Hippopotamus

Quick Take

• The hippo's closest living relative isn't another land mammal, which is something that will completely change how you see it.
• Those enormous tusks look built for tearing, yet the hippo never seems to use them to eat. See how hippos really eat →
• Hippos can't sweat, but their skin produces something far more useful, and surprisingly it also doubles as medicine. Discover the skin secretion →
• A hippo's stumpy legs look built for slow, so the speed they can actually hit on land is unsettling. Check the surprising top speed →

The hippopotamus is a large, semi-aquatic mammal found wallowing in the rivers and lakes across sub-Saharan Africa. Despite its appearance, the hippopotamus is actually thought to be most closely related to whales, as the two are believed to have had a common ancestor that existed roughly 55 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 endangered. There are fewer than 2,500 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 gray 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) that can grow up to one meter (about 39 inches) long and are used for fighting. Because the hippopotamus is an animal that spends most of its life resting in the water, they have several 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, it is 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, it is 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 its natural habitats, mainly caused by land clearance for agriculture.

Behaviour and Lifestyle

The hippopotamus spends up to 16 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 times. The hippopotamus tends to live in herds containing between 10 and 30 individuals that are comprised of females with their young. The herd is led by the dominant male, who will fiercely guard his stretch of riverbank 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.

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. 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.

Diet and Prey

The hippopotamus is a herbivorous animal, meaning that despite its enormously long and sharp teeth, it is a vegetarian. Different species of grasses are the main source of food for the hippopotamus, which 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 while 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.

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 several 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, with its vast mouth being able to open up to 150 degrees and revealing its large tusks, which can grow over half a metre long. 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, it is actually able to run at quite remarkable speeds and is capable of reaching around 19 to 28 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 “River 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 to find food, they are seen as pests by farmers who not only fear for their livelihood but also for their lives. 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 to 20%. However, the hippopotamus is still considered to be abundant throughout much of its current natural range, except for 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 the 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 amphibius) is native to sub-Saharan Africa and is one of the largest land mammals. Adult males can weigh up to 9,920 pounds, while females weigh up to 3,000 pounds, and hippos stand about 4 feet 7 inches 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 weigh 400 to 600 pounds. They are limited to protected areas in West Africa that are forested. Shy and reclusive, this hippopotamus is mostly nocturnal.