Overview

A dewlap is a flap or fold of skin that projects beneath the throat of an animal. The term is used broadly: in reptiles and amphibians it often denotes a colorful display structure, in birds and mammals it can mean a fleshy wattle or caruncle, and in casual human description it may refer to a double chin. Different authors and fields sometimes use related words such as wattle, gular pouch, or caruncle for similar structures; see the terminology section below for distinctions.

Structure and occurrence

Dewlaps vary in size, shape and composition. In many lizards the dewlap is an extendable, often pigmented skin flap supported by cartilage or musculature. In birds and some mammals the feature is a fleshy outgrowth composed of skin and connective tissue. Dewlaps appear in a wide range of animals, including domestic cattle and zebu breeds, some breeds of rabbits, turkeys and other birds, and anole and iguana lizards. See examples in comparative anatomy here.

Functions and behavior

Dewlaps commonly serve as visual or acoustic signals. In many lizards they are used during courtship and territorial displays: males display a brightly colored dewlap to attract mates or warn rivals. In birds and mammals the structure can signal health, hormonal status or breeding condition. Dewlaps may also assist in thermoregulation by increasing surface area for heat exchange, and in some species provide material used in nesting; for example, a female rabbit’s dewlap can supply loose fur for lining a nest when she is ready to breed (breeding cues).

Examples and notable cases

  • Anole lizards: males have extendable, often brightly colored dewlaps used for species recognition and courtship — see a general review on display traits.
  • Domestic cattle and zebu: pronounced dewlaps are common and sometimes associated with heat tolerance; they also differ by breed (breed traits).
  • Birds and turkeys: fleshy throat protuberances called caruncles or wattles are functionally similar and used in display (avian caruncles).

Distinctions and terminology

Wattle, dewlap, gular pouch and caruncle overlap in meaning but often carry technical nuances: "wattle" usually refers to loose skin on the throat of birds, "gular" to throat regions, and "caruncle" to small fleshy excrescences. In frogs the term dewlap sometimes describes a vocal sac used to amplify calls; for a discussion of amphibian vocal sacs see amphibian anatomy. For further reading and resources consult general references on animal morphology and signaling here.