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===Adaptations to cold=== | ===Adaptations to cold=== | ||
The emperor penguin breeds in the coldest environment of any bird species; air temperatures may reach −40 °C (−40 °F), and wind speeds may reach 144 km/h (89 mph). Water temperature is a frigid −1.8 °C (28.8 °F), which is much lower than the emperor penguin's average body temperature of 39 °C (102 °F). The species has adapted in several ways to counteract heat loss.[24] Feathers provide 80–90% of its insulation, and it has a layer of sub-dermal fat which may be up to 3 cm (1.2 in) thick before breeding. This resultant blubber layer impedes the mobility of emperor penguins on land compared to their less fat-insulated cousins, the Magellanic penguins.[26] While the density of contour feathers is approximately 9 per square centimeter (58 per square inch), a combination of dense afterfeathers and down feathers (plumules) likely | The emperor penguin breeds in the coldest environment of any bird species; air temperatures may reach −40 °C (−40 °F), and wind speeds may reach 144 km/h (89 mph). Water temperature is a frigid −1.8 °C (28.8 °F), which is much lower than the emperor penguin's average body temperature of 39 °C (102 °F). The species has adapted in several ways to counteract heat loss.[24] Feathers provide 80–90% of its insulation, and it has a layer of sub-dermal fat which may be up to 3 cm (1.2 in) thick before breeding. This resultant blubber layer impedes the mobility of emperor penguins on land compared to their less fat-insulated cousins, the Magellanic penguins.[26] While the density of contour feathers is approximately 9 per square centimeter (58 per square inch), a combination of dense afterfeathers and down feathers (plumules) likely plays a critical role for insulation. Muscles allow the feathers to be held erect on land, reducing heat loss by trapping a layer of air next to the skin. Conversely, the plumage is flattened in water, thus waterproofing the skin and the downy underlayer. Preening is vital in facilitating insulation and in keeping the plumage oily and water-repellent. | ||
The emperor penguin is able to thermoregulate (maintain its core body temperature) without altering its metabolism, over a wide range of temperatures. Known as the thermoneutral range, this extends from −10 to 20 °C (14 to 68 °F). Below this temperature range, its metabolic rate increases significantly, although an individual can maintain its core temperature from 38.0 °C (100.4 °F) down to −47 °C (−53 °F). Movement by swimming, walking, and shivering are three mechanisms for increasing metabolism; a fourth process involves an increase in the breakdown of fats by enzymes, which is induced by the hormone glucagon. At temperatures above 20 °C (68 °F), an emperor penguin may become agitated as its body temperature and metabolic rate rise to increase heat loss. Raising its wings and exposing the undersides increases the exposure of its body surface to the air by 16%, facilitating further heat loss. | The emperor penguin is able to thermoregulate (maintain its core body temperature) without altering its metabolism, over a wide range of temperatures. Known as the thermoneutral range, this extends from −10 to 20 °C (14 to 68 °F). Below this temperature range, its metabolic rate increases significantly, although an individual can maintain its core temperature from 38.0 °C (100.4 °F) down to −47 °C (−53 °F). Movement by swimming, walking, and shivering are three mechanisms for increasing metabolism; a fourth process involves an increase in the breakdown of fats by enzymes, which is induced by the hormone glucagon. At temperatures above 20 °C (68 °F), an emperor penguin may become agitated as its body temperature and metabolic rate rise to increase heat loss. Raising its wings and exposing the undersides increases the exposure of its body surface to the air by 16%, facilitating further heat loss. | ||