In Uganda's Budongo forest, the chimpanzees have a new healthy recipe in hand. A new study says that they have started to boost the minerals in their diet by eating clay which also helps them 'detox' and digest their food.
This change in diet may be partly due to the widespread destruction of raffia palm trees that chimps relied on for their minerals in the past, the study noted. But "the wide range of minerals present in their diet suggests that clay is eaten as a general mineral supplement", said lead author Vernon Reynolds, emeritus professor of biological anthropology at Oxford University.
In this long-term study started in 1990, the international team of researchers observed the chimps using leaves like clay 'sponges', dipping the leaves in the clay water and returning to their mouths where they squeezed the liquid out with their tongues. They were also seen using their fingers to extract lumps of clay directly from the ground before eating it.
An analysis of the clay and termite soils shows they are very high in a range of minerals, but the clay was particularly high in aluminium - a feature of kaolinite clays eaten by a range of species, including humans, to aid digestion and detoxification.
Clays, such as kaolinite, also contain sodium, calcium, iron, magnesium and potassium, the study pointed out. The chimps' diet, which consists mainly of fruits and leaves, is very high in tannins and the researchers believe that the clay provides an important way for chimpanzees to neutralise these.
It is common practice for local women in Budongo to drink or eat forest clay mixed with water for stomach problems and during pregnancy. Now the Budongo chimps too seem to have discovered the the benefits of eating clay. The study was published in the early version of the journal PLOS ONE