Social factors influence solo and rat dyads exploration of an unfamiliar open field.

Exploring new and unfamiliar environments is critical for survival, providing information on food, shelter, mates, and sources of danger. The open field paradigm is commonly used to study exploration and anxiety-like behaviors in the lab. Many social animals, like humans and rats, may explore their environments in social groups; however, relatively few studies have investigated the influence of conspecifics on open field activity. Here, we provide a comparison of individual (solo) or pairs of male rats (dyads) exploring and interacting across repeated exposures to an unfamiliar (Day 1) or more familiar (Day 2) open field. Both solo rats and dyads explored a larger area, traveled further, and spent less time near the maze walls on the second maze exposure. Solo rats explored a larger area and spent less time near the maze walls than dyads on both days because dyads spent more time socializing rather than exploring the environment. Furthermore, we compared familiar dyads that were co-housed for seven days versus stranger dyads that met for the first time in the open field. While familiar and stranger dyads did not differ in maze exploration, strangers spent more time interacting nose to nose than nose to anogenital. These results indicate that the degree of familiarity with the environment does not interact with the tendency of dyads to socialize rather than explore the environment.