Standard metabolism and thermoregulation in a prosimian Perodicticus potto

Abstract o 1. The standard metabolic rate of the potto has been measured under various conditions and found about 45 per cent below the “normal” value. 2. Colonic temperature was recorded between 0 and 40°C T a. 3. In the neutral thermal zone 25–29°C it is variable but approximately 2–3°C lower than in other monkeys. 4. This arboreal tropical animal is cold hardy. It is very well insulated and its conductance remains stable between 25 and 0°C T a but at 10°C T a it may behave like an heterotherm. 5. Although the potto does not shiver the heat production increases 2·36 times between 25 and 5°C T a. 6. At high ambient temperature, the oxygen consumption rises, the conductance doubles, evaporative heat losses—mainly by panting—are inadequate and T co rises. 7. Despite some deficiencies the thermoregulation can hardly be called “primitive”.