About the Hippopotamus: All you need to know

the-hippopotamus

The hippopotamus is a large, semiaquatic mammal native to sub-Saharan Africa. Although their name comes from the Greek for “river horse”—because of the time they spend in the water—their closest living relatives are whales, dolphins, and pigs. Hippos are some of the earth’s largest land animals. These silly-looking yet ferocious animals are in zoos and colouring books everywhere, making them one of the most famous creatures around. As such, people want to know more about them and what exactly makes them special. Let’s take a look and learn about hippos.

Overview of the Hippopotamus

These huge herbivores are known for their enormous teeth, aggressive nature, and the myth that they sweat blood. Here’s what you need to know about one of Africa’s most dangerous animals.
They can’t swim, breathe underwater, or even float—but they have developed a tactic that lets them nap underwater.
Weighing up to 8,000 pounds, the hippopotamus is the heaviest land animal after the elephant. Hippos seek refuge from the heat by living in water during the day, and at night they come ashore to feed on short, soft grasses and fallen fruit. The eyes and ears of a hippopotamus are on top of its head, so it can keep watch for enemies—mainly crocodiles—while lying low in the water. These giants are currently at risk from habitat loss.

The General Characteristics and Appearance of the Hippopotamus

hippos in a pool

The hippopotamus has a bulky body on stumpy legs, an enormous head, a short tail, and four toes on each foot. Each toe has a nail-like hoof. Males are usually 3.5 metres (11.5 feet) long, stand 1.5 metres (5 feet) tall, and weigh 3,200 kg (3.5 tons).
In terms of physical size, males are the larger sex, weighing roughly 30% more than females.
The hippopotamus is well adapted to aquatic life. The ears, eyes, and nostrils are located high on the head so that the rest of the body may remain submerged. The ears and nostrils can be folded shut to keep out water.
The body is so dense that hippos can walk underwater, where they can hold their breath for five minutes. Although often seen basking in the sun, hippos lose water rapidly through the skin and become dehydrated without periodic dips. They must also retreat to the water to keep cool, for they do not sweat. Numerous skin glands release an oily reddish or pinkish “lotion,” which led to the ancient myth that hippos sweat blood; this pigment acts as a sunblock, filtering out ultraviolet radiation.
These muscular animals have round torsos and pinkish-brown bodies with two-inch-thick, waterproof skin, and short, stout legs. They might not look aerodynamic, but hippos can reach speeds of up to 22 miles per hour on land over short distances.
The mouth is half a metre wide and can gape 150° to show the teeth. The lower canines are sharp and may exceed 30 cm (12 inches). Their molars are used for eating while their long, sharp canines—which can reach 20 inches—are for fighting. Their remarkably strong jaws can open to 180 degrees and their bite is nearly three times stronger than a lion’s. One bite from a hippo can cut a human body in half.

What does a hippopotamus mouth look like

a hippopotamus mouth

Hippo mouths are often the last thing that animals see if wandering too close! Thankfully, we can learn about them from a distance. Let’s take a look at a hippo’s mouth and see what it looks like.
As one of the largest in the animal kingdom, it’s no wonder that their mouths are built to match. Generally, the first thing that people notice is their teeth. Hippos have three sets of teeth: incisors, canines, and molars. The most noticeable ones are the incisors and molars as they are specially adapted to stick out from their mouths like weapons.
Aside from their teeth, we can see their gummy lips and interiors. Hippo lips are specially adapted to be large and bony. Per day, they need around 100 lbs of food to keep their weight up, and all of it is from vegetation. Since their days are almost exclusively spent foraging the river banks and bottoms for plants, their lips have adapted to allow them to grasp and pull. With their immense strength and special lips, hippos can pull even deeply rooted plants out of the mud to eat.
When a hippopotamus opens its mouth, one of the most distinctive elements you can see is its orbicular muscle. When their mouths are closed it’s not visible, but it’s actually what allows them to open their mouths so wide. The muscle is on the inside of their cheeks and can unfold (similar to an accordion) when stretched. This allows them to open their mouths wide without hurting themselves.
Hippos are known for their size, and their mouths may be their most defining characteristic. Although the blue whale holds the top spot for the largest mouth on earth, the hippopotamus may just take the cake as the largest mouth on land.
Generally, hippo mouths measure 2 feet wide (from left to right) when closed. It’s when they open it, however, that it gets big. Hippos can open their mouths 150 degrees, essentially a flat line from top to bottom. This is often used to display their teeth to a threat, but it also happens when they yawn. At full stretch, hippo mouths can measure 4 feet tall, enough for a toddler to stand up in.
For comparison, a human jaw can only stretch 26 degrees from a closed position. That means that a hippopotamus can open its jaws nearly six times wider than a human.

How strong is a hippopotamus mouth

Hippos are some of the strongest animals on earth and resultingly, have one of the strongest mouths on earth. When you combine that strength with their immense size, it’s no wonder that hippos are responsible for the majority of animal deaths in Africa.
It’s generally accepted that hippos have a bite force of 1,827 psi. The figure was measured while looking at hippo bite victims in a medical lab, so it’s reasonable to trust it. This bite force is truly astonishing and is around 10 times the strength of a human. While it may feel like a hippo should be more than 10 times the strength of a human (in terms of bite force), it’s important to remember that hippos are exerting this force across a surface area that is many, many times the size of humans. In relative terms, it means that a hippo’s mouth is hundreds of times stronger than a human’s.
There is a common belief that a hippopotamus could “bite a crocodile in half,” but it’s not true. It’s better to think of it as hyperbole, although there is some truth to the underlying claim. Hippos and crocodiles do share the same territory in Africa, and that often results in fights.

Behaviour of the Hippopotamus

Hippos favour shallow areas where they can sleep half-submerged (“rafting”). Their populations are limited by this “day living space,” which may become quite crowded; as many as 150 hippos may use one pool in the dry season. In times of drought or famine, they may embark on overland migrations that often result in many deaths. By night, hippos walk along familiar paths as far as 10 km (6 miles) into surrounding grasslands to feed for five or six hours. The long canines and incisors are used strictly as weapons; grazing is accomplished by grasping grass with the tough wide lips and jerking the head. Near the river, where grazing and trampling are heaviest, large areas may be denuded of all grass, which results in erosion. Hippos, however, eat relatively little vegetation for their size (about 35 kg [80 pounds] per night), as their energy requirement is low because they are buoyed in warm water much of the time. Hippos do not chew cud but retain food for a long time in the stomach, where protein is extracted by fermentation. Their digestive process cycles tremendous quantities of nutrients into the African rivers and lakes and thereby supports the fish that are so crucial as a protein source in the diet of the local people.

Reproduction and Life Cycle of the hippo

a hippo in a pool

In the wild, females (cows) become sexually mature between ages 7 and 15, and males mature slightly earlier, between ages 6 and 13. In captivity, however, members of both sexes may become sexually mature as early as ages 3 and 4. Dominant bulls more than 20 years old, however, initiate most of the mating.

Bulls monopolize areas in the river as mating territories for 12 years or more. Subordinate males are tolerated if they do not attempt to breed. Cows aggregate in these areas during the dry season, which is when most mating takes place. Rare battles may erupt when strange bulls invade territories in the mating season. Most aggression is noise, splash, bluff charges, and a yawning display of the teeth, but opponents may engage in combat by slashing upward at each other’s flanks with the lower incisors. Wounds can be fatal despite the thick skin there. Adjacent territorial bulls will stare at each other, then turn, and, with their rear end out of the water, flip faeces and urine in a wide arc by rapidly wagging their tail. This routine display indicates that the territory is occupied. Territorial and subordinate males alike make dung piles along pathways leading inland, which probably function as olfactory signposts (scent markers) at night. Hippos recognize individuals by scent and sometimes follow one another nose-to-tail on night treks.

Distribution of hippos in Africa

A map of hippos population in Africa

Trampling and crop raiding by hippos led to early and determined efforts to exterminate them; their hides and meat were also valued. Hippos were extinct in northern Africa by 1800 and south of Natal and the Transvaal by 1900. They are still fairly common in East Africa, but populations continue to decrease continentwide. There remains a demand for hippo teeth as a fine-grained “ivory” that is easy to carve; it was once used to make false teeth. After the international elephant ivory ban went into effect in 1989, hunting pressure on hippos increased, and hippo populations declined. A population assessment performed in 2008 estimated that between 126,000 and 149,000 individuals remained.

Threats to Hippopotamus Survival

The International Union for Conservation of Nature classifies hippos as vulnerable to extinction. Although the hippopotamus doesn’t have many predators, it is threatened by poaching for its meat, fat, and ivory teeth. Other threats include the loss of its habitat and human-hippo conflicts. Because the species is slow to reproduce, threats can significantly impact population numbers.
The only other living hippopotamus species, the pygmy hippo, is an endangered species native to West Africa.
As ecosystem engineers—a species whose presence changes, creates, destroys, or maintains a habitat—the loss of hippos also affects the wider ecosystem. When hippos defecate in the water during the daytime, their dung—which is rich in nutrients—washes through the waterways and delivers important elements like nitrogen and phosphorus to other species in the ecosystem.
Human impacts can interfere with this important cycle. If rivers do not flow—due to climate change or human developments—the hippos’ nutrient-rich dung cannot be circulated through the ecosystem, and aquatic animals and plants suffer. In the areas where the waste then builds up, it can reach such a high concentration that most species cannot survive the resulting high levels of algae and low levels of oxygen.
The once-healthy population of hippos in Virunga National Park in the Democratic Republic of the Congo—which was around 29,000 in the 1970s—was devastated by poachers until there were fewer than 900 remaining in 2005. Thanks to better enforcement and conservation initiatives, the Virunga population has started to recover, and hippo populations around the world are currently stable.