Within their distribution range animals are often confronted with different environmental conditions which can result in diverse vital rates in populations of the same species. Therefore, investigations on different local populations are necessary to reveal general insights into the biology of a species.
Edible dormice are small, arboreal hibernators that reproduce only in mast years of beech or oak. It has been shown previously that reproduction clearly affects their survival to the subsequent year, as their survival rates were twice as high in non-reproductive years. However, the actual causes for this impaired survival remained unclear. In this study we compared the spatiotemporal variation of survival rates in five populations of edible dormice at distant sites in Europe (in Austria, Czechia, England, Germany and Italy), as determining the patterns of survival rates can provide insights into possible causes of mortality. Capture-Mark-Recapture studies were conducted in all five areas, and we used Cormark-Jolly Seber models as implemented in program Mark to estimate monthly survival rates depending on season, sex, area and discriminating between reproductive and non-reproductive years.

Results/Conclusions

We found very high survival rates during winter, which indicates that edible dormice do not starve due to insufficient energy reserves during the hibernation period. Increased mortality in early summer was most likely caused by a high predation risk and high energy demands. As expected, survival was always lower in reproductive years than in non-reproductive years. Also, recapture probabilities indicated that dormice were more active in reproductive years, which probably increased predation risk and enhanced the effects of high energy demands on mortality. Females always had higher survival rates than males, which may be caused by the negative effects of androgens on male immunocompetence. Although similar temporal patterns could be found in all areas, there were also considerable differences in average survival rates. These differences could not be explained by climate, but were most likely due to differences in predation pressure. Variation in survival rates resulted in differences in mean lifetime reproductive success between populations, that was 40% higher in the study site in Italy than in Germany. Further, it seems that edible dormice have adapted their survival strategies to maximize their lifetime reproductive success depending on the frequency of mast seeding events in a specific area.