A comparison of thermoregulatory responses in the japanese macaque (macaca fuscata) and the crabeating macaque (macaca irus) during cold exposure

Abstract

Thermoregulatory responses in four male adult Japanese macaques and four male adult crab-eating macaques, weighing 6-12 kg and 6.2-8 kg, 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±1.7 W/M2; tissue conductance; 11.9±0.8 and 8.9±0.8 W/M2/°; respiratory evaporative heat loss; 4.1±0.3 and 3.2±0.5 W/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. © 1975, PHYSIOLOGICAL SOCIETY OF JAPAN. All rights reserved.