Effect of parental environment on pup isolation calls in a monogamous rodent, the mound-building mouse

In altricial mammal species, isolation calls are vocalisations the young produce when they are separated from the mother. While mother/offspring interactions during the postnatal period affect pups' isolation calls rate, the contribution of interactions with other adults in shaping this response remains to be explored. We took advantage of the variation in the composition of the parental environment in the wild in a monogamous species (Mus spicilegus) to investigate how the vocal response of pups during separation could be affected by the number of adults that provide daily care in the nest. Three types of parental environments were studied: monoparental, biparental and polygynous. First, we quantified the parental care received by pups during the first postnatal week in the different parental units. Second, pups' vocal responses to isolation were recorded on postnatal day 9. Pups received less care (licking and handling) in monoparental than in biparental or polygynous units, and no difference was observed between biparental and polygynous units. Pups that emitted higher call rates in response to isolation were the ones which were less often left alone in the nest and which received a larger amount of maternal care.