Body temperature, metabolic rate, and insulation in winter and summer acclimatized mute swans (Cygnus olor)

Abstract

1. Oxygen consumption and body temperature were measured at various ambient temperatures in summer and winter acclimatized mute swans. 2. In summer acclimatized birds the basal metabolic rate was 0.654 ml O2·gs.w.−1·h−1 and the body temperature was 39.5°C. The thermoneutral range extended from 1 to 15°C. Below the lower critical temperature (T1c) the oxygen consumption increased according to the formula: $$\dot V_{O_2 } = 0.665 - 0.014 T_A .$$ 3. In winter acclimatized birds, theT1c was above 5.5°C. In the range of ambient temperatures between −35.0°C and 5.5°C the oxygen consumption was given by the formula: $$\dot V_{O_2 } = 0.931 - 0.007 T_A .$$ 4. At low ambient temperatures the summer acclimatized birds had a significantly lower body temperture, being 39.0°C against 39.7°C in the winter acclimatized birds. 5. During cold exposure at ambient temperatures below theT1c, the winter acclimatized swans continued to rely on reduced conductance for thermal homeostasis, while summer swans similary cold exposed depended primarily on increased heat production, i.e. a metabolic response.