Foraging actively can be advantageous in heterogeneous environments

A wealth of evidence indicates that behavioural polymorphism is widespread in nature. While some organisms search for food by moving almost continuously throughout their environment, other organisms forage in one place for long periods of time. Although such a dichotomy has been previously documented in Drosophila melanogaster, the question remains which foraging strategy is better suited to maximize energy intake in a particular environment. We designed an experiment to evaluate whether the configuration of food in the environment alters the foraging behaviour of two larval strains. Assuming that one of the strains acquires more food than the other in a given environment, we examined whether variation in growth occurred between them. Our results indicate that foraging behaviour is a plastic trait, shaped by the configuration of food in the environment. Regardless of the foraging strategy, we found that larvae generally increased their locomotion when food was patchy rather than clumped. Even though we observed that some individuals actively sought food while others stayed foraging at nearby sites, we found no differences in growth rate between them. However, we suggest that foraging actively may be advantageous in polymorphic populations because such behaviour facilitates local adaptation via founder effect and gene flow.