Penguins fascinate, delight and amuse with their imperious demeanour and waddling walks. Though not all penguins live in the extreme cold, the ones that do have had to adapt. They cannot, for instance, allow their bodies to cool down. They lose mobility if this happens. And in the frigid Antarctic, lying out in the sun to warm up is just not an option. The penguin's bodies and behaviours present various ways of staying warm.
One advantage the penguin has is its relatively large size, for a bird. Emperor penguins, for instance, reach adult weights of up to 29.9kg. The smallest of the Antarctic penguins, the rockhopper, can itself reach an adult weight of over 2.27kg. Larger animals lose less surface heat and are able to retain their internal temperature more easily.
Penguins carry their own internal insulation in their bodies. Under the feathers and skin is a layer of fat that keeps the penguin warm. The fat layer insulation is particularly valuable when the penguin is swimming in cold water, where the penguin spends much of its time. The penguin's feathers also serve a purpose. When cold, they fluff their short feathers out to trap air for better insulation. When they are overheated, they fluff their feathers to shoo out trapped warm air. Heat and cooling exchanges between the penguin's flippers and feet and the rest of the body also aid in regulating temperature.
Penguins also stay warm by making sure that as little as possible of its large body touches the ice or snow. It does this by staying upright and rocking back on its heels, keeping the toes above the ice. Its tail feathers rest on the ice and provide balance, but not a way for heat to escape. In this position, the only warm-blooded part of the penguin touching the ice are its two small heels.
When the temperatures are really extreme and there is a biting wind, penguins get in a huddle. This huddle is sometimes made up of thousands of penguins sharing their body heat. Though most of those inside the huddle are shielded from the wind, those on the outer edges are most exposed. Penguins have solved this problem by rotating from time to time. Those on the perimeter come inward and others rotate out to take the brunt of the cold and winds. This cooperation keeps the penguins warm using far less energy than would be required of one penguin alone.