( od deep body temperature decreased pro...)Huddling and a drop in metabolism allow penguins to survive the South Pole cold

od, deep body temperature decreased progressively from 37.5°C to 36.5°C, associated to a significant temperature drop of 0.5°C during huddling. In case of egg loss, body temperature continued to decrease to 35.5°C, with a further 0.9°C decrease during huddling. By contrast, a constant core temperature of 36.9°C was maintained during successful incubation, even during huddling, suggesting a trade-off between the demands for successful egg incubation and energy savings. The average core temperature measured (36.7°C) was on average 1°C lower than those previously reported for captive emperor penguins during rest within their thermo neutral zone, of about 37.5°C to 38°C. This temperature range corresponds to the core temperature recorded at mid-pairing (from 37.1 to 38.1°C). A core temperature reduction during the pairing period to 36.5°C and a mean core temperature of 36.7°C (when averaged over the entire breeding cycle), may therefore amount to significant energy savings during the breeding cycle of emperor penguins. However, it cannot explain the already observed 25 percent drop in average metabolic rate, which suggests that emperor penguins depress their metabolic rate by 50 percent during half of the time when they are in dense huddles.

Metabolic Rate in Dense Huddles May Become Depressed

The researchers have also found that the ambient temperature in a dense huddle increases up to 35°C. Yet there is no rise in the body temperature of these birds although the body temperature of individuals exposed to only 20°C in the laboratory goes up to 40-41°C. The team believes that a possible explanation for the constancy (or slight decrease) of core temperature inside the dense huddles, in contrast to the expected temperature rise, is the depression of metabolic rate. Such depression could be achieved by entering sleep. In fact, during tight huddles, birds were observed with their eyes closed. It is known that the proportion of sleep increases durin
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Source:American Physiological Society

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