Ant Foragers Compensate for the Nutritional Deficiencies in the Colony

Summary Achieving nutritional homeostasis is crucial for the fitness of all living organisms [ 1 ]. Using “collective wisdom,” ants have been shown to excel at making rapid and appropriate decisions under various contexts [ 2 , 3 ], including foraging [ 4 , 5 , 6 , 7 ]. Ants often use pheromone trails to share information about food resources [ 8 , 9 , 10 ], a process allowing them to focus their foraging activity on the best food source available [ 7 ,  11 , 12 , 13 , 14 ]. However, what constitutes the best food source depends on the nutritional context of the colony in relation to its food environment [ 15 ]. In this study, we exposed ant colonies to various nutrient deficiencies and observed their compensatory nutritional responses. Ants were deprived of carbohydrate, sterol, protein, a subset of amino acids, or a single amino acid. We found that ants were rapidly able to match their foraging decisions to their nutritional needs, even if the deficiency concerned a single amino acid. An individual-based model demonstrates that these impressive feats of nutritional compensation can emerge from the iterative process of trail-laying behavior, which relies on a simple individual decision: to eat or not to eat. Our results show that, by adjusting their feeding behavior at the individual level, ants sustain homeostasis at the colony level.