Hippopotamus

The hippo is a very big animal.

It has a large, round body. Its legs are quite short. The hippo has very little hair. Its skin is thick and dark.

Its eyes and ears are on top. This lets it see and hear. It can stay under the water. It can still breathe air.

Its mouth can open very wide. It has large teeth for fighting. It uses flat lips to eat grass. It eats at night.

Hippos are very strong animals. They are the third largest land animals. They are found in Africa.

The hippo is a very big animal. It is the third largest land mammal. Only elephants and rhinos are bigger.

Hippos live in rivers and lakes in Africa. They spend much of the day in water or mud. This helps them stay cool.

Their bodies are shaped like barrels. They have short legs and very little hair. Their eyes, ears, and nostrils are high on their heads. This lets them see and breathe while swimming.

A hippo can open its mouth very wide. It has large teeth called canines. These teeth are for fighting, not eating. They use flat lips to pull in grass.

Their skin is thick and dark. It makes its own sunscreen. This is a red liquid that protects them from the sun. It also stops germs from growing on their skin. Even though they look chubby, they have very little fat.

The hippopotamus is a huge mammal found in sub-Saharan Africa. People often call them hippos or river horses. They are the third largest land mammal on Earth. Only elephants and rhinoceroses are bigger than them. Hippos are very special because they live in both water and on land. They spend their days in rivers, lakes, or mangrove swamps.

To stay cool, hippos spend most of the day in water or mud. They have barrel-shaped bodies and very short legs. Their eyes, ears, and nostrils sit high on their heads. This lets them see and breathe while their bodies stay underwater. Their bones are very dense and heavy. This helps them sink to the bottom of the water to move around.

Scientists used to think hippos were related to pigs. However, new tests on DNA show a different story. Their closest living relatives are actually cetaceans, which are whales and dolphins. These two groups split from a common ancestor about 55 million years ago. This shows how much animals can change over a long time.

Adult hippos are very large and heavy animals. A male, called a bull, can weigh about 1,500 to 3,000 kilograms. A female, called a cow, is usually a bit smaller. Some very large males have even reached 4,500 kilograms. Their mouths can open very wide, between 100 and 110 degrees. They use large canine teeth for fighting rather than eating.

Even though they look chubby, hippos have very little fat. Instead, they have thick skin that needs protection. Their skin makes a red substance that acts like sunscreen. It starts out colorless but turns red-orange in a few minutes. This liquid also stops germs from growing on them. It is not actually blood or sweat, even though some call it blood sweat.

The hippopotamus, often called the common hippo, is a massive semiaquatic mammal. It is native to the sub-Saharan regions of Africa. This animal is a megaherbivore, meaning it is a very large plant-eater. In fact, it is the third largest land mammal on Earth. Only elephants and some rhinoceros species are larger than the hippo. Within its specific group, the even-toed ungulates, it is the largest living member.

To understand how a hippo moves, we must look at its unique anatomy. Their skeletal structure is described as graviportal, which means it is built to support enormous weight. They have very dense bones and a low center of gravity. These features allow them to sink and walk along the bottom of rivers or lakes. Because the water supports much of their mass, they can have relatively short legs. Their toes are webbed to help with movement, and their pelvis sits at a 45-degree angle.

A hippo's body is specially designed for a life shared between land and water. Their eyes, ears, and nostrils are located high on the roof of the skull. This placement allows them to see, hear, and breathe while the rest of their body stays submerged. When they go fully underwater, their nostrils and ears can close tightly. They also have nictitating membranes, which are clear layers that cover and protect their eyes. Even their voices are adapted, as they have horizontal vocal folds similar to those found in baleen whales.

The hippo's mouth is one of its most famous features. Their jaws are powered by massive muscles called the masseter and digastric muscles. The jaw hinge is positioned far back, allowing them to open their mouths at a wide angle of 100 to 110 degrees. This wide gape is possible because of large, droopy cheeks that provide extra muscle attachment space. While they have large canine tusks that can reach 50 centimeters, these are used for combat rather than eating. For food, they use flattened, horny lips to pull up grasses, which are then chewed by their molars.

For a long time, scientists thought hippos were related to pigs because of their teeth. However, modern science has revealed a much different history. By studying DNA and blood proteins, researchers discovered that their closest living relatives are actually cetaceans. This group includes whales, dolphins, and porpoises. The lineage that led to hippos and whales split from other even-toed ungulates about 55 million years ago. This shows how evolutionary paths can diverge in surprising ways.

Evolutionary history shows that hippo ancestors likely entered Africa from Asia. One possible ancestor, the genus *Kenyapotamus*, lived in Africa between 15 and 5 million years ago. The oldest records of the modern *Hippopotamus* genus date back to the Pliocene epoch, roughly 5.3 to 2.6 million years ago. Throughout history, different species have lived in various places. For example, the *Hippopotamus gorgops* was much larger than modern hippos, with a body mass exceeding 3,000 kilograms.

Physical size and weight vary between the sexes and species. An adult male, or bull, typically weighs between 1,500 and 3,000 kilograms. Some exceptionally large males have reached 4,500 kilograms. Females, known as cows, are generally smaller and stop growing around age 25. While bulls continue to grow throughout their lives, cows reach a stable maximum weight.

Finally, we must look at how hippos protect their skin. They have thick, nearly hairless skin that secretes a special substance. This liquid is not actually blood or sweat, even though people sometimes call it "blood sweat." It is a secretion containing two acidic pigments: hipposudoric acid and norhipposudoric acid. These pigments act as a natural sunscreen by absorbing ultraviolet light. They also serve an important biological role by inhibiting the growth of disease-causing bacteria.