Trap-response heterogeneity of house mice (Mus musculus) in outdoor enclosures

We studied extrinsic and intrinsic factors affecting trap-response heteroge neity in house mice (Mus musculus) in eight 0.1-ha outdoor enclosures. Chan ges in density did not significantly affect proportions of mice captured. O verall, greater proportions of males than females were captured. Adults wer e captured more often than subadults, and subadults were captured more ofte n than juveniles. Extrinsic factors including relative humidity, temperatur e, and decreased vegetative cover affected proportions of mice captured for various age and sex classes. Two measures of individual trap-response hete rogeneity were used: percentage of times an individual could have been capt ured that it actually was and mean number of trap sessions between captures . Significant yearly variation occurred in both measures. Trap response het erogeneity among sexes did not emerge until the mice were subadults or adul ts. There was significant yearly variation in proportions of recruits enter ing traps as juveniles, subadults, or both. Our findings indicate that ther e is substantial intrinsic heterogeneity, modified by external factors, in capture rates of the house mouse. Data collected to assess population size, survival rates, home range, and other life-history characteristics collect ed by live trapping warrant cautious interpretation.