Collective sensing in the slime mold Physarum polycephalum

Collective sensing (the enhanced ability of groups to track features of the environment) is one of the most common benefits of group living. Acting as a distributed sensing array, an animal group may access more information from the environment and therefore make improved decisions. While collective sensing has been observed in many social animal species, it is less well understood in non-animals, such as plant roots, fungal networks, and slime molds, where their physical structure and mechanism of information transfer may be quite different than in ‘classic’ collective systems, such as bird flocks and fish schools. Here, we test whether the slime mold Physarum polycephalum benefits from collective sensing by recording samples, varying in size, traveling across a surface containing a chemical gradient. We find that, indeed, the ability to detect and follow the environmental gradient improves with the size of the slime mold. A simulation model of slime mold behavior recapitulates our experimental results. Together, our results shed light on the robustness of collective benefits despite significant differences in the details of the collective systems themselves.