Termites' Massive Mounds Ventilate Like Lungs, Researchers Say

Researchers recently discovered that large termite mounds actually act like lungs, taking in air and pushing it out once a day as temperature changes. This study was recently published in the journal Proceedings of the National Academy of Sciences and is the first to describe in detail how these massive mounds are ventilated.

"The direct measurements essentially overthrow the conventional wisdom of the field," L. Mahadevan, Lola England de Valpine Professor of Applied Mathematics at Harvard, said in a news release. "The classic theory was that if you have wind blowing over the mounds that changes the pressure, and can lead to suction of CO2 from the interior...but that was never directly measured. We measured wind velocity and direction inside the mounds at different locations. We measured temperature, CO2 concentrations...and found that temperature oscillations associated with day and night can be used to drive ventilation in a manner not dissimilar to a lung. So the mound 'breathes' once a day, so to speak."

The researchers conducted tests on live and dead mounds in India using custom probes. They took temperature readings every day and night for several weeks. To do this, they covered the mounds with tarps and blew air over them. They then tested for suction by using a vacuum cleaner. 

So what did they discover? The researchers found that the mounds were built around a large central chimney, which reaches from where the colony lives underground to the top. While the outside of the mound was found to be relatively thin, the mound's interior had much larger, structural walls. The researchers explained that the exterior was thinner to allow for the exchange of gases.

"What you get is a convection cell," Mahadevan explained in the release. "The warm air can't move through the walls quickly enough, but it has to go somewhere, and the only possibility is for it to go down into the interior through the central chimney. At night, as the exterior cools, the airflow reverses, and it pulls the air up from the central part of the mound."

Mahadevan added in the release that, "But what's remarkable here is how the termites are using transients. The temperature outside the mound is oscillating, and they have developed a method to harness that to ventilate their mounds."

While developing more efficient ventilation systems for buildings is not a new idea, the researchers suggested that architects might be able to learn from these tiny insects.

"In a large building like the one we're sitting in we have windows and doors that allow us a certain amount of seclusion and privacy, but that also means you have a harder time pushing air around from one part of the building to another," Mahadevan said in the release. "Rather than spending a great deal of energy for a fan and air conditioning in every room, with the end result being that some people are too hot and some people are too cold... perhaps we should think of the entire thing as a system and these new measurements suggest that if the architecture is appropriate, ventilation can occur by using environmental transients -- something for us to think about."

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