Effects of partial cage dividers on animal welfare and social behavior in California mice (Peromyscus californicus).

California mice (Peromyscus californicus) are an important model species for studying social behaviors that are not readily expressed in standard laboratory mouse and rat lines. Under natural conditions, this species is highly territorial, and both males and females exhibit high levels of aggression in laboratory conditions. Like other rodent species, fighting among cage-mates can create animal welfare problems for California mice. Here we tested whether the use of partial cage dividers could reduce the impact of cage-mate fighting in California mice. Partial cage dividers were made of polycarbonate and extended approximately halfway down the center of the cage. Dividers allowed individual mice to move throughout the cage and created additional complexity that may allow individuals to avoid one another. For California mice raised without dividers, males were significantly more likely than females to have tail wounds. There was a non-significant trend for a lower probability of tail wounds in male California mice raised with dividers versus control males without dividers. Effects of dividers were more evident on approach to a novel object and social approach, two behaviors that are stress sensitive. Females raised with dividers approached an empty cage more than control animals, whereas this difference was not significant in males. Dividers also reduced effects of stress on social approach in females but not males. Overall, our results suggest that raising California mice with partial cage dividers has anxiolytic effects on behavior and can have beneficial effects on animal welfare, especially for males.