AWI recently attended the annual meeting of the American Association for Laboratory Animal Science (AALAS) in Baltimore—the largest meeting on laboratory animals in the United States. At this year’s meeting, several presentations focused on solving the issue of aggression in group-housed mice. Group-housing of social species has important animal welfare benefits, but it can also be associated with aggression. Researchers from Stanford University and the Swedish University of Agricultural Sciences, who studied the factors that contribute to aggressive behavior in group-housed mice, found that aggression is higher in mice housed on corncob bedding compared to aspen chip bedding. This is an important finding, because corncob bedding is widely used across North American research institutions. Previous research has shown that corncob bedding is also associated with other welfare concerns, such as lower sleep quality in rats. Housing mice on bedding other than corncob may not only lead to better group cohesion—it may also help them (and caretakers) sleep better.