November
19, 2018, Cell Press
Researchers
reporting in Current Biology on November 19 have found that a vast
array of regularly spaced, still-inhabited termite mounds in northeastern
Brazil—covering an area the size of Great Britain—are up to about 4,000 years
old.
The
mounds, which are easily visible on Google Earth, are not nests. Rather, they
are the result of the insects' slow and steady excavation of a network of
interconnected underground tunnels. The termites' activities over thousands of
years has resulted in huge quantities of soil deposited in approximately 200
million cone-shaped mounds, each about 2.5 meters tall and 9 meters across.
"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,"
says Stephen Martin of the University of Salford in the UK. "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."
"This
is apparently the world's most extensive bioengineering effort by a single
insect species," adds Roy Funch of Universidade Estadual de Feira de
Santana in Brazil. "Perhaps most exciting of all—the mounds are extremely
old—up to 4,000 years, similar to the ages of the pyramids."
The
mounds are largely hidden from view in the fully deciduous, semiarid,
thorny-scrub caatinga forests unique to northeastern Brazil. They'd only really
come into view by "outsiders," including scientists, when some of the
lands were cleared for pasture in recent decades.
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.
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