Can Hippos Swim? How Hippos Really Move Through Water

How hippos move through water

The hippo’s skeleton is built to carry great weight, and its bones are dense. Together with a heavy body and relatively little fat, this means an adult hippo sinks rather than floats. In shallow water it simply stands or walks on the bottom with only its eyes, ears and nostrils showing.

In deeper water, a hippo moves with long, bouncing strides. It pushes off the riverbed with its legs, glides forward for a moment, then touches down and pushes again, a little like an astronaut moving in low gravity. Film of hippos in clear water shows them almost galloping along the bottom with surprising grace. Their toes are slightly webbed, which may help them on soft mud.

Because they depend on touching the bottom, hippos usually avoid water that is too deep for them. They prefer slow rivers, lakes and pools with gently sloping banks, where they can rest with their bodies covered and their heads above the surface.

Is it true that hippos cannot swim at all?

Scientists still discuss exactly how to describe it. Hippos are clearly excellent at moving in water, and when needed they can cross rivers and channels. But they do not paddle at the surface like a dog or a deer, and adults do not float. Most experts therefore say that hippos do not swim in the usual sense; they walk, bound and push their way through water.

Calves are a partial exception. Young hippos are more buoyant and can paddle at the surface for short periods, but in deeper water they often climb onto their mother’s back to rest.

How long can hippos hold their breath?

An adult hippo usually surfaces to breathe every 3–5 minutes, and calves breathe more often, every few minutes. Some sources give longer maximum times, but these are poorly documented, and typical dives are short.

When a hippo submerges, its slit-like nostrils close and its small ears fold shut to keep water out. A clear membrane, sometimes called a third eyelid, slides across each eye. Because the eyes, ears and nostrils sit high on top of the head, a hippo needs to raise only a small part of its head to breathe and look around.

Do hippos sleep underwater?

Yes, sometimes. Hippos often sleep in shallow water with their nostrils above the surface, or on sandbanks and riverbanks. They can also sleep fully submerged: a sleeping hippo rises to the surface, takes a breath and sinks again, apparently without waking. This is an automatic reflex, so the animal does not drown during sleep.

Unlike whales and dolphins, which can rest one half of the brain at a time, hippos sleep with both halves of the brain at once, like other land mammals.

Why do hippos spend so much time in water?

Water solves several problems for a hippo. It keeps a huge body cool in the African heat and protects the bare, thin outer skin from drying out and cracking in the sun. Water also supports the hippo’s great weight, saving energy during the long hours of rest.

The skin produces a reddish secretion that works as a natural sunscreen, but it is not enough to protect a hippo for long in strong sun. That is why hippos spend the day in water or mud and come out mainly at night to graze. Read more in Do hippos sweat blood?

Many important events in a hippo’s life also happen in water. Hippos mate in the water, calves are often born in shallow water, and calves can suckle underwater, closing their ears and nostrils while they feed.

How do hippos compare with other water animals?

Hippos are semiaquatic: they need water, but they feed on land. Their closest living relatives, the whales and dolphins, went much further and became fully aquatic, with streamlined bodies, flippers and tails that allow true swimming. See Are hippos related to whales? for that story.

The smaller pygmy hippopotamus of West Africa spends less time in water and more time in forest, but it also uses rivers and swamps to keep cool and to escape danger. Another big river animal, the Nile crocodile, shares many hippo rivers, but crocodiles are true swimmers, driven along by powerful sweeps of the tail.

How fast can hippos move in water and on land?

There are few reliable measurements of hippo speed in water, but observers agree that they can move fast when bounding along the bottom, far faster than a person can wade. On land, hippos trot and can briefly run at speeds reported up to about 30 km/h (19 mph), although this figure has rarely been measured carefully.

Hippos cannot jump, but they can climb steep riverbanks, and they regularly walk several kilometers each night between their resting pools and their grazing grounds.