Polar Bear

:"Polar Bear" is also the name of White Bear Township, Minnesota and a trade name for a type of scuba diver's warm undersuit to be worn under a drysuit.

Fur and skin

The nose and skin are black. The fur is whiteish in appearance—pure white after molt, yellowish in summer due to oxidation by sun, and sometimes greenish (due to algal growth inside the shaft of hollow guard hairs) in captive bears kept too warm. This fur is good camouflage as well as insulation. The bear is often thought to cover its visible black nose while hunting, though no scientist has observed this. They will, however, cover their muzzles while sleeping, probably for insulation. Stiff hairs grow on the soles of its paws; these insulate and provide traction on ice.

Related Topics:
Fur - White - Camouflage

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Unlike other arctic mammals, polar bears never shed their coat for a darker shade in the summer. The individual hairs are transparent and unpigmented (like a single water drop in a cloud). The fur is white rather than transparent for the same reasons as clouds, water foam, and cotton (reflection and dispersion of visible light). The fur absorbs ultraviolet light. The hair does not have fiber-optic properties nor does it transmit light or heat to the skin (an urban legend). The coat does however insulate the bears to the point where they overheat at temperatures above 10°C (50°F) and are nearly invisible in the infrared: only their breath and muzzles can be seen.http://www.biologicaldiversity.org/swcbd/species/polarbear/nat-hist.html

Related Topics:
Arctic - Summer - Hair - Unpigmented - Reflection - Dispersion - Visible light - Ultraviolet - Light - Fiber-optic - Urban legend - Infrared

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In July 2005, several polar bears in the Brookfield Zoo turned green as a result of algae growing in their hollow hair tubes. Chicago experienced an extremely hot, humid and dry summer that year. However, the zoo took no action since it has been shown the algae does not negatively affect the bears in any way. The staff believed that exposing the bears to chlorine or bleach would be more harmful than letting the algae run its course. Previously, in February 2004, two polar bears in the Singapore Zoo turned green due to algae growth. A zoo spokesman said that the algae had formed as a result of Singapore's hot and humid conditions. The bears were washed in a peroxide blonde solution to restore their expected colour. A similar algae grew in the hair of three polar bears at San Diego Zoo in the summer of 1979. They were cured by washing the algae away in a salt solution.

Related Topics:
2005 - Brookfield Zoo - Algae - 2004 - Singapore Zoo - Peroxide blonde - San Diego Zoo

~ ~ ~ ~ ~ ~ ~ ~ ~ ~