Nest relocation and encounters between colonies of the seed-harvesting ant Messor andrei

Nest relocation in ants may be an attempt to escape areas of high competition. Encounters between colonies have been suggested to be the proximate cause of nest relocation. I examined the relation between nest relocation and encounters in a population of the seed-harvesting ant Messor andrei, a native of the western United States. Over 80% of colonies relocated their nest site during a year. Colonies moved up to ten times in a year, and new nest-sites were more distant from their nearest neighbour. However, encounters did not precipitate nest relocation. Relocation was not more likely to occur directly after an encounter, and colonies that moved did not experience more encounters than other colonies. Other possible cues for nest relocation, including predation, disease, microclimatic effects, and local resource depletion, are discussed.