Foraging preferences of ants: nitrogen concentration and ease of retrieval.

Abstract

Animals must forage to obtain the nutrients necessary for their survival. Foraging patterns of ants have been the subject of many studies. However, most of these studies have focused on energy even though ants encounter nitrogen as their limiting nutrient. We will attempt to answer the following questions: Do ants selectively forage for the food source with the highest concentration of nitrogen? When presented with food sources of variable size, do ants selectively forage for the food that maximizes nutrient acquisition per unit time? When presented with food sources of variable size and nitrogen concentration, do ants selectively forage for the food that maximizes nutrient acquisition per unit time. We determined whether ants forage for the food source with the highest concentration of nitrogen by offering ants pellets of the same size but with varying nitrogen concentrations of 0%, 0.1%, 1%, and 3%. We found that the ants had a significant preference for the pellets of higher concentration. To ascertain whether ants foraged for the most profitable size food, we gave ants pellets that varied in size but had a constant concentration. In order to calculate a reward rate for the different sized pellets we divided nutrient acquisition by handling time. We found that ants did not forage for a specific sized pellet, even though reward rates differed for each food source. Since the ants did not forage for the pellet size that maximized reward rate, they logically could not consider both pellet size and nitrogen concentration when foraging. We, therefore, did not perform an experiment to determine if ants selectively foraged for the most profitable combination of pellet size and nitrogen concentration.