When European visitors first came to the caves in Mount Elgon, they found strange carvings on the walls and believed them to be the work of Ancient Egyptians. But that's now known not to be the case. So just what is creating these carvings? Infra-red cameras are set up so that David Attenborough can keep watch on the cave as night falls. Bats leave the cave at dusk, and then a bushbuck enters looking extremely nervous - it can sense a buffalo nearby in the cave, but the pitch darkness means they cannot see each other. The bushbuck seems to be eating something, and David realises it's licking salt off the floor. Then a sound like distant thunder rumbles through the cave. A huge male elephant picks his way through the narrow cave, placing each foot really carefully in the complete darkness. He repeatedly bumps his head on the cave roof and walls. His rumbles may be a signal to the others outside that are now arriving up the steep slope. All the elephants follow the exact path of the male. At some points the cave is so narrow the male can only just squeeze through. He uses his tusks to gouge salt off the rocks sucking it into his trunk before blowing it into his mouth. The elephants in particular need this salt to supplement their diet of plants, and its this need that drives them to make the tricky journey up to the cave. Generations of these large animals have been coming to the caves for their mineral riches. Could this great cavern even have been created by them?