A team at MIT has figured out exactly how otter and beaver fur keeps the animals warm in cold water. Seals, whales and walruses all happily splash about in chilly ocean waters—kept warm by a thick layer of blubber. Sea otters, though just as happy zipping through cold waters, are relatively svelte in comparison. The reason? Their magnificent fur coats. The thick fuzz is roughly 1,000 times more dense than human hair and can trap air bubbles, which insulate the otters in frigid water.
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