Literature skeptical of, or debunking the fiber optic polar bear myth:

Scientific journals:

• "If we assume that the UV absorption coefficient of polar bear keratin is not vastly different from that of horsetail keratin, then it is difficult to escape the conclusion that polar bear pelts are black in the UV because of absorption. Even though particles with dimensions of several hundred microns or greater may appear nearly transparent, it does not take much absorption in a single particle for a collection of them to be black."

"Although the polar bear may utilize UV radiation very efficiently, by whatever mechanism, it appears to avail him little because he lives in an environment relatively impoverished of such radiation."
Bohren, Craig F. and Sardie, Joseph M., "Utilization of solar radiation by polar animals: an optical model for pelts; an alternative explanation", Applied Optics 20 (11), 1894-6 (1981).
• "These measurements showed an exponential decay of 2, 3, 5, and 8 dB/mm at 650, 589, 545, and 450nm, respectively, which is consistent with the keratin data of Bendit and Ross [Appl. Spectrosc. 15, 103 (1961).] cited by Bohren and Sardie.[Appl. Opt. 20, 1894-6 (1981).]"

Koon, Daniel W., "Is polar bear hair fiber optic?", Applied Optics 37, 3198 (1998).

• "The observation that individual polar-bear hairs are 'actually colorless, not white',...pertained only to visible and near-infrared radiation, not to UV. And to compare a polar-bear hair to a 'quartz fiber' is nonsense. Quartz transmits near-UV...whereas, as the piece correctly notes, polar-bear hair absorbs UV."

"Now it is proposed that the UV is captured by the outer solid part of the hair...and aimed 'toward the skin.' Once again there is a serious problem: the 'shaft' of the polar-bear hair is not transparent to UV; it absorbs it."
Lavigne, D. M., Letter, Scientific American, 258 (9), 8 (Sept. 1988).
• "According to Steven Amstrup, though, the business about UV light traveling down the shaft of hair and warming the polar bear appears now to be largely untrue. He said, 'David Lavigne at the University of Guelph who discovered that polar bears absorbed UV light has now written a couple of compelling analyses demonstrating that although they do trap UV, any energy gains are likely to be minuscule and of little consequence in the energetics of polar bears.'"

Interview with Steve Amstrup, Earth and Sky, (Feb. 5, 1996) ("More information on 'Polar Bears'"), http://www.earthsky.com/1996/mi/esmi960205.html (defunct link).
• "First, while polar bear fur is relatively clear at visible wavelengths, the idea that the hairs function as light guides to warm the animal is a scientific 'urban myth.' For more details, see the letter by D. M. Lavigne, on p. 8 of the September 1988 Scientific American. His major points are that polar bear fur is black in the ultraviolet, and traps the ultraviolet light, helping raise the animal's skin temperature."

"Second, a hollow transparent tube can guide light more weakly than an optical fiber by a different effect. The fraction of light reflected by a surface increases with the steepness of the angle it hits the surface at. That is, the smaller the angle between the light rays and the surface, the higher the reflectivity. This effect works for materials with refractive index higher than air; you can find the equations in a good college optics text. It would guide light along hollow fibers, but not as efficiently as total internal reflection guides light through clear glass. (Total internal reflection works for light trapped in a medium with higher refractive index than the surrounding material -- i.e., a bare glass fiber in air, or a fiber with a high-index core surrounded by a low-index cladding."
Hecht, Jeff, "Re: _Sinosauropteryx_ fibers", Letter to the Dinosaur mailing list (dinosaur@usc.edu), http://www.cmnh.org/fun/dinosaur-archive/1997Nov/msg00018.html
• "And older theories are being challenged. It was believed that the bear's outer hairs were hollow, in order to transmit light to its black skin, a form of solar heating, but Jane [Waterman]'s analysis of the hair exploded that theory...'It did not transmit light and if you think about it, it really doesn't make any sense to have a system where you use light to warm yourself up if its minus forty degrees Celsius and twenty-four hour darkness, it doesn't do you any good.'"

Deborah Burgess, writer/producer, "Great Canadian Parks: Wapusk National Park (Manitoba)", Good Earth Productions for Discovery Channel Canada, http://www.interlog.com/~parks/show21/n21tran.txt, Feb. 26, 1997
• "The optical loss was found to be approximately 2 decibels per mm from 550 to 725nm. This value of loss essentially eliminates the possibility that the polar bear's pelt is behaving like an optical fiber in order to transmit light to the bear's skin for conversion to heat."

Hutchins, Reid, "Examining the Optical Properties of the Polar Bear Pelt", unpublished, St. Lawrence University Physics Dept. (1997).
• "The myth that polar bear hairs act as optical fibers for ultraviolet light...is easily debunked in an undergraduate laboratory."

Koon, Daniel W., "Ursus Fiberopticus: The Myth of Fiber-Optic Polar Bear Hair", American Association of Physics Teachers Winter Meeting, Jan. 7, 1998.
• "This hypothesis rested on two suspect extrapolations. It assumed that the transparency of the hair shaft extends into the ultraviolet. But if the reflectance of the pelt is so starkly different in the visible and the ultraviolet, why should the transparency be similar? And it equated transparency across a hair (about 0.1 millimetres thick) with transparency along the length of the hair. Although a pane of glass appears to be transparent and colourless when viewed normally, it appears green when viewed edge-on. This glass is not perfectly transparent to red light, even if it appears to be through a window."

Koon, Daniel W., "Power of the polar myth", New Scientist, Vol. 158, No. 2131, p. 50 (April 25, 1998).
• "[Koon and Hutchins'] research revealed that the popular notion was not correct, they found that less than .001 percent of red light and less than a trillionth of the violet light transmitted traveled the length of a typical, inch-long hair. Even less ultraviolet light made it from the tip to the base of the hair...As writer Bertrand Russell pointed out, even Aristotle--the most famous scientist of his day--claimed that women have fewer teeth than men, though it never occurred to him to check Mrs. Aristotle's mouth. The moral of Koon's study is that a little dose of skepticism never hurts.

Rozell, Ned, "Alaska Science Forum #1390: Debunking the Myth of Polar Bear Hair", http://www.gi.alaska.edu/ScienceForum/ASF13/1390.html, May 28, 1998.

Literature supportive of the fiber optic polar bear myth:

Scientific journals:

• "Some light energy is conveyed to the collector, in this case the skin, by a complex process involving scattering form the inner core surface and reflection from the relatively smooth outer surfaces of the hairs. In this respect, the hairs are acting as light guides...The efficiency of transmission of solar radiation to the skin must be particularly high for the UV, since the pelts appear black when viewed in the UV while the hairs themselves appear quite transparent."

Grojean, R. E., Sousa, J. A., Henry, M. C., "Utilization of solar radiation by polar animals: an optical model for pelts", Applied Optics 19 (3), 339 (1980).
• "If we assume that absorption of solar radiation takes place in the hairs, we would expect most of the absorption to take place in the outer layers of the pelt. However, [i]nfrared sensing of the arctic homeotherms has been largely unsuccessful, since the outer layers of the fur are at temperatures very close to ambient."

Grojean, R. E., Sousa, J. A., Henry, M. C., "Utilization of solar radiation by polar animals: an optical model for pelts; authors' reply to an alternative explanation", Applied Optics 20 (11), 1896-7 (1981).
• "Fluorescence light collection is therefore a mechanism which has to be considered in the optical properties of hairs of polar bears."

"The morphological, optical and scanning light microscopical studies performed with polar bear hair leave little doubt that light from the environment is coupled into the light conducting shaft of the hair by scattering processes."
Tributsch, H., Goslowsky, H., Küppers, U., and Wetzel, H., "Light collection and solar sensing through the polar bear pelt", Solar Energy Materials 21, 219-36 (1990).

• "[Malcolm] Henry and his colleagues, John A. Sousa and Northeastern University's Richard E. Grojean, concluded that the polar bear's hairs are really miniature light pipes, funneling only ultraviolet light down through its hollow core."

Anonymous, "Furry funnels", Time Magazine, 112 (23) 82-4 (Dec. 4, 1978).
• "Was the low-density core of the bear's hair acting as a 'light pipe', permitting the absorbed ultraviolet energy (perhaps now transformed into another form of energy) to be transmitted into the bear's hide through internal reflections? A mathematical model of polar bear hair showed that this was entirely possible."

Hansen, John V. E., "Clothing for Cold Climes", Natural History 90 (10), 90 (Oct. 1981).
• "A friend in the Arctic writes that scientists now believe that the hollow core of a polar bear's individual hairs acts as a kind of solar cell, transmitting the sun's energy into the bear's hide: When he suns himself on an ice floe, he may feel as warm as a turtle on a log in Georgia."

"Dragons of Winter", New York Times, Late City Final Edition, Section 4, p. 16, Feb. 26, 1984.
• "A white fur coat has obvious camouflage benefits and, now, biologists who study polar bears believe it offers an added solar radiation advantage as well. The lack of pigmentation allows the hair to perform like fibre optics to carry sunlight to the polar bear's black hide by internal refraction. In this way, the skin is provided extra warmth."

Kruser, Ben, "How they survive", http://www.interlog.com/~speirs/leader/art141.htm, originally published in "The Leader" http://www.scouts.ca/leader.htm, Canada, Dec. 1985.
• "What's white and black and warm all over? A polar bear under the Arctic sun. The polar bear is almost a perfect solar converter, says electrical engineer Richard Grojean of Northeastern University in Boston...Like light within an optical fiber, [ultraviolet] radiation is conducted along the hairs to the skin. This summertime energy supplement provides up to a quarter of the bear's needs."

"This fur collects ultraviolet light coming from any direction."
Anonymous, "Solar bear technology", Science News 129, p. 153 (Mar. 8, 1986).
• "MOSCOW, August 19 -- Soviet scientists have discovered that the fur of polar bears is not white but transparent, the youth daily Komsomolskaya Pravda reported today. "'The fur concentrates dispersed ultraviolet radiation and every hair, directing that radiation at the perfect right angle to the surface of the animal's hide, works as a sort of lens.' the newspaper said.

"The hide, converting solar energy into heat, is a perfect 'prototype of a solar power station', it added."
"What color are polar bears?", Reuters News Service, August 19, 1986.
• "Two scientists from Northeastern University in Boston [Grojean and Kowalski] inadvertently have discovered that the thick, shaggy coats of polar bears are capable of incredibly sophisticated and efficient solar energy conversion, changing light that hits the fur to heat that warms the body...[W]hen [Lavigne and Oritsland] used ultraviolet equipment, which registers short-wave, invisible rays at the end of the light spectrum, the bears stood out dramatically, indicating an abundance of ultraviolet light on the bear's fur...Grojean says that a single hair of white polar bear fur, viewed under a microscope, is actually transparent. The clear, smooth-surfaced hair has an opaque, hollow, rough-surfaced core, called the medulla, that scatters light hitting the fur and somehow conducts 95 percent of the ultraviolet light down to the polar bear's black skin, where it is converted into heat."

McClintock, Mike, "Solar Energy -- Do polar bears hold the secret? The bears' white fur may be the most efficient solar collector there is", Washington Post, Home Section, p. T5, March 26, 1987.
• "Scientists at Northeastern University here have discovered that the white fur of polar bears converts the sun's ultraviolet rays into useable heat with 95 percent efficiency."

"Grojean was fascinated by the fact that polar bears virtually vanish under an infrared lens. He discovered that each white polar bear hair is actually transparent, with an inner hollow core about one-third the diameter of the hair. In this core, ultraviolet light is scattered, and by some unknown mechanism is converted into heat."
Grow, Glenn S., "Polar bears have solar hairs. And that could be good news for homeowners and the military", The Christian Science Monitor, Nov. 2, 1987, p. 24.
• "Scientists at Northeastern University here have discovered that the shaggy fur of polar bears is 95 percent efficient in converting the sun's ultraviolet rays into usable heat."

"According to researchers, the hairs act in much the same way as optical fibers now used in telephone transmission lines."
"Grojean and his colleagues at Northeastern, Gregory Kowalski and Charles DiMarzio, have launched a detailed study of the polar-solar phenomenon and are seeking funding from several groups, including the United States Department of Energy. Once adequate funding is available and the mechanics of the polar-solar effect are found, prototypes of revolutionary solar collectors could be available within five years."
Grow, Glenn S., "Warming up to polar bears' solar secrets", The Christian Science Monitor, Dec. 1, 1987, p. 19.
• "There exists, however, a natural collector that converts part of the solar-radiation spectrum into heat with an efficiency exceeding 95 percent. The remarkable device is polar bear fur."

"Polar bear hair may be a natural fiber-optic cable. A cross section (right) shows a solid shaft surrounding a reticulated core. The shaft apparently can trap ultraviolet light and aim it toward the skin (above)."
"Grojean believes the hair shaft somehow conducts scattered radiation to the surface of the skin (which is actually black), where it is absorbed and converted into heat."
Mirsky, Steven D., "Solar Polar Bears", Scientific American, 258(3), 24-5 (Mar. 1988).
• "Based on their research, Grojean and Kowalski say the secret to the bear's success to be that its pigmentless hair traps and transmits to the skin 90 percent of sunlight in the invisible ultraviolet portion of the spectrum, but only 10 percent of the light in the visible spectrum."

"Through thermal balance equations, Grojean calculated that the bears trap 90 percent of ultraviolet light and 17 percent from the entire solar spectrum. The figures were confirmed by an Irish Arctic research team in the early '80s."
"So how do the bears do it? [Grojean] doesn't know exactly, but believes the smooth-surfaced hollow hairs, with their labyrinthine, rough-surfaced cores, work like optical fibers."
Croke, Vicki, "Solar Polar Bears? Two Boston Scientists Think So.", Boston Globe, June 4, 1990, p. 41.
• (Same story)
  Croke, Vicki, "Solar bears: what's black, and white, and studied all over for energy efficiency?", Chicago Tribune, Tempo Section, p. 8, Zone C (June 17, 1990).
• "[Polar bear] hair retains heat and passes solar radiation through hollow cores to the bear's black skin."

Wolkomir, Richard and Joyce, "Hair, Glorious Hair", National Wildlife 31(1), 4-11 (Dec. 92/Jan. 93).
• "Nanuq is a triumph of evolutionary engineering. Living in a world where temperatures can drop as low as 60 degrees below zero, he functions like a massive solar battery. His dense-packed fur, which looks white, is actually a forest of colorless fibers that sip sunlight and carry heat into his body, which is covered by a four-inch-thick blanket of fur."

Anonymous, "Where does an 1800 pound polar bear sleep? Anywhere it pleases...", Life, Feb. 1994, p. 80.
• "It seems that in ultraviolet film, polar bears appeared black, apparently because their hair has the unique ability to 'suck' that form of energy into their bodies, said Alfred [University] researcher Alexis Clare...Clare, an assistant professor of glass science, is interested in polar-bear hair's ability to transmit UV light, which could be useful in making fiber guides for UV lasers."

Bellinger, Bob, "Stealth Bears", Electronic Engineering Times, July 4, 1994.
• "British scientists have discovered that polar bears have hairs that 'suck' in ultraviolet light and use it to warm their bodies, even though it is not conventionally a source of heat energy. If Clare could simulate the behaviour of bear fur, it would be possible to carry much higher energy light, strong enough to blast electrons apart and fine enough for pinpoint eye surgery."

Glaskin, Max, "Polar bear's fur holds clues to better lasers", Sunday Times (London), Features section, April 16, 1995.
• "A spokeswoman for [Alfred University] said the [polar bear] hair's ability to transmit ultraviolet light could lead to an instrument that better directs lasers used for surgery."

Anonymous, "Polar-bear fur: good for more than rugs", Chronicle of Higher Education, March 17, 1995.
• "Clare's interest in the fur involves its ability to transmit UV light, a property that may be useful in making fiber guides for UV lasers...Clare is trying to determine what gives the fur its ability to transmit UV light."

Anonymous, "Bears have 'fur real' properties", Optical Material Engineering News, Lenses and Glasses; v. 5, n. 8, April 1995.
• "[Polar bear] apparently transmits ultraviolet light very efficiently into cells that convert the light into energy...Alexis Clare, an assistant professor of glass science at Alfred University in New York, is studying whether the hairs can help improve ultraviolet laser waveguides."

Anonymous, "Hairy Research", Photonics Spectra 29 (7), 184, (July 1995).
• "The normally white bears became black bears on the UV film because polar bear hair appears to transmit ultraviolet light, 'sucking' it into the bear's body, said Alexis Clare, assistant professor of glass science at the New York State College of Ceramics at Alfred University"

Anonymous, "Arctic Animal May Bear Clues for Better UV Fiber Guide", Biophotonics International, May/June 1995, 27.
• "The translucent white hairs cover thick fat and a dense layer of underfur. The hairs direct solar heat to the bear's black skin, helping it maintain a normal body temperature, even when the mercury drops to frigid lows."

Sunquist, Fiona, "The colorful world of black white.black and white animals", International Wildlife, vol. 26 (3), p. 12, May, 1996.
• "In 1995, British scientists discovered that polar bear hairs block infra-red radiation and seem to suck in ultraviolet light which is used to heat their bodies. Possible applications include better lasers for eye surgery, more efficient solar panels covered with polar bear fur, and military camouflage undetectable by infra-red cameras."

Anonymous, "A history of the world in 101/2 inches; 19 Polar bears", The Independent (London), Back pages miscellany; page 30, Sept. 5, 1996.
• "Each hair is a clear (not white), hollow prism that may conduct light to the bears' black skin for absorption."

Drew, Lisa, "Tales of the Great White Bear", National Wildlife, Dec. 96/Jan 97, p. 16.
• "Looked at under an electron microscope, polar bear hair is solid and totally transparent, acting like a fibre optic, conducting light down the hair to the animal's black skin."

"Polar bear's nose for warmth: Answers to correspondents", Daily Mail (London), p. 57, Jan. 29, 1997.
• "Polar bears aren't white at all, but are transparent. Under intense microscopic imaging their hairs are hollow tubes, without color. This allows them to act like miniature fiber-optic tubes, trapping the warmth of the ultraviolet rays and funneling them back into the bear's body"

"Fiber-optics was created by God at the beginning of time and only discovered, not developed, by technological researchers."
Toland, Janet, "Prayer Retreat Held At Smithpeter Home", The Gurdon (AR) Times, Sep. 17, 1997, http://www.pcfa.org/times/1997/19970917.html .
• "Each hair is a transparent filament that conducts heat to the animal's black skin, much as a fiber-optic cable transmits light."

Bourne, Will, "The long wait: polar bears must wait for the arctic summer to end so that their food supply, seals, are abundant in the area again", Audubon, No. 1, Vol. 100, p. 64 (January 11, 1998).
• "It is believed that part of their metabolism may be solar powered, with the hairs acting as optic fibers sending ultraviolet rays to the heat-absorbing black skin."

Croke, Vicki, "Baby bear Triton is drawing record crowds to zoo in Providence; Animal Beat", Boston Globe, May 16, 1998, p. C1.

• "[Malcolm Henry] concluded that each hair is a miniature light pipe that funnels only ultraviolet light down through its core to be absorbed by the black skin. What this means in practical terms is that the polar bear pelt is nearly ideal as a solar heat-converter. The fur produces a greenhouse effect, trapping solar energy where it can be stored with slight losses by conduction, convection, or radiation, and operating independently of solar angle."

Davids, Richard C., "Lords of the Arctic: A journey among the polar bears" (Macmillan: New York, 1982), p. 25.
• "[P]olar bear guard hairs work like light pipes. They funnel short-wavelength energy from the sun to the bear's black skin, where it plays an as yet incompletely understood role in the bear's complex system of heat regulation."

Lopez, Barry, "Arctic Dreams" (Charles Scribner's Sons: NY, 1986), p. 85.
• "These hollow hairs have recently been discovered to act as a kind of ultraviolet radiation trap; they conduct it, like light within an optical fiber, to the bear's skin -- which is black, as are its nose and lips. Scientists at Northeastern University in Boston have discovered that polar bear fur has an amazingly 95 percent efficiency in converting the sun's ultraviolet rays into usable heat."

"Unlike solar collectors that must be aimed for maximum gain, polar bear hairs trap light coming from every direction."
Domico, Terry, "Bears of the World" (Facts on File: New York, 1988.), p. 68
• "The hairs of the polar bear are transparent light pipes that direct ultraviolet light to its skin -- which is guess what color? Black! So what's white and black and warm all over? A polar bear under the arctic sun."

Hewitt, Paul G., "Conceptual Physics" (Scott, Foresman, & Co.: Glenview, IL, 6th Ed. 1989), p. 501.
• "Each hair functions as a light trap, a conduit that takes the sun's rays...the last few inches to his dark skin. This energy-capturing system is more efficient than anything human engineers have been able to assemble."

"Nanook's hair is 95 percent effective."
"The fur light pipes will trap sunshine coming from any direction."
Feazel, Charles, "White Bear" (Henry Holt: New York, 1990.), p. 30 and illustration following p. 114.
• "Zoologists studying polar bear fur with electron microscopes recently discovered that these hairs are hollow: they function in the manner of tiny fiber-optic tubes -- miniature conduits for light that collect solar energy, then funnel it beneath the pelage to warm the bears' pitch-black skin."

Krasemann, Stephen J., "Diary of an Arctic Year" (Chronicle Books: San Francisco, 1991), p. 162.
• "Each hair actually is a highly efficient fiber-optic device, capable of conducting much of the solar radiation that strikes it right down to that black, radiation-absorbing skin."

Ashworth, William, "Bears: Their Life and Behavior" (Crown: New York, 1992), p. 88.
• "The hollow surface guard hairs work like a solar collector, directing the sun's warm rays onto the bear's light-absorbing black skin."

Rosing, Norbert, "The World of the Polar Bear", (Firefly: Buffalo, 1996), p. 20. (Originally "Im Reich des Polar Baeren", Tecklenborg: Steinfurt, 1994)
• "It has been determined that the hair does transmit ultraviolet energy, to a certain extent, along the hair, not through or across it."

Gardner, Matthew T., "The Assessment of Polar Bear Hair as a Transmitter of UV Light", B.S. thesis, Alfred University, Dec. 1994.
• "Like the snow and ice of the its habitat, the polar bear's coat is unpigmented; it derives its whiteness from internal reflections from the snow and ice in the nearly hollow shafts of its hairs. By capturing the sun's ultraviolet energy, this also serves to keep the animal warm."

Dewey, Donald, "Bears" (Friedman/Fairfax: New York, 1994), p. 68.
• "The hairs are also hollow, which allows them to work as efficient solar collectors. The hollow hairs conduct the heat of ultraviolet light, carrying it to the bear's skin, which is black, a color ideal for absorbing radiant heat."

Ovsyanikov, Nikita, "Polar Bears: Living with the White Bear" (Voyageur Press: Stillwater, MN, 1996), 46.
• "The hollow hairs are thought to function like optical fibers, transporting ultraviolet radiation to the bear's black skin, which stores the heat."

Ovsyanikov, Nikita, "Polar Bears " (Voyageur Press: Stillwater, MN, 1998), 18.
• "Polar bears and Arctic foxes, in fact, have hollow hairs for buoyancy, better insulation, and absorbing the sun's energy."

"Polar bear fur isn't really white -- it's transparent, or clear."
National Science Foundation, "Polar Connections: Exploring the World's Natural Laboratories" (NSF: Washington, DC, 1998), 39, 42.

• "The polar bears coat serves a variety of purposes. It provides excellent camouflage for the bear in its Arctic habitat. Although the glossy fur looks white, it actually is made of transparent, hollow guard hairs. These act as solar collectors, conducting ultraviolet radiation to the black skin beneath."

Anonymous, "Arctic Adaptations", Newton's Apple Episode 1103, KTCA Public Television, (1993-4) http://ericir.syr.edu/Projects/Newton/11/animals.htm.
• "Well, it acts kind of like an optical fiber, like communications fibers in telephone links, except for one thing. Instead of having to put light in just at one end and have it come out at the other end, it seems to accept light along the fiber, as opposed to just one end, which is very, very useful if you want to get lots of light into the fiber and transmit it down."

Clare, Alexis G., Interview with Daniel Zwerdling, National Public Radio's "All Things Considered", March 5, 1995.
• "[Polar bear hairs] trap the sunlight, acting like fiber optic wires, and conduct it to the bear's skin, which is black."

Francis, Lisa, "Fiber optic fur of the polar bear", WICN (radio) Science Moment #79, http://www.nesc.org/publications/moments/79.html (defunct link).
• "translucent hollow hairs that act like optic fibers to conduct..."

[This reference has since been removed, but may still be be circulating in old copies of the film.]
Casey, George (director), Novros, Paul & Casey, George (producers), Heston, Charlton (narrator) "Alaska: Spirit of the Wild", Graphic Films Corp. for Alaska Partners Ltd. in collaboration with the Houston Museum of Natural History, an Omnimax film, Apr. 1997.
• "The young bear is not put out by the cold. For the white fur is hollow, directing the rays of the sun down to the black skin, which quickly absorbs what little warmth there is to be had."

Regent, Petra (writer/producer), "Polar Bears - Shadows on the Ice", Discovery Channel, Oct. 28, 1997.
• "Remarkably the polar bear's skin is black. Hollow white hair follicles, like optical fibers, conduct warmth down to the skin."

Bayer, Wolfgang and Oyster, David F. (producers), "Polar Bears: Arctic Terror", ABC, Dec. 15, 1997.
• "Despite appearances, polar bear hairs are not white. Instead, they're colorless and hollow, like fiber optic wires. They conduct the sun's ultraviolet rays down to the black skin, where they are absorbed. This can be so effective that the polar bears may actually overheat. And so to cool down, they spread themselves out on the ice."

Clark, Barry (producer), "The Ultimate Guide -- Bears", Discovery Channel, Jan. 24, 25, Feb. 1, 1998.
• "Yeah, it does, yeah. They -- they also have the hairs -- the fibers are real hollow. They act pretty much like fiber optic cables. So it's just a way of keeping warm."

Wright, David, Interview with Miles O'Brien and Bobbie Battista, CNN Saturday Morning News, March 7, 1998.

• "The central core of each hair fiber is rough and scatters the incoming light in random directions. It is believed that this causes the light to be internally reflected within the hair in a way similar to the internal reflection of man-made fiber optic cables. This internal reflection conducts the light to the surface of the bear's skin, which is colored a light-absorbing black, and results in the conversion of UV radiation to heat with an efficiency in excess of 95%."

Lindsay, Amy, "Polar Bear Fur Reflects Nature's Genius", Structures of Nature, 3 (1), http://www.ioi.com/mvmntbac/mvmnts3/nature.html.
• "See river otters play, understand the fiber optic quality of polar bear fur, touch a starfish, measure the length and majesty of an eagle's wing."

New England Science Center (Worcester, MA), http://www.nesc.org/publications/presskit/brochure.html (defunct link).
• "Although the polar bear's coat appears white, each individual hair is actually a clear, hollow tube which tunnels the heat of the sun's rays to the bear's skin and helps it stay warm. Some of the sun's rays bounce off the fur, making the polar bear's coat appear white."

U.S. Dept. of the Interior, http://biology.usgs.gov/features/kidscorner/polarb.html
• "Although the polar bear's coat appears white, each individual hair is actually a clear, hollow tube which tunnels the heat of the sun's rays to the bear's skin and helps it stay warm. Some of the sun's rays bounce off the fur, making the polar bear's coat appear white."

U.S. Fish and Wildlife Service, http://www.fws.gov/~r9extaff/biologues/bio_pola.html
• "Polar bears' fur is not white, it's clear."

"Polar bear skin is actually black. Their hair is hollow and acts like fiber optics, directing sunlight to warm their skin."
No Title, http://www.erols.com/ocean3/uselessfacts.htm
• "Polar bears' fur is not white, it's clear."

"Polar bear skin is actually black. Their hair is hollow and acts like fiber optics, directing sunlight to warm their skin."
List 'O' Neat Facts, http://home.sprynet.com/sprynet/khuska/Neatstuf/neatfact.htm
• "Polar bears also use fibre optics to help maintain body temperature. The hollow guard hairs of the Polar Bear act like light pipes, conducting the energy from sunlight through to the bear's skin, which is black. Once absorbed by the skin, the energy changes wavelength, insulating the bear and ensuring the energy is not conducted away from the skin along the same fibre optic cables."

Anstee, E. David, "Animal Technology", http://www.kcs.com.au/~glenn/tscaniml.htm "Animal Technology", "Technoscape" column #308, 3D World Magazine, Sydney, Australia.
• "Scientists have recently discovered that the hairs on a polar bear are hollow and can channel ultraviolet light from the sun down to the bear's black skin, which absorbs it. This means that the bear's body is somewhat like a greenhouse, trapping solar energy and then storing it in the form of heat."

Wyles, Alex, "The Polar Bear" http://www.thewildones.org/SFC/Seana/alexW.html
• "[P]olar bears are equipped with hollow, translucent hairs to funnel available sunlight to their skin,..."

[The wording at this website has since been changed to: "It has long been believed that polar bears' hollow, translucent hairs act as heat conductors, funneling available sunlight to their black skin. Recently, however, physicists have taken a stab at disproving this theory, stating that, while the hairs are hollow, the shaft absorbs rather than transmits light. Clearly, the issue has come down to just that -- splitting hairs."]
Mangelsen, Thomas D., "Images of nature online" http://www.imagesofnature.com/Print2534.htm
• "Eine der Glanzleistungen der Natur beim Kälteschutz ist das Fell der Eisbären. Der Trick der Evolution: Die Haarschäfte des Bärenfells sind hohl und besitzen innen eine aufgerauhte Oberfläche. Dadurch erscheinen die Haare nicht nur schneeweiss, sie erhalten auch die Eigenschaften einer Glasfaser: Jedes einzelne Haar dient als hochwirksame Lichtfalle, die das auftreffende Sonnenlicht auf die schwarze Haut der Bären leitet, dort wird es als Wärme aufgesogen.Bis zu 95 Prozent der eingefangenen Sonnen-UV-Strahlung kann das Eisbärenfell in Wärme umwandeln."

[Translation: One of Nature's masterworks of thermal protection is the polar bear's pelt. Evolution's trick: the shafts of the bear's hairs are hollow and possess a roughened inner surface. Thus the hairs not only appear as white as snow, but also have the properties of a glass fiber: every single hair serves as a highly efficient light trap, which directs the incident sunlight to the black skin of the bear, where it is absorbed as heat. The pelt can convert up to 95% of the captured solar UV radiation into heat.]
Willmann, Urs and Schneider, Reto U., "Überleben in der Eiszeit" [Survival in the Ice Age], Facts Magazine (Switzerland), formerly at http://www.facts.ch/facts03/magazin/m_wis_txt.htm (defunct link).
• "The skin of the polar bear is black to conserve 80-90% of the solar energy trapped and channelled down the hollow hairs of its fur."

"Alaska 1995" http://www.bernhard.de/alska/alanhang/seiten/schwbaer.htm (defunct link).
• "The skin of the polar bear is black to conserve 80-90% of the solar energy trapped and channelled down the hollow hairs of its fur."

Andy Richards, "Wildlife: Polar Bear", http://dialspace.dial.pipex.com/andyrich/pbear.htm
• "Despite what our eyes tell us, a polar bear's fur is not white. Each hair is pigment-free and completely transparent...A polar bear's fur is a highly efficient solar collector. The hollow hairs trap ultraviolet light and conduct it to the bear's black skin, which absorbs and stores the radiant heat...A polar bear is so well-insulated that it experiences almost no heat loss."

Polar bears alive, http://www.polarbearsalive.org/facts3.htm
• "The clear, hollow fur warms the bear by trapping and transmitting ultraviolet light to the black skin underneath, while at the same time providing insulation from the cold. The ability of the fur to act as a solar heater supplies as much as 25% of the bear's energy needs during the sunny summer months."

The Learning Kingdom, "Cool Fact of the Day, 2-9-98", http://www.learningkingdom.com/press/coolfact/s2-9-98.html
• "Their fur, which appears white is actually clear and hollow and focuses solar heat down to the bear's black skin."

"Sounds from the Bear Den", http://www.bearden.org/sounds2.html
• "Polar bear hairs, according to Charles Feazel in White Bear, have "...an empty core in the center of each strand. Each hair functions as a light trap, a conduit that takes the sun's rays... the last few inches to his dark skin."

"Bear Hunting Network", http://www.bowhunting.net/bearhunting.net/bear2.html#thermoreg
• "[E]ach individual hair is actually a clear, hollow tube which tunnels the heat of the sun's rays to the bear's skin and helps it stay warm."

 http://www.geol.umd.edu/~candela/pb.html 
 

• "[T]he hair is two to six inches long; it collects heat: each hair is a hollow transparent tube that reflects and scatters the sun's rays to the black skin where the heat is absorbed; hairs change ninety-five percent of the sun's rays to heat."

[The 95% figure appears to come from Grojean and Kowalski, apparently from mathematical modeling of the pelt. It has never appeared in the technical literature. But how can 95% of the sun's rays be converted to heat when most of those rays are at wavelengths for which over half of the incident light is reflected?]
Brown, Gary, "The Great Bear Almanac" (Lyons & Burford: New York, 1993), p. 68.
• "If you look very carefully at the fur on a polar bear you see that each hair is transparent. When the bear is in the sunshine, the light goes right through his hairs, right to the bear's skin. This means that almost all the heat from the sun warms the bear's body, and then the long hairs keep the heat from going back into the air. The fur on a polar bear is like the glass on a greenhouse: the light and the warmth of the sun comes through, and then most of it is kept inside."

[Again, most of the sun's light is reflected off the pelt, giving the bear its white appearance.]
Larson, Thor, "The Polar Bear Family Book" (Picture Book Studio: Saxonville, MA, 1990).
• "Its fur consists of clear hollow hairs, through which most sunlight passes and is then absorbed by the black skin , for maximum warmth. The sun also warms the air trapped in the hollow hairs, so that the polar bear's coat acts like a thick warm sweater. Some sunlight is reflected off the clear hair, which gives a white appearance."

[Ditto]
"SFZoo: Bears", San Francisco Zoo, http://www.sfzoo.com/html/map.bears.html 
• "...and their fur consists of hollow, clear (not white) hairs that trap heat."

[This is a recurring but misguided notion -- that polar bear hair or fur is not white, but clear or transparent. The material that makes up the shaft of the hair is transparent in the visible (although not perfectly so), but the inner core is highly reflecting, so the hair is as white as snow (each flake of which is made up of 'transparent' ice).]
McKay, Dr. George, Consulting Editor, "Mammals" (Nature Company Discovery Library -- Time-Life Books: San Francisco, 1996), p. 39.
• "Pelsen består av lange dekkhår som nesten er gjennomskinnelige og fargeløse. Hårene slipper maksimal mengde lys gjennom slik at varmestrålene kan absorberes i huden. Huden er svart og over 95 % av varmestrålene som treffer huden blir absorbert. Kombinasjonen av pels og hud maksimerer varmeabsorbsjon om minimerer varmeutstråling. Det skapes en slags drivhuseffekt. "

[Translation: The fur consists of long guard hair that are almost transparent and colourless. The hairs let a maximum amount of light through so the heat rays can be absorbed by the skin. The skin is black and more than 95% of the heat rays that hit the skin are absorbed. The combined fur and skin maximize heat absorbency and minimize heat radiation so it creates a kind of greenhouse effect.]
[There's that 95% figure again. The amount of sunlight making it through the pelt has been variously reported in the literature at about 10-20%, not what I would call maximal.]
"Isbjorn: Biologi og levesett", http://www.lby.npolar.no/insyn/Arter/Isbjørn/biologi.htm
• "The individual hairs are clear and hollow, to conduct ultraviolet radiation to the bears' black skin, which allows the maximum solar heat gain. Polar bears are 95% efficient at converting ultraviolet light to usable heat."

Roger Williams Park Zoo, "Polar Bear Facts and Factoids" 
• "Like a giant solar panel, the skin of the bear is black to draw every bit of possible heat from the sunlight. The hairs of the pelt appear to be white, but are actually translucent and transmit the light down to the skin. "

[Most of the available heat from the sun is reflected back into space. Hence the bear appears white -- its pelt is highly reflecting in the visible.]
Bears.org (Gary Coulbourne, Phil Pollard), "Species Polar Bear" http://www.bears.org/animals/polar/
• "The polar bear's fur, which can range from white to creamy off-white in color to the casual observer, is actually translucent as well as hollow in the middle. This combination allows the energy of the sun, even on a cloudy day, to be efficiently absorbed by the bear."

["The...fur...is...hollow in the middle."?! Muddled language is usually the mark of a muddled understanding, as in this case. Always mistrust someone who uses 'fur' and 'hair' interchangeably, or 'heat', 'light', and 'energy', as is done in other sources.]
http://www.lycanthrope.org/~isbjorn/pbears.html
• "Their skin is translucent, not white, this is why they blend in so well with their environment."

[Their skin is black. Here is another example of how the original [incorrect] message gets further garbled upon retelling.]
Gomez, Miguel, "Polar World, A place where Polar Bears can live in piece [sic] with their Polar Bear friends", http://www.arches.uga.edu/~elsanto/polar.html (defunct link). 
• "Actually, there is something that breaks these creatures' parallel with great white sharks: Polar bears are not white at all. Their fur is perfectly clear -- and their skin is black. It's only the reflective properties of light that make them look white to the human eye."

[Fuzzy language again. The fur reflects most of the incident visible light. If it transmitted that light, you might be able to say that the fur was 'perfectly clear'. But you would also catch sight of the bear's black skin through its fur.]
"Discovery Online, Nature -- Animal House, Previous Dispatches 11/8", http://www.discovery.com/area/nature/zoo/dispatches/patch5.html
• "Warm in Winter: Hair stands up to let sun (ultraviolet rays) penetrate to the surface of the black skin which absorbs heat and the thick layer of blubber holds it in."

[As Bohren pointed out in 1981, the fraction of the Arctic solar spectrum which is in the ultraviolet is piddly. My own lab measurements show that if anything, a smaller fraction of ultraviolet light makes it to the skin of the bear than the fraction of infrared and visible that does. If the sign simply left out the "(ultraviolet rays)", it would probably be correct.]
Sign outside the polar bear exhibit, Toronto Zoo.
• "Individual polar bear hairs are actually colorless, not white. Under a microscope the transparent hair resembles a quartz fiber. The central core of each hair shaft scatters incoming radiation, giving the hairs their white appearance. A similar scattering effect accounts for the snowflake's whiteness. (Progress in English: Book 6)"

[Why a quartz fiber? Because that's what Grojean et al. wrote, and quartz, unlike glass and polar bear hair, transmits ultraviolet light. Grojean et al. tried to model polar bear hair by using quartz capillary tubes -- because of quartz's transparency to UV -- without first checking whether the hairs were also transparent to UV. They are not.]
"I didn't know...(No. 126-150) http://www.ikeda.osaka-kyoiku.ac.jp/~higuchim/know-j126-150.html,  http://www.ikeda.osaka-kyoiku.ac.jp/~higuchim/know126-150.html


---

Care to respond? dkoon@stlawu.edu