Responses to nutritional challenges in ant colonies

Abstract

In social insects, food collection for the entire colony relies on a minority of its workers. How can the colony performance in the choice of resources, the allocation of workers, and the flexibility of food storage strategies emerge from the foraging decisions taken only by a minority? We addressed this question by posing nutritional challenges in the trap-jaw ants Odontomachus hastatus and explored their response in term of survival, foraging behaviour and energy storage. In the first challenge, ants alternated between long periods of confinement to a high protein diet to short periods of confinement to a high carbohydrate diet. In the second challenge, ants alternated between long periods of confinement to a high carbohydrate diet to short periods of confinement to a high protein diet. In the third challenge, ants were given simultaneously the high protein diet and the high carbohydrate diet. First, we showed that (i) mortality increased with protein consumption (ii) short access to a high carbohydrate diet lessened the negative consequence of high protein consumption (iii) ants given a choice of complementary diets regulated intake to minimize mortality. Second, we demonstrated that ants are using an energy saving strategy to overcome challenging nutritional environments. Third, we demonstrated that ants have an extraordinary capacity to regulate the amounts of food entering the nest: (i) at the collective level by allocating more workers to foraging on a high protein diet (ii) at the individual level by collecting more food on a high carbohydrate diet. Our study provides new insights into the strategies used by ants facing nutritional challenges and deepens our understanding of the nutritional ecology of ants, thereby, their vast ecological success.