Alloparental behaviour in Sinai spiny mice Acomys dimidiatus : a case of misdirected parental care?

Communal breeding, where reproducing females share a nest and the care of their pups, occurs in many animal species. According to kin selection theory, alloparental behaviour should occur predominantly among closely related conspecifics. However, familiarity between females, a prerequisite for reciprocal altruism, may also play a role. The aim of our study was to analyse the effect of kinship and familiarity on the occurrence of two types of alloparental care—nursing and the retrieval of pups wandering from the nest—in a communally breeding rodent, the Sinai spiny mice Acomys dimidiatus . In addition, the effects of other factors that may also have an impact on alloparental care were tested; these included age difference between litters, pup age, maternal experience, pup sex ratio, litter size, group age, and mother’s weight. We found that kinship and familiarity had no effect on alloparental care. The nursing of alien pups depended on the maternal reproductive experience measured as the number of weaned litters and also on the age difference between the litters of both females. Less experienced females nursed alien pups more often than experienced ones. With increasing age difference between litters, females preferentially nursed their own pups. Similarly, the retrieval of alien pups was affected by the age disparity between the litters; with increased age difference, the females more readily retrieved their own pups. These results indicate that the occurrence of alloparental care in the Sinai spiny mouse may be more related to misdirected parental care than to kin selection.