Effects of weather and season on the summer activity of dormice Muscardinus avellanarius

Activity schedules of dormice were investigated in relation to weather and seasonal factors, by automatic monitoring of temperatures in nests of free-living animals. Data were obtained for two years and 294 dormouse-nights. The principal exogenous factor influencing pan-seasonal activity was photoperiod, activity beginning about 30 min after sunset and ending about 50 min before sunrise. However, on a seasonal scale, activity start time, end time and length were all strongly affected by ambient temperature and rainfall; higher temperatures appeared to lengthen activity, whereas rainfall reduced it. Diurnal activity was rare and took place when ambient air temperatures at midnight fell below 9 degrees C. There were large differences in activity schedules between years, which were also correlated with weather conditions. Dormice are thus directly affected by weather, which also strongly influences the availability of their food. Weather may in general heavily influence small hibernators, because they can utilise facultative torpor to overcome adverse conditions. Our results imply that weather may have a profound effect on dormouse life history, especially in Britain's maritime climate where summers are frequently cool and wet.