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Chimps Binge on Clay


Wild Chimpanzees in Uganda are supplementing their diets with clay, according to international research led by the University of Oxford.

An article in PLOS ONE reported that researchers saw wild chimps in the Budongo forest eating and drinking from clay pits and termite mounds. The researchers believe the clay-eating is connected to the widespread destruction of raffia palm trees, which had supplied the chimps with dietary minerals.  The clay also helps the chimps “detox” and digest their food.

Vernon Reynolds, Emeritus Professor of Biological Anthropology at Oxford University, led the research team. He was assisted by biologists from the universities of St. Andrews, Kent, Brighton, Utrecht, and Neuchatel. His team saw chimps using leaves as clay sponges, dipping the leaves into clay water and squeezing the liquid into their mouths. The chimps also dug lumps of clay out of the ground with  their fingers.

Analysis of clay soils and termite mounds in the Budongo forest confirmed that they are high in essential dietary minerals. One of the most important is aluminum, an element of kaolinate clays eaten by a wide range of species, including humans, for a digestive and detoxification aid. The clay helps to neutralize tannins in the chimps’ diet of fruit and leaves.  The clays also contain high concentrations of calcium, iron, magnesium, potassium, and sodium.

Humans in Budongo also consume forest clay to aid digestion, and women in the area believe it eases pregnancy.

Before about A.D. 2000, chimps in Budongo fed heavily on raffia palms. The decaying piths of the palms was an important source of minerals.  By about 2005, though, the raffia palms had declined significantly, and the chimps had to find another source of vital dietary minerals.

This is not the first time wild animals have been proven to supplement their diets with clay. National Geographic published a feature story several years ago about parrots in the Amazon River Basin. The story was illustrated with photos of huge flocks of macaws, the largest parrots, mobbing clay deposits on river banks and hillsides.

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