Behavioral thermoregulatory responses of single- and group-housed mice

The ambient temperature (T-a) to house and study laboratory rodents is critical for nearly all biomedical studies. The ideal T-a for housing rodents and other animals should be based on their thermoregulatory requirements. However, fundamental information on the behavioral thermoregulatory responses of single- and group-housed rodents is meager. To address this issue, thermoregulatory behavior was assessed in individual and groups of CD-1 mice housed in a temperature gradient. Mice were housed in groups of five or individually while selected T-a and motor activity were monitored. Single- and group-housed mice displayed a circadian oscillation of selected T-a and motor activity with relatively warm T(a)s Of similar to 29 degrees C selected during 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 similar for single- and group-housed animals. The operative T-a of mice housed in standard facilities was estimated by measuring the cooling rate of "phantom" mice modeled from aluminum cylinders. The results show that the typical housing conditions for single- and group-housed mice are cooler than their T-a for ideal thermal comfort. (C) 1998 Elsevier Science Inc.