Fur

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Like many mammals, grizzly bears are covered in thick fur. GrizzlyBearJeanBeaufort.jpg
Like many mammals, grizzly bears are covered in thick fur.

Fur is a thick growth of hair that covers the skin of almost all 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 that keeps the animal warm. [1]

Contents

The fur of mammals has many uses: protection, sensory purposes, waterproofing, and camouflaging, with the primary usage being thermoregulation. [2] The types of hair include [3] : 99 

Hair length is negligible in thermoregulation, as some tropical mammals, such as sloths, have the same fur length as some arctic mammals but with less insulation; and, conversely, other tropical mammals with short hair have the same insulating value as arctic mammals. The denseness of fur can increase an animal's insulation value, and arctic mammals especially have dense fur; for example, the muskox has guard hairs measuring 30 cm (12 in) as well as a dense underfur, which forms an airtight coat, allowing them to survive in temperatures of −40 °C (−40 °F). [3] : 162–163  Some desert mammals, such as camels, use dense fur to prevent solar heat from reaching their skin, allowing the animal to stay cool; a camel's fur may reach 70 °C (158 °F) in the summer, but the skin stays at 40 °C (104 °F). [3] : 188  Aquatic mammals, conversely, trap air in their fur to conserve heat by keeping the skin dry. [3] : 162–163 

A leopard's disruptively colored coat provides camouflage for this ambush predator. Great male Leopard in South Afrika-JD.JPG
A leopard's disruptively colored coat provides camouflage for this ambush predator.

Mammalian coats are colored for a variety of reasons, the major selective pressures including camouflage, sexual selection, communication, and physiological processes such as temperature regulation. Camouflage is a powerful influence in many mammals, as it helps to conceal individuals from predators or prey. [4] Aposematism, warning off possible predators, is the most likely explanation of the black-and-white pelage of many mammals which are able to defend themselves, such as in the foul-smelling skunk and the powerful and aggressive honey badger. [5] In arctic and subarctic mammals such as the arctic fox (Vulpes lagopus), collared lemming (Dicrostonyx groenlandicus), stoat (Mustela erminea), and snowshoe hare (Lepus americanus), seasonal color change between brown in summer and white in winter is driven largely by camouflage. [6] Differences in female and male coat color may indicate nutrition and hormone levels, important in mate selection. [7] Some arboreal mammals, notably primates and marsupials, have shades of violet, green, or blue skin on parts of their bodies, indicating some distinct advantage in their largely arboreal habitat due to convergent evolution. [8] The green coloration of sloths, however, is the result of a symbiotic relationship with algae. [9] Coat color is sometimes sexually dimorphic, as in many primate species. [10] Coat color may influence the ability to retain heat, depending on how much light is reflected. Mammals with darker colored coats can absorb more heat from solar radiation and stay warmer; some smaller mammals, such as voles, have darker fur in the winter. The white, pigmentless fur of arctic mammals, such as the polar bear, may reflect more solar radiation directly onto the skin. [3] : 166–167  [2]

Opossum fur Opossum fur.jpg
Opossum fur

The term pelage –first known use in English c. 1828 (French, from Middle French, from poil for 'hair', from Old French peilss, from Latin pilus [11] ) –is sometimes used to refer to an animal's complete coat. The term fur is also used to refer to animal pelts that have been processed into leather with their hair still attached. The words fur or furry are also used, more casually, to refer to hair-like growths or formations, particularly when the subject being referred to exhibits a dense coat of fine, soft "hairs". If layered, rather than grown as a single coat, it may consist of short down hairs, long guard hairs, and in some cases, medium awn hairs. Mammals with reduced amounts of fur are often called "naked", as with the naked mole-rat, or "hairless", as with hairless dogs.

An animal with commercially valuable fur is known within the fur industry as a furbearer. [12] The use of fur as clothing or decoration is controversial; animal welfare advocates object to the trapping and killing of wildlife, and the confinement and killing of animals on fur farms.

Composition

Down, awn and guard hairs of a domestic tabby cat Down Awn and guard hairs of cat 2012 11 13 9203r.JPG
Down, awn and guard hairs of a domestic tabby cat

The modern mammalian fur arrangement is known to have occurred as far back as docodonts, haramiyidans and eutriconodonts, with specimens of Castorocauda , Megaconus and Spinolestes preserving compound follicles with both guard hair and underfur.

Fur may consist of three layers, each with a different type of hair.

Down hair

Down hair (also known as underfur, undercoat, underhair or ground hair) is the bottom –or inner –layer, composed of wavy or curly hairs with no straight portions or sharp points. Down hairs, which are also flat, tend to be the shortest and most numerous in the coat. Thermoregulation is the principal function of the down hair, which insulates a layer of dry air next to the skin.

Awn hair

The awn hair can be thought of as a hybrid, bridging the gap between the distinctly different characteristics of down and guard hairs. Awn hairs begin their growth much like guard hairs, but less than halfway to their full length, awn hairs start to grow thin and wavy like down hair. The proximal part of the awn hair assists in thermoregulation (like the down hair), whereas the distal part can shed water (like the guard hair). The awn hair's thin basal portion does not allow the amount of piloerection that the stiffer guard hairs are capable of. Mammals with well-developed down and guard hairs also usually have large numbers of awn hairs, which may even sometimes be the bulk of the visible coat.

Guard hair

Guard hair (overhair [13] ) is the top—or outer—layer of the coat. Guard hairs are longer, generally coarser, and have nearly straight shafts that protrude through the layer of softer down hair. The distal end of the guard hair is the visible layer of most mammal coats. This layer has the most marked pigmentation and gloss, manifesting as coat markings that are adapted for camouflage or display. Guard hair repels water and blocks sunlight, protecting the undercoat and skin in wet or aquatic habitats, and from the sun's ultraviolet radiation. Guard hairs can also reduce the severity of cuts or scratches to the skin. Many mammals, such as the domestic dog and cat, have a pilomotor reflex that raises their guard hairs as part of a threat display when agitated.

Mammals with reduced fur

Computer generated image of wet fur Wet Fur - CGI.jpg
Computer generated image of wet fur

Hair is one of the defining characteristics of mammals; however, several species or breeds have considerably reduced amounts of fur. These are often called "naked"[ citation needed ] or "hairless". [14]

Natural selection

Some mammals naturally have reduced amounts of fur. Some semiaquatic or aquatic mammals such as cetaceans, pinnipeds and hippopotamuses have evolved hairlessness, presumably to reduce resistance through water. The naked mole-rat has evolved hairlessness, perhaps as an adaptation to their subterranean lifestyle. Two of the largest extant terrestrial mammals, the elephant and the rhinoceros, are largely hairless. The hairless bat is mostly hairless but does have short bristly hairs around its neck, on its front toes, and around the throat sac, along with fine hairs on the head and tail membrane. Most hairless animals cannot go in the sun for long periods of time, or stay in the cold for too long. [15] Marsupials are born hairless and grow out fur later in development.

Humans are the only primate species that have undergone significant hair loss. The hairlessness of humans compared to related species may be due to loss of functionality in the pseudogene KRTHAP1 (which helps produce keratin) [16] Although the researchers dated the mutation to 240 000 ya, both the Altai Neandertal and Denisovan peoples possessed the loss-of-function mutation, indicating it is much older. Mutations in the gene HR can lead to complete hair loss, though this is not typical in humans. [17]

Artificial selection

At times, when a hairless domesticated animal is discovered, usually owing to a naturally occurring genetic mutation, humans may intentionally inbreed those hairless individuals and, after multiple generations, artificially create hairless breeds. There are several breeds of hairless cats, perhaps the most commonly known being the Sphynx cat. Similarly, there are some breeds of hairless dogs. Other examples of artificially selected hairless animals include the hairless guinea-pig, nude mouse, and the hairless rat.

Use in clothing

Fur has long served as a source of clothing for humans, including Neanderthals. Historically, it was worn for its insulating quality, with aesthetics becoming a factor over time. Pelts were worn in or out, depending on their characteristics and desired use. Today fur and trim used in garments may be dyed bright colors or to mimic exotic animal patterns, or shorn close like velvet. The term "a fur" may connote a coat, wrap, or shawl.

The manufacturing of fur clothing involves obtaining animal pelts where the hair is left on the animal's processed skin. In contrast, making leather involves removing the hair from the hide or pelt and using only the skin.

Fur is also used to make felt. A common felt is made from beaver fur and is used in bowler hats, top hats, and high-end cowboy hats. [18]

Common furbearers used include fox, rabbit, mink, muskrat, leopard, beaver, ermine, otter, sable, jaguar, seal, coyote, chinchilla, raccoon, lemur, and possum.

See also

Related Research Articles

<span class="mw-page-title-main">Camouflage</span> Concealment in plain sight by any means, e.g. colour, pattern and shape

Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the battledress of a modern soldier, and the leaf-mimic katydid's wings. A third approach, motion dazzle, confuses the observer with a conspicuous pattern, making the object visible but momentarily harder to locate. The majority of camouflage methods aim for crypsis, often through a general resemblance to the background, high contrast disruptive coloration, eliminating shadow, and countershading. In the open ocean, where there is no background, the principal methods of camouflage are transparencying, silveringing, and countershading, while the ability to produce light is among other things used for counter-illumination on the undersides of cephalopods such as squid. Some animals, such as chameleons and octopuses, are capable of actively changing their skin pattern and colors, whether for camouflage or for signalling. It is possible that some plants use camouflage to evade being eaten by herbivores.

<span class="mw-page-title-main">Hair</span> Protein filament that grows from follicles found in the dermis, or skin

Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fine vellus hair. Most common interest in hair is focused on hair growth, hair types, and hair care, but hair is also an important biomaterial primarily composed of protein, notably alpha-keratin.

<span class="mw-page-title-main">Mammal</span> Class of animals with milk-producing glands

A mammal is a vertebrate animal of the class Mammalia. Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles and birds, from which their ancestors diverged in the Carboniferous Period over 300 million years ago. Around 6,400 extant species of mammals have been described and divided into 27 orders. The study of mammals is called mammalogy.

<span class="mw-page-title-main">Skin</span> Soft outer covering organ of vertebrates

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.

<span class="mw-page-title-main">Cornish Rex</span> Breed of cat

The Cornish Rex is a breed of domestic cat. The Cornish Rex has no hair except for down hair. Most breeds of cat have three different types of hair in their coats: the outer fur or "guard hairs", a middle layer called the "awn hair"; and the down hair or undercoat, which is very fine and about 1 cm long. Cornish Rexes only have the undercoat. The curl in their fur is caused by a different mutation and gene than that of the Devon Rex. The breed originated in Cornwall, Great Britain.

<span class="mw-page-title-main">Endotherm</span> Organism that maintains body temperature largely by heat from internal bodily functions

An endotherm is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions instead of relying almost purely on ambient heat. Such internally generated heat is mainly an incidental product of the animal's routine metabolism, but under conditions of excessive cold or low activity an endotherm might apply special mechanisms adapted specifically to heat production. Examples include special-function muscular exertion such as shivering, and uncoupled oxidative metabolism, such as within brown adipose tissue.

<span class="mw-page-title-main">Thermoregulation</span> Ability of an organism to keep its body temperature within certain boundaries

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature as its own body temperature, thus avoiding the need for internal thermoregulation. The internal thermoregulation process is one aspect of homeostasis: a state of dynamic stability in an organism's internal conditions, maintained far from thermal equilibrium with its environment. If the body is unable to maintain a normal temperature and it increases significantly above normal, a condition known as hyperthermia occurs. Humans may also experience lethal hyperthermia when the wet bulb temperature is sustained above 35 °C (95 °F) for six hours.

<span class="mw-page-title-main">Cat coat genetics</span> Genetics responsible for the appearance of a cats fur

Cat coat genetics determine the coloration, pattern, length, and texture of feline fur. The variations among cat coats are physical properties and should not be confused with cat breeds. A cat may display the coat of a certain breed without actually being that breed. For example, a Neva Masquerade could wear point coloration, the stereotypical coat of a Siamese.

<span class="mw-page-title-main">Guard hair</span> Longest, most coarse hairs in a mammals coat

Guard hair or overhair is the outer layer of hair of most mammals, which overlay the fur. Guard hairs are long and coarse and protect the rest of the pelage (fur) from abrasion and frequently from moisture. They are visible on the surface of the fur and usually lend a characteristic contour and colour pattern. Underneath the contour hair is the short, dense, fine down. There are three types of guard hair: awns, bristles, and spines.

<span class="mw-page-title-main">Awn hair</span> Intermediate hairs in a mammals coat

Awn hairs are the intermediate hairs in a mammal's coat. They are shorter than the guard hairs and longer than the down hairs. They help with insulation and protect the down hairs underneath. Most of the visible coat is made of this kind of hair.

<span class="mw-page-title-main">Dog coat</span> Hair that covers its body

The coat of the domestic dog refers to the hair that covers its body. Dogs demonstrate a wide range of coat colors, patterns, textures, and lengths.

<span class="mw-page-title-main">Rabbit hair</span> Fur from rabbit

Rabbit hair is the fur of the common rabbit. It is most commonly used in the making of fur hats and coats, and is considered quite valuable today, although it was once a lower-priced commodity in the fur trade.

<span class="mw-page-title-main">Arctic ground squirrel</span> Species of rodent

The Arctic ground squirrel is a species of ground squirrel native to the Arctic and Subarctic of North America and Asia. People in Alaska, particularly around the Aleutians, refer to them as "parka" squirrels, most likely because their pelt is good for the ruff on parkas and for clothing.

<span class="mw-page-title-main">Animal coloration</span> General appearance of an animal

Animal colouration is the general appearance of an animal resulting from the reflection or emission of light from its surfaces. Some animals are brightly coloured, while others are hard to see. In some species, such as the peafowl, the male has strong patterns, conspicuous colours and is iridescent, while the female is far less visible.

<span class="mw-page-title-main">Silver fox (animal)</span> Melanistic form of red fox

The silver fox, sometimes referred to as the black fox, or blue fox, is a melanistic form of the red fox. Silver foxes display a great deal of pelt variation. Some are completely glossy black except for a white colouration on the tip of the tail, giving them a somewhat silvery appearance. Some silver foxes are bluish-grey, and some may have a cinereous colour on the sides.

<span class="mw-page-title-main">Snow camouflage</span> Camouflage coloration for winter snow

Snow camouflage is the use of a coloration or pattern for effective camouflage in winter, often combined with a different summer camouflage. Summer patterns are typically disruptively patterned combinations of shades of browns and greys, up to black, while winter patterns are dominated by white to match snowy landscapes.

<span class="mw-page-title-main">Coloration evidence for natural selection</span> Early evidence for Darwinism from animal coloration

Animal coloration provided important early evidence for evolution by natural selection, at a time when little direct evidence was available. Three major functions of coloration were discovered in the second half of the 19th century, and subsequently used as evidence of selection: camouflage ; mimicry, both Batesian and Müllerian; and aposematism.

Nakedness and clothing use are characteristics of humans related by evolutionary and social prehistory. The major loss of body hair distinguishes humans from other primates. Current evidence indicates that anatomically modern humans were naked in prehistory for at least 90,000 years before they invented clothing. Today, isolated Indigenous peoples in tropical climates continue to be without clothing in many everyday activities.

<span class="mw-page-title-main">Gray fox fur</span> Type of fur

Gray fox fur is a type of fur obtained from the gray fox, a species distinguished from most other canids by its grizzled gray upper parts. It also has reddish coloration on parts of its body, including the legs, sides, feet, chest, and back, as well as on the sides of the head and neck. The white color is seen on the ears, throat, chest, belly, and hind legs. Moreover, the gray fox has a stripe of black hair that runs along the middle of its tail and ends in a black tip as well. The species occurs from southern Canada to northern South America.

References

  1. ↑ "Fur | animal skin". Encyclopedia Britannica. Retrieved 2018-10-30.
  2. 1 2 Dawson, T. J.; Webster, K. N.; Maloney, S. K. (2014). "The fur of mammals in exposed environments; do crypsis and thermal needs necessarily conflict? The polar bear and marsupial koala compared". Journal of Comparative Physiology B. 184 (2): 273–284. doi:10.1007/s00360-013-0794-8. PMID   24366474. S2CID   9481486.
  3. 1 2 3 4 5 Feldhamer, George A.; Drickamer, Lee C.; Vessey, Stephen H.; Merritt, Joseph H.; Krajewski, Carey (2007). Mammalogy: Adaptation, Diversity, Ecology (3 ed.). Baltimore: Johns Hopkins University Press. ISBN   978-0-8018-8695-9. OCLC   124031907.
  4. ↑ Caro, Tim (2005). "The Adaptive Significance of Coloration in Mammals". BioScience. 55 (2): 125–136. doi: 10.1641/0006-3568(2005)055[0125:tasoci]2.0.co;2 .
  5. ↑ Caro, Tim (February 2009). "Contrasting coloration in terrestrial mammals". Philos Trans R Soc B. 364 (1516): 537–548. doi:10.1098/rstb.2008.0221. PMC   2674080 . PMID   18990666.
  6. ↑ Mills, L. Scott; Zimova, Marketa; Oyler, Jared; Running, Steven; Abatzoglou, John T.; Lukacs, Paul M. (April 2013). "Camouflage mismatch in seasonal coat color due to decreased snow duration". PNAS. 110 (8): 7360–7365. Bibcode:2013PNAS..110.7360M. doi: 10.1073/pnas.1222724110 . PMC   3645584 . PMID   23589881.
  7. ↑ Bradley, Brenda; et al. (2012). "Coat Color Variation and Pigmentation Gene Expression in Rhesus Macaques (Macaca Mulatta)" (PDF). Journal of Mammalian Evolution. 20 (3): 263–70. doi:10.1007/s10914-012-9212-3. S2CID   13916535. Archived from the original (PDF) on 2015-09-24.
  8. ↑ Prum, Richard O.; Torres, Rodolfo H. (2004). "Structural colouration of mammalian skin: convergent evolution of coherently scattering dermal collagen arrays" (PDF). Journal of Experimental Biology. 207 (12): 2157–72. doi: 10.1242/jeb.00989 . hdl:1808/1599. PMID   15143148. S2CID   8268610.
  9. ↑ Suutari, Milla; Majaneva, Markus; Fewer, David P.; Voirin, Bryson; Aiello, Annette; Friedl, Thomas; Chiarello, Adriano G.; Blomster, Jaanika (2010). "Molecular evidence for a diverse green algal community growing in the hair of sloths and a specific association with Trichophilus welckeri (Chlorophyta, Ulvophyceae)". Evolutionary Biology. 10 (86): 86. Bibcode:2010BMCEE..10...86S. doi: 10.1186/1471-2148-10-86 . PMC   2858742 . PMID   20353556.
  10. ↑ Plavcan, J. M. (2001). "Sexual dimorphism in primate evolution". American Journal of Physical Anthropology. 116 (33): 25–53. doi: 10.1002/ajpa.10011 . PMID   11786990. S2CID   31722173.
  11. ↑ "Pelage". Merriam-Webster. Retrieved January 9, 2013.
  12. ↑ Peterson, Judy Monroe (2011-01-15). Varmint Hunting. The Rosen Publishing Group. ISBN   9781448823666.
  13. ↑ B. J. Teerink. Hair of West European mammals: atlas and identification key. Cambridge: Cambridge University Press, 2003.
  14. ↑ Dean, Matthew D (30 December 2022). "Evolution: How (some) mammals lost their hair". eLife. 11: e84865. doi: 10.7554/eLife.84865 . PMC   9803347 . Retrieved 22 July 2023.
  15. ↑ Thomson, Paul (2002). "Cheiromeles torquatus". Animal Diversity Web. Retrieved 29 October 2013.
  16. ↑ Winter, H.; Langbein, L.; Krawczak, M.; Cooper, D. N.; Jave-Suarez, L. F.; Rogers, M. A.; Praetzel, S.; Heidt, P. J.; Schweizer, J. (2001). "Human type I hair keratin pseudogene phihHaA has functional orthologs in the chimpanzee and gorilla: Evidence for recent inactivation of the human gene after the Pan-Homo divergence". Human Genetics. 108 (1): 37–42. doi:10.1007/s004390000439. PMID   11214905. S2CID   21545865.
  17. ↑ Abbasi, Amir Ali (2011). "Molecular evolution of HR, a gene that regulates the postnatal cycle of the hair follicle". Scientific Reports. 1: 32. Bibcode:2011NatSR...1E..32A. doi:10.1038/srep00032. PMC   3216519 . PMID   22355551.
  18. ↑ Chamber's journal, Published by Orr and Smith, 1952, p. 200, Original from the University of Michigan.
"Fur-Bearing Animals". Encyclopedia Americana . 1920.

"Fur-Bearing Animals". New International Encyclopedia . 1905.

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