Fur: Difference between revisions

[[File:GrizzlyBearJeanBeaufort.jpg|thumb|300px|Like many mammals, [[grizzly bear]]s 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|guard hair]] on top and thick [[#Down hair|underfur]] beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an [[thermal insulation|insulating]] blanket that keeps the animal warm.<ref>{{Cite encyclopedia|url=https://www.britannica.com/topic/fur-animal-skin#ref114471|title=Fur {{!}} animal skin|encyclopedia=Encyclopedia Britannica|access-date=2018-10-30|language=en}}</ref>

* ''velli'', often called "down fur,", which insulates newborn mammals; and

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.<ref name="bioscience.oxfordjournals.org">{{cite journal |last1=Caro |first1=Tim |year=2005 |title= The Adaptive Significance of Coloration in Mammals |journal=BioScience |volume= 55 | issue = 2 |pages= 125–136 |doi=10.1641/0006-3568(2005)055[0125:tasoci]2.0.co;2|doi-access=free }}</ref> [[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]].<ref>{{cite journal |last1=Caro |first1=Tim |title=Contrasting coloration in terrestrial mammals |journal=Philos Trans R Soc B |date=February 2009 |volume=364 |issue=1516 |pages=537–548 |doi=10.1098/rstb.2008.0221 |pmc=2674080 |pmid=18990666}}</ref> In arctic and subarctic mammals such as the [[arctic fox]] (''AlopexVulpes lagopus''), [[collared lemming]] (''Dicrostonyx groenlandicus''), [[stoat]] (''Mustela erminea''), and [[snowshoe hare]] (''Lepus americanus''), [[seasonal polyphenism|seasonal color change]] between brown in summer and white in winter is driven largely by camouflage.<ref>{{cite journal |last1=Mills|first1=L. Scott |last2=Zimova|first2=Marketa |last3=Oyler|first3=Jared |last4=Running|first4=Steven |last5=Abatzoglou|first5=John T. |last6=Lukacs|first6=Paul M. |title=Camouflage mismatch in seasonal coat color due to decreased snow duration |journal=PNAS |date=April 2013 |volume=110 |issue=8 |pages=7360–7365 |pmc=3645584 |pmid=23589881 |doi=10.1073/pnas.1222724110|bibcode=2013PNAS..110.7360M|doi-access=free }}</ref> Differences in female and male coat color may indicate nutrition and hormone levels, important in mate selection.<ref name="eva.mpg.de">{{cite journal |last1=Bradley |display-authors=etal |first1=Brenda |year=2012 |title=Coat Color Variation and Pigmentation Gene Expression in Rhesus Macaques (Macaca Mulatta) |journal=Journal of Mammalian Evolution |volume=20 |issue=3 |pages=263–70 |doi=10.1007/s10914-012-9212-3 |s2cid=13916535 |url=http://www.eva.mpg.de/pks/staff/widdig/pdf/Bradley_et_al_2012.pdf |url-status=dead |archive-url=https://web.archive.org/web/20150924004623/http://www.eva.mpg.de/pks/staff/widdig/pdf/Bradley_et_al_2012.pdf |archive-date=2015-09-24 }}</ref> 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]].<ref>{{cite journal |last1=Prum |first1=Richard O. |last2=Torres |first2=Rodolfo H. |year=2004 |title=Structural colouration of mammalian skin: convergent evolution of coherently scattering dermal collagen arrays |journal=Journal of Experimental Biology |volume=207 |pages=2157–72 |doi=10.1242/jeb.00989 |pmid=15143148 |issue=12|hdl=1808/1599 |s2cid=8268610 |url=https://kuscholarworks.ku.edu/bitstream/1808/1599/1/2157.pdf |doi-access=free }}</ref> The green coloration of sloths, however, is the result of a [[symbiosis|symbiotic]] relationship with algae.<ref>{{cite journal|first1=Milla |last1=Suutari |first2=Markus |last2=Majaneva |first3=David P. |last3=Fewer |first4=Bryson |last4=Voirin |first5=Annette |last5=Aiello |author-link5=Annette Aiello |first6= Thomas |last6=Friedl |first7=Adriano G.|last7=Chiarello |first8=Jaanika |last8=Blomster |year=2010 |title=Molecular evidence for a diverse green algal community growing in the hair of sloths and a specific association with ''Trichophilus welckeri'' (Chlorophyta, Ulvophyceae) |journal=Evolutionary Biology |volume=10 |issue=86 |pages=86 |doi=10.1186/1471-2148-10-86 |pmid=20353556 |pmc=2858742 |doi-access=free }}</ref> Coat color is sometimes [[sexual dimorphism|sexually dimorphic]], as in [[Sexual dimorphism in non-human primates#Pelage color and markings|many primate species]].<ref>{{cite journal |first=J. M. |last=Plavcan |year=2001 |title=Sexual dimorphism in primate evolution |journal=American Journal of Physical Anthropology |volume=116 |issue=33 |pages=25–53 |doi=10.1002/ajpa.10011 |pmid=11786990|s2cid=31722173 |doi-access=free }}</ref> 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 [[vole|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.<ref name=hair/>{{rp|166–167}}<ref name=dawson2014/>

The term ''pelage''{{spaced ndash}}first known use in English {{ca|1828}} (French, from Middle French, from {{lang|frm|poil}} for 'hair', from [[Old French]] {{lang|fro|peilss}}, from [[Latin]] {{lang|la|pilus}}<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/pelage|title=Pelage|publisher=Merriam-Webster|access-date=January 9, 2013}}</ref>){{spaced ndash}}is sometimes used to refer to an animal's complete [[coat (animal)|coat]]. The term fur is also used to refer to animal pelts whichthat 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 (animal)|coat]], it may consist of short down hairs, long [[wikt:guard hair|guard hairs]], and in some cases, medium [[awn hair]]s. Mammals with reduced amounts of fur are often called "naked", as with the [[naked mole-rat]], or "hairless", as with [[hairless dog]]s.

An animal with commercially valuable fur is known within the [[Fur trade|fur industry]] as a [[List of types of fur|furbearer]].<ref>{{Cite book |url=https://books.google.com/books?id=cCVW72oz2O8C&pg=PA54|title=Varmint Hunting|last=Peterson|first=Judy Monroe |date=2011-01-15|publisher=The Rosen Publishing Group| isbn=9781448823666 |language=en}}</ref> The use of [[fur clothing|fur as clothing]] or decoration is controversial; [[animal welfare]] advocates object to the trapping and killing of wildlife, and to the confinement and killing of animals on [[Fur farming|fur farms]].

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"{{fact|date=July 2023}} or "hairless".<ref>{{cite web |last1=Dean |first1=Matthew D |title=Evolution: How (some) mammals lost their hair |url=https://elifesciences.org/articles/84865 |website=eLife |access-date=22 July 2023}}</ref>

Some mammals naturally have reduced amounts of fur. Some [[List of semiaquatic tetrapods|semiaquatic]] or [[aquatic animal|aquatic]] mammals such as [[cetacean]]s, [[pinniped]]s 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 life-stylelifestyle. 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.<ref name=ADW>{{cite web|last=Thomson|first=Paul|title=Cheiromeles torquatus|url=http://animaldiversity.ummz.umich.edu/accounts/Cheiromeles_torquatus/|publisher=Animal Diversity Web|access-date=29 October 2013|year=2002}}</ref> [[Marsupial|Marsupials]] are born hairless and grow out fur later in development.

Humans[[Human]]s 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]])<ref>{{Cite journal| doi = 10.1007/s004390000439 | last1 = Winter | first1 = H. | last2 = Langbein | first2 = L. | last3 = Krawczak | first3 = M. | last4 = Cooper | first4 = D. N. | last5 = Jave-Suarez | first5 = L. F. | last6 = Rogers | first6 = M. A. | last7 = Praetzel | first7 = S. | last8 = Heidt | first8 = P. J. | last9 = Schweizer | first9 = J. | title = 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 | journal = Human Genetics | volume = 108 | issue = 1 | pages = 37–42 | year = 2001 | pmid = 11214905 | s2cid = 21545865 }}</ref> Although the researchers dated the mutation to 240 000 ya, both the [[Altai Mountains|Altai]] [[Neanderthal|Neandertal]] and [[Denisovan]] havepeoples possessed the loss-of-function mutation, indicating it is much older. Mutations in the gene HR can lead to [[Alopecia universalis|complete hair loss]], though this is not typical in humans.<ref>{{cite web|url=http://www.nature.com/srep/2011/110706/srep00032/full/srep00032.html|access-date=2012-03-13journal|title=Molecular evolution of HR, a gene that regulates the postnatal cycle of the hair follicle|year=2011 |doi=10.1038/srep00032 |last1=Abbasi |first1=Amir Ali |journal=Scientific Reports |volume=1 |page=32 |pmid=22355551 |pmc=3216519 |bibcode=2011NatSR...1E..32A }}</ref>

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 that are hairless. There are several breeds of hairless cats, perhaps the most commonly known being the [[Sphynx (cat)|Sphynx cat]]. Similarly, there are some breeds of [[hairless dog]]s. Other examples of artificially selected hairless animals include the [[Skinny pig|hairless guinea-pig]], [[nude mouse]], and the [[hairless rat]].

[[List of types of fur|Common furbearers]] used include [[fox]], [[rabbit]], [[mink]], [[muskrat]], [[leopard]], [[beaver]], [[Stoat|ermine]], [[otter]], [[sable]], [[jaguar]], [[pinniped|seal]], [[coyote]], [[chinchilla]], [[raccoon]], [[lemur]], and [[Phalangeriformes|possum]].