Habitat-related aggressive behaviour between neighbouring colonies of the polydomous wood ant Formica aquilonia

Ant species of the late succession stages usually have several queens and a polydomous colony structure, where several colonies occupy the same territory without competing. The wood ant Formica aquilonia is a good example of such a species in boreal forests. In this species, the lack of intraspecific competition may be caused by the stable environment and abundant food resources (e.g. excretions of tree-living aphids). We studied how habitat destruction, in the form of clear-cutting, affects aggressiveness between neighbouring colonies in F. aquilonia. Intercolonial relationships were more hostile in clear-cuts than in forest interiors. This aggression may be the result of increased intraspecific resource competition or alienation of neighbouring colonies caused by the loss of visual orientation cues. We suggest that the original polydomous relationships between colonies decline and colonies may start aggressive competition for the remaining resources.