Spatial behaviour of the yellow-necked mouse (Apodemus flavicollis, Melchior 1834) at contrasting population density and resource availability

I present the results of a two-year study on the spatial organization and mating system of the yellow-necked mouse, Apodemus flavicollis. I monitored the movements of 64 mice by radio tracking during the breeding season in 2005 (high population density) and 2006 (low population density). Male home ranges were significantly larger than those of females and overlapped with both female and male ranges. Female home ranges overlapped amongst themselves and monopolized core areas, thus showing intra-sex territoriality. Individual mice used many burrows simultaneously with mixed sex pairs being the most common association, and female pairs being absent. These results indicate a promiscuous mating system. The use of space changed seasonally and among years, likely indicating a dependence on resource abundance and distribution. After an evident decrease in habitat quality, I observed substantial adult dispersal, both in males and females, from the end of September to early October 2005. In a rodent species relying on patchy and slowly renewed resources, females showed a flexible social and spatial behaviour, in response to variations in habitat quality and environmental constraints, whilst males appeared to consistently attempt to maximise encounters with receptive females.