Hippopotamus

Classification and Evolution

The hippopotamus is a large semi-aquatic mammal that is found wallowing in the rivers and lakes across sub-Saharan Africa. Despite its appearance, the hippopotamus is an animal that is actually thought to be most closely related to whales, as the two are thought to have had a common ancestor that existed roughly 54 million years ago. Also known as the common hippopotamus, it is one of two hippo species that are found on the African continent, with the other being the solitary and forest-dwelling pygmy hippopotamus, which is only found in western Africa and is now critically endangered. There are only 3,000 pygmy hippos left in existence. Although the common hippopotamus remains an abundant and widespread animal throughout its current range, numbers are reportedly declining due to both hunting and habitat loss.

Anatomy and Appearance

The hippopotamus has an enormous grey barrel-shaped body that can measure up to 16 feet in length and weigh more than four tons, and which is held up by short and stocky legs. One of the hippopotamus’s most distinctive features is its enormous jaws which contain two long canine teeth (tusks) which can grow up to 20 inches long and are used for fighting. Due to the fact that the hippopotamus is an animal that spends most of its life resting in the water, they have a number of excellent adaptations to aid its semi-aquatic lifestyle, including four webbed toes on each foot that help with swimming and walking on slippery banks, and the eyes, ears, and nostrils of the hippopotamus are situated on the top of its head. This means that when the hippopotamus’s body is immersed in the water, they are still able to see, hear, and breathe whilst keeping cool in the hot sun.

Distribution and Habitat

Although historically, the hippopotamus would have once been found across Europe and Asia, today, they are confined to Africa south of the Sahara Desert. The hippopotamus is always found close to the water and tends to prefer areas close to grasslands, where they feed during the night. Hippos are most commonly found in the deep and slow-moving rivers and lakes in eastern and southern countries, with only a few smaller and more isolated populations still found in the west. The hippopotamus is also a resident of the seasonal wetlands, where they wade through the swampy waters by day and graze on the small islands at night. Although the hippopotamus is still common throughout much of sub-Saharan Africa, their numbers have been declining, with one reason being the loss of their natural habitats, mainly caused by land clearance for agriculture.

Behaviour and Lifestyle

The hippopotamus spends up to 18 hours a day in the water to keep cool, but when darkness falls, they venture out onto land and follow well-trodden paths to their feeding grounds before returning to the water in the morning. The hippopotamus is one of the largest and most feared animals in Africa, as both males and females are known to be incredibly aggressive at points. The hippopotamus tends to live in small herds containing between 10 and 20 individuals that are comprised of females with their young. The herd is led by the dominant male, who will fiercely guard his stretch of river bank from both intruders and rival males, threatening them by opening his enormous mouth to expose the 18-inch long tusks. If this fails, the two will fight, and deadly injuries are often caused. Although the dominant male will allow other males to enter his territory, providing they are well-behaved, he holds the breeding rights with the females in the herd.

You can check out incredible hippopotamus facts.

Reproduction and Life Cycles

After a gestation period that lasts for around eight months, the female hippopotamus gives birth to a single calf, generally during the rainy season. Although like many other activities (including mating), the hippopotamus often gives birth in the water, it is not actually that uncommon for their young to be born on land. The female protects her calf fiercely, and it rides on her back to keep it safe. Hippopotamus calves are fully weaned by the time they are 18 months old but tend to remain with their mother until they are fully grown, often not leaving her until they are 7 or 8 years old. Although young males will become more independent and find their own patch of the bank to patrol, females will join a herd of other females and young. Despite this seemingly sociable behavior, they do not seem to interact socially and will even graze on their own when they leave the water at night.

Read more about the hippo’s lifespan here.

Diet and Prey

The hippopotamus is a herbivorous animal, meaning that despite its enormously long and sharp teeth, they are vegetarians. Different species of grasses are the main source of food for the hippopotamus that is found growing on plains relatively close to water. When they come onto land at night, hippos may travel up to three miles during the night to get to their feeding grounds which they do by following paths that are marked with dung. Oddly enough, the hippopotamus doesn’t even use its large canines for eating at all but instead has strong lips that are used to clip the grasses and cheek teeth which then grind them up. Despite its large size, the hippopotamus only eats around 88 pounds of food a night as it uses very little energy whilst floating in the water for most of the day. In areas that are close to human settlements, hippos have also been known to invade crops consuming mainly rice plants and simply trampling over others. For a complete list of the food a hippopotamus eats, have a look at our “What Do Hippos Eat?” page!

Predators and Threats

The hippopotamus is one of the largest mammals on the African continent. Although mature adults are much harder for predators to kill, they are still preyed on by a number of predators throughout the wetlands. Big cats such as lions and other animals like hyenas and crocodiles are the most common predators of the hippopotamus, particularly of young or sick individuals. It is because of this that females are thought to congregate in herds, as larger numbers are more intimidating to hungry carnivores. The hippopotamus is also threatened by people, not only from the loss of their natural habitats but also from hunting. The hippopotamus has been hunted by people for both its meat and its teeth which are made of ivory. Since the ban on trading elephant ivory, the number of hippos killed for their teeth has risen dramatically.

Interesting Facts and Features

The hippopotamus has an enormous head that makes up around a third of its total body weight, with its vast mouth being able to open up to 150 degrees and revealing its large tusks, which can weigh up to 6 pounds each. Due to the way that the skin of the hippopotamus is made up, the animal cannot sweat, so when it comes into contact with air, the skin easily dries up. Although this is not a problem in the water, to combat this the rest of the time, a pink, oily substance is secreted through glands in the skin, which is not only thought to prevent sunburn but also may have anti-bacterial properties that help to keep wounds clean and prevent infection from the dirty water. Even though the hippopotamus looks like it would be slow on land thanks to its short and stubby legs, they are actually able to run at quite remarkable speeds and are capable of reaching 30 miles per hour when running.

Relationship with Humans

The hippopotamus can be found in all kinds of ancient African folklore, with its name in Greek actually meaning “Water Horse.” Despite this fascination with the hippopotamus, hunting them for their meat and tusks has wiped them out from vast areas of their once large natural range, and numbers continue to fall, particularly in certain areas due to habitat loss. In these areas where the hippopotamus is often forced to raid crops in order to find food, they are seen as pests by farmers who do not only fear for their livelihood but also for their lives themselves. The hippopotamus is known to be an aggressive animal that is considered by many to be among Africa’s most dangerous mammals, as attacks on people (particularly fishermen) are not unheard of.

Conservation Status and Life Today

Today, the hippopotamus is listed by the IUCN as an animal that is Vulnerable in its natural environment. Over the past 10 years, their populations have declined by 7-20%. However, the hippopotamus is still considered to be abundant throughout much of its current natural range, with the exception of populations in western Africa that are becoming more and more isolated. Although hippopotamus populations are considered stable in a number of countries in the south and the east of the continent, they are declining in many others. They are particularly threatened by continuing poaching of them for their tusks.

2 Types of Hippopotamus

There are two hippo species, both found in Africa. The common hippopotamus (also called the large hippopotamus) and the pygmy hippopotamus.

Large/Common Hippopotamus: The common hippopotamus (Hippopotamus amphibious) is native to sub-Saharan Africa and is one of the largest land mammals. An adult hippo can weigh 3,300 pounds and stand 5.5 feet tall at the shoulder.

Pygmy hippopotamus: The pygmy hippo (Choeropsis liberiensis) is a much smaller species of hippo, about half as tall as the common hippo. Adults stand a little over three feet tall and are 400-600 pounds. They are limited to protected areas in West Africa that are forested. Shy and reclusive, this hippopotamus is mostly nocturnal.

More on Hippopotamus

• Hippo Mouth: Size and Facts
• How Fast Can a Hippo Run?
• What was the Largest Prehistoric Hippo?