Skull variability of mice and voles inhabiting the territory of a great cormorant colony

We investigated the influence of a colony of great cormorants on the skull morphometry of yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) of three age groups trapped in the territory of the colony in 2011-2014. In general, most of the skull differences in both species were related to character length (skulls tended to become longer). In A. flavicollis, the skull size differences between zones were most expressed in subadult and adult individuals, while in M. glareolus they were most expressed in juveniles, with only a few characters different in adults and none in subadult voles. For both species, the largest skull characters were found mostly in the zone characterized by both the greatest number of cormorant nests and the longest and strongest influence by the colony. Concluding we confirm that the great cormorant colony has an influence on the skull morphometry of A. flavicollis and M. glareolus and we hypothesize that these differences enhance the ability of survival in specific conditions.