EN
Habitat preference, home range size and intra-specific overlap were investigated in summer 1998 among field voles Microtus agrestis (Linnaeus, 1761) in Słowiński National Park (N Poland). Eight individuals (2 females, 6 males) were radio-tracked for one week in August. Field voles were shown to exhibit a marked preference for meadow and the ecotone between grassland and habitats with common reed, while avoiding alder forest and proper reedbeds. No significant differences between night and day in habitat-use of voles were noted. The results suggest that, at the end of the breeding season, it was food resources, rather than the risk of predation, played an important role in the voles' utilisation of space. The home ranges of males were larger and more diverse than those of females; their sizes being correlated with body mass, such that heavier males had larger home ranges. This further suggests that intra-sexual competition exists between males for females. The low number of females influenced their spatial behaviour, as females had completely exclusive home ranges. Four males (out of six) had overlapping home ranges with other males; three of the overlaps were of less than 20%. Attributes of promiscuity (such as a 3.5:1 operational sex ratio of males to females, intra-sexual competition between males and the territorial exclusivity of females) influenced the social system. However, the period of radio-tracking during this study was too short to define accurately the social system in the field vole population.