BOILY, P.; KNIGHT, F.M.*; Univ. New Orleans, LA; Univ. of the Ozarks, AR: Adaptive significance of cold induced fever

When exposed to cold temperatures, some mammals, notably the nine-banded armadillo (Dasypus novemcinctus) and the Siberian hamster (Phodopus sungorus), exhibit an increase in core temperature that is proportional to the intensity of the cold stimulus i.e. colder air temperatures result in higher core temperatures. This response is incompatible with the typical negative-feedback mechanisms of temperature regulation in mammals where an increase in core temperature inhibits heat production, resulting in a core temperature that cannot exceed the thermoneutral value during cold exposure. Furthermore, this response appears maladaptive because it increases the animal�s rate of heat loss by increasing the thermal gradient between the animal�s core and its environment. Using theoretical heat transfer calculations combined with preliminary empirical measurements of body temperatures and metabolic rates, we examined the energetic consequences of this response as well as its potential impact on the ability to survive severe cold exposure. The results indicate that cold-induced fever can be energetically costly but may allow the nine-banded armadillo and Siberian hamster to survive severe cold exposure by increasing peak metabolic rates, which leads to a decrease in their lower lethal temperature.