Environmental enrichment. The new Shepherd Shack appeals to rodents' natural behavior of nest building. It provides an activity center for mice to climb on, and it can be chewed and shredded to build a nest. In fact, the interior of the Shepherd Shack is a perfect place for a nest. Reduced litter stress. Bedding can be easily changed in the area around the Shack without disturbing the litter inside. Reduced aggression. The Shepherd Shack caters to rodents' natural subterranean instincts. It can actually help reduce aberrant behavior of some of the more aggressive strains while offering mice a safe refuge from their more dominant cage mates. Clean and consistent. Manufactured from unprinted, uncoated white book publisher-grade paper, the Shepherd Shack is extremely clean and consistent. Autoclavable. It is easily autoclaved, and is available irradiated.