Increase in Skull Size of Red Fox (Vulpes vulpes) in the Second Half of the XX Century in Northeastern Europe

Abstract

Based on the skulls of red fox collected in northeastern Europe for 20 years, we obtained new data on directed temporal variation. The increase in skull size is closely related to an increase in the mean annual temperature, i.e., global warming. It was found for the first time that some skull traits increase at different rates, both within and between structural population groups. The phenomenon of increasing skull size with increases in the mean air temperature contradicts Bergmann’s rule. The causes of such increase are especially important for an understanding the adaptive role of processes in populations resulting from climate changes.