LAUSR

Nest sharing in rodents and other vertebrates is believed to be promoted by the gain of thermoregulatory advantages, reproductive imperatives or to be a by-product of other benefits to group living. Here, we studied the patterns of nest box sharing over a yearly cycle in a wild population of the arboreal, nocturnal and heterothermic woodland dormouse (Graphiurus murinus). We evaluated whether the timing of dormouse aggregations and group composition were compatible with thermoregulatory or reproductive imperatives. Nest box sharing between two or more dormice was observed throughout the year and was not correlated with monthly minimum temperatures. Therefore, the observed aggregations could not be exclusively related to the gain of a thermoregulatory advantage. All-male and all-female aggregations were more frequent during the mating season, following which some females seemed to engage in communal nesting and continued to share nests with some of their offspring well beyond the weaning period. Our data suggest that nest sharing was only partly affected by basic reproductive needs. We hypothesize that dormouse aggregations were ultimately favoured by a high level of intra-sexual tolerance elicited by the presence of numerous kin-related and familiar individuals in the population. This seems to stem from the high inter-individual spatial overlaps and the promiscuous mating system previously reported in this species. Further studies focusing on natural resting sites and genetic relatedness between individuals are needed to confirm our findings and test our hypothesis.