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The story behind Brazil's 200 million termite mounds

One of the 200 million termite mounds found in northeastern Brazil One of the 200 million termite mounds found in northeastern Brazil Stephen Martin
10 Jan
2019
The recent discovery of more than 200 million termite mounds in northeastern Brazil, the extent of which had never been understood before, throws up more questions than it answers

Professor Stephen Martin, a social insects expert from the University of Salford was driving along the roads near Lencois, a small Brazilian town popular with backpackers, when he was intrigued by lines of perfectly formed soil mounds at the roadside. At first he suspected construction work but the presence of the mounds within the scrub forest that bordered the road suggested otherwise. ‘Half an hour later I was thinking, gosh there’s a lot of these things,’ says Martin.

Having teamed up with other scientists in the area, he learnt that these regularly spaced mounds, each about 2.5 metres tall and 9 metres across, were termite mounds. Most extraordinary of all was the discovery that they covered an area of 230,000 square kilometres (more than that of Great Britain) and could be viewed on Google Maps. What’s more, initial ageing of the mounds revealed them to be at least 4000 years old.

Mounds2An aerial view of the mounds (Image: Roy Funch)

For the people living in this sparsely populated region of Brazil the mounds are little more than a nuisance. Impossible to knock down without a bulldozer they have to be worked around. ‘You’ll see people’s houses and they’ll have them in their garden,’ says Martin. ‘They’ll sit on them and have a barbecue inside.’ But for an insect expert they posed several questions.

One termite mound usually equals one termite colony, with the mound acting as a home for the insects, but Martin knew that there wasn’t enough of the termites’ preferred food (dead leaves) to feed that many insects. ‘When we cut into the mounds, there was nothing in there,’ he adds. To crack the problem he began to study a smaller group of about 50 mounds in a nearby forest. The first clue was that none of the individuals around the mounds were fighting, which meant they were all from one colony rather than 50 separate ones. By digging, the team then started to unearth a vast underground network – the mounds, rather than providing homes, were merely the result of excavation work with the termites living in the subterranean tunnels. The amount of soil excavated by this process is over 10 cubic kilometres and represents one of the biggest structures built by a single insect species.

roy on moundsProfessor Roy Funch, one of the authors of the resulting report, provides a clue as to the size of the mounds (Image: Stephen Martin)

Many questions still remain. In this dry area of thorny scrub forest, known as caatinga or ‘white forest’, food is only available for one or two months every year when the rains come and the forest blooms. Martin doesn’t yet know how the termites store enough leaf matter to survive. Other intrigues include the fact that it’s not clear how the termites breath. ‘You often hear of termites having amazing ventilation systems to get rid of the carbon dioxide, but these are completely sealed,’ says Martin. ‘It may be that they are highly adapted to living in low oxygen levels. I suspect there is a lot of very unique biology involved.’  Then there’s the fact that despite a high frequency of forest fires in neighbouring areas, the caatinga suffers almost none. Again, Martin suspects that the millennia-old termite population could be the reason why – by eating all the dead leaves the insects remove any tinder.

There’s plenty of work to be done, but for now Martin is enjoying the wonder of discovery. ‘It’s staggering that this type of thing, on this scale, has never really been seen. No one had worked out the extent. That’s because a lot of us work behind screens, and it’s only getting into the field where you can see it. It’s been a real joy being involved, because it’s only once in your lifetime that you ever get to find something like this.’

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