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Licking is the
action Action may refer to: * Action (narrative), a literary mode * Action fiction, a type of genre fiction * Action game, a genre of video game Film * Action film, a genre of film * ''Action'' (1921 film), a film by John Ford * ''Action'' (1980 fil ...
of passing the
tongue The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...
over a surface, typically either to deposit
saliva Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be ...
onto the surface, or to collect liquid, food or minerals onto the tongue for
ingestion Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in a substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms ingest ...
, or to communicate with other animals. Many animals both groom themselves and
eat Eating (also known as consuming) is the ingestion of food, typically to provide a heterotrophic organism with energy and to allow for growth. Animals and other heterotrophs must eat in order to survive — carnivores eat other animals, herbi ...
or
drink A drink or beverage is a liquid intended for human consumption. In addition to their basic function of satisfying thirst, drinks play important roles in human culture. Common types of drinks include plain drinking water, milk, juice, smoothies a ...
by licking.


In animals

Grooming: Animals commonly clean themselves through licking. In
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s, licking helps keep the
fur Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket t ...
clean and untangled. The tongues of many mammals have a rough upper surface that acts like a brush when the animal licks its fur. Certain reptiles, such as
gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates throughout the world. They range from . Geckos ar ...
s, clean their
eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...
s by licking them. Mammals typically lick their offspring clean immediately after
birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...
; in many species this is necessary to free the newborn from the
amniotic sac The amniotic sac, also called the bag of waters or the membranes, is the sac in which the embryo and later fetus develops in amniotes. It is a thin but tough transparent pair of membranes that hold a developing embryo (and later fetus) until shor ...
. The licking not only cleans and dries the offspring's fur, but also stimulates its
breath Breathing (or ventilation) is the process of moving air into and from the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxygen. All aerobic creatures need oxygen for cellular ...
ing and digestive processes. Food and water acquisition:
Hummingbird Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With about 361 species and 113 genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropics aro ...
s are often said to "sip" nectar, but in fact they up nectar on their long tongues. Their tongues have fringed edges, which help both in nectar-eating and in catching tiny insects. Mother hummingbirds also lick their chicks after a rainstorm to dry them by licking water droplets from the coats of the chicks to avoid them chilling. Many animals drink by licking. While young mammals drink milk from their mothers' teats by
sucking Suction is the colloquial term to describe the air pressure differential between areas. Removing air from a space results in a pressure differential. Suction pressure is therefore limited by external air pressure. Even a perfect vacuum cannot ...
, the typical method of drinking for adult mammals involves dipping the tongue repeatedly into water and using it to scoop water into the mouth. This method of drinking relies in part on the water adhering to the surface of the tongue and in part on muscular control of the tongue to form it into a
spoon A spoon is a utensil consisting of a shallow bowl (also known as a head), oval or round, at the end of a handle. A type of cutlery (sometimes called flatware in the United States), especially as part of a place setting, it is used primarily for ...
like shape. Cattle, horses and other animals lick rocks, salt licks or other objects to obtain mineral nutrients. Gustation: Animals also use their tongues to enhance their sense of
smell Smell may refer to; * Odor, airborne molecules perceived as a scent or aroma * Sense of smell, the scent also known scientifically as olfaction * "Smells" (''Bottom''), an episode of ''Bottom'' * The Smell, a music venue in Los Angeles, Californ ...
. By licking a surface or extending the tongue beyond the mouth, molecules are transferred via the tongue to the olfactory receptors in the
nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes th ...
and in some animals, to the
vomeronasal organ The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory (smell) sense organ located in the soft tissue of the nasal septum, in the nasal cavity just above the roof of the mouth (the hard palate) in various tetrapods. ...
. In some mammals, the tongue is used to "lick" the air during the
flehmen The flehmen response (; from German ''flehmen'', to bare the upper teeth, and Upper Saxon German ''flemmen'', to look spiteful), also called the flehmen position, flehmen reaction, flehmen grimace, flehming, or flehmening, is a behavior in which ...
response to assist transfer of
pheremones A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
. Similarly, snakes use smell to track their prey. They smell by using their
forked tongue A forked tongue is a tongue split into two distinct tines at the tip; this is a feature common to many species of reptiles. Reptiles smell using the tip of their tongue, and a forked tongue allows them to sense from which direction a smell is co ...
s to collect airborne particles, then passing them to the vomeronasal organ. They keep their tongues constantly in motion, sampling particles from the air, ground, and water, analyzing the chemicals found, and determining the presence of prey or predators in the local environment. Communication: Dogs and cats use licking both to clean and to show affection among themselves or to humans, typically licking their faces. Many animals use licking as a submissive or appeasement signal in
dominance hierarchies In biology, a dominance hierarchy (formerly and colloquially called a pecking order) is a type of social hierarchy that arises when members of animal social groups interact, creating a ranking system. A dominant higher-ranking individual is som ...
. Thermoregulation: Some animals use licking to cool themselves. Cats do not
sweat Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals. Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. The eccrine sweat glands are distribut ...
the way humans do and the saliva deposited by licking provides a similar means of
evaporative cooling An evaporative cooler (also known as evaporative air conditioner, swamp cooler, swamp box, desert cooler and wet air cooler) is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning sy ...
. Some animals spread saliva over areas of the body with little or no fur to maximise heat loss. For example,
kangaroo Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern gre ...
s lick their wrists and
rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' ( pack rats), ''Bandicota'' (bandicoot ...
s lick their testicles. Mating behavior: Post-
copulatory Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetrat ...
genital grooming often occurs in male rats and
prosimian Prosimians are a group of primates that includes all living and extinct Strepsirrhini, strepsirrhines (lemurs, Lorisoidea, lorisoids, and Adapiformes, adapiforms), as well as the Haplorhini, haplorhine tarsiers and their extinct relatives, the O ...
primates. This behavior may prevent disease transmission.


In primates

Ring-tailed lemurs lick each other's babies as a means of collective grooming and of reinforcing social cohesion within the community. Macaques and other primates lick leaves for water in addition to dipping their arms into tree crevices and licking the water off. Chimpanzees use licking in a variety of ways: licking objects, such as dead trees, that others in their community have licked,楽天が運営するポータルサイト : 【インフォシーク】Infoseek
. Mahale.web.infoseek.co.jp (2000-01-01). Retrieved on 2013-03-30.
licking each other's body parts for grooming and sex and licking rocks for salt. Gorillas use licking in addition to other senses to determine the nature of an object.


In humans

Compared to most other mammals, licking has a minor role for
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s. The human tongue is relatively short and inflexible, and is not well adapted for either grooming or drinking. Instead, humans prefer to wash themselves using their hands and drink by
sucking Suction is the colloquial term to describe the air pressure differential between areas. Removing air from a space results in a pressure differential. Suction pressure is therefore limited by external air pressure. Even a perfect vacuum cannot ...
or pouring fluid into their mouth. Humans have much less hair over their skin than most other mammals, and much of that hair is in places which they cannot reach with their own mouth. The presence of
sweat glands Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial sur ...
all over the human body makes licking as a cooling method unnecessary. Nonetheless, licking does play a role for humans. Even though humans cannot effectively drink water by licking, the human tongue is quite sufficient for licking more
viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inter ...
fluids. Some foods are sold in a form intended to be consumed mainly by licking, e.g.
ice cream Ice cream is a sweetened frozen food typically eaten as a snack or dessert. It may be made from milk or cream and is flavoured with a sweetener, either sugar or an alternative, and a spice, such as cocoa or vanilla, or with fruit such as str ...
cones and
lollipop A lollipop is a type of sugar candy usually consisting of hard candy mounted on a stick and intended for sucking or licking. Different informal terms are used in different places, including lolly, sucker, sticky-pop, etc. Lollipops are availa ...
s. Though useful, in some cultures it is considered improper
table manners Table manners are the rules of etiquette used while eating, which may also include the use of utensils. Different cultures observe different rules for table manners. Each family or group sets its own standards for how strictly these rules are ...
to clean one's fingers by licking during a meal. Some people in the
Afar Afar may refer to: Peoples and languages *Afar language, an East Cushitic language *Afar people, an ethnic group of Djibouti, Eritrea, and Ethiopia Places Horn of Africa *Afar Desert or Danakil Desert, a desert in Ethiopia *Afar Region, a region ...
tribe of Ethiopia have been reported to have used their tongues to lick other humans, as a way of cleaning them from the dust that accumulates on them in a very water-scarce region. Humans use licking for a number of other purposes. For example, licking can moisten the
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...
surfaces of
stamp Stamp or Stamps or Stamping may refer to: Official documents and related impressions * Postage stamp, used to indicate prepayment of fees for public mail * Ration stamp, indicating the right to rationed goods * Revenue stamp, used on documents to ...
s or
envelope An envelope is a common packaging item, usually made of thin, flat material. It is designed to contain a flat object, such as a letter or card. Traditional envelopes are made from sheets of paper cut to one of three shapes: a rhombus, a shor ...
s. Many people lick a fingertip (usually the one of the
index finger The index finger (also referred to as forefinger, first finger, second finger, pointer finger, trigger finger, digitus secundus, digitus II, and many other terms) is the second digit of a human hand. It is located between the thumb and the mid ...
) for some extra grip when turning a page, taking a sheet of paper from the top of a pile or opening a plastic bag. In
sewing Sewing is the craft of fastening or attaching objects using stitches made with a sewing needle and thread. Sewing is one of the oldest of the textile arts, arising in the Paleolithic era. Before the invention of spinning yarn or weaving fabr ...
, thread ends are commonly wet by licking to make the
fibre Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...
s stick together and thus make threading them through the eye of a
needle Needle may refer to: Crafting * Crochet needle, a tool for making loops in thread or yarn * Knitting needle, a tool for knitting, not as sharp as a sewing needle * Sewing needle, a long slender tool with a pointed tip * Trussing needle, a long sl ...
easier. Another practice considered uncivilized is licking one's hand and using it to groom one's hair. Humans also use their tongues for
sexual Sex is the biological distinction of an organism between male and female. Sex or SEX may also refer to: Biology and behaviour *Animal sexual behaviour **Copulation (zoology) **Human sexual activity **Non-penetrative sex, or sexual outercourse ** ...
purposes, such as during
cunnilingus Cunnilingus is an oral sex act performed by a person on the vulva or vagina of another person. The clitoris is the most sexually sensitive part of the human female genitalia, and its stimulation may result in a woman becoming sexually aroused ...
,
anilingus Anilingus (from the Latin ''anus'' + ''-lingus'', from ''lingere'', "to lick", variantly spelled "analingus") is the oral and anal sex act in which a person stimulates the anus of another by using the mouth, including lips, tongue, or teeth. I ...
, foot licking, and whilst
French kiss A French kiss, also known as cataglottism or a tongue kiss, is an amorous kiss in which the participants' tongues extend to touch each other's lips or tongue. A kiss with the tongue stimulates the partner's lips, tongue and mouth, which are sens ...
ing, where two people lick each other's tongues.


Abnormal licking

Self-licking can sometimes become abnormally frequent occasionally resulting in a
lick granuloma A lick granuloma, also known as acral lick dermatitis, is a skin disorder found most commonly in dogs, but also in cats. In dogs, it results typically from the dog's urge to lick the lower portion of one of their legs. The lesion can initially be ...
. The most common cause of lick granuloma appears to be psychological, related to stress, anxiety,
separation anxiety Separation anxiety disorder (SAD) is an anxiety disorder in which an individual experiences excessive anxiety regarding separation from home and/or from people to whom the individual has a strong emotional attachment (e.g., a parent, caregiver ...
, boredom, or compulsiveness. Lick granulomae are especially seen in active dogs left alone for long periods of time. One theory is that excessive licking causes
endorphin Endorphins (contracted from endogenous morphine) are chemical signals in the brain that block the perception of pain and increase feelings of wellbeing. They are produced and stored in an area of the brain known as the pituitary gland. Hist ...
release, which reduces pain and makes the dog feel temporarily
euphoric Euphoria ( ) is the experience (or affect) of pleasure or excitement and intense feelings of well-being and happiness. Certain natural rewards and social activities, such as aerobic exercise, laughter, listening to or making music and da ...
. This provides the animal with positive feedback from the licking, and subsequent addiction to the behaviour. Animals in captivity sometimes develop a licking
stereotypy A stereotypy (, or ) is a repetitive or ritualistic movement, posture, or utterance. Stereotypies may be simple movements such as body rocking, or complex, such as self-caressing, crossing and uncrossing of legs, and marching in place. They are ...
during which surfaces (walls, bars, gates, etc.) are repeatedly licked for no apparent reason. This has been observed in captive giraffes and camels.Video of a giraffe licking wall


Gallery

File:Real love!! (4294586131) (2).jpg, Wolves licking to indicate social status File:Cleaning (2876339550).jpg, A domestic cat licking its paw during grooming File:Sumatratiger-004.jpg, A tiger "licking" the air during the flehmen response File:Puerto Rican boa snake with tongue shown epicrates inornatus.jpg, A snake licking a leaf to detect prey


References

{{reflist


External links


Grooming in cats

Hummingbird Licking Behavior

Mice Licking Responses to Sweeteners





Video of a giraffe licking a wall
Eating behaviors Ethology Saliva Tongue Hygiene Animal communication Mating