Mortality (percentage of mice that died during the study).

Sexes are combined. aFor details of floor space for each density group, see Table 1. Mortality did not differ significantly among density groups, but it did differ among strains.雌雄个体合并统计。 ① 各密度组的饲养空间详情见表1。 不同密度组间的死亡率无显著差异，但不同品系间的死亡率存在显著差异。