The content of the exhibition «Gibbons in Danger» in the Great Ape house is the threat to the small Great Apes. The main cause is the destruction of their natural habitat, the rainforests, but also hunting and illegal trade in the animals. A special feature of the gibbons is their «songs», which can last up to twenty minutes and are often elaborate duets between males and females. This is how they mark their territory. Each gibbon species has its own typical song.
You can listen to the song of the cap gibbon here: