The word hippopotamus comes from Greek. Hippos means 'horse'. Potamus means 'river'. The Chinese word for hippopotamus is also 'river horse'. The hippo spends a lot of its time in the water. But it also comes out onto land.

Some scientists think that around 55 million years ago, the hippo came from the same species as the whale. The whale is a mammal that lives in the sea.

Huge mammal

Only elephants and white rhinoceroses are bigger than hippos. An adult male hippo usually weighs 1,500-1,800kg. Females usually weigh around 1,300kg. Male hippos probably keep growing all their lives. Some of them can reach more than 4,000kg.

Hippos are about 4 metres long. They can be much longer. They are not very tall, though - only between 1.5m and 2m tall. That's about the same as adult humans.

Hippos live for around 40-50 years. The oldest known hippo lived in a zoo in Germany. She died in 1995 aged 61.

Keeping out of the sun

Although hippos live in Africa, they don't like strong sunlight. If they are not careful, they will get sunburnt. This is because, like other animals who spend a lot of time in water, they don't have much hair. Their eyes, ears and nostrils are high up on their heads. They can lie in the water with just the top of their heads sticking out.

If hippos go out into the sun, their body creates a natural sunscreen. It comes out of their skin. It is red. In the old days, people used to say that hippos sweated blood in the sun.

Hippos used to be found in colder climates, such as Europe. The only ones left are now in Africa.

Hippo killing fields

Virunga National Park in the Democratic Republic of Congo (DRC) used to have one of the world's largest hippo populations. Thirty years ago, 29,000 hippos lived there.

But there has been a terrible civil war in the DRC. Hundreds of thousands of people have died, and 95 per cent of the hippos have died, too. Soldiers hunt them for meat, and also for their teeth.

Like the tusks of elephants, hippos' huge teeth are very valuable. Things can be carved out of them, just like ivory. In 2006, hippos joined 26,000 other animal species around the world that are in danger of dying out - or becoming extinct.

now do this

1 Hippos and ... probably share the same ancestors.

a. horses

b. pigs

c. whales

2 Hippos are easily sunburnt because ...

a. they spend so much time underwater.

b. they don't have much hair.

c. they sweat too much.

3 At Virunga National Park in the Democratic Republic of Congo, ... of hippos have died in 30 years.

a. 90 per cent

b. 85 per cent

c. 95 per cent

Answers:

September 30:

1. b, 2. c, 3. a