The Explutrientoration of Macronutrient Regulation in the Desert Leafcutter

Nutritional balance is a requirement for the survival of all species. This balance is important for complex eusocial organisms as it influences the growth and development of the colony. Leafcutter ants function as tri-trophic systems, harvesting mixed vegetation to cultivate a fungus garden that in return supplies the colony with food. Examining how the colony deals with nutrient balance is of particular interest because this species forages to provide nutrients for the fungus. There seems to be a feedback system between the fungus and the workers that influences how much of a particular macronutrient should be collected. The objective of this thesis study was to examine the foraging behavior of the desert leaf cutter ant, Acromyrmex versicolor. This study asked how nutrition, in particular the ratio of carbohydrates to proteins, influences the foraging behavior of the colony. It was hypothesized that given a choice of high protein and high carbohydrate diets the leafcutters would forage towards a balance ratio. The results from this experiment showed that A. versicolor forage towards a target ratio of protein to carbohydrate to based diets. This p:c ratio was calculated to be 1:6.2; 1 gram of protein to 6.2 grams of carbohydrate. When colonies were restricted to the high carbohydrate diet, they increased food consumption, consistent with the expectation that they would forage to reach their protein nutrient requirement, however, they reduced foraging on that diet. This suggests that ants avoid overconsuming protein, even when doing so provided more optimal carbohydrate intake. From this study I concluded that nutritional balance is a foraging goal for ant societies, similar to organisms. These results also open the question of how nutrient regulation by leafcutter ants is regulated around their mutualist relationship with another organism, the fungus.