Data from: They like it cold, but only in winter: climate‐mediated effects on a hibernator

Variations in ambient temperature (Ta) profoundly influence energy
consumption in endotherms and therefore their survival and fitness. But
depending on whether endotherms are hibernating or active, the same
changes in Ta may have opposing consequences for their energy
consumption. The aim of this study was therefore to investigate how
variations in Ta, occurring during hibernation and during the active
period of a hibernator, affect different fitness relevant traits. To
understand whether changes in Ta impact phenology, body mass and
reproduction in a small mammalian hibernator, we analysed
Ta variations and detailed capture-mark-recapture data on edible
dormice (Glis glis) collected between 1993 and 2016 in South-West Germany.
Results revealed that during hibernation a Ta increase of 1°C
advanced the date of first capture after hibernation by 6 days, but only
if food availability during the preceding year was low. In contrast, after
years of comparatively high food availability, date of first capture was
not affected by Ta, but dormice had a significantly lower body mass after
emergence, if Ta during hibernation was elevated (3 to 6g per
1°C). We presume that an earlier emergence as well as a lower body mass
after emergence potentially reduce the chance to survive. During the
active period of edible dormice, mean spring Ta a did not affect
the date of birth but was positively associated with litter size,
potentially improving reproductive success. Results of this study
highlight that, depending on the physiological state of a hibernator, an
increase in Ta can have positive and negative effects on fitness
relevant traits.