Developmental changes in factors limiting colony survival and growth of the leaf-cutter ant Atta laevigata

Many species of leaf-cutter ants (Atta and Acromyrmex) increase in abundance following natural or anthropogenic disturbances in the vegetation. However, the mechanisms responsible for such an increase are still poorly understood. We evaluated the effects of nesting site and the availability of palatable forage on survival and growth of Atta laevigata colonies at different developmental stages. Foundress queens transplanted into man-made clearings (dirt roads) had a much higher survival than those transplanted into the adjacent undisturbed savannah vegetation. Similarly, incipient colonies (>= 3-months old) had significantly greater survival and growth rates in dirt roads. In contrast, nesting site did not influence performance of young colonies (>= 15-months old). Both incipient and young colonies responded strongly and positively to experimental supplementation of palatable forage, and this effect was independent of the nesting habitat. Colonies that received extra food grew faster and had a significantly greater survival rate than control colonies. These results suggest that performance of A. laevigata is affected by the generally greater availability of suitable nesting sites and palatable vegetation in disturbed habitats. This may explain how these ants maintain high densities in these habitats, and since the relative importance of these factors changed with colony ontogeny, our findings highlight the importance of evaluating potential limiting factors throughout the full range of an organism's developmental stages.