Fig. 1

Timeline beginning at 21 days old. Weekly weights collected at 28–90 days old and 133–180 days old. Behavioral assessments began at 56 days old and continued through 90 days old. Following 42 days of “rest” to age the animals, home cage behavior was recorded and bite wounds counted. At 133 days old, aggression observations served as baseline for the remainder of the study. In a cross-over study design, the cage divider was removed from divided cages or a new divider was introduced to standard cages at 151 days old during a cage change. Both 7 day and 28 day after the removal or introduction of a cage divider were recorded between cage changes