Hippopotamuses are large, round, water-loving animals that are native to Africa. Though they're sometimes thought of as cute and cuddly, hippos can actually be quite dangerous; they kill about 3,000 per year, according to the National Wildlife Federation.
Hippos are very rotund animals and are the third largest living land mammals, after elephants and white rhinos, according to Animal Planet. They grow to 10.8 to 16.5 feet (3.3 to 5 meters) long and up to 5.2 feet (1.6 m) tall from hooves to shoulders. The tail adds another 13.75 to 19.75 inches (35 to 50 centimeters) to its length. The average female weighs around 3,000 lbs. (1,400 kilograms) while males weigh 3,500 to 9,920 lbs. (1,600 to 4,500 kg) according to the San Diego Zoo.
Hippos live in sub-Saharan Africa. They can only survive in areas with abundant water, though, so they live in areas with rivers and lakes. Hippos are amphibious animals and spend up to 16 hours per day in the water, according to National Geographic. The water keeps them cool in the African heat. They spend all day in the water and then hunt for food at night.
They are very social and hang out in groups called schools, bloats, pods or sieges. Schools of hippos usually consist of 10 to 30 members of both females and males. Some documented groups of hippos have had as many as 200 members. No matter the size, usually the school is led by a dominant male.
Hippos are very aggressive creatures and are very dangerous. They have large teeth and tusks that they use for fighting off others that they see as threats, including humans. Sometimes, their young are the victims of their temper. During a fight between two adults, a young hippo can be hurt or crushed.
Though hippos move quite quickly through the water, they can't swim. According to the San Diego Zoo, hippos move through the water by pushing themselves off other objects.
Hungry, hungry hippos
A hippo eats about 80 lbs. (35 kg) of grass each night, according to National Geographic. They travel up to 6 miles (10 kilometers) in a night to get their fill. They also eat fruit that they find during their nightly scavenging.
Females have a gestation period of eight months and have only one baby at a time, according to the San Diego Zoo. At birth, the baby, called a calf, is a whopping 50 to 110 lbs. (23 to 50 kg). For 18 months, the baby nurses while its mother is on land, or it swims underwater to suckle. When it dives, the calf closes its nose and ears to block out water. All hippos have this ability. They also have membranes that cover and protect their eyes while they are underwater.
At 5 to 7 years old, the hippo calf is fully mature, according to the San Diego Zoo. The median life expectancy of a hippo is 36 years.
The taxonomy of hippos, according to the Integrated Taxonomic Information System (ITIS), is:
- Kingdom: Animalia
- Subkingdom: Bilateria
- Infrakingdom: Deuterostomia
- Phylum: Chordata
- Subphylum: Vertebrata
- Infraphylum: Gnathostomata
- Superclass: Tetrapoda
- Class: Mammalia
- Subclass: Theria
- Infraclass: Eutheria
- Order: Artiodactyla
- Family: Hippopotamidae
- Genus: Hippopotamus
- Species: Hippopotamus amphibius (common hippopotamus)
- Subspecies: Hippopotamus amphibius amphibius, Hippopotamus amphibius capensis, Hippopotamus amphibius kiboko
According to the IUCN, the common hippo population isn't endangered, but it is vulnerable, because their numbers have declined by 7 to 20 percent over the past 10 years, and likely will continue to decline. The IUCN estimates that there are between 125,000 and 148,000 common hippos remaining in the wild.
The primary threats to hippos are poaching (for their ivory tusks and their meat), and loss of habitat, as more water is diverted for agriculture, according to the IUCN.
The word "hippopotamus" comes from the Greek word for "water horse" or "river horse." However, hippos and horses are not closely related. The closest living relatives to hippos are pigs, whales and dolphins, according to the San Diego Zoo.
A hippo must stay moist, because if its skin dries out, it will crack. Its skin also secretes a red fluid that is thought to be an antibiotic, sunscreen and skin moisturizer. People once thought that the red secretions were blood and that hippos sweat blood.
Hippos can stay underwater for up to 5 minutes without coming up for air, according to National Geographic. When they sleep in the water, their bodies automatically bob up to the top of the water so that they can take a breath, and then they sink back to the bottom.
Hippos' eyes and nostrils are on top of their head. This allows them to breath and look around while the rest of their body is submerged.
Hippos are fast for their size. They can run up to 14 mph (23 km/h), according to the San Diego Zoo.
Hippos are very loud animals. Their snorts, grumbles and wheezes have been measured at 115 decibels, according to the San Diego Zoo — about the same volume as being 15 feet (4.6 m) from the speakers at a rock concert. Hippos also use subsonic vocalizations to communicate.
Hippos can store food in their stomachs and go three weeks without eating.
The common hippo's cousin, the pygmy hippo (Hexaprotodon liberiensis or Choeropsis liberiensis) is smaller and less aquatic. They are also rarer, and endangered. They are found only in forests in West Africa, mainly Liberia. Little is known of their habits in the wild, according to the San Diego Zoo. They were not discovered by Western scientists until 1840.