The wild boar population in Europe has been constantly growing since the 1980s. This is more and more becoming a problem for agriculture when animals raid the fields, looking for feed. "It is not so easy to determine the number of wild boars in Europe," says wildlife biologist and first author of the study, Sebastian Vetter. "Therefore we analysed data on hunting bags and road accidents involving wild boar. Doing this we were able to depict the growth of the wild boar population." More wild boars after mild winters

Vetter and his colleagues compared annual wild boar population growth to temperature and precipitation data from twelve European countries, with data being available for up to 150 years in some regions. They identified a clear trend. "There is a sharp increase in the number of wild boars after mild winters. As mild winters are becoming more frequent, also wild boar populations are growing exponentially," Vetter explains.

One reason is thermoregulation. If temperatures are very low, a lot of energy is necessary in order to maintain a high body temperature. As a consequence, less energy is available for reproduction and rearing the offspring in the following year. Furthermore, harsh winters claim the lives of many young animals. In warmer winters, more piglets survive.