Emperor penguins spend most of their time in the water, coming to the shore to breed. There is nothing on the ice to make a nest, so after the female lays her one egg in winter, the male puts the egg on his feet to keep it warm until spring. This can be from 65 to 75 days. He has a special fold of skin on his stomach which can fold over and cover the egg to keep it warm. This is a difficult action to swap the egg from the female to the male; if it sits for too long on the ice it will freeze. He does not eat during this time, and can lose up to half his weight. To keep warm, all the male penguins huddle together. Those on the outside of the group will slowly shuffle their way into the middle; the group is always moving and can move as much as in 24 hours. The female comes back in spring when the egg hatches, while the male will go back to sea to eat, but comes back to help look after the chick. The chick lives on its parents feet for about 50 days until it becomes strong enough to survive the cold.