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Weird Animal Fact: Sea Otters Have the Densest Fur

The Southern Sea Otter has the densest fur in the animal kingdom, with about 1,000,000 hairs per square inch of its body. An adult male otter can have as many as 800 million hair fibers covering its body.

The thickness of an otter's fine, velvety coat varies throughout its body, from about 170,000 to 1,062,000 hairs per square inch. The highest hair density is on the critter's sides, forearms and rump, while the lowest density is on its legs, feet and chest.

Its extraordinarily dense fur insulates the otter's body, helping to maintain its temperature in frigid waters. Otters lack the layer of blubber, or fat, that serves that purpose for other marine mammals , so otters must rely on their thick hair to stay warm.

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