Behavioral thermoregulatory responses of single- and group-housed mice

The ambient temperature (T-a) to house and study laboratory rodents is crit ical for nearly all biomedical studies. The ideal T-a for housing rodents a nd other animals should be based on their thermoregulatory requirements. Ho wever, fundamental information on the behavioral thermoregulatory responses of single- and group-housed rodents is meager. To address this issue, ther moregulatory behavior was assessed in individual and groups of CD-1 mice ho used in a temperature gradient. Mice were housed in groups of five or indiv idually while selected T-a and motor activity were monitored. Single- and g roup-housed mice displayed a circadian oscillation of selected T-a and moto r activity with relatively warm T(a)s Of similar to 29 degrees C selected d uring the light phase; during the dark phase selected T-a was reduced by 4 degrees C, whereas motor activity increased. Selected T, of aged (11 months old) mice housed individually was similar to 1.0 degrees C warmer than the group-housed mice. Thermal preference of younger mice (2 months old) was s imilar for single- and group-housed animals. The operative T-a of mice hous ed in standard facilities was estimated by measuring the cooling rate of "p hantom" mice modeled from aluminum cylinders. The results show that the typ ical housing conditions for single- and group-housed mice are cooler than t heir T-a for ideal thermal comfort. (C) 1998 Elsevier Science Inc.