A wattle is a fleshy, often pendulous growth or fold of skin that hangs from the head or neck of an animal. This specialized anatomical feature is found across various species and is part of a broader category of fleshy outgrowths known as caruncles. While the term is most accurately applied to specific biological structures in animals, it is also used colloquially to describe a similar-looking feature in humans. The wattle’s exact composition and function vary significantly depending on the species possessing it.
The Anatomical Structure in Birds
In avian species, the wattle is a type of caruncle, which is a fleshy, often unfeathered outgrowth of skin. The structure is highly vascularized, meaning it contains a dense network of blood vessels near the surface, and it typically hangs below the chin or from the sides of the throat. A true wattle is generally a paired structure, with one on each side of the head or neck. When an animal possesses a single, unpaired flap of skin beneath the throat, it is often more accurately termed a dewlap.
The wattle must be distinguished from other caruncles found on a bird’s head, such as the comb (a fleshy crest on the top of the head) and the snood (an appendage that hangs over the beak, notably seen in turkeys). Wattles are sometimes composed of erectile tissue, allowing them to engorge with blood and change size or color rapidly. They are primarily characterized by their bare skin, though they can sometimes be partially covered with small feathers.
Diverse Biological Functions
The presence of wattles and similar structures like dewlaps serves multiple biological purposes across birds, reptiles, and some mammals.
Sexual Selection
One of the most common functions is in sexual selection and mating displays. The color and size of the wattle are indicators of the animal’s health, nutritional status, and high testosterone levels, signaling genetic quality to potential mates. For instance, a brighter red color in a bird’s wattle often correlates with superior immune function and overall vigor.
Thermoregulation
The structures are also employed for thermoregulation, particularly in animals that live in warm environments or have a large body mass. The highly vascularized, bare surface area allows blood flowing through it to cool more efficiently before returning to the body’s core. This heat dissipation mechanism is thought to be a primary function in very large animals, such as certain species of antelope, where a low surface-area-to-volume ratio makes internal cooling difficult.
Territorial Defense
A third function is in territorial defense and social signaling, where the structure is used for intimidation. Animals like iguanas and anole lizards will extend a dewlap as part of a territorial display to appear larger and more threatening to rivals. The rapid changes in size and color possible in these appendages make them effective nonverbal communication tools during both male-male competition and courtship rituals.
Distinguishing the Human Reference
When the term “neck wattle” is used in reference to humans, it is a colloquial expression for what is medically known as submental fullness or a double chin. This feature is not a specialized caruncle like those found in birds or lizards, but rather a collection of fat and loose soft tissue in the submental triangle beneath the chin. The anatomical composition involves the accumulation of fat in the subcutaneous compartment, which is situated directly beneath the skin, and sometimes in the deeper subplatysmal compartment.
The appearance of this fullness is often compounded by the laxity of the platysma muscle, a thin sheet of muscle in the neck, and a low position of the hyoid bone. These factors collectively contribute to a blunting of the cervico-mental angle, which is the defined line between the neck and the chin. Therefore, the human reference is a descriptor for an aesthetic contour change, whereas the animal wattle is a genetically determined, functional organ.