Abstract
Thermoregulatory responses in four male adult Japanese macaques and four male adult crab-eating macaques, weighing 6-12kg and 6.2-8kg, respectively, were compared at ambient temperatures (Ta) ranging from 5° to 25°. The average values±S. E. for some physiological measurements made at Ta of 25° in the Japanese macaque and the crab-eating macaque, respectively, were as follows: resting metabolic rate; 47.6±5.0 and 42.5±1.7W/M2; tissue conductance; 11.9±0.8 and 8.9±0.8W/M2/°; respiratory evaporative heat loss; 4.1±0.3 and 3.2±0.5W/M2; rectal temperature; 38.6±0.1 and 37.4±0.2°; mean skin temperature; 34.0±0.3 and 31.2±0.1°. When Ta was lowered stepwise from 25° to 20, 15, 10, and 5° successively, and maintained constant at each temperature level for 1 hr, metabolic heat production gradually increased in both species. When Ta was lowered from 10° to 5°, the crab-eating macaque did not show further increase in heat production and the result was a loss of thermal equilibrium with rectal temperature continuing to fall. On the other hand, the Japanese macaque maintained thermal balance even at Ta of 5°. Tissue conductance, which was significantly higher in the Japanese macaque than in the crab-eating macaque at Ta of 5, 15, and 25°, decreased in both species as Ta was lowered from 25° to 15 and 5°. The specific differences in thermoregulatory responses are considered to be adaptational, relative to the natural habitat of the two species studied. Received
