Thermoregulation of the Japanese macaque living in a snowy mountain area.

A field investigation was conducted to study the thermoregulatory responses in nine Japanese macaques (Macaca fuscata) living in a snowy mountain area, Jigoku-Dani (Hell Valley, about 1,000 m above sea level) in Shiga Heights in central Japan in late January 1975. At about the same time, a laboratory study was made on four Japanese macaques reared in mild climate in an outdoor cage in Inuyama City. In the Hell Valley (HV) monkeys, no significant change in metabolic rate was observed at Ta between -1.4 and 28.3 degrees C, while the rectal temperature was maintained at normal level. In the cold environment, the skin temperatures of HV monkeys were significantly higher than those of the monkeys living indoors previously studied. Similar patterns of metabolic and thermal responses were observed in Inuyama monkeys living outdoors, but to a lesser degree. The hair on the back and abdomen in the HV monkeys was significantly longer than that of Iuyama monkeys living indoors. It is suggested that the thick fur of HV monkeys may account for, if not all, the thermoregulatory responses of the Japanese macaque in snowy mountain areas.