Which Animal Has the Densest Fur?

It’s cold in the ocean waters off the California coast, but the ubiquitous sea otters that frolic there have a clever way to stay warm: Air bubbles, coupled with the densest fur of any mammal on Earth.

To keep warm, a sea otter has over one million hairs on every square inch of its body – the densest fur of any mammal.
To keep warm, a sea otter has over one million hairs on every square inch of its body – the densest fur of any mammal.

Although otters lack the blubber of seals, whales, and walruses, there are up to one million dense, spiky hairs per square inch on a sea otter’s body. This thick fur is roughly 1,000 times more dense than the hair on a human head. Otters add another layer of protection by blowing air bubbles into their fur to help with insulation and buoyancy, and to keep their bodies almost completely dry and toasty warm.

A hairy situation:

  • Sea otter pelts feel smooth and soft, but seen with a microscope, their coat is covered in tiny, geometric barbs that trap the air and offer excellent insulation against the often-chilly waters of the Pacific Ocean.

  • On the downside, this air-blown fur coat makes diving for food – such as sea urchins, various mollusks and crustaceans, and some species of fish – much more of a chore.

  • A covering of hair sets mammals apart from other animals, ranging from the sparse hair on a human to the more formidable bristles on a boar, or the fleece on a ram. Hair is actually keratinized filament, the same substance found in human fingernails.

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    • To keep warm, a sea otter has over one million hairs on every square inch of its body – the densest fur of any mammal.
      By: Wolfram Burner
      To keep warm, a sea otter has over one million hairs on every square inch of its body – the densest fur of any mammal.