Stephen J. Martin noticed large mounds, about 10 feet high, 30 feet wide, along the side of the road while driving through a remote part of northeastern Brazil.
"After 20 minutes, we kept driving and started saying:" Well, what are they? ", Said Martin, an entomologist at the University of Salford in England, who was in Brazil to investigate the global decline in bees. .
He thought there could be piles of earth displaced from the construction of the highway. Instead, his companions said, "Oh, they're just mounds of termites."
Martin remembered his incredulous response: "And I said," Are you really sure about that? "And they said to me:" Well, I do not know. I think so. & # 39; & # 39; & # 39;
On a subsequent trip, Martin met Roy R. Funch, an ecologist at the Feira de Santana State University in Brazil, who was already making arrangements to make radioactive citations to determine the age of the mounds.
"I said," Look, there must be thousands of these mounds. "And he left," Nah, there are millions. "
But Funch had underestimated.
In research published in the journal Current Biology, Martin, Funch and his colleagues report on the findings of several years of research.
How many mounds About 200 million, scientists estimate.
The cone-shaped mounds are the work of Syntermes dirus, among the largest termite species: they are about half an inch long. The mounds, separated by an average of 60 feet, extend into an area as large as Great Britain.
"As human beings, we have never built such a big city, anywhere," Martin said.
Scientists were also surprised when they received the results of the radioactive dating of 11 mounds. The youngest was about 690 years old. The oldest was at least 3,820 years old, or almost the age of the great pyramids of Giza in Egypt. "That made me get out of the water," said Funch.
The scientists also estimated that to build 200 million mounds, termites excavated 2.4 cubic miles of land, a volume equivalent to some 4,000 great pyramids of Giza. "This is the best known example of ecosystem engineering by a single insect species," the scientists wrote.
Another surprise was that the mounds turned out to be just mounds.
Other termites build mounds with complicated tunnel networks that provide ventilation for underground nests.
But cutting off some of the mounds, Funch and Martin found a single central tube that leads to the top, and they never found any nests.
These mounds were not ventilation structures, but simply heaps of earth. As the termites dug tunnel networks beneath the landscape, they needed a place to dispose of the excavated earth. So they carried the dirt through the central tube to the top of a mound and threw it.
The young, active mounds grow 4 to 5 feet tall in a couple of years, said Funch. Most of the older mounds seem inactive. Scientists do not know if that means that the termites have left or if they simply do not need to dig further into the area after building the necessary tunnels.
Although the people living in the region knew about the mounds of termites, few outsiders knew it. The extension of the termite construction was hidden by a scrub forest.
"That's why they were not discovered for so long," Funch said. "You can not see them in the native vegetation, and not many scientists go this way."