A wattle is a fleshy caruncle hanging from various parts of the head or neck in several groups of birds and mammals. A caruncle is defined as 'A small, fleshy excrescence that is a normal part of an animal's anatomy'. Within this definition, caruncles in birds include those found on the face, wattles, dewlaps, snoods and earlobes. Wattles are generally paired structures but may occur as a single structure when it is sometimes known as a dewlap. Wattles are frequently organs of sexual dimorphism. In some birds, caruncles are erectile tissue and may or may not have a feather covering.
Wattles are often such a striking morphological characteristic of animals that it features in their common name. For example, the southern and northern cassowary are known as the double-wattled and single-wattled cassowary respectively and there is a breed of domestic pig known as the red wattle.
In birds, wattles are often an ornament for courting potential mates. Large wattles are correlated with high testosterone levels, good nutrition, and the ability to evade predators, which in turn indicates a potentially successful mate. It has also been proposed that ornamental organs such as wattles are associated with genes coding for disease resistance. In umbrellabirds the wattle serves to amplify the birds' call. 
Birds with wattles include:
- From the neck or throat
- Birds of the genus Casuarius: the northern, southern, and dwarf cassowaries
- Galliformes (e.g., wild turkeys, chickens)
- Some vultures
- Some lapwings
- The male of the wattled starling
- Some Australian wattlebirds (Anthochaera spp.)
- The New Zealand wattlebirds (Callaeidae), which include the kokako, tieke or saddleback, and the huia
- The wattled crane (Bugeranus carunculatus)
- From below or around the eyes
Mammals with wattles include:
A common pheasant (Phasianus colchicus) with bright red facial wattles
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- John James Audubon, Dean Amadon, John L Bull. 1967 The Birds of America
- Richard Bowdler Sharpe. 1888. Catalogue of the Birds in the British Museum, British Natural History Museum, Department of Zoology
- Baratti, Mariella; Ammannati, Martina; Magnelli, Claudia; Massolo, Alessandro; Dessì-Fulgheri, Francesco (2010). "Are large wattles related to particular MHC genotypes in the male pheasant?". Genetica. 138: 657–665. doi:10.1007/s10709-010-9440-5.
- The Hutchinson encyclopedia - Page 1087 https://books.google.co.uk/books?isbn=1859862888 (Oxford) Helicon Publishing Ltd, Jane Anson, Michael Broers - 2000 - The Amazonian species Cephalopterus ornatus, the ornate umbrella bird, has an inflatable wattle at the neck to amplify its humming call, and in display elevates a long crest (12 cm/4 in) lying above the bill so that it rises umbrella-like above ...
- Hogan, C. Michael "Wild Turkey: Meleagris gallopavo", GlobalTwitcher.com, ed. N. Stromberg 2008
- John White. 1790. Voyage to New South Wales