Body Adaptions That Retain Heat

• Penguins have several adaptions that keep them warm in the frozen tundra of the Antarctica. Penguins have a torpedo-shaped body with a large amount of fat below the skin. These birds also have a special circulatory system in their feet and legs to restrict warm blood to the feet and wings. This system can keep the feet at a temperature as low as 42F, while the penguin's main body stays at about 102F. This process reduces the amount of heat loss in winter, but the penguin can also reverse this process to stay cool during warmer weather. Penguins also have a special heat exchange system in their nasal passages to recover heat lost from breathing and respiration.
  
  

Techniques Used to Stay Warm

• To stay warm in the frigid waters, the penguins' bodies must use more energy, so their metabolic rate is raised when swimming or diving. On land, they utilize different techniques, like huddling, to stay warm while staying still. Penguins retain heat by huddling in groups, sometimes up to ten penguins per a square yard. The penguins in the center of the huddle are the warmest. However, the "windbreakers" alternate so each penguin has a turn at being in the center.
  
  

Growing a Feather Layer

• For penguin chicks, their initial feathers are quite sparse. They do not require heavy insulation, since they are shielded by the adults in their early days, and these light feathers aid in heat transfer. At the end of the brood period, they start to grow heavier and better-insulating feathers. When the adults go out to look for food, the chicks start to grow a thicker and fluffier feather layer. While this layer provides better insulation, it is not waterproof, since these small penguins are not ready to swim. When the chicks mature and can maintain their own body temperature, they eventually grow the waterproof feathers, just like the adult penguins.
  
  

Molting and the Importance of Feathers

• For adult penguins, their worn-out feathers must be renewed every year. Molting is a two- to four-week period for all adult penguins when new feathers replace the old ones. During this period, the penguins experience greater levels of heat loss and use a lot of energy. They must stay on land during molting, since their coat is not fully waterproof until all the new feathers come in. The penguins must fast during molting since they cannot bring food from the sea. They usually undergo an intense feeding period before the molting to increase their fat reserves.
  
  When the penguins are on land, they use their muscles in their feathers to tightly hold their feathers close to their skin. This technique produces a layer of warm air to insulate against the cold winds. The feathers of an adult penguin also have tufts of down on the main shaft to provide extra insulation.