Group foraging decisions in nutritionally differentiated environments

Abstract

1. Foraging behaviour must be flexible enough to adapt to heterogeneities in the distribution and quality of food resources. Accurate models of optimal foraging behaviour should acknowledge the extent to which animals can detect and regulate their intake of food based on smaller scale differences in food types. In particular, consideration of macro-nutrient distribution and how animals perceive this is limited in studies of optimal foraging, particularly in vertebrates and for animals that forage in groups. 2. Here, we track shoals of eight mosquitofish as they forage in two environments that contain equal amounts of available energy but differ in their distribution of macro-nutrients. We provide empirical evidence that fish will distribute themselves within an environment in relation to the distribution of specific macro-nutrients. 3. Also, fish make foraging decisions based on the macronutrient composition of patches, such that their durations on patches are longer when they have a higher concentration of protein and lower concentration of carbohydrate. The ratio of protein to carbohydrate does not affect the probability of a fish joining a patch, however, with low numbers of fish on the patch the probability of a fish leaving is greater per unit time step in the patches with a low protein to carbohydrate ratio than the patches with a high protein to carbohydrate ratio. 4. This study confirms the importance of considering the macro-nutrient composition of foods when considering the movement decisions of foraging groups and thus has important consequences for developing more accurate foraging models that take into account the distribution of macro-nutrients in the environment. The results suggest the spatial distribution of nutrients on a landscape scale could influence grouping patterns and social interactions, thus affecting population dynamics.