Today’s Wonder of the Day was inspired by Lilly. Lilly Wonders, “How big are hippos?” Thanks for WONDERing with us, Lilly!

If you love games, you may have played Hungry Hungry Hippos at one time. The plastic hippos in the game like to gobble up marbles. But what about real hippos? Do they eat marbles? If not, what exactly do they eat? And are they really hungry all the time?

The hippo is also known by its full name (hippopotamus) or its scientific name (Hippopotamus amphibius). Its name comes from the ancient Greek words for “river horse," because these large mammals spend much of their time in the water.

After the elephant and the rhinoceros, the hippo is the third largest land mammal. Although hippos somewhat resemble pigs and other land-dwelling creatures, their closest living relatives are actually whales and porpoises!

This fact might explain why hippos are semi-aquatic. They spend much of their day (up to 16 hours or more) in the water. Living in rivers, lakes, and mangrove swamps in Africa, hippos stay in the water or the mud to keep cool. At night, they head for land to graze on grass and other plants.

Despite a diet of mostly grasses and plants, hippos grow to be quite large. How large? Adult hippos can weigh as much as 8,000 pounds! They eat over 80 pounds of grasses and other plants each night.

So, hippos really are hungry, but not as hungry as you might expect. They only eat about 1% of their total body weight each day. Other animals, such as cows, can eat up to 2.5% of their body weight each day.

Hippos are easily recognized by their large, barrel-shaped bodies, huge mouths and teeth, stubby legs, and almost-hairless bodies. Given their short legs and huge size, you might think hippos would be slow. But you would be wrong! Hippos can easily outrun a human over short distances.

If you ever find yourself near a hippo, watch out! Not only can hippos outrun you over short distances, they're also known for being very aggressive. This trait makes them one of the most dangerous animals in all of Africa.

Hippos can hold their breath underwater for up to five minutes or more. Their eyes and nostrils are on the tops of their heads, which helps them stay mostly underwater while still being able to see and breathe.

Occasionally, you'll see hippos sunbathing on the shoreline. Don't be alarmed, though, if it looks like they're sweating blood. Their thick skin actually secretes an oily red substance that moisturizes the skin and acts like sunscreen to protect their skin from the sun and germs.

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