An international team of entomologists has found that numerous termite mounds in Brazil are between 690 to 3,820 years old.
The termite mounds are found in dense, low, dry forest and can be seen when the land is cleared for pasture. Image credit: Roy Funch.
The vast array of termite mounds covers an estimated 230,000 km2 (roughly the size of Great Britain) of seasonally dry tropical forest in a relatively undisturbed region of northeastern Brazil.
It includes approximately 200 million cone-shaped soil mounds that are 2.5 m tall and approximately 9 m in diameter.
These mounds are not nests, but rather they are generated by the excavation of vast inter-connecting tunnel networks.
“These mounds were formed by a single termite species — known as Syntermes dirus — that excavated a massive network of tunnels to allow them to access dead leaves to eat safely and directly from the forest floor,” said study lead author Professor Stephen Martin, a researcher at the University of Salford, UK.
“The amount of soil excavated is over 10 km3, equivalent to 4,000 great pyramids of Giza.”
“This is apparently the world’s most extensive bioengineering effort by a single insect species,” added co-author Dr. Roy Funch, from the Universidade Estadual de Feira de Santana, Brazil.
“Perhaps most exciting of all — the mounds are extremely old — up to 4,000 years, similar to the ages of the pyramids.”
Soil samples collected from the centers of 11 mounds and dated indicated that the mounds were filled 690 to 3,820 years ago. That makes them about as old as the world’s oldest known termite mounds in Africa.
The researchers investigated whether the strangely regular spatial pattern of the mounds was driven by competition amongst termites in neighboring mounds.
Their behavioral tests found little aggression at the mound level. That’s compared to obvious aggression amongst termites collected at greater distances from one another.
The findings led the team to suggest that the over-dispersed spatial mound pattern isn’t generated by aggressive interactions.
Instead, the pattern arose through self-organizational processes facilitated by the increased connectivity of the tunnel network and driven by episodic leaf-fall in the dry forest.
“A pheromone map might allow the termites to minimize their travel time from any location in the colony to the nearest waste mound,” the scientists said.
“The vast tunnel network apparently allows safe access to a sporadic food supply, similar to what’s been seen in naked mole-rats, which also live in arid regions and construct very extensive burrow networks to obtain food.”
“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,” Professor Martin said.
“There are many questions still to pursue. For instance, no one knows how these termite colonies are physically structured because a queen chamber of the species has never been found,” the entomologists said.
The research is published in the journal Current Biology.
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Stephen J. Martin et al. 2018. A vast 4,000-year-old spatial pattern of termite mounds. Current Biology 28 (22): 1292-1293; doi: 10.1016/j.cub.2018.09.061
