Body temperatures of house mice artificially selected for high voluntary wheel-running behavior: repeatability and effect of genetic selection

We studied rectal body temperatures of house mice (Mus domesticus) that had been artificially selected for high voluntary wheel running. 1. At generation 17, mice from the four replicate selected lines ran, on av erage, 2.5-times as many revolutions/day as did mice from the four random-b red control lines. 2. During the day, repeatability of individual differences in body temperat ure measured 4 days apart was low; at night, repeatability was statisticall y significant across three time scales (1 day, 1 week, 2 weeks). 3. During the day, body temperatures of selected and control animals did no t differ; at night, mice from selected lines had higher body temperatures. However, when amount of wheel running immediately prior to measurement was included as a covariate, the difference was no longer statistically signifi cant. Higher body temperatures, associated with increased activity, might enhance locomotor abilities through Q10 effects, increase metabolic rate and food requirements, affect sleep patterns, and alter expression of heat-shock pro teins. (C) 2000 Elsevier Science Ltd. All rights reserved.