Spatial and social structure of rewilded laboratory mice

As an essential biomedical model organism, house mice have been studied intensely under laboratory conditions, yet they evolved to survive and reproduce in complex and dynamic environments. There has been recent interest in the study of ‘rewilded’ mice reared in complex outdoor environments, particularly for understanding the brain and behavior. Yet little work has examined lab mouse behavior under free-living conditions. Here, we characterize the emergent spatial and social structure of replicated populations of C57BL/6J (C57) mice over 10 days in large outdoor field enclosures and compare them to populations of recently wild-derived outbred house mice under the same conditions. We observed shared aspects of space use and social structure across all trials but found that C57 societies differed from those emerging from outbred mice across multiple dimensions. Males of both genotypes rapidly established and then defended territories. Female C57 mice spent more time with other individuals and explored more space relative to all other groups. These behavioral differences resulted in C57 mice rapidly forming less stable, but more densely connected, social networks than outbred wild-derived mice. These data suggest that laboratory domestication has had larger effects on female mouse social organization than their male counterparts. Importantly, this work demonstrates that C57 mice recapitulate many, but not all, aspects of social structures generated by wild mice in outdoor conditions. Rewilding allows for tractable, replicable, and ecologically realistic approaches to studying mouse behavior and can facilitate the study of the biological basis of higher order social organization. HIGHLIGHTS We describe emergent spatial and social structures of rewilded C57BL/6J (C57) lab mice across replicated trials in outdoor field enclosures and compare them to wild-derived outbred mice Both C57 and outbred males rapidly establish and maintain territories C57 females explore the field enclosures substantially more than any other group With the exception of C57 females, most mice spent the majority of their recorded time alone The resulting societies formed by C57 mice are less modular, more densely connected, and less stable than those formed by wild-derived outbred mice