why do polar bears have white fur

Ursus maritimus вthat's the Latin name of the, the world's largest
who inhabits the far northern regions of Greenland, Siberia, and Canada. Its name means в," which is quite appropriate since bears spend most of their lives in, on or around water в mainly on the of the. bears are among the largest land on Earth. Male bears can weigh 700 to 1,400 pounds and stand 8 to 10 feet tall. While bears are excellent swimmers, they prefer to stay on top of the that covers the Arctic most of the year. Why do they spend so much time on the frigid Arctic? The Arctic waters and floes are where their favorite food в seals в can be found. bears will also occasionally eat other animals, including walruses and dead whales, but seals are by far their favorite food. Seals can be tricky to catch, though, so bears must hunt with great and. Fortunately, their white coloring helps them blend in with their icy surroundings. So how did bears that live in a snowy-white world come to have white fur? Believe it or not, their hair isn't actually white! Their long outer hairs, which protect their soft, thick undercoat, are mostly and. The thinner hairs of their undercoat are also colorless. hair looks white because the air spaces in the hairs scatter light of all.

When something reflects all of the visible wavelengths of light, we see the color white. Some scientists believe the was once a close relative to the brown. They think that, over time, bears moved to the Arctic, where they adapted to their surroundings by developing fur that would help them blend in with the harsh, white Arctic. Not all bears look white, though. If you've ever seen a in a zoo, you may have noticed that its fur can appear almost green. Scientists discovered that from the pond waters in the bears' enclosures made the bears turn green. They learned these were found not on the surface of the hairs but inside the hairs! Polar bears are white, right? Not quite. Though closely related to the brown bears you might find in the most northern regions of the United States, polar bears have a special set of adaptations that allow them to live in the cold Arctic. The most famous of these adaptations is their bright white coloring, which lets them blend in as they roam across ice and snow in search of seals to eat. Can you imagine a dark brown bear trying to hide against bright, white snow? Although while polar bears usually look white, their fur isnвt white at all.

And their skin is black! Polar bear fur is actually see-through, but it takes on a white color because of its structure. Your hair gets its color from something called pigment. Different types of pigment form in different amounts to create various colors when light hits them, sort of like when you mix shades of paint. But polar bear hair has a structural color, which comes from the way light bounces around the structure of the hair itself в no pigments required. Unlike human hair, polar bear fur is hollow like a straw. These tubes are too small to see without a microscope, but thereвs enough room for light to scatter inside. When the bears stand in the sun and all that light bounces off them, they look white. Some scientists used to think these hollow hairs might do more than just help bears blend in. They thought the structure of the hair, along with the black skin beneath, allowed polar bears to absorb way more heat from sunlight than other animals can. Itвs a nice idea, because one wonders how animals manage to keep so toasty warm in Arctic conditions. But experiments showed that very little sunlight actually makes it all the way down the hairy tubes to touch bare bear skin.

That makes sense, because the time of year when bears actually have to worry about keeping warm в the Arctic winter в is almost totally dark. It would be silly if their hairs were designed to collect as much warmth as possible during the sunny, warm summer. If you occasionally see a polar bear who looks a little green, hollow hairs are to blame. Tiny plants called algae sometimes grow inside their hollow hairs. The space where light would usually scatter to create white coloring is filled with green stuff instead, so the bears look like they just took a tumble in some fresh-cut grass. This happens only when itвs quite balmy. Climate change is raising the temperature in the Arctic. But green bears have been spotted more often in zoos, where the weather can be even warmer than an unusually hot Arctic summer. Zookeepers have found a solution, according to Julie Hartell-DeNardo of the St. Louis Zoo: Chilled, salty water with a good filtration system can keep algae growth at bay, so even captive bears can generally maintain their bright white sheen all year round. Read more Ever Wondered columns:

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