(Credit: Sergey Uryadnikov/Shutterstock)

Within the rainforests of Salonga National Park, in the heart of the Democratic Republic of the Congo, bonobos wade through swamps. The slender, three-and-a-half-foot tall apes are searching for rushes and white water lilies. They pluck the herbs from the water and then discard the flowers and leaves. The bonobos are after the soft pith at the base of the leaves and other parts of the plants that grow underwater.

Now researchers find the aquatic h