Hippopotamuses still live in central and southern Africa, but they are under threat there. Farming is destroying the habitat of these huge, semi-aquatic animals.
Now wildlife conservation projects aim to move wild hippos to protected areas, for example in Swaziland's national parks. Researchers and animal keepers are getting help from Theo Pagel, the director of the Cologne Zoo. The zoologist contributes his scientific know-how to the collaboration - expertise that he has also demonstrated in designing a new enclosure for the zoo for hippos and other animals. Our report takes us to Cologne and Swaziland.