Hippopotamus

Species

Also called the river horse, there are two species of hippo.

Hippopotamus amphibius
Choeropsis liberiensis

Common hippo
Pygmy hippo

Population

The common hippo was assessed by the IUCN in 2016 as being vulnerable. Numbers are estimated to be between 115,000 and 130,000 according to the WWF.
Pygmy hippo was assessed by the IUCN in 2015 as being endangered with <3,000 animals and decreasing.

Size

The Common hippo is 2 - 5 metres in length, 1.5 metres tall and weighs 1.4 - 5 tons. The Pygmy hippo is 1.5 - 1.75 m in length, one metre tall and weighs 160 - 275 kg.
Male hippos tend to keep growing but females stop growing at about 25 years old.

Habitat & distribution

Common hippos are found in wetlands, rivers and swamps. (Pygmy hippos are also found in forests).
While the common hippo is found in over 30 African countries, the pygmy hippo is found in a few countries in West Africa. Their ranges do not overlap.
In the Democratic Republic of Congo, the common hippo has decreased by >95%.

Hippos secrete a red fluid

Hippos do not have sweat or sebaceous (oil) glands. To keep cool, they stay in water or wallow in mud. Hippos secrete a viscous (thick) red fluid which acts as a sunscreen. It contains hipposudoric and norhipposuoric acid and also has anti-bacterial properties.

Diet

Hippos are herbivores. They graze night. They can eat up to 40 kg of grass and will sometimes eat fruit. Although they have four chambered ruminant stomachs, they do not ferment their food or chew their cud.

Interesting facts

Hippos can open their jaws 150°. Their tusks are actually teeth (the upper incisors and lower canines). These teeth continually grow and the lower tusks, in males, can measure 50 cm (they are longer in males than females). These tusks contain ivory meaning they have been hunted for them (dentures have been made from hippo teeth).
Hippos also have 4 webbed toes (although the pygmy hippos toes are less webbed).
Adult hippos can hold their breaths underwater for 5 minutes.

Group

Common hippos have a flexibles social system. They form mixed groups from 20-100 individuals led by a territorial bull. However, during drought conditions, larger numbers of hippos are force together. These groups are called schools or pods. In contrast, pygmy hippos are solitary and not territorial.
Common hippos are more vocal than pygmy hippos.

Breeding & lifespan

The gestation period for hippos is 10 months. A baby hippo can weigh up to 50 kg at birth (which is either on land or in shallow water).
The lifespan of a hippo in the wild is, on average, 36 years.
A pygmy hippo pregnancy lasts around 6.5 months and the calf typically weighs between 3.4-6.4 kg. They are born on land. Pygmy hippos live to around 27 years in the wild.

Predators & threats

Predator of baby common hippos include: lions. crocodiles and hyenas. Leopards may prey on pygmy hippos.
Humans pose a threat to hippos. Hippos are often killed to prevent hippos from damaging crops of if they are perceived to be a danger. Even though low fences and ditches deter hippos, people still kill them.
Hunting of hippos for their ivory, meat and fat has seen hippos numbers decline over the past 200 years. Restrictions on hippo ivory aren't as tough as elephant ivory. Habitat loss is also a threat.