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Elephants have been digging caves for thousands of years for salt, scientists have discovered. It was thought that these caves were made by Egyptians looking for diamonds, but in fact these huge mammals are responsible for the feat.
Large herbivores, such as elephants, commonly seek out natural ore deposits to replenish their sodium intake because the minerals present in plants and water do not have enough.
Elephants dig a cave on Mount Elgon (Image: Richard Preston via Atlas Obscura)
Elephants Dig Cave in Kenya
On the border between Kenya and Uganda, elephants have figured out how to exploit the sodium-rich rocks in a volcano that went dormant about 24 million years ago in Mount Elgon, which is the oldest extinct volcano in East Africa.
The foot of the hill is 80km wide, and the top is over 3,000. The elephants prefer to stay on the lower slopes, where the salt caves are. These are huge caves, 150m long, 60m wide and about 10m high.
It is not uncommon for elephants to consume salty soil and lick sodium-rich rocks. They use ivory to break down cave walls, and then chew and swallow the detritus, leaving long scratches across the walls.
The animals take several hours at this, and consume large amounts of salt each time, because they don't return to the site until a few weeks later.
A small elephant in Kenya's Aberdare National Park eats about 14 to 20kg of salty soil in 45 minutes. 
The route can be dangerous, as the skeletons of young elephants have been found to have probably fallen into holes in the cave. (Image: Mount Elgon Foundation)
Besides elephants, other animals like zebra fish and buffalo also consume cave salt. Some predators like leopards and hyenas take advantage of this, hiding in the dark parts of the caves, attacking elephants, buffalo and antelopes.
Unfortunately, hunters also discovered this trick in the 1980s. They hide in cave entrances, and ambush the elephants as they approach.
The hunt has completely changed the habit of the elephants, which now act more carefully, avoiding the most frequented caves. The number of elephants on Mount Elgon used to be 1200, and has now dwindled to less than a hundred.
