Clay licks put simply are exposed areas of clay where animals gather to eat or lick clay. Over 50 different animals use clay licks to obtain clays or salts. Light might be shed on this behaviour by looking at our own history and medical treatments:
Clay licks & Humans
Humans eat products from the Earth for many reasons. Although we don’t visit clay licks in the same way as other animals, we commonly eat materials from earth like salt, loess (a mixture of clay and silt), and powdered limestone. Antacid pills as an example contain calcite or carbonate as a main ingredient, and the reason for eating these earth products are probably the same for either a macaw or tapir.
We take pills containing earthly compounds to treat nutrient deficiency, detoxifying something we have eaten, or to treat an illness. Ancient Romans would use clay tablets to help gastrointestinal problems and one physician in particular, named Galen, used to carry thousands of clay coins to give soldiers waiting for battle.
Reflecting the use by Galen, one study recorded 20 known earth materials used in various health and medical practices. These included different clays as antacids or to treat ulcers, toxins, infections and allergies. The FDA recognises at least two for use as anti-diarrheals.
To show how effective these materials are, clay was even used successfully to treat Cholera. The patient would stop showing symptoms of the disease within a few hours. It might be worth looking into this material a little closer as this locally available material could help modern day cholera epidemics occurring in poorer countries. Other uses of different clays are as antidotes for various poisons, including chemical warfare agents and herbicides.
Clay Licks & Animals
Scientifically named geophagy, eating material directly from the earth is quite common and researchers have listed over 50 animals behaving in this way. It has long been known that primates, elephants and many other animals eat different types of clay. These various clay licks contain different chemicals, and an important chemical is salt. Salt is vital for all animals to maintain a healthy nervous system as well as a healthy heart and muscles. This may be an additional explanation for the common although strange behaviour.
Frequently seen in documentaries, elephants are a classic example of animals eating clay. They will go to great lengths to reach clay licks and either eat it or cover themselves in it. Elephants will track back to certain specific sites, suggesting they are looking for some particular chemical. Other records include monkeys eating termite mounds (containing clay as a major component) and Jane Goodall made frequent notes of chimpanzees eating clay. A suggestion for why they did this was to detoxify something they had eaten.
Toxins found in the fungus growing on some plants can cause numerous health problems like decreased milk and egg production, liver damage, and a lowered immune system. Clays have been suggested to neutralise these toxins so the animal can continue eating plants without side effects.
When we look at animals engaging in this seemingly bizzare behaviour, we can understand the activity by looking at our own behaviour and medical history. It seems that many animals, including humans, have an ingrained or cultural knowledge for obtaining the many essential chemicals we require.
Limpitlaw, Ulli G.(2010) ‘Ingestion of Earth materials for health by humans and animals’, International Geology Review, 52: 7, 726 — 744, First published on: 19 March 2010 (iFirst)