A dewlap is a loose flap of skin that hangs down from the neck or throat of certain animals. If you've ever seen a rooster with that wobbly red pouch under its beak, or a bulldog with wrinkly folds of skin drooping beneath its chin, you've seen a dewlap.

Different animals have dewlaps for different reasons. In cattle and some lizards, the dewlap helps regulate body temperature: when it's hot, blood flows through this extra skin and cools down before circulating back through the body. For other animals, like roosters and iguanas, the dewlap serves as a display feature: males can puff out or shake their dewlaps to look more impressive or to warn rivals away.