Thermoregulation and heat balance in the dik-dik antelope (Rhynchotragus kirki): a field and laboratory study.

Experiments were conducted in the field to study the physiological responses of dik-dik antelope to direct solar radiation and shade. The results were compared to those obtained in the laboratory. The rates of metabolic heat production when the animals were exposed either to the sun or the shade were identical. Dik-dik antelopes lost about 50% more heat evaporatively when exposed to the sun compared to the shade at an ambient temperature (Ta) of 28 degrees C or a Ta of 40 degrees C in a climatic chamber. Heat storage in the laboratory at Ta 40 degrees C or at Ta 28 degrees C in the shade accounted for between 30 and 35% of the total heat production. The corresponding value in the sun was 55%. The net rate of heat gain under the sun was four times greater than under shade at 28 degrees C or in the laboratory at 40 degrees C. Behavioural mechanisms for avoidance of high insolation must constitute important adaptations that the dik-dik uses to avoid dehydration and dependence on drinking water in their natural environment.