Roberto Refinetti published an article in the Journal of Thermal Biology titled “Circadian rhythms of body temperature and locomotor activity in the antelope ground squirrel, Ammospermophilus leucurus.”
The article studied the behavior and body temperature of a squirrel species that lives in the Owyhee desert. The antelope ground squirrels are active during the day and unlike other close relatives, do not hibernate. However, their body temperature oscillates on a daily basis, rising during daily activity and decreasing by as much as 4.6 degrees Celsius while resting at night.
However, this body temperature rhythm persisted in period of 24 hours of continuous darkness. Through the study, Refinetti found evidence that although muscular heat production associated with physical movement can affect body temperature, the cyclical nature of the squirrels’ body temperature is not simply a consequence of the circadian rhythm of activity.