Burrowing by Common Voles (microtus Arvalis) in Various Social Environments

Female common voles live in groups in large burrows whereas males are probably solitary and promiscuous. At high population density, when burrows become a limiting factor, some females are forced to emigrate from their group. To investigate whether these emigrants could share new common burrows with unrelated neighbours, we analysed in the laboratory burrowing and social behaviour in dyads of unrelated wild females before and during their cohabitation. They were compared to wild male dyads. In solitary voles, no sexual difference in burrowing pattern was observed but females built a burrow more quickly than males. In both sexes, the Ž rst encounters happened in one of the burrow and were of aggressive nature; during them intruders used burrowing during offensive approaches. While males displayed hierarchy and nested for themselves, females rapidly became friendly and nested together. They reshaped their burrows in response to social nesting and had more complex burrows than solitary females or intolerant males. We may conclude that in common voles at least unrelated non breeding females may contribute to the formation of social groups. To investigate whether, within a matriarchal group, females may co-operate with their own daughters in building a new common burrow, we analysed burrowing behaviour in dyads comprising either an experienced wild mother with one of her naive daughters or two naive familiar daughters. No co-operative behaviour could be detected but experience in burrowing speeded up the building. The results strongly suggest that, within a short time, young females may improve their burrowing.