California sea otters have the densest fur of any mammal on Earth, allowing them to live in cold water even though they don’t have blubber like whales.
With up to a million hairs per inch, the super-soft coats were once such a lure for hunters that they nearly led to the otters’ demise in the early 1900s. But now, the federally protected species is free to use its luxurious fur for one key purpose: to keep warm in the often chilly Pacific Ocean, particularly during winter months.
But, as this video in the PBS Deep Look series explains, it is not just the fur’s density that keeps out the cold. Scanning electron microscope images show that each hair is coated with barbed scales that allow the fur to form a nearly waterproof layer.