Sunscreen made at home
Why Do Hippos Sweat Red?
A hippo oozes a red liquid that looks alarming and is actually sun cream and antiseptic at once.
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Step 1 of 5
It has no fur to hide behind.
Almost all the hippo's skin is bare. Fur normally shades an animal and holds moisture against the skin, and without it a hippo would burn and dry out in a single afternoon.
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Step 2 of 5
So it makes its own sun cream.
Glands in the skin ooze a clear liquid that turns red within minutes as it reacts with air. The red pigment soaks up the sunlight that would otherwise burn the skin.
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Step 3 of 5
The same stuff fights germs.
Hippos fight constantly and carry deep wounds, and they live in water full of bacteria. The red secretion kills many of those bacteria, so the wounds heal that should not.
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Step 4 of 5
Water does the cooling.
Even with sunscreen a hippo overheats in the open. It spends the hot hours submerged with only eyes, ears and nostrils above the surface, and comes out to feed at night.
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Step 5 of 5
Eyes, ears and nose in one line.
All three sit on top of the head at the same height, so a hippo can see, hear and breathe with the rest of itself hidden. Everything else is under the surface.
A hippo cannot really swim. It walks and pushes off along the bottom, and being heavier than water is an advantage down there.
The short version
A hippo has no fur, so it makes a red secretion that blocks sunlight and kills germs, and stays submerged through the heat of the day.
Try it yourself
Notice how sunscreen sits on the skin rather than soaking in. The hippo's works the same way — a layer that absorbs the light first.