Food quality affects search strategy in the acellular slime mould, Physarum polycephalum

When searching for resources, organisms can increase the efficiency of search and exploitation behavior by using information about the quality of a current resource patch in their decision making. The search strategy used by an organism can in turn affect its performance in different landscapes. Here we examine the effect of resource quality on 2 foraging decisions: how much time to allocate to explore the environment for new resources and what search strategy to use during exploration. We used the slime mould Physarum polycephalum as our model system. Physarum polycephalum is an amoeboid organism that forages as a flowing mass of pseudopods. We quantified the search pattern of plasmodia after engulfment of food of 6 different qualities. Food quality had a significant, positive effect on how long plasmodia waited before resuming search behavior and on how long it took to abandon food disks. Food quality had a positive effect on fractal dimension, indicating that the amount of localized search performed by plasmodia increased with food quality. Our results suggest that increasing food quality results in a shift from extensive to intensive search. Next, we examined foraging performance in landscapes with different patch structures. Plasmodia in correlated landscapes (half the patches contained only high-quality food, half contained only low-quality food) gained more weight than plasmodia foraging in noncorrelated landscapes (patches contained both high- and low-quality food disks). Our results show that food quality affects exploitation and search behavior and that both behaviors influence foraging performance in different landscapes.