Temperature gradients in the legs of cold-acclimatized pheasants

Abstract

Ring-necked pheasants were kept outdoors throughout the year. Cloacal and subcutaneous leg temperatures were taken in January, February, and June. In cold-adapted birds the temperature averaged 37.5 C in the muscular, feather-covered region of the thigh. Within a distance of 2 cm below the termination of muscle and feathers the average subcutaneous temperature dropped to 9.7 C, and in the toe to 2.7 C. A more gradual fall in leg temperatures was found in summer. The leg vasculature was injected with latex and macro- and microstructure were observed. The preparations disclosed an extensive venous network surrounding the artery in the thigh, and a much reduced network in the lower leg. Anatomically the vasculature was similar to countercurrent heat-exchanger structures found in other animals. It was concluded that heat production and insulation accounted for the warm thigh, and that vasoconstriction and heat exchange between venous and arterial blood explained the steep temperature gradients in the legs of cold-adapted birds.