Geophagy is the intentional consumption of earth or soil-like substances, such as clay, chalk, or termite mounds, by animals. This widespread behavior serves specific purposes for various species across different environments. Documented in over 100 primate species and hundreds of other vertebrates, geophagy represents a behavioral adaptation observed in mammals, birds, and reptiles that contributes to their health and survival.
Reasons for Dirt Consumption
Animals engage in geophagy primarily for mineral supplementation, as soil can provide essential nutrients often lacking in their regular diet. Soil can be a source of minerals like calcium, sodium, iron, and zinc, which are particularly important during periods of increased physiological demand, such as pregnancy or antler growth in deer. Elephants, for example, actively dig and consume soil from specific geological formations or termite mounds to acquire these minerals.
Another reason for consuming soil is detoxification. Certain clay minerals within the earth can bind to harmful compounds ingested by animals, preventing their absorption into the body. This is especially relevant for herbivores that consume plants containing secondary compounds or unripe fruits, as the clay helps to neutralize these toxins and aids in their excretion.
Geophagy may also play a role in parasite control. Ingesting soil helps expel internal parasites or coat the intestinal lining, making it less hospitable for parasitic organisms. This protective mechanism helps animals mitigate the effects of pathogens and maintain gastrointestinal health, particularly in environments where parasites are prevalent.
Animals That Engage in Geophagy
Many species of South American parrots, including macaws, and sulphur-crested cockatoos in Papua New Guinea, are known to consume clay. This behavior is often linked to detoxifying plant toxins present in their diet, as the clay binds to these harmful compounds.
Primates, such as chimpanzees and gorillas, frequently engage in geophagy, consuming soil rich in clay minerals. This practice is thought to provide mineral supplements and help metabolize toxic compounds from the leaves they consume.
Ungulates like deer, elephants, and other herbivores regularly visit mineral licks or consume soil directly. Elephants, for instance, utilize their tusks to break up topsoil or consume soil from termite mounds, which are often richer in mineral elements. This behavior helps them obtain sodium and other minerals scarce in their vegetation-based diets.
Insects, such as caterpillars, have been observed consuming soil for mineral intake or to assist digestion. Additionally, reptiles and amphibians are known to engage in geophagy. Domestic animals like chickens and dogs may also consume soil, with reasons often mirroring those of their wild counterparts, such as mineral needs or digestive aid.