Fur
[1] The fur of mammals has many uses: protection, sensory purposes, waterproofing, and camouflaging, with the primary usage being thermoregulation.
[3]: 188 Aquatic mammals, conversely, trap air in their fur to conserve heat by keeping the skin dry.
[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.
The white, pigmentless fur of arctic mammals, such as the polar bear, may reflect more solar radiation directly onto the skin.
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.
Guard hair repels water and blocks sunlight, protecting the undercoat and skin in wet or aquatic habitats, and from the sun's ultraviolet radiation.
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.
Hair is one of the defining characteristics of mammals; however, several species or breeds have considerably 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 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.
Today fur and trim used in garments may be dyed bright colors or to mimic exotic animal patterns, or shorn close like velvet.
[18] Common furbearers used include fox, rabbit, mink, muskrat, leopard, beaver, ermine, otter, sable, jaguar, seal, coyote, chinchilla, raccoon, lemur, and possum.
