There is also a layer of soft down close to the skin to keep them warm. Just below the skin is a layer of fat which also provides insulation from the cold. Penguins have short legs which cause them to waddle over land. On snow-covered slopes, they prefer to toboggan on their bellies. They have bluish-grey backs, unlike most penguins which have black backs.
Most species have white undersides.
They use their webbed feet and tails as rudders when swimming and are known to come up out of the water, get air, then dive back under in dolphin-like fashion. Penguins eat small forms of sealife, such as fish and krill, which abound in the waters off the coast of Antarctica. Their predators are mainly seals, and sea birds such as skuas. In breeding season, the female emperor lays an egg and the male puts it on his feet. He then covers it with his brood pouch, which is a flap of abdominal skin used to keep the egg warm until it hatches.