EFFECT OF FAMILIARITY WITH THE MOTHER AND KINSHIP ON INFANTICIDAL AND ALLOPARENTAL BEHAVIOR IN VIRGIN HOUSE MICE

Experienced male and female house mice encountering a newborn pup can display indifference, parental or infanticidal behaviour. Characteristics of the pup such as sex and strain do not seem to influence the likelihood of infanticide, in contrast to attributes of the adult subjects (age, sex, strain, sexual experience, previous cohabitation with the mother, reproductive condition). This study investigated the effect of kinship and/or familiarity with the mother on male and female behaviour towards pups. The subjects were 100-day-old Swiss-Webster virgin male and female mice. After 24 hours of isolation, a 24-36 hrs old pup was introduced into their home-cage and their behaviour was recorded for 15 min. Male and female mice killed related as well as unrelated pups. Females killed fewer offspring of females with whom they had cohabited until 3 weeks before the study, in comparison with the offspring of completely unfamiliar females. When females were exposed to the offspring of females of comparable familiarity but different relatedness, they devoted more parental behaviour towards more related pups. This suggests that, even if familiarity plays a major role in determining females' behaviour, kin recognition occurs and is responsible for differences in alloparental care distribution. The behavioural strategies adopted by male and female mice are interpreted on the basis of differences in activity range of the sexes within a deme (breeding group).