The Weights of Wild House Mice (Mus Musculus L.) Living in Confined Colonies

Wild house mice supplied with excess food and confined in pens rapidly became grossly overcrowded. The mean body weights at specified ages of mice born when overcrowding was acute have been compared with those of mice born earlier, in order to test the hypothesis that overcrowding depresses body weight. In three of the four pens studied the more crowded animals were lighter, but in the fourth they were heavier. There is evidence of great inherent variability in body weight in the species.