Dense populations of the dice snake (Natrix tessellata) and grass snake (Natrix natrix) occur syntopically at the Baćina lakes in southern Croatia. Aspects of putative interspecific competition regarding feeding habits, habitat use and...
moreDense populations of the dice snake (Natrix tessellata) and grass snake (Natrix natrix) occur syntopically at the Baćina lakes in southern Croatia. Aspects of putative interspecific competition regarding feeding habits, habitat use and activity have been studied. During two years of investigation, we found that differences in feeding habits
were the most important factors preventing putative competition between these two species. The dice snake fed exclusively on eight species of fish, whereas the diet of the grass snake consisted mainly of amphibians, but occasionally included also fish with six different species recorded. Differences concerning fish types and habitat use have also been observed. Dice snakes consumed more benthic fish and preferred slow running (lotic) aquatic systems compared to grass snakes that inhabited more often quiet (lentic) systems, such as ponds. Although both species prefer substratum with an abundance of plants, significantly more dice snakes were associated with stony substratum. The two species differed also in their positions in the water column. Dice snakes were frequently found foraging on the benthic ground and in the middle of the water body, whereas grass snakes were almost always observed on the surface.
