Strength of preference for nesting material as environmental enrichment for laboratory mice

The present paper describes two experiments in which preferences of laboratory mice for materials which could serve as cage enrichment were investigated. In the first experiment, presence of nesting material (paper towel or tissue) and the presence of a nest box (perforated metal or clear perspex box) were tested against each other. On average, the 47 mice tested spent significantly more time in the cage with the nesting material (more than 69% of their total time, whereas less than 25% of their time in the cage with the nest box). In the second experiment,the preferred nesting material (tissues) was placed in a cage with a grid floor (previously found to be avoided) and the nest box (perforated metal) was placed in another cage, connected to the first, with a solid floor covered with sawdust bedding material. In this experiment, 24 female mice were tested and on average they spent more than 67% of their time in the cage with the nesting material, despite the presence of a grid floor. Thus, it is concluded that providing a cage with nesting material (in addition to bedding) may be essential for the well-being of laboratory mice. (C) 1998 Elsevier Science B.V.