Research News

UB geographer finds pattern in vast, ancient network of termite mounds

termite mounds in Brazil.

This image shows mound fields. The mounds are found in dense, low, dry forest caatinga vegetation and can be seen when the land is cleared for pasture. Photo: Roy Funch

By CHARLOTTE HSU

Published January 3, 2019

headshot of Eun-Hye Yoo.
“As a geographer, it’s a routine task to examine the spatial pattern of any subject matter, whether they are trees, human mobility, cities or even termite mounds. We find so many hidden stories by carefully exploring their spatial patterns.”
Eun-Hye “Enki” Yoo, associate professor
Department of Geography

In 2012, UB geography researcher Eun-Hye “Enki” Yoo took an overnight bus to Lençóis, a remote tourist town in northeastern Brazil.

She wanted to go hiking. But while she was there, she also embarked on a second, serendipitous adventure, this one scientific.

Roy R. Funch, a biologist at the Universidade Estadual de Feira de Santana in Brazil, had heard that Yoo — an expert in geographic information science (GIS) — was in Lençóis. He tracked her down and asked if she might lend her skills to a study of nearby termite mounds.

The two scientists drove out together to see the earthen structures. That impromptu trip led to a research project that made international headlines this November.

It turns out that the mounds they viewed are a part of a vast ancient network. About 200 million of the structures are spread out over more than 88,000 square miles (an area the size of Minnesota, as reported by The Washington Post).

Each mound is about 8 feet tall and 30 feet wide. To make all of them, generations of termites had to displace about 2.4 cubic miles of dirt — equivalent in volume to about 4,000 of the great pyramids of Giza.

According to a news release posted by the research team to EurekAlert, “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.” In other words, as The New York Times put it, they are “garbage piles.”

The study was published on Nov. 19 in the journal Current Biology. Co-authors include Funch, Yoo, Stephen J. Martin of the University of Salford and Paul R. Hanson of the University of Nebraska-Lincoln.

Plotting products of termites’ labor

To learn about the mounds, Yoo and her student Jiyang Zhang located them in Google Earth and plotted them as points of data on a map. Then, Yoo used analytical techniques to study the spacing between the structures. She found that the mounds are configured in a regular pattern, with an average distance of about 66 feet between them.

“As a geographer, it’s a routine task to examine the spatial pattern of any subject matter, whether they are trees, human mobility, cities or even termite mounds,” says Yoo, associate professor of geography in the College of Arts and Sciences. “We find so many hidden stories by carefully exploring their spatial patterns.

“The identification of the termite mounds’ unique pattern was helpful to tease out some hypotheses and to explain why they were built in a certain way. For example, if they happened to be clustered, we would have been interested in explaining why they were clustered — for what? Food or water sources?”

Yoo’s spatial analysis showed that the mounds weren’t clustered or random. To explore the mystery of the mounds’ even spacing, researchers conducted behavioral tests to see if competition between termites could explain why the structures are spread apart at regular intervals. But the experiments showed insects in neighboring mounds were on friendly terms.

So what explains the mounds’ configuration? According to The New York Times, the scientists “concluded the pattern was simply an efficient spacing of garbage piles.”

Still more to dig into

Yoo hopes to continue researching the mounds. She has lots of questions. As a geographer, she’d like to get detailed measurements of the height and shape of the 200 million-plus mounds. She also wonders if climate change might impact their spacing.

Amazingly, the termites are still at it, too: When the researchers dated 11 mounds, they found that the oldest had been around for about 3,820 years. Four millennia later, new mounds are still being created as the termites continue to dig — the industrious inheritors of an ancient, sprawling civilization.

There is much more to learn.