Oral Presentation- Symposium 12th International Mammalogical Congress

Weather drives population dynamics in common European forest and field rodents (#43)

Jens Jacob 1 , Christian Imholt 1 , Daniela Reil 1
  1. Vertebrate Research, Julius Kuehn-Institute, Federal Research Centre for Cultivated Plants, M√ľnster, Germany

Voles of the genera Microtus and Myodes are distributed in many regions of the world. Microtus and Myodes species are particularly abundant in Central Europe where population dynamics are characterised by multi-annual fluctuations. Population outbreaks occur about every 2-5 years. They affect the ecosystem well beyond the small mammal community because of cascading effects through the food web, impact on soil composition, seed bank, etc. We used long-term time series (standard snap-trapping or active burrow counts) covering several decades of rodent abundance to assess effects of weather conditions on vole abundance and potential effects of long-term climate change on outbreak frequency. Analyses were based on boosted regression trees and classification and regression trees. Weather conditions were highly correlated to outbreak risk/abundance in common voles and bank voles. Results indicate bottom-up regulation in both species. Most of the relevant weather parameters connected to common vole abundance originated in the preceding winter and early spring. In contrast, there were delayed effects in bank voles and field voles, which responded to weather parameters affecting seed mast of forest trees in the previous year. Based on the A1B CO2 emission scenarios we estimated the future occurrence of weather conditions that favour bank vole outbreaks. Results indicate that such conditions are likely to occur more frequently in the future than it is the case presently. This may also be the case in other rodent species if dynamics are similarly related to weather conditions. This can potentially cause ecosystem-wide effects at several trophic levels.