A dewlap is a longitudinal flap of

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

or similar flesh that hangs beneath the

lower jaw In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

neck The neck is the part of the body in many vertebrates that connects the head to the torso. It supports the weight of the head and protects the nerves that transmit sensory and motor information between the brain and the rest of the body. Addition ...

of many

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

s. More loosely, it can be various similar structures in the neck area, such as those caused by a double chin or the submandibular vocal sac of a

frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...

. More generally, it can be any hanging mass of skin, such as a fold of loose skin on an elderly

person A person (: people or persons, depending on context) is a being who has certain capacities or attributes such as reason, morality, consciousness or self-consciousness, and being a part of a culturally established form of social relations suc ...

's neck, or the wattle of a

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

. Dewlaps can be considered as a ''caruncle'', defined as "a small, fleshy excrescence that is a normal part of an animal's anatomy".

Etymology

The word is first attested in the mid 1300s as ''dewelappe'' ("fold of skin that hangs from the throat of oxen and kine"), from ''lappe'' ("loose piece", from

Old English Old English ( or , or ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the Early Middle Ages. It developed from the languages brought to Great Britain by Anglo-S ...

), but the first element ''*dew(e)-'' is of nebulous origin and meaning; it probably was altered by

folk etymology Folk etymology – also known as (generative) popular etymology, analogical reformation, (morphological) reanalysis and etymological reinterpretation – is a change in a word or phrase resulting from the replacement of an unfamiliar form by a mo ...

with "

dew Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening due to condensation. As the exposed surface cools by thermal radiation, radiating its heat, atmospheric moisture condenses at a rate grea ...

". Old English had ''fræt-læppa'' in the aforementioned sense (and

Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman Conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old English pe ...

''fresh-lappe''). There also seems to be a

cognate In historical linguistics, cognates or lexical cognates are sets of words that have been inherited in direct descent from an etymological ancestor in a common parent language. Because language change can have radical effects on both the s ...

to Danish dialectal ("flap of skin that sweeps dew from grass, especially on the neck of an ox"), but this might be a parallel independent development. From the 1580s onward, it was applied to the fleshy fold or wattle of a

turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...

and also to a flaccid, elderly human throat.

Mammals

Many mammals such as dogs,

rabbit Rabbits are small mammals in the family Leporidae (which also includes the hares), which is in the order Lagomorpha (which also includes pikas). They are familiar throughout the world as a small herbivore, a prey animal, a domesticated ...

s and

moose The moose (: 'moose'; used in North America) or elk (: 'elk' or 'elks'; used in Eurasia) (''Alces alces'') is the world's tallest, largest and heaviest extant species of deer and the only species in the genus ''Alces''. It is also the tal ...

possess dewlaps. In

zebu The zebu (; ''Bos indicus''), also known as indicine cattle and humped cattle, is a species or subspecies of Bos taurus, domestic cattle originating in South Asia. Zebu, like many Sanga cattle breeds, differs from taurine cattle by a fatty hump ...

cattle, the dewlap is colloquially known as the "briefcase folds". The dewlap is also seen in both sexes of

. The giant eland and

common eland The common eland (''Taurotragus oryx''), also known as the southern eland or eland antelope, is a large savannah and plains antelope found in East Africa, East and Southern Africa. An adult male is around tall at the shoulder and can weigh up ...

both have skin flaps to aide in thermoregulation. Due to its high surface area to volume ratio, it may allow for efficient thermoregulation in larger common elands with larger dewlaps.

Rabbits

In rabbits, the dewlap is a

secondary sex characteristic A secondary sex characteristic is a physical characteristic of an organism that is related to or derived from its sex, but not directly part of its reproductive system. In humans, these characteristics typically start to appear during pubert ...

female An organism's sex is female ( symbol: ♀) if it produces the ovum (egg cell), the type of gamete (sex cell) that fuses with the male gamete (sperm cell) during sexual reproduction. A female has larger gametes than a male. Females and ...

rabbits which grows once the doe reaches sexual maturity. In laboratory conditions, when a butyl alcohol extract of the urine of

pregnant Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...

women was administered to male rabbits, they developed a dewlap, which then gradually disappeared once the administration ceased. If a female rabbit is ovarectomized before reaching maturity, the dewlap never develops, and even when an ovarectomy is performed on a mature female rabbit with a dewlap, the dewlap disappears gradually afterwards. Near the end of pregnancy, the female rabbit will pluck fur from the dewlap to line a nest for her young.

Reptiles and birds

Many reptiles have dewlaps, most notably the

anole Dactyloidae are a family of lizards commonly known as anoles (singular anole ) and native to warmer parts of the Americas, ranging from southeastern United States to Paraguay. Instead of treating it as a family, some authorities prefer to treat ...

family and

Sitana ''Sitana'' is a genus of lizards, collectively known as the fan-throated lizards, in the family Agamidae. They are found in Nepal, India, Sri Lanka, and Pakistan. The genus comprises fourteen species, including several recently discovered ones, t ...

genus of

lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...

s, which have large skin dewlaps they can extend and retract. The anole family has been found to have enhanced vision for color and depth perception. This family is able to see dewlap coloration from a distance, giving the dewlap use and importance. These dewlaps are usually of a different color from the rest of their body and, when enlarged, make the lizard seem much bigger than it really is. The dewlap is primarily used when indicating territorial boundaries and for males to attract females during the mating season. The pigments generating this color are

pterin Pterin is a heterocyclic compound composed of a pteridine ring system, with a " keto group" (a lactam) and an amino group on positions 4 and 2 respectively. It is structurally related to the parent bicyclic heterocycle called pteridine. Pter ...

s and

carotenoid Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...

s. These two pigments are the most easily seen through the anole's eyes. Pterin and carotenoid pigments are located throughout the tissue of the dewlap, creating yellow and red hues. Lizards usually accompany dewlap movement with head bobs and other displays. The dewlap moves through extension and contraction. The muscles creating this movement are the ceratohyoid muscles and are connected to the hyoid apparatus in the throat and larynx area. Though the purpose of these displays is unclear, the colors of the dewlap and the movements during the displays are thought to be a way of standing out against visual background noise. Iguana Dewlap Labeled

Many birds also have dewlaps, including domestic chickens, some cracids and some guans.

References

External links