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

Summary

Adelie penguins (Pygoscelis adeliae) experience a wide range of ambient temperatures (T _a) in their natural habitat. We examined body temperature (T _b), oxygen consumption ($\dot V_{{\text{O}}_2 }$), carbon dioxide production ($\dot V_{{\text{CO}}_2 }$), evaporative water loss ($\dot m_{{\text{H}}_2 {\text{O}}}$), and ventilation atT _a from −20 to 30 °C. Body temperature did not change significantly between −20 and 20°C (meanT _b=39.3°C).T _b increased slightly to 40.1 °C atT _a=30°C. Both$\dot V_{{\text{O}}_2 }$ and$\dot V_{{\text{CO}}_2 }$ were constant and minimal atT _a between −10 and 20°C, with only minor increases at −20 and 30°C. The minimal$\dot V_{{\text{O}}_2 }$ 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 allT _a. Values of$\dot m_{{\text{H}}_2 {\text{O}}}$ were low at lowT _a, but increased to 0.21 g/min at 30°C, equivalent to 0.3% of body mass/h. Dry conductance increased 3.5-fold between −20 and 30°C. Evaporative heat loss (EHL) comprised about 5% of MHP at lowT _a, rising to 47% of MHP atT _a=30°C. The means of ventilation parameters (tidal volume [VT], respiration frequency [f], minute volume [I], and oxygen extraction [${\text{E}}_{{\text{O}}_{\text{2}} }$]) were fairly stable between −20 and 10°C (VT did not change significantly over the entireT _a range). However, there was considerable inter- and intra-individual variation in ventilation patterns. AtT _a=20–30°C,f increased 7-fold over the minimal value of 7.6 breaths/min, and I showed a similar change.${\text{E}}_{{\text{O}}_{\text{2}} }$ fell from 28–35% at lowT _a to 6% atT _a=30°C.