Dewlap Dewlap A dewlap is a longitudinal flap of skin that hangs beneath the lower jaw or neck of many vertebrates. While the term is usually used in this specific context, it can also be used to include other structures occurring in the same body area with a similar aspect, such as those caused by a double chin or the submandibular vocal sac of a frog. In a more general manner, the term refers to any pendulous mass of skin, such as a fold of loose skin on an elderly person's neck, or the wattle of a bird. Dewlaps can be
Gular skin other prey while hunting. In cormorants, the gular skin is often colored, contrasting with the otherwise plain black or black-and-white appearance of the bird. This presumably serves some function in social signalling, since the colors become more pronounced in breeding adults. In frigatebirds, the gular skin (or gular sac or throat sac) is used dramatically. During courtship display, the male forces air into the sac, causing it to inflate over a period of 20 minutes into a startling huge red balloon. Because cormorants are closer relatives of gannets and anhingas (which have no prominent gular pouch) than of frigatebirds or