Hippopotamuses are enormous animals that spend almost their entire day in the water. Most of their body is usually underwater, including their mouths.
But hippos are mammals, so how are they able to breathe below the water?
Hippos don’t actually breathe underwater. Instead, they take deep breaths and hold them for five minutes or more at a time. They can even resurface for air when they’re sleeping without waking up. When they’re not completely underwater, they breathe through their noses. Their noses are at the top of their heads along with their ears and eyes.
Hippos Can Hold Their Breath For Five Minutes
Hippopotamuses are mammals and can’t breathe underwater. They rely on their lungs to pull oxygen from the air.
But they still spend a lot of time in the water, so how do they do it? The answer does lie in their lungs, in fact, as well as their eyes and noses. Hippos can hold their breath for five minutes or longer.
A hippo’s nostrils close (adducting) completely while underwater. This helps prevent water from entering their lungs. They also have a clear membrane over their eyes that lets them safely see under the water.
Hippopotamuses do underwater, but that doesn’t mean they’re breathing down there.
Instead, they have an evolutionary reflex that allows them to push themselves to the surface without waking up. There, they take the breaths they need, then sink back down below the water.
How Much Time Do Hippos Spend Underwater?
Because they don’t actually breathe underwater, hippos are not amphibious.
Instead, they’re “semi-aquatic” mammals because they spend almost the entire day in the water. This is in part because of how hot and dry their native habitat is.
Hippopotamuses are native to sub-Saharan Africa where it’s hot, dry, and sunny.
The temperatures there can regularly reach over 100°F (40.5°C) during the hottest parts of the year. It is also rare for temperatures to drop below 60°F (15.5°C) even in winter.
Hippos live at lower elevations in wetlands, lakes, and slow-moving rivers. Lower elevations are often warmer than in the mountains.
These areas are also much more open with little tree coverage. This means they also receive more sun exposure than other areas.
In order to keep themselves cool, hippos have to stay in the water, either partially or fully submerged. They’ll stay in the water as much as possible during the day.
Hippos likely spend 16 hours or more each day either underwater or standing on shallow banks. They may also wallow in areas of deep mud to try to keep cool.
They then come out after the sun goes down in order to eat. Hippos graze for six hours or so, eating one to one-and-a-half percent of their body weight.
A male hippo can weigh between 3,500 to 9,920 pounds (1,600-4,500 kg). They’re also over ten feet long and can be about five feet high at the shoulder.
Moving bodies that large around can be exhausting. If they’re not eating, hippos are often inactive to conserve energy.
However, they may have to travel for miles in order to find food. Hippos eat short grass and fruit that falls from trees.
It may take a hippo all night to find food and eat enough to keep them going. Even so, they’ll return to the water by daybreak in order to avoid the heat and sun.
Hippos Don’t Have Normal Sweat
It’s more important for hippos to spend time out of the sun than most animals. This is because they don’t have normal sweat glands. Instead, they secrete a thick red fluid from their layer of inner skin.
There’s a myth that this fluid is blood, but it only appears like blood because of its color and viscosity. Instead, this “blood sweat” fluid works as a sunblock for a hippo’s sensitive skin.
It also helps protect them against infections. Hippos can spend a lot of time in dirty water contaminated by waste and bacteria. Despite this, they don’t have a higher rate of infection than other animals.
Hippos Have Special Adaptations For Water
Since they need to be in the water for most of the day, hippos have physical adaptations to help them.
Not only do their eyes have a protective membrane, but they are also on top of a hippo’s head. This allows hippos to keep an eye out for threats even if the rest of their body is underwater.
This is also true of their ears and eyes. By being on top of the hippo’s head, they allow the hippo to both keep alert and also breathe safely. Like their nostrils, a hippo’s ears also seal themselves shut when they submerge.
Hippos even give birth underwater, although they sometimes do so on land as well. Baby hippos, or calves, are not as strong as their parents.
They also can’t hold their breath as long, usually about 40 seconds or so at first. After birth, the mother pushes their baby to the surface so they can take a breath.
Then, the mother hippo will go for days without food to stand watch over their young. The babies take a few days before they have enough strength to leave the water for grazing.
Baby hippos nurse for eight months; the mothers can even nurse them while underwater.
Can Hippos Swim?
For an animal that spends so much time in the water, hippos can’t actually swim. In fact, they can’t even float due to how much density their bodies have. This is why they spend so much time in shallow water.
When they do need to move underwater, though, they simply walk along the bottom of the river. They can also push themselves off the bottom in a kind of bouncing gait.
They have webs between their toes to help them push through the water.
Dangers In The Water
Though they’re herbivores, hippos can be extremely dangerous to humans and other animals. Hippos can be very aggressive, in particular around their young.
There were attacks on 40 people in 2020 on Lake Naivasha, resulting in 14 deaths.
Some experts estimate that up to 500 people die per year from hippo attacks. However, there is no conclusive data about the true number of deaths.
Hippos also have enormous incisors and canines, which they use for fighting, that grow all the time.
It’s clear that hippos are more than capable of protecting themselves. But they do still face dangers from some predators – and even themselves.
Young hippos are in danger of predators that otherwise don’t take on full-size hippos. Crocodiles may swim up to snatch a juvenile hippo. Even a group of lions may take interest in a young hippo at the edge of the water.
This is part of the reason why they’re so protective of their young. Hippos live in large groups known as pods or sieges. Each pod can contain 200 hippos, but the average is around 40.
Even so, male hippos are very territorial and they will fight other hippos they think are a threat. But in the process of protecting themselves and their pod, they can cause real problems.
They have violent altercations during which they can injure or kill smaller hippos.
Like all mammals, hippos have to have oxygen from their air in order to breathe. They can’t breathe underwater like fish or amphibians.
Hippos do have special adaptations for being in the water, though. They can hold their breaths for a long time and even go to the surface for air while they’re sleeping. Their eyes, ears, and noses are also on top of their heads. That way they can observe their surroundings while underwater.
Hippos need to have good adaptations to water since they need it to keep cool. Their skin is very sensitive to sunlight and they don’t have normal sweat glands. Staying in the water helps keep their skin moist and cool.