- Some 200 million conical termite mounds rise from the ground in northeastern Brazil, each about 2 to 4 meters high and about 9 meters wide, visible on Google Earth.
- Researchers dated the soil from 11 of these mounds and found that the piles are up to about 4,000 years old, making them almost as ancient as the pyramids of Giza.
- The mounds are still inhabited by the termite species, Syntermes dirus, that first made them.
- The mounds themselves lack any definite internal architecture, but there are extensive networks of underground tunnels that the termites use to safely access fallen leaves on the forest floor.
In the thorny-scrub forests of northeastern Brazil, some 200 million conical termite mounds rise from the ground. The densely packed piles, visible on Google Earth, are not only large — about 2 to 4 meters (6.5 to 13 feet) high and about 9 meters (30 feet) wide — but also really old, dating back to about 4,000 years, a new study has found. This makes the mounds almost as ancient as the pyramids of Giza.
The mounds are still inhabited by the termite species, Syntermes dirus, that first made them. The mounds are not nests, researchers say in the study published in Current Biology. Rather, these are giant piles of soil without any defined internal architecture.
There are extensive networks of underground tunnels, though, that the termites dug out over the millennia, the study found. The termite excavation generated huge quantities of extracted soil that deposited over time to form large and regularly spaced mounds covering an area the size of England. The termites use the underground tunnel networks to safely reach the forest floor where their preferred leaves fall, via an array of tiny temporary tubes excavated from below, the researchers write. After use, the temporary tubes are sealed shut.
“These mounds were formed by a single termite species that excavated a massive network of tunnels to allow them to access dead leaves to eat safely and directly from the forest floor,” Stephen Martin, a professor at the University of Salford in the U.K., said in a statement. “The amount of soil excavated is over 10 cubic kilometers, equivalent to 4,000 great pyramids of Giza, and represents one of the biggest structures built by a single insect species.”
Previously hidden in the forests, the mounds became visible when people started clearing vegetation in the area for grazing land in recent decades. Researchers dated soil samples collected from the centers of 11 mounds and determined them to be between 690 and 3,820 years old, comparable to the world’s oldest known termite mounds in Africa. There could be even older mounds that the team did not sample.
The mounds are, in fact, the “greatest known example of ecosystem engineering by a single insect species,” the researchers say.
“It’s incredible that, in this day and age, you can find an ‘unknown’ biological wonder of this sheer size and age still existing, with the occupants still present,” Martin said.
Martin, S. J., Funch, R. R., Hanson, P. R. and Yoo, E-H (2018) A vast 4000-year-old spatial pattern of termite mounds. DOI:https://doi.org/10.1016/j.cub.2018.09.061