Olfactory Disruption Restructures Collective Behavior and Increases Cohesive Group Dynamics

Olfaction plays a central role in mammalian social behavior, yet its contribution to group coordination remains poorly understood. Here, we show that olfactory impairment in adult C57BL/6J mice (Mus musculus) leads to the spontaneous emergence of structured group behavior not observed in controls. Mice with disrupted olfactory input consistently engaged in close-contact interactions that increased over time. We quantified these events and found that aggregation occurred significantly more often than expected by chance, with olfaction-impaired mice exhibiting coordinated dyadic, triadic, and quartet configurations that were spatially enriched, temporally stable, and showed consistent patterns of progression between the states. Unsupervised behavioral modeling revealed that these formations were preceded by structured approach and stationing behaviors. Our findings suggest that olfactory input is a key contributor to maintaining typical social dynamics, and that its absence may lead to altered patterns of group interaction potentially driven by reduced sensory input. This work positions olfaction as a key scaffold for social structure and offers a novel framework for understanding how animals adapt to sensory loss in complex group settings.