Researchers have found about 200 million cone-shaped mounds hiding in plain sight in northeastern Brazil. They stand roughly 8 feet tall and 29.5 feet across. They cover 88,800 square miles (23,000 square kilometers) of dry tropical forest — roughly the size of Great Britain or Oregon.
These mounds aren't architectural relics of an ancient civilization. No, these long-standing marvels were built by, and are still being used by, termites.
Outlined in a report published in Current Biology, these mounds, which are also visible from space, don't appear to be nests. Most species of termites typically build mounds that are nests, but these structures, built by Syntermes dirus termites, lack internal structures. Instead, they're just mounds of, well, dirt — some 2.6 trillion gallons of it.
"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 from the University of Salford in the United Kingdom, said in a statement.
The process of building those subterranean tunnels resulted in a lot of discarded dirt over the centuries, and the termites heaped all that extracted dirt into these piles, each spaced roughly 65 feet apart.
The mounds aren't the result of aggressive interactions between termites — indeed, termites near the mounds seem to be friendlier towards each other than termites spotted 31 miles away — and they don't represent the termite version of "keeping up with the Joneses" to see who can build a bigger mound. Instead, the researchers suggest the mounds were simply the end result of building a vast, interconnected tunnel network that minimizes travel time from any location in the colony to the nearest waste mound. That allowed the termites to focus on reaching the dead foliage, which is what these termites eat and is only available sporadically.
These mounds haven't received the same level of attention as termite-built structures in Africa. Researchers chalk up the lack of interest to the fact that these mounds are located in an area that's hot, difficult to reach and comes with plenty of thorny vegetation. As a result, there's plenty to learn.
"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.
Related on MNN: Elderly termites are sent into battle to die first