Nesting behavior of house mice (Mus domesticus) selected for increased wheel-running activity

Nest building was measured in "active" (housed with access to running wheel s) and "sedentary" (without wheel access) mice (Mus domesticus) from four r eplicate lines selected for 10 generations for high voluntary wheel-running behavior, and from four randombred control lines. Based on previous studie s of mice bidirectionally selected for thermoregulatory nest building, it w as hypothesized that nest building would show a negative correlated respons e to selection on wheel-running. Such a response could constrain the evolut ion of high voluntary activity because nesting has also been shown to be po sitively genetically correlated with successful production of weaned pups. With wheel access, selected mice of both sexes built significantly smaller nests than did control mice. Without wheel access, selected females also bu ilt significantly smaller nests than did control females, but only when bod y mass was excluded from the statistical model, suggesting that body mass m ediated this correlated response to selection. Total distance run and mean running speed on wheels was significantly higher in selected mice than in c ontrols, but no differences in amount of time spent running were measured, indicating a complex cause of the response of nesting to selection for volu ntary wheel running.