The Fantastic Fur of Sea Otters | Deep Look


Here’s one word to describe the Northern
California coast: COLD. If you or I were in those waves without a wetsuit right now, we’d get hypothermia in minutes. But sea otters have figured out how to survive here. Which is amazing, especially when you consider that this little guy has to maintain an internal body temperature around 100 degrees Fahrenheit. Sure, whales do it. Sea lions do it. But those
mammals have had tens of millions of years to adapt to life in the ocean. Evolutionarily speaking, sea otters are newcomers…
land animals that waded into the ocean a mere couple of million years ago. Unlike other ocean mammals, they have no blubber. And they’re small, meaning they are constantly
losing heat. Their ace in the hole– is fur. Sea otters have the thickest fur on the planet.
Up to a million hairs per square inch. It’s what keeps them alive. It also almost killed them — back around
the 19th century sea otters were hunted nearly to extinction to make hats and coats. But it’s not really the fur, per se, that
keeps the otter warm. It’s air. Fur works by trapping air near the skin’s
surface, like a down comforter. Sea otter fur is so dense it’s basically
waterproof. You can see how dry it is close to the skin. That layer of air gives the
otter’s fur a glossy look as it tumbles through the water. Baby sea otters? Their fur traps so much air
that they bob at the surface — their fluffiness makes them buoyant. That is, until
they shed the pup fur and learn to dive. This excellent insulation comes at a price. Every time a sea otter dives, some of the
air in their fur gets forced out — see those bubbles? And so the otter has to groom
himself all over again, to pump more air in. Let’s take a closer look at this fur. As you can see, sea otter fur is actually
made up of two kinds of hair: under fur, the insulating part, and those longer, protective
guard hairs. Under a microscope, you can see how the individual
hairs are scaly and rough. That roughness is important. Those barbs on the hair shafts let the fur mat together. That’s what traps the air in. For comparison – here’s a coyote. Coyotes, of course, don’t live in the freezing ocean, and their hairs don’t have the barbs. Their fur keeps them warm on land, but they wouldn’t stay dry in the ocean. In a lot of ways, otters have more
in common with land animals. But many years ago, otters took an evolutionary leap into these icy waters. And today they’re making it work.

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