<b><i>Bacillus subtilis</i></b><b> modifies scatter-hoarding behavior by regulating gut </b><b><i>Akkermansia muciniphila</i></b><b>-mediated spatial memory in squirrels</b>

The gut-brain axis mediates communication between the gut microbiota and cognitive function, but its role in complex, ecologically relevant behaviors remains poorly understood. Here, we demonstrate that the probiotic <i>Bacillus subtilis</i> enhances scatter-hoarding—a spatial memory-dependent foraging behavior—in rodents by acting as an ecological engineer of the gut microbiome. Supplementation with <i>B. subtilis</i> in Pallas’ squirrels (<i>Callosciurus erythraeus</i>) significantly increased scatter-hoarding intensity, an effect associated with a marked enrichment of the gut commensal <i>Akkermansia muciniphila</i>. This microbial shift elevated cecal levels of short-chain fatty acids, including hexanoate, and increased serum tryptophan. In the mouse model, direct <i>A. muciniphila</i> oral gavage improved spatial memory and activated hippocampal pathways for synaptic plasticity, such as long-term potentiation and glutamatergic signaling. Our findings reveal a novel gut-brain pathway wherein <i>B. subtilis</i> promotes cognitive performance via <i>A. muciniphila</i>, suggesting that microbiome-mediated enhancement of spatial memory may underlie adaptive foraging strategies in wild rodents, with potential implications for cognitive health and probiotic therapeutics.