The costs of locomotor activity? Maximum body temperatures and the use of torpor during the active season in edible dormice

Measuring T (b) during the active season can provide information about the timing of reproduction and the use of short bouts of torpor and may be used as a proxy for the locomotor activity of animals (i.e., maximum T (b)). This kind of information is especially important to understand life-history strategies and energetic costs and demands in hibernating mammals. We investigated T (b) 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 T (b)’s 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 T (b) was recorded 1 week prior to hibernation (40.45 ± 0.07 °C). At the beginning of the active season and immediately prior to hibernation, the mean maximum T (b)’s were lower. The time dormice spent at T (b) above 40 °C varied between sexes, depending on mast conditions. The date of parturition could be determined by a sudden increase in mean T (b) (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.