An infrared thermographic study of surface temperature in relation to external thermal stress in the Mongolian gerbil, Meriones unguiculatus.

1. Temperatures of different body surface regions and deep body temperature (Tb) of unrestrained adult Mongolia gerbils exposed to ambient temperatures (Ta) of -10-35 degrees C were measured using infrared (i.r.) thermography and a thermocouple. 2. A strong positive linear relationship between the surface temperature and Ta was found. For Ta range -4-35 degrees C, the slope was lowest for the areas around the eyes and dorsal head, and steepest for the body extremities. At -10 degrees C, surface temperatures of the areas around the eyes and dorsal head were significantly lower then predicted. 3. Tb was lowest at Ta of 25 and 30 degrees C, increased at all temperatures above and up to Ta of -4 degrees C below this range, and began decline at -10 degrees C. 4. The thermoneutral zone (TNZ) is probably between 28 and 32 degrees C, and the absolute lower critical temperature (Tabsl) is probably -4 degrees C. 5. The Mongolian gerbil shows little control of surface temperature and in contrast to larger mammals it has not developed any special thermoregulatory surface areas to regulate heat exchange with its environment. At temperatures below -4 degrees C, this species is unable to maintain the surface temperature of body extremities above the freezing point. 6. It is suggested that the Mongolian gerbil uses mainly behavioral and ecological adaptive strategies to attenuate the stressful effects of its habitat.