Thermoregulation, gas exchange, and ventilation in Adelie penguins (Pygoscelis adeliae)

Adelie penguins (Pygoscelis adeliae) experience a wide range of ambient temperatures (Ta) in their natural habitat. We examined body temperature (Tb), oxygen consumption (VO2), carbon dioxide production (VCO2), evaporative water loss (mH2O), and ventilation at Ta from -20 to 30 degrees C. Body temperature did not change significantly between -20 and 20 degrees C (mean Tb = 39.3 degrees C). Tb increased slightly to 40.1 degrees C at Ta = 30 degrees C. Both VO2 and VCO2 were constant and minimal at Ta between -10 and 20 degrees C, with only minor increases at -20 and 30 degrees C. The minimal VO2 of adult penguins (mean mass 4.007 kg) was 0.0112 ml/[g.min], equivalent to a metabolic heat production (MHP) of 14.9 Watt. The respiratory exchange ratio was approximately 0.7 at all Ta. Values of mH2O were low at low Ta, but increased to 0.21 g/min at 30 degrees C, equivalent to 0.3% of body mass/h. Dry conductance increased 3.5-fold between -20 and 30 degrees C. Evaporative heat loss (EHL) comprised about 5% of MHP at low Ta, rising to 47% of MHP at Ta = 30 degrees C. The means of ventilation parameters (tidal volume [VT], respiration frequency [f], minute volume [VI], and oxygen extraction [EO2]) were fairly stable between -20 and 10 degrees C (VT did not change significantly over the entire Ta range). However, there was considerable inter- and intra-individual variation in ventilation patterns. At Ta = 20-30 degrees C, f increased 7-fold over the minimal value of 7.6 breaths/min, and VI showed a similar change.(ABSTRACT TRUNCATED AT 250 WORDS)