Hippos might be cute, but these tough animals are rough and tumble. While they can't breathe underwater, they can rise to take breaths in their sleep to keep from drowning. Now, if only they could swim. Let’s take a closer look at these fascinating animals.
The River Horse
Now hippos don't really look like horses, but the name hippopotamus comes from the Greek language and means "river horse." These semi-aquatic mammals are actually more closely related to whales than horses. There are two different species of hippos: The common or river hippo (Hippopotamus amphibious) and the pygmy hippo (Choeropsis liberiensis)
Hippos are big: males can be 16.5 feet long. Out of all the terrestrial animals on Earth, only elephants and white rhinos are bigger. All that size, and they're herbivores who graze on grasses and plants throughout the day.
Hippos are known to be territorial and can be downright aggressive when their territory or young are threatened. They've got the bite force to back it up, too. A hippo bite can cut a human completely in half!
Where Do Hippos Live?
Hippos live in Sub-Saharan Africa. Within this region of the world, hippos tend to spend much of their time in the water, living in areas like lakes and rivers.
This vulnerable species at one time lived throughout Sub-Saharan Africa, but now their populations are mostly localized to East African countries where they are protected. Habitat loss and hunting have been the major contributors to hippos decreasing in population.
Why Do Hippos Spend So Much Time in the Water?
Hippos are big and tough, with incredibly thick skin: roughly 2 inches! And, as you can probably imagine, that skin is waterproof. They don't develop wrinkly hippo skin when they’ve been in the river for hours, unlike when you've been in a bath for too long.
As thick as their skin is, hippos are very prone to sunburn. Staying in the water helps protect them from the sun's rays. Being in the water also aids hippos in staying cool under the hot African sun.
Don't worry though, hippos also secrete an oily substance (which happens to be pink) that helps act as hippo sunblock. It's also this compound that waterproofs their skin and gives rise to the incorrect assumption that they sweat blood.
For an animal that spends so much time in the water, you might think that they're great swimmers. In fact, they can't swim. They can't even float – they're much too dense.
That said, hippos can walk or run along the bottom of the river or waterway they're in. (They can get up to speeds off 22 miles per hour!)
So, Can Hippos Breathe Underwater?
Of all the nifty things to learn about hippos, it might seem a little disappointing to learn that hippos cannot breathe underwater. But they can hold their breath for a few minutes.
- Adult hippos can hold their breath for about 5 minutes in one go.
- Newborn hippos can only hold their breath for about 40 seconds.
Babies may be born in or out of the water. If they're born in the water, the momma hippo has to push the new baby to the water's surface to breathe.
Adaptations for Staying in the Water
One of the biggest reasons hippos can so easily spend time in water is because their eyes and nostrils are placed high up on their heads. With this positioning, they can see their surroundings and breathe with their eyes and nose above the waterline.
Another nifty adaptation for staying in the water is that hippos can close their nostrils (and their ears), keeping water from rushing into those areas. When they submerge, they don't have to worry about water running up their nose.
Hippos nap a lot, especially during the day. Because of this napping schedule, hippos have developed a subconscious reflex. To keep them from drowning, their bodies push off from the ground to take a breath – all without waking up. This reflex is important because hippos can spend up to 16 hours each day in the water.
Hippos have other adaptations that allow them to spend significant time in the water. They have a clear membrane over their eyes, so even if they're fully submerged, they can still see. It’s like wearing goggles when you go swimming.
The pink substance that they secrete like sweat may help prevent infections, a real risk for animals that live in less than sanitary conditions and tend to fight with canine teeth that can be almost 2 feet long!
To move through the water, their toes have slight webbing between them. Interestingly, pygmy hippos have less webbing between their toes than river hippos.