Araki, A. 2010. Using environmental enrichment to reduce fighting in mice. Tech Talk [The Newsletter for Laboratory Animal Science Technicians] 15(4), 6.

A colony of mice (base strain C57Bl6) was transferred to Oregon State University. Fighting was observed in six cages of males (2 to 5 mice per cage) at cage change, but not during daily checks. After discussion with the principal investigator, environmental enrichments were added in an effort to reduce or eliminate aggression. For environmental enrichment, each cage received one mouse igloo (Bio-Serv, Frenchtown, NJ), one Nestlet (Ancare,Bellmore, NY), Enviro-dri (Shepherd Specialty Paper,Hubbard, OR), and a treat at cage change. Giving each cage a Nestlet for environmental enrichment is standard practice at our facility. The igloo was added to provide a visual barrier between cagemates. Initially, each cage received one raisin per mouse. A couple of weeks later, samples of Fruit Crunchies and Supreme Mini-Treats from Bio-Serv (Frenchtown, NJ) were used for treats. Each mouse received one whole treat and one crushed treat. The whole treat served to distract them immediately at cage change. Distraction for a longer period of time was provided by foraging for the crushed treat. After 3 months of this regimen, Enviro-dri was added to the cages. The cages with 3 or more males seemed to receive the greatest benefit from the addition of the Enviro-dri. The Enviro-dri provided the mice with a second nest, which seemed to allow the mice to feel more secure and less inclined to fight. Using all of these enrichments together did not completely eliminate disagreements at cage change, but did significantly reduce fighting. Of all the cages on the enrichment program, only one male had to be separated for aggressive fighting.