Thermoregulation in Erythrocebus patas: a thermal balance study

A thermal balance study over an ambient temperature (Ta) range of 15-40 degrees C was performed on six nonacclimated patas monkeys (Erythrocebus patas) weighing between 3.9 and 6.0 kg. O2 consumption, CO2 production, mean weighted skin temperature (Tsk), rectal temperature (Tre), respiratory evaporative water loss (Eresp), and total evaporative water loss (Etot) were measured continuously after equilibration at each Ta. Tsk increased as Ta increased, whereas Tre was maintained between 37.6 and 38.4 degrees C at Ta from 15 to 40 degrees C. Total evaporative heat losses increased with increasing Ta to a mean value of 76 W/m2 at 40 degrees C. Eresp was relatively constant and increased from 1.0 to 8.0 W/m2 at 15 and 40 degrees C, respectively. Whole-body conductance was similar to that previously reported for Macaca mulatta except at the highest Ta (40 degrees C), where the values for the patas monkey were significantly lower than those reported for the rhesus monkey (rhesus = 72 W/m2; patas = 33 W/m2). The data demonstrate that the patas monkey can maintain its core temperature within a narrow range over a wide range of Ta values. Additionally, Etot in the patas monkey is significantly higher than what has been reported in other nonhuman primates and approaches that reported in humans.