Large herbivores such as elephants often seek out natural mineral deposits such as rocks and soil to supplement their dietary intake of sodium whenever the mineral is not obtained in adequate quantities from woody plants and natural water which elephants consume. So it is not uncommon to find elephants devouring soil and licking rocks high in sodium content. In Mount Elgon National Park on the Kenya-Uganda border, elephants have taken this activity a step further—they have learned to quarry sodium-rich rocks on the base of a 24-million-years-old extinct volcano called Mount Elgon.
Mount Elgon is believed to be the oldest extinct volcano in East Africa. Because of its unusually large form—an 80 kilometer wide base and a peak that rises 3,000 meters from the surrounding plains— Mount Elgon doesn’t have the typical sharp rise of a volcanic mountain. The rise is more gradual, and as the land rises the vegetation changes and so does the climate. The forest becomes thicker and air becomes chilled. Many rare plants and animals seek shelter in the higher slopes of Mount Elgon to escape the heat of the plains.
The elephants prefer to stay in the lower slopes where there are a number of caves and salt is plenty. These caves are quite voluminous, with up to 150 meters long, 60 meters wide, and some 10 meters high. There is evidence that these caves have been artificially expanded by thousands of years of mining—not by humans, but by the pachyderms.
The elephants use their tusks to break off pieces of the cave wall, which they then chew and swallow, leaving long scratch marks all over the cave walls. The elephants chisel the rocks for several hours and eat large quantities of salt at a time, since they usually do not return until several weeks later. The elephants have a voracious appetite for salt. One young bull elephant at the Aberdare National Park in Kenya was observed to consume 14 to 20 kg of salty soil in 45 minutes. From another observation of a young calf feeding himself rocks inside Kitum Cave in Mount Elgon, researchers estimate that on average an elephant excavate about two liters volume of rocks from the cave.
Illustration credit: Ian M. Redmond
Aside from elephants, other animals such as bushbuck and buffaloes are also drawn to the salt in the caves. It’s unlikely the animals know they need salt in their diet. The behavior is mostly instinctive, developed over thousands of years, and by leading their young into the caves, the knowledge has been passed on through the generations.
Some predators such as leopards and hyenas take advantage of this behavior by hiding in the darken interior of the caves and attack weaker animals such as elephant calves, buffaloes and bushbucks. The worst happened during the 1980s when poachers discovered this trick. They hid near the entrance to the caves and ambushed the elephants as they approached. From more than 1,200, the population of Mount Elgon's elephants fell to under one hundred. Poaching radically altered the behavior of the elephants—they became more secretive and started avoiding the better-known caves.
The fall in ivory prices in the 1990s and a more determined anti-poaching effort by the Kenyan government gave the elephants some respite. The situation has improved since the last two decades, but the future is anything but bright.
Tusk marks on the wall of the caves.
