Late-born intermittently fasted juvenile garden dormice use torpor to grow and fatten prior to hibernation: consequences for ageing processes

International audienceTorpor is thought to slow age-related processes and to sustain growth andfattening of young individuals. Energy allocation into these processesrepresents a challenge for juveniles, especially for those born late in theseason. We tested the hypothesis that late-born juvenile garden dormice(Eliomys quercinus) fed ad libitum (‘AL’, n ¼ 9) or intermittently fasted(‘IF’, n ¼ 9) use short torpor bouts to enhance growth and fat accumulationto survive winter. IF juveniles displayed more frequent and longer torporbouts, compared with AL individuals before hibernation. Torpor frequencycorrelated negatively with energy expenditure and water turnover. Hence, IFjuveniles gained mass at the same rate, reached similar pre-hibernation fatteningand displayed identical hibernating patterns and mass losses as ALanimals. We found no group differences in relative telomere length (RTL),an indicator of ageing, during the period of highest summer mass gain,despite greater torpor use by IF juveniles. Percentage change in RTL wasnegatively associated with mean and total euthermic durations among allindividuals during hibernation. We conclude that torpor use promotes fatteningin late-born juvenile dormice prior to hibernation. Furthermore, weprovided the first evidence for a functional link between time spent ineuthermy and ageing processes over winter