THE EFFECT OF NEIGHBORS ON THE MORTALITY OF HARVESTER ANT COLONIES

1. This study investigates how the density and size of conspecific nei ghbours affected the mortality of established colonies. Data were from a population of 250-300 colonies of the red harvester ant [Pogonomyrm ex barbatus (F. Smith)], on a 10-ha site, from 1988 to 1995. 2. Coloni es are more likely to die as they grow older. 3. Small neighbours tend to lower the probability of dying. 4. The probability of dying varied significantly from year to year. 5. There was little effect of crowdi ng on mortality. 6. There appeared to be no spatial effects, on the sc ale of 25 m, on the probability of dying. 7. Previous work shows effec ts of density on the founding of new colonies and on the reproductive output of established ones. The results presented here indicate that c ompetition with neighbours rarely causes the death of established colo nies.