“…Indeed, when studying digging and burrowing behavior in laboratory mice, it has been demonstrated that such behaviors persist in cages that already contain extensive burrow networks. However, although digging and burrowing are natural and persistent under laboratory conditions, even in the offspring of captive-bred animals (Adams & Boice, 1981;Weber & Hoekstra, 2009), such behaviors are subject to modification by a number of factors, including preexposure to the burying substrate-which results in decreased, albeit persistent, burrowing activity (Schultz, 1972)-as well as the burying substrate itself, which can influence the number of burying episodes and the overall measurable digging activity (Layne & Ehrhart, 1970;Webster et al, 1981). Furthermore, gross digging behavior can also be influenced by genetics, even in closely related species, which can exhibit notably different burrow architecture and digging activity (Dudek, Adams, Boice, & Abbott, 1983;Layne & Ehrhart, 1970;Weber & Hoekstra, 2009;Webster et al, 1981).…”