Hippos will have vanished from a part of Africa by the end of the year unless something is done to stop people hunting them, a wildlife group says.
More than 400 hippos have been killed in the Virunga National Park in the last two weeks, and it's thought there are only about 500 left.
They're being killed for their meat and the ivory in their teeth by an armed group who are camped in the park.
Hippo numbers in the park have dropped from about 22,000 in 1988.
It's thought the armed group, who are fighting the government of the Democratic Republic of Congo, have also killed elephants and buffalo.
A team of rangers has been set up to protect the hippos and other animals in Virunga.
But the Zoological Society of London says cash is needed to train them to protect the hippos.