[An estimation of comfortable temperature for rats using thermograph (author's transl)]

For estimating optimum environmental temperature accepted as comfortable by rats themselves, we measured tail skin temperatures by thermograph and observed behaviors in adult rats at the room temperatures of 20, 22, 24, 26 and 28 degrees C. The five rats grouped in a plastic cage were inclined to be in a tight squeeze at 20, 22 and 24 degrees C whereas they set themselves separately each other at 28 degrees C. At 26 degrees C, the behaviors of the rats were the intermediate of these two types. The tail skin temperatures of these grouped five rats were kept high and the lowest was 28.5 degrees C at the room temperature of 20 degrees C. On the contrary, the tail skin temperature of the single rat in another same type cage was much lower at the room temperatures of 24 degrees C and lower and reaches to 20 degrees C at the room temperature of 20 degrees C, although it was close to those of grouped rats at 26 degrees C and almost equal to those at 28 degrees C. The inside temperatures of the cage containing five rats were higher than the room temperature but the differences were less than 2 degrees C. At the room temperature of 28 degrees C, both of the single rat and the grouped rats smeared themselves with their saliva to increase heat dissipation. From these results, we considered the ambient temperature range in which a single rat can hold the high tail skin temperature and the salivation is not necessary as the comfortable temperature range for rats.