Wildlife TV

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Geophagia: Eat dirt!

on May 19, 2013

We’ve talked in a previous post about osteophagia (the eating of bones) but this seemingly unusual eating habit is not the only one worth mentioning. Today we can look at ‘geophagia’ which is the behaviour of eating raw materials from the Earth; this might include rocks and soil and so forth; not a very delicious concept I’m sure you’ll agree, but it does serve a variety of useful purposes.

In perhaps its simplest form, geophagia might involve simply eating the soil and a wide range of different species, over 200 in fact, have been observed doing just that. Humans too have been known to dine on some soil from time to time, especially in times of famine, or sickness. But why eat soil? The answer is simple enough; many types of soil contain minerals that can be digested and metabolised by animals; the same minerals that can be found in food sources, minerals such as iron, sodium, calcium etc. When conditions are poor, animals might supplement their diet by practicing geophagia to gain those minerals that they are not currently receiving enough of from their food.

Elephants have commonly been observed practicing geophagia by, most often, eating clay like soils; especially those found at the bottom of water sources. It is believed that they eat these clays because they are rich in salts which provides them with sodium; an important nutritional mineral. Elephants may sometimes be seen digging through sediment with their trunk, looking for the salty clay that they need.

African elephants (Loxodonta africana) crossing a river, drinking water and digging for salty clay along the way.

African elephants (Loxodonta africana) crossing a river, drinking water and digging for salty clay along the way.

Many birds practice geophagia, but not necessarily for nutritional reasons, but still to aid in digestion. Birds have a specialised organ in their digestive tract called a gizzard which is used in the grinding up of food stuffs (birds do not have the luxury of chewing as they don’t have teeth). The gizzard is composed of strong muscular tissue that  crushes and grinds food to allow for more effective chemical digestion, but many birds enhance their gizzard’s effectiveness by swallowing small stones or grit that stay in the organ, breaking down food particles, these pieces of stone are referred to as gastroliths.

Ostriches (Struthio camelus) can carry gastroliths as big as 10cm.

Ostriches (Struthio camelus) can carry gastroliths as big as 10cm.

Crocodiles, which are surprisingly close relatives of birds, also consume gastroliths, but not just to help in the grinding up of food for easy digestion; by holding rocks inside their bodies these aquatic reptiles are able to affect their buoyancy in water and more effectively control their ability to float or sink as needed for temperature control or for ambushing prey.

So it seems that although geophagia might appear to be an unappetising prospect at first, it actually has useful purposes; in fact, many animals would not be able to survive without it. We humans can even give it a go too (not that WildlifeTV recommends it!) in certain cases.

Much love,




If you liked this entry, make sure you check out our Diet category.
Previous Diet entries:
Coprophagia: Poop is Food
Osteophagia: An unusual eating habit that actually isn’t very unusual.

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