Interaction and Habitat Selection in the Mice Apodemus Flavicollis and A. Sylvaticus

Males of Apodemus flavicollis (Melchior) and A. sylvaticus (L.) were given a choice between a grassland and a beech-wood habitat. Newly caught animals were tested alone or together in three types of enclosures ranging from small indoor to large outdoor pens. Distributions were recorded by direct observation, automatically by an event recorder, and by trapping. Interactions and other behavioural traits relevant to habitat selection were studied. In all three types of enclosures, the relative distribution pattern of the two species was such that A. flavicollis occurred about as much in both habitats, whereas A. sylvaticus occurred more in the grassland. A. flavicollis was also more active in a novel environment and showed a stronger tendency to climb. In interspecific encounters this species clearly dominated A. sylvaticus, generally in a passive way. It was less aggressive in intraspecific encounters than A. sylvaticus. The presence of A. flavicollis inhibited activity of A. sylvaticus and increased its occurrence in the grassland. When tested together the two species tended to segregate vertically.