Abstract
Mice are increasingly used in research. In particular, their wheel running is often used as a measure of activity, and as a marker of phase of circadian rhythms. Learning about the preferences of mice for different types of wheel may improve their welfare and suggest ways of increasing activity levels. Mice, Mus musculus, were given a choice between different types of running wheel by putting them in cages equipped with two wheels. Strong preferences were shown for wheels with a plastic mesh flooring, rather than the standard metal rods only. The mesh was even preferred over a solid base, although this effect was not seen in mice that had been given access only to wheels with the solid base immediately prior to the choice test. Small diameter wheels, sometimes sold as mouse wheels, were preferred less than standardsized wheels with rods. The results suggest that types of running wheel often used in laboratories can be improved by considering the animals' preferences. The types of wheel tested here are easy to maintain and entail little additional cost, while increasing the mouse's interest in running and exercise.