Inhibition of the lateral hypothalamus emboldens adult female spiny mice to huddle with an established group of novel peers.

Animals of large group-living species that exhibit dispersal or have overlapping territories with other groups frequently encounter novel conspecifics. To avoid injury, successfully obtain a mate, integrate into a new group, and/or to determine one's social rank, it is crucial to accurately assess social information. The lateral hypothalamus (LH) is critical for learning about food-related cues and shifting behavior toward or away from salient events. While the LH facilitates risk assessment in dyadic social competitions, how the LH modulates social behavior in non-aggressive contexts with novel peers remains unknown. In the highly colonial spiny mouse (Acomys dimidiatus), we used chemogenetics to inhibit the LH of females as they interacted with novel peers in a novel vs. familiar preference test, a group size preference test, and a group interaction test. Although control females were investigative and prosocial (e.g., affiliative proximity), they exhibited significant social avoidance of a novel peer group. However, we found that inhibition of the LH induced a preference for social novelty, decreased social avoidance, and promoted affiliative proximity and huddling with a novel, previously established group of peers. These findings suggest that the LH may function to promote cautious behavior, potentially via risk assessment, in novel social environments.