Licking
Encyclopedia
Licking is the action of passing the tongue
over a surface, typically either to deposit saliva
onto the surface, or to collect liquid onto the tongue for ingestion
, or to provide pleasure. Many animals both groom
themselves and drink
by licking.
Licking is a common way for animals to clean themselves. In mammal
s, licking helps keep the fur
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
s, clean their eye
s by licking them.
Mammals typically lick their offspring clean immediately after birth
; in many species this is necessary to free the newborn from the amniotic sac
. The licking not only cleans and dries the offspring's fur, but also stimulates its breathing and digestive
processes.
Some animals, such as cat
s, also use licking to cool themselves. As cats do not sweat
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 sucking
, 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
like shape.
Hummingbird
s 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 smell
. By licking a surface, molecules on it are transferred via the tongue to the olfactory receptors in the nose
and in the vomeronasal organ
.
Dogs and cats use licking both to clean, and to show affection among themselves or to humans typically licking their faces.
Cattle, horses and other animals lick rocks, salt licks or other objects to obtain mineral nutrients.
Compared to most other mammals, licking has a minor role for human
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
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 dishware and cutlery
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 cream
cone and a lollipop
.
Some people in the Afar
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.
There are a number of other uses for licking in humans. For example, licking can be used to moisten the adhesive
surfaces of stamp
s or envelope
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 sewing
, thread
ends are commonly wet by licking to make the fibres stick together and thus make threading them through the eye of a needle
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 purposes, such as during cunnilingus
, and whilst french kissing, where two people lick each others tongues.
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
over a surface, typically either to deposit saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
onto the surface, or to collect liquid onto the tongue for ingestion
Ingestion
Ingestion 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
Personal grooming is the art of cleaning, grooming, and maintaining parts of the body. It is a species-typical behavior that is controlled by neural circuits in the brain.- In humans :...
themselves and drink
Drinking
Drinking is the act of consuming water or a beverage through the mouth. Water is required for many of life’s physiological processes. Both excessive and inadequate water intake are associated with health problems.-Physiology:...
by licking.
Licking in animals
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s, licking helps keep the fur
Fur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives 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 animal...
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
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....
s, clean their eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s by licking them.
Mammals typically lick their offspring clean immediately after birth
Birth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...
; in many species this is necessary to free the newborn from the amniotic sac
Amniotic sac
The amniotic sac is the sac in which the fetus develops in amniotes. It is a tough but thin transparent pair of membranes, which hold a developing embryo until shortly before birth. The inner membrane, the amnion, contains the amniotic fluid and the fetus. The outer membrane, the Chorion,...
. The licking not only cleans and dries the offspring's fur, but also stimulates its breathing and digestive
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....
processes.
Some animals, such as cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, also use licking to cool themselves. As cats do not sweat
Sweating
Perspiration 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.
Suction
Suction 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 spoon
Spoon
A 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.
Hummingbird
Hummingbird
Hummingbirds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm range. Indeed, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They can hover in mid-air by rapidly flapping their wings...
s 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 smell
Olfaction
Olfaction is 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 nose
Nose
Anatomically, 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. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes through the pharynx, shared with the...
and in the vomeronasal organ
Vomeronasal organ
The vomeronasal organ , or Jacobson's organ, is an auxiliary olfactory sense organ that is found in many animals. It was discovered by Frederik Ruysch and later 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.
Cattle, horses and other animals lick rocks, salt licks or other objects to obtain mineral nutrients.
Licking in humans
Human
Humans are the only living species in the Homo genus...
s. The human tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
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
Suction 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 dishware and cutlery
Cutlery
Cutlery 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 cream
Ice cream
Ice cream is a frozen dessert usually made from dairy products, such as milk and cream, and often combined with fruits or other ingredients and flavours. Most varieties contain sugar, although some are made with other sweeteners...
cone and a lollipop
Lollipop
A 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...
.
Some people in the Afar
Afar
Afar may refer to:*Afar people, ethnic group principally residing in Djibouti, Eritrea and Ethiopia*Afar Insurgency, alternative name for the Djiboutian Civil War of November 1991-December 1994*Afar Triangle, a geological depression near the Horn of Africa...
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.
There are a number of other uses for licking in humans. For example, licking can be used to moisten the adhesive
Adhesive
An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...
surfaces of stamp
Postage stamp
A postage stamp is a small piece of paper that is purchased and displayed on an item of mail as evidence of payment of postage. Typically, stamps are made from special paper, with a national designation and denomination on the face, and a gum adhesive on the reverse side...
s or envelope
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....
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 sewing
Sewing
Sewing is the craft of fastening or attaching objects using stitches made with a needle and thread. Sewing is one of the oldest of the textile arts, arising in the Paleolithic era...
, thread
Yarn
Yarn is a long continuous length of interlocked fibres, 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 needle
Sewing needle
A 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 18K gold plated for corrosion resistance. The highest quality embroidery needles are plated with two-thirds platinum and...
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 purposes, such as during cunnilingus
Cunnilingus
Cunnilingus is an oral sex act performed on a female. It involves the use by a sex partner of the mouth, lips and tongue to stimulate the female's clitoris, vulva, or vagina...
, and whilst french kissing, where two people lick each others tongues.
Other primates
- Ring-tailed lemurs use licking as a social function, licking each other's babies 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:
- lick objects, such as dead trees, that others in their community have licked
- lick body parts of others for grooming and sex
- lick rocks for salt
- Gorillas use licking in addition other senses to determine the nature of an object