Measuring Tb during the active season can provide information about the timing of reproduction, the use of short bouts of torpor and may be used as a proxy for the locomotor activity of animals (i.e. maximum Tb). This kind of information is especially important to understand life-history strategies and energetic costs and demands of hibernating mammals. We investigated Tb throughout the active season in edible dormice (Glis glis), since they i) have an expensive arboreal life-style, ii) are known to show short bouts of torpor and iii) are adapted to pulsed resources (mast of beech trees). We show here for the first time that maximum Tbs in free-living active dormice (during the night) increase regularly and for up to 8 h above 40°C, which corresponds to slight hyperthermia, probably due to locomotor activity. The highest weekly mean maximum Tb was recorded one week prior to hibernation (40.45 ± 0.07°C). At the beginning of the active season and immediately prior to hibernation, the mean maximum Tbs were lower. The time dormice spent at Tb above 40°C varied between sexes, depending on mast conditions. The date of parturition could be determined by a sudden increase in mean Tb (plus 0.49 ± 0.04°C). The occurrence of short torpor bouts (< 24 h) was strongly affected by the mast situation with much higher torpor frequencies in mast failure years. Our data suggest that locomotor activity is strongly affected by environmental conditions, and that sexes respond differently to these changes.