Abstract
The field activity patterns of C. glareolus and A. sylvaticus during the summer at an artificial feeding site are described. Apodemus was nocturnal with a single major peak of activity. Clethrionomys, although recorded during each hour of the day, was predominantly diurnal with peaks of activity at dawn and dusk. This is in contrast to periods of activity throughout the 24 h, with little indication of a diel preference, which were shown in laboratory studies. The possibility that interspecific avoidance reactions affect their temporal patterns of activity is discussed.