Figure 3.

Cumulative number of weaned offspring from inbred (■) and outbred (□) mice in the enclosures. (A) Males. Outbred males produced twice as many young as inbred males during the first 8 weeks of pup production and eight times as many during the last 8 weeks of the experiment (8-week time periods chosen arbitrarily) (n = 265, χ² = 14.7, P < 0.001). (B) Females. There was no significant difference in the reproductive success of inbred and outbred females during the first 8 weeks; however, outbred females produced 1.5 times as many offspring as inbred females during the last 8 weeks of the experiment (n = 521, χ² = 5.2, P < 0.025). Weekly nest checks were stopped from weeks 33 to 38.