Sci. Rep. 8, 713 (2018)

How much space does a lab mouse need? Guidelines exist, but empirical results are limited and often ambiguous. Jeremy Bailoo, Hanno Würbel and colleagues at the University of Bern in Switzerland recently investigated. Using a fully factorial design, the team tested combinations of sex (male and female), strain (C57BL/6ByJ and BALB/cByJ), floor area (370, 820, and 2400 cm2) and group size (3, 5, and 8 mice per cage) against a variety of welfare measures, including growth, stress physiology, emotionality, brain function, and home cage behavior. With the exception of male aggression, which was negatively impacted by increasing group size, the space allowances tested did not appear to have a significant impact on welfare-related outcomes, or at least the measures chosen for the current study.