Licking is the action of passing the
tongueThe tongue is a muscle on the floor of the mouth that manipulates food for chewing and swallowing . It is the primary organ of taste, as much of the upper surface of the tongue is covered in papillae and taste buds. A secondary function of the tongue is speech, in which the organ assists...
over a surface, typically either to deposit
salivaSaliva is the watery and usually frothy substance produced in the mouths of humans and most other animals. Saliva is produced in and secreted from the salivary glands...
onto the surface or to collect liquid onto the tongue for
ingestionIngestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking...
or to provide pleasure. Many animals both
groom
Personal grooming is the art of cleaning, grooming, and maintaining parts of the body. In animals, it is a species-typical behavior that is controlled by neural circuits in the brain.- In humans :...
themselves and
drinkDrinking is the act of consuming water through the mouth. Water is required for many of life’s physiological processes...
by licking.
Licking is a common way for animals to clean themselves. In
mammalMammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...
s, licking helps keep the
furFur is a synonym for hair, used more commonly in reference to non-human animals, usually mammals; particularly those with extensive body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to...
clean and untangled. The tongues of many mammals have a rough upper surface that acts like a brush when the animal licks its fur.
Licking is the action of passing the
tongueThe tongue is a muscle on the floor of the mouth that manipulates food for chewing and swallowing . It is the primary organ of taste, as much of the upper surface of the tongue is covered in papillae and taste buds. A secondary function of the tongue is speech, in which the organ assists...
over a surface, typically either to deposit
salivaSaliva is the watery and usually frothy substance produced in the mouths of humans and most other animals. Saliva is produced in and secreted from the salivary glands...
onto the surface or to collect liquid onto the tongue for
ingestionIngestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking...
or to provide pleasure. Many animals both
groom
Personal grooming is the art of cleaning, grooming, and maintaining parts of the body. In animals, it is a species-typical behavior that is controlled by neural circuits in the brain.- In humans :...
themselves and
drinkDrinking is the act of consuming water through the mouth. Water is required for many of life’s physiological processes...
by licking.
Licking in animals
Licking is a common way for animals to clean themselves. In
mammalMammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...
s, licking helps keep the
furFur is a synonym for hair, used more commonly in reference to non-human animals, usually mammals; particularly those with extensive body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to...
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
geckoGeckos are small to average sized lizards belonging to the family Gekkonidae, found in warm climates throughout the world. Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos. An estimated 2,000 different species of geckos exist...
s, clean their
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
s by licking them.
Mammals typically lick their offspring clean immediately after
birthBirth is the act or process of bearing or bringing forth offspring . The offspring is brought forth from the mother...
; in many species this is necessary to free the newborn from the
amniotic sacThe amniotic sac is the sac in which the fetus develops in amniotes. Its wall is the amnion, the inner of the two fetal membranes. It encloses the amniotic cavity and the embryo. The amniotic cavity contains the amniotic fluid...
. The licking not only cleans and dries the offspring's fur, but also stimulates its breathing and
digestiveDigestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be absorbed, for instance, by a blood stream. Digestion is a form of catabolism.that means break down of macro food molecules to smaller one....
processes.
Some animals, such as
catThe cat , also known as the domestic cat or housecat to distinguish it from other felines and felids, is a small carnivorous mammal that is valued by humans for its companionship and its ability to hunt vermin and household pests...
s, also use licking to cool themselves. As cats do not
sweatPerspiration is the production of a fluid, consisting primarily of water as well as various dissolved solids , that is excreted by the sweat glands in the skin of mammals...
the way humans do, the saliva deposited by licking provides a similar means of evaporative cooling
Many animals also drink by licking. While young mammals drink milk from their mothers' teats by
suckingSuction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not...
, 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
spoonA spoon is a utensil consisting of a small shallow bowl, oval or round, at the end of a handle. A type of cutlery , especially as part of a place setting, it is used primarily for serving. Spoons are also used in food preparation to measure, mix, stir and toss ingredients...
like shape.
Hummingbirds are often said to "sip" nectar, but in fact they lap up nectar on their long tongues. Their tongues have fringed edges, which help in both 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 chill.
Animals also use their tongue to enhance their sense of
smellOlfaction refers to the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
. By licking a surface, molecules on it are transferred via the tongue to the olfactory receptors in the
noseAnatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration in conjunction with the mouth....
and in the
vomeronasal organThe vomeronasal organ , or Jacobson's organ, is an auxiliary olfactory sense organ that is found in many animals. It was discovered by Ludwig Jacobson in 1813....
.
Dogs and cats use licking both to clean, and to show affection among themselves or to humans typically licking their faces.
Licking in humans
Compared to most other mammals, licking has a minor role for
humanHumans are bipedal primates belonging to the species Homo sapiens in Hominidae, the great ape family. They are the only surviving member of the genus Homo. Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving...
s. The human
tongueThe tongue is a muscle on the floor of the mouth that manipulates food for chewing and swallowing . It is the primary organ of taste, as much of the upper surface of the tongue is covered in papillae and taste buds. A secondary function of the tongue is speech, in which the organ assists...
(primarily used for speech) 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
suckingSuction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not...
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 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 fluids. The practice of licking
dishwareDishware is the general term for the dishes used in serving, and eating food, including plates and bowls. Dinnerware is a synonym, especially meaning a set of dishes, including serving pieces....
and
cutleryCutlery refers to any hand implement used in preparing, serving, and especially eating food in the Western world. It is more usually known as silverware or flatware in the United States, where cutlery can have the more specific meaning of knives and other cutting instruments. This is probably the...
clean, though often considered uncivilized, is nonetheless quite common. Some foods are sold in a form intended to be consumed mainly by licking, e.g. an
ice creamIce cream or ice-cream is a frozen dessert usually made from dairy products, such as milk and cream, combined with fruits or other ingredients and flavours. Most varieties contain sugar, although some are made with other sweeteners. In some cases, artificial flavourings and colorings are used in...
cone and a
lollipopA lollipop, pop, lolly, sucker, or sticky-pop is a type of confectionery consisting mainly of hardened, flavored sucrose with corn syrup mounted on a stick and intended for sucking or licking. They are available in many flavors and shapes.- Types :Lollipops are available in a number of colors and...
.
There are a number of other uses for licking in humans. For example, licking can be used to moisten the
adhesiveAdhesive or glue is a compound in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. Some modern adhesives are extremely strong, and are becoming increasingly important in modern construction and industry...
surfaces of
stampA postage stamp is adhesive paper evidence of a fee paid for postal services. Usually a small rectangle attached to an envelope, the stamp signifies the person sending it has fully or partly paid for delivery...
s or
envelopeAn envelope is a packaging product, usually made of flat material such as paper or cardboard, and designed to contain a flat object, which in a postal-service context is usually a letter, card or bills. The traditional type is made from a sheet of paper cut to one of three shapes: the rhombus , the...
s. A habit of many people is licking a finger to help turning a page, taking a sheet of paper from the top of a pile or opening a plastic bag. This is often considered unhygienic and it is questioned whether there really is any necessity to do so although the people who do it claim that, for example, in certain situations turning a page is difficult and that it goes much easier after licking the top of the finger used to turn that page for some extra grip. In
sewingSewing or stitching or Tailoring is the fastening of cloth, leather, furs, bark, or other flexible materials, using needle and thread. Its use is nearly universal among human populations and dates back to Paleolithic times...
,
threadYarn is a long continuous length of interlocked fibers, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery and ropemaking. Thread is a type of yarn intended for sewing by hand or machine. Modern manufactured sewing threads may be finished with wax or...
ends are commonly wet by licking to make the fibres stick together and thus make threading them through the eye of a
needleA sewing needle is a long slender tool with a pointed tip. The first needles were made of bone or wood; modern ones are manufactured from high carbon steel wire, nickel- or gold plated for corrosion resistance. The highest quality embroidery needles are made of platinum...
easier. Another practice considered uncivilized is licking one's hand and using it to groom one's hair.
Other primates
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