AGGRESSION IN FEMALE HOUSE MICE

It has been suggested that the sex-dependent pattern of mother-pup int eraction that occurs early in infancy can affect some aspects of the a nimal's behaviour repertoire in adulthood. The aim of this study was t o investigate the effects of litter gender composition (LGC) on subseq uent maternal behaviour and aggression in the female house mouse. Albi no mouse litters were reduced at birth to six pups according to two co nditions: FM (3 females and 3 males) and FF (all females). At weaning (day 21), all mice were rehoused in unisexual groups. At adulthood (70 -90 days) the females were mated and litters culled at birth to 6 pups (3 females and 3 males). On days 2, 4, and 6 after delivery the femal es were tested for maternal behaviour (10 min) and retrieval of pups. On day 6, at the end of the recording of maternal behaviour, the femal es were also tested for maternal aggression towards a strange adult ma le conspecific (5-min exposure). In absence of differences in maternal behaviour scores, FM females showed shorter latencies for retrieval o f the first pup on postnatal days 2 and 4. Maternal aggression was als o significantly affected by the two conditions. FM females showed high er scores of both duration and frequency of aggressive grooming, defen sive upright postures, fleeing and of the number of attacks. FF female s spent more time self-grooming, crouching, and on nest. These results support the hypothesis that a series of factors, such as olfactory, t actile, and acoustic stimulation provided by the pups, the variation o f maternal behaviour depending upon LGC, and the qualitative and/or qu antitative variation in social interaction with the opposite sex in in fancy, contribute to the broad interindividual plasticity to cope in d ifferent environmental situations.