Heat exchange by the pinna of the African elephant (Loxodonta africana).

1. Surface temperatures of the pinnae of four female African elephants were measured at ambient temperatures between 14 and 32 degrees C using infrared thermography. Instantaneous heat losses calculated using those values ranged from 10.67 to 76.2 W under the observed conditions. 2. Using a value of 17 kcal/kg/day, those heat losses account for 0.65-4.64% of the animals' standard metabolic rates, considering one side of one ear only. 3. A model of heat flow across a flat vertical plate was constructed and compared to the actual values. Up to 100% of an African elephant's heat loss needs can be met by movement of its pinnae and by vasodilation. 4. Thermography indicates that the temperature distribution pattern across the pinna changes with ambient temperature and that areas of specialized motor control exist.