One of the goals of soft robotics is to achieve spontaneous behaviors similar to real organisms. To gain insight into these behaviors, we examined the long (16-hour) spontaneous exploratory locomotion of Tegula nigerrima, an active foraging snail from an intertidal rocky shore. Specifically, we tested the critical brain hypothesis that the nervous system is inherently near a critical state that is self-organized to drive spontaneous animal behavior. The hypothesis was originally proposed for vertebrate species, but may also be applicable to other invertebrate species. We first investigated the power spectra of snail locomotion speed (N=39). The spectra exhibited 1/f^α fluctuations, which are a signature of self-organized criticality. The α value was estimated to be approximately 0.9. We further examined whether the spatial and temporal quantities showed multiple power laws and scaling relations, which are rigorous criteria for criticality. Although these criteria were satisfied over a limited range and provided limited evidence of self-organization, multiple power laws and scaling relations were satisfied overall. These results support the generalizability of the critical brain hypothesis.

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