Seasonal changes in social behaviour and spatial structure ofCrocidura leucodon in north-western Bulgaria

The patterns of social behaviour and spatial structure ofCrocidura leucodon (Hermann, 1780) were studied against the background of the seasonal changes in its density and demographic features. Field and lab research were conducted. Field investigations (with CMR method) were conducted from 1997 to 1999 in north-western Bulgaria, in a grassland with patches of tree-shrub vegetation. In the lab, the social interactions were studied in male-male, female-female and male-female dyadic encounters during summer and autumn. A total of 26 shrews were tested. The number ofC. leucodon was lowest in spring and greatest in autumn. In early summer the sex ratio was balanced, the home range of one male overlapped that of one female, and aggressiveness and marking activity was increased. So, it can be assumed that in this period males and females form pairs, which possess defended territories. Higher aggressiveness and marking activity displayed by males suggest their greater role in defending the territories. In autumn the home ranges overlapped greatly and amicable interactions prevailed over agonistic ones probably due to shifting to a gregarious way of life. So, the patterns of spatial structure and social behaviour undergo the seasonal changes inC. leucodon life-cycle and its density dynamics.