Observations on the prevalence of nest-building in non-breeding TO strain mice and their use of two nesting materials.

The spontaneous performance of nest-building behaviour by non-breeding laboratory mice suggests that routinely providing nesting material might be a suitable environmental enrichment. If nesting material is to be provided routinely, this should have characteristics which are preferred, or at least accepted by a considerable proportion of the animal population; it should also be inexpensive. The present study therefore examined the prevalence of nest-building behaviour in 39 individually-housed, non-breeding, female mice, and their preferences for a commercial nesting product and a less expensive source of material (paper towels). Within minutes of the materials being placed in the cages, the mice began manipulating the paper towels. Thirty-six of the mice subsequently constructed nests during the first dark phase after the materials had been placed in the cage--the remaining three mice constructed nests during the following 48 h. The nests were usually constructed from a mixture of the two materials, though observations indicated the mice might have preferred characteristics of the inexpensive paper towels. There was a strong tendency to build nests in the same location used for sleeping prior to the nesting material being provided, and similarly, the mice were conservative in the site chosen to build a second nest after the first was removed. The most frequently chosen site for nest-building was under the feeder. Other studies have reported a high motivation for nest-building behaviour, widespread performance amongst many strains, and nest-building as a thermoregulatory behaviour by animals housed in standard laboratory air temperature. In conjunction with these findings, the present results suggest that routinely providing paper towels is an inexpensive and practical means of environmental enrichment for non-breeding, laboratory mice.