Climate Control in Termite Mounds
Photo courtesy of Hunter King and Sam Ocko
Many species of fungus-harvesting termites build largely empty, massive mound structures which protrude from the ground above their subterranean nests. It has been long proposed that the function of these mounds is to facilitate exchange of heat, humidity, and respiratory gases; this would give the colony a controlled climate in which to raise fungus and brood. However, the specific mechanism by which the mound achieves ventilation has remained a topic of debate, as direct measurement of internal air flows has remained difficult.
Postdoctoral fellow Hunter King and graduate student Samuel Ocko, working with Prof. L. Mahadevan, devised a sensor to measure the elusive, tiny air flows in the mounds of the species Odontotermes obesus in India and reported at the recently concluded APS Division of Fluid Dynamics meeting in San Francisco that the mound architecture takes advantage of daily oscillations in ambient temperature to drive convection and gas transport. This contradicts previous theories, which point to internal metabolic heating and external wind as driving forces. The results of this study, a novel example of deriving useful work from a fluctuating scalar parameter, not only shed light on how termites may build such complex structures, but may also contribute to the development of innovations in human architecture.