How do sea otters keep warm?
It is a universally accepted truth that sea otters are adorable. But did you know the wettest of weasels are extremely hardy little critters too? They live among the kelp forests that grow off the west coast of North America, Alaska and Russia – where the water temperature can be as low as one degree Celsius (33.8 degrees Fahrenheit) – and almost never come ashore. Heat loss in water is 27 times faster than in air of the same temperature, meaning sea otters face a constant battle to maintain their core body temperature and stay alive.
Unlike other marine mammals, otters don’t have a layer of insulating blubber to keep them warm in chilly waters. Instead, they rely entirely on their velvety fur. At up to a million hairs per square inch (for comparison, you probably have as many hairs on your entire head), it is officially the densest fur in the world.
Sea otters’ coats are composed of two layers: long waterproof guard hairs and a fluffy underlayer. The guard hairs form a waterproof barrier and are kept oiled with sebaceous secretions from glands in the otter’s skin. Bundled around each guard hair are ten to 100 underhairs. These hairs are covered in microscopic barbs that enable the hairs to tangle together and trap a layer of insulating air next to the otter’s skin, providing four times the amount of insulation as the same amount of blubber.
￼How does a sea otter spend its day?
￼Besides their plush fur, sea otters employ another trick to keep themselves warm: they eat an awful lot! Their high metabolic rate – two or three times that of a comparatively sized land mammal – keeps them cosy from within, but means they must consume about 25 per cent of their own weight in food every day.
Favourite meals include crabs, mussels and sea urchins, which they smash and pry open with rocks, using their chests as dining tables as they float on their backs on the surface. Equally active during the day and night, they typically spend several hours foraging at sunrise, several more in the afternoon until sunset, and again around midnight.
Because they’re so reliant on the quality of their fur for survival, sea otters devote a huge chunk of their day to grooming. Air is forced out of their coats whenever they dive for food, so they compulsively ruffle and rub at it with their paws to clean and re-fluff it with air bubbles.
When they’re not tending to their appetites or their coats, otters like to kick back and relax. By wrapping themselves in fronds of kelp, they anchor themselves in place, free to bob in the currents, snooze and let their cares drift away.
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