Edible dormice are extremely long-lived for their size, thanks to their seasonal dormancy. The animals are veritable record holders in longevity, with hibernation periods lasting between at least six and a maximum of 11 months. The factors influencing the variable duration of the hibernation period, apart from the specific environmental conditions, have so far been unknown. Researchers at Vetmeduni Vienna hypothesised that older animals should shorten their winter dormancy in favour of a reproductive advantage. This hypothesis has now been confirmed in a database analysis, published in Scientific Reports, of dormice populations living in large outdoor enclosures. The shortened winter hibernation of aging males and females were due to an increase in reproductive activity. Older animals also delay the onset of hibernation and emerge earlier in the season.