There are dirt mounds like these all over the place in northern South Africa. I thought I remembered from TV nature shows that they were ant hills. I wondered why they so often have a tree growing out of them, so I asked our ranger.
Nelson told me that these are termite mounds. These particular termites don’t eat trees, but they sometimes build the mound around a tree for structural support. That was sort of interesting. But the really fascinating thing he told me about these insects is that they are farmers. The termite mound is like the tip of an iceberg – there is a gigantic termite complex down under the ground, with many chambers. The termites are busy working down there. They need a certain kind of fungus to help them digest the grasses that they eat, and they actually cultivate the fungus in those underground chambers. This fungus is very sensitive to temperature, so the termites are constantly striving to regulate the heat in their subterranean fungal gardens. The mound that you see above ground functions as a chimney, to release excess heat.