When we send travelers on safari, we always tell them to pack a broad-brimmed hat and plenty of sunscreen. But how do the animals keep from getting baked to a crisp? If you’re not one of the creatures lucky enough to have a thick coat of hair (or unlucky enough, depending on how high the temperatures soar), how do you keep your skin protected?
If you’re a hippo, the answer is simple: it comes naturally.
Unlike many large mammals, hippos are nearly hairless (and they spend long hours in the sun).
They’re uniquely adapted to address this, however, since their skin secretes an oily substance which acts as a natural sunscreen. Though this secretion comes out colorless, it quickly turns a brownish-red color in the air, which led ancients to believe the animals were actually sweating blood (don’t worry, two acidic compounds make up the secretion…and neither of them is sweat or blood). The acids in this oily substance also protect hippos in another way: from germs. The secretion simultaneously acts as a natural antibiotic.
The sunscreen keeps harmful rays from damaging hippos’ skin, but the skin itself works pretty hard to protect the hippos from just about everything else. Six inches thick, it’s a natural barrier to most predators. And while packs of lions, hyenas, and crocodiles have been known to attack young hippos, adults—with their massive size, thick skin, and well-known tempers—don’t really have any predator problems.
But you can’t just get magical, self-protecting, wall-thick skin without a trade-off. For the hippos, it’s a dependence on the water where they spend most daylight hours; if they stay out of it for too long, their skin will dry out and crack.
So they’re forced to just hang out in the pool all day, not being bothered by any predators, safely soaking up the rays. Tough life those hippos have. Tough life.