According to the World Wildlife Fund (WWF), there are about 18 species of penguins, and the majority of them are in the Southern Hemisphere. The only penguins found north of the equator are the Galapagos penguins and the African penguins. African penguins are currently classified as endangered. The largest living species is the Emperor penguin, which can grow to about 3 feet and 7 inches tall and could attain a weight of up to 77 pounds. The smallest is the tiny blue penguins of Australia and New Zealand who attain a height of about 16 inches and weigh about 2.2 pounds. Although penguins are birds, they have flippers instead of wings, and they cannot fly. While on land, the penguins waddle by walking upright and occasionally when the conditions are right on the snow, they slide on their bellies. Inside water penguins are remarkable swimmers, and some species can attain speeds of up to 15 miles per hour. Most of the penguins living in the extreme cold climate of Antarctica have particular adaptations that have enabled them to survive in these harsh environments.
Penguins have a layer of fat beneath the skin, which helps them keep warm, and it also serves as a source of energy. Although the penguins have feathers that give warmth when they dive into the water to swim, they have an added advantage of the fat layer. Therefore one of the primary defenses against cold, particularly in water is the fat deposit that lies under their skin. Up to 30% of the penguin’s body is fat.
However, when penguins are on land, the feathers play a significant role in keeping the penguins warm. Penguins have unique fathers that differ from the feathers of other birds. Their feathers are short, and they also have an underlayer that appears like wool. Their feathers are also unique in that they are the best in shedding water, especially after the penguins emerge from swimming. These feathers are also arranged in an overlapping manner to give a better-streamlined effect when they are inside the water and an excellent wind shedding capability when they are outside water. The arrangement of feathers creates a surface that is almost impermeable to water or wind. These waterproof feathers are critical to the survival of penguins when they are in the water, where temperatures in the Antarctic reach as low as 28 degrees F, and hardly go above 35.6 degrees F. Penguins also have a unique behavior of puffing their feathers when it becomes frigid, and this is an ingenious way of trapping more air to offer better insulation. When it becomes hot, the penguins often fluff their feathers out to drive the warm air and allow the cold air to enter and therefore cool the body. The penguins have the highest density of feathers per unit area compared to other birds. The air trapped by the feathers accounts for 80% to 84% of the penguins’ thermal insulation. When penguins dive into the water, the compressed air trapped in their feathers can only dissipate if they prolong their dive. The penguins, like other birds, can rearrange their feathers by preening.
Penguins' Posture Helps Minimize Heat Loss
The penguins’ posture is an adaptive trait to minimize loss of body heat. The penguins do not only stand upright on their feet, but they also rock backward on heels and hold their feet up to minimize contact with the ground. They support themselves with the stiff tail feathers, which does not have blood flow. Even when they are nesting, they hold the egg between their feet and tip-up their feet. Lying on snow would expose a large surface area of the body and eventually losing more body heat.
Feet And The Flippers
The feet and the flippers are the only parts of the penguins which are poorly insulated. Although this may seem to be a problem because body heat is lost through these parts, they play a critical role in helping the penguin to cool down when they use much energy and generating excess heat. Both the flippers and the feet are controlled by tendons attached to bones of the wrist, ankle, and toes. This mechanism works like a remote operation using a string or a wire. Therefore the feet and the flippers can still be operated as usual even if they become are excessively cold.
Penguins, like all other animals living in extreme environments, have a rete mirabile, which is a mesh of blood capillaries and blood veins lying close to each other. The blood coming to the feet, which are significantly warmer than the blood leaving the feet, flow past each other exchanging heat. The same process happens in the flippers. The blood in the flippers and feet are always cold compared to blood in other parts of the body. The same blood is warmed up by the time it re-enters other parts of the body. The feet of the penguins can never get below freezing point because the flow of blood is finely tuned so that they are always above that point. When the temperatures are deep low or when they are in the sea, the flow of blood to the flippers and feet is minimized to conserve body heat.
Penguins Huddle Together
Penguins also huddle together in large numbers to keep themselves warm, which is also an ingenious way to conserve energy. According to scientists, a solitary penguin in a hostile environment like Antarctica could burn as much as 200 grams of fat every day to stay alive and keep warm, but when they huddle together each would only need to burn about 100 grams each day. Chick penguins also huddle together for warmth when the parent penguins leave them behind as they go fishing for food. Without huddling, penguins would not be able to breed during winter. As much as 6,000 emperor penguins can huddle together, and they are the species inhabiting the southernmost regions.
Adelie penguins are the second most southerly species after the emperor penguins. The engage in seasonal migration breeding in the far south and migrate northward following the onset of winter. In early summer, they migrate south again to take advantage of the abundance of food.