Digging and marble burying in mice: simple methods for in vivo identification of biological impacts.

Mice exhibit various species-typical behaviors such as digging and burrowing. They dig in the ground to find food, to hoard food, to create a refuge from predators or cold and to make a safe nursery area for the young. In the laboratory, mice dig vigorously in deep bedding such as wood chips. This behavior is sensitive to strain differences and drugs. For example, the effects of anxiolytics and 5-HT-active compounds, including those used clinically for obsessive-compulsive disorder (OCD), can be detected. Digging can be quantified by manual timing. Alternatively, the bedding can be covered with glass marbles and the number buried can be counted after a set time. These behaviors can be assessed using very little specialized equipment, and results can be obtained from ten animals in about an hour. Species-typical behaviors may be sensitive to a wide variety of treatments, and their simplicity and ability to yield robust quantitative data might be particularly useful in assessing genetically modified mice, even in laboratories not primarily oriented to behavioral work.