Across the forests and prairies of Asia, and vast savannahs of Africa, live secret societies of architects. They are masters of construction, their sophisticated and innovative green-energy designs perfectly capturing the current trend for environmentally friendly construction. And yet these architects don’t like to share their secrets: exactly how – and why – they build their towering constructions has until recently remained somewhat mysterious.
Who are these master builders? They are the mound-building termites. Although they resemble whitish brown grains of rice with big heads and hedge-trimmers for mouthparts, these insects are ecological heavy hitters. Termites control a significant portion of the flows of carbon and water through dry savannah ecosystems, says Scott Turner, a professor of biology at the State University of New York. “They can build anywhere there is grass and water.”
Scientists have wondered why termites build mounds that can be 30ft high
Part of the reason termite mounds are the focus of so much scientific attention is that the insects don’t really live inside them. They choose instead to build their nests – which can be home to thousands or even millions of individuals – in the ground below the mound. In fact, they only travel into the mounds to repair them and defend the city below from invading ant armies and other threats.
For decades, scientists have wondered why termites go to all the trouble of building mounds that, for some species, can be 30ft (9.1m) high. There have been hypotheses, but in recent years, new science has debunked some of them. Engineers, biologists, and architects that study termites are now developing a new theory to explain the spectacular mounds – and their findings may help revolutionise the way we construct our own buildings.
Like us, termites build an environment that suits them rather than adapting to their environment. They sometimes live in arid regions that would dry out their bodies, for instance: their mounds help counteract the problem by maintaining an environment that is cool and humid.
The humidity isn’t just important to the termites. The termites make a living farming a fungus (Termitomyces) on structures known as fungus cones. The fungus helps breakdown dead plant and woody material into more digestible and nutritious food for the termites, and they in turn help maintain the environment for the fungus. It’s a mutually beneficial arrangement.
The mound is like a physiological extension of the termites themselves: a giant lung
There’s a lot of hustle and bustle in the termite nest, and both the fungi and the termites produce a lot of carbon dioxide. The problem, says Hunter King, a postdoctoral student at Harvard University, is that eventually they need to get rid of it.
Though there has been previous research investigating how carbon dioxide is swapped for oxygen in the mound, King says that in those studies, nobody measured the flows directly.
That’s why King, along with colleague Samuel Ocko from the Massachusetts Institute of Technology and supervisorLakshminarayanan Mahadevan from Harvard Universitydesigned a study that would allow them to directly measure temperature, carbon dioxide and humidity in the mounds ofOdontotermes obesus termites.
Turns out, it’s tricky to take gas measurements within a termite mound.
It’s a lot of work to build a mound, and so naturally, termites go to great lengths to make sure it has solid defences. It’s that defence system – like a state of the art burglar alarm – that makes measurements inside so difficult to take.