AJP - Regulatory, Integrative and Comparative Physiology, Vol 240, Issue 3 156-R165, Copyright © 1981 by American Physiological Society
Thermoregulation in the only nocturnal simian: the night monkey Aotus trivirgatus
Y. Le Maho, M. Goffart, A. Rochas, H. Felbabel and J. Chatonnet
The night monkey, a tropical monkey, is the only nocturnal simian; its
thermoregulation was studied for comparison with other nocturnal or diurnal
primates and other tropical mammals. Resting metabolic rate was 2.6 W
(closed-circuit method) and 2.8 W (open-circuit method), 24 and 18% below
the value predicted from body mass. The thermoneutral zone was very narrow;
the lower critical temperature (LCT) was 28 degrees C and the upper
critical temperature (UCT) was 30 degrees C. The body temperature (Tb) was
at its minimum (38 degrees C) at an ambient temperature (Ta) of 25 degrees
C, thus below the LCT. At low Ta, the increase in metabolic rate (MR) was
smaller than predicted by the Scholander model, since MR intersected to a
Ta 13 degrees C above Tb when extrapolated to MR = 0; this was attributed
to a decrease of body surface area by behavior. The thermal conductance at
the LCT was low: 2.3 W . m-2 . degrees C-1. Above the UCT, panting was the
major avenue of heat loss. The response pattern of nocturnal habits, low
resting metabolic rate, low thermal conductance, and panting in the night
monkey, unique among simians, is found in many other mammals of tropical
and hot desert habitats; it may be considered as an alternative adaptation
to the thermal environment.
