LARGE GROUP FORMATION IN EUROPEAN ROE DEER - AN ADAPTIVE FEATURE

The European roe deer (Capreolus capreolus) has locally colonized open agricultural lands for some decades. In the present paper, size of th e winter groups of this species is compared at six sites of various op enness, as well as in two of the sites for different population densit ies. Mean group size, reaching eight deer in the most open cultivated area, is found to increase with both habitat openness and population d ensity. As the European roe deer probably evolved in mainly forest env ironments until recently, it is difficult to interpret its tendency to flock in large groups in agricultural plains as a feature set by natu ral selection. In this species, the increase of group size with habita t openness and population density could be the simple consequence of g roup instability. Large group formation might of course enhance the fi tness of the deer now colonizing open agricultural lands, but it would in this case have to be considered as an <<exaptation>> (in the sense of Gould and Vrba) and not a genuine adaptation.