Differences in position and shape of burrow openings of black‑tailed prairie dogs create passive ventilation from wind energy by altering air pressure.

Prairie dogs are highly social rodents that build extensive underground burrows in the plains of North America to house their family groups. The burrows can reach 10 m (32 ft) in length, and this size means that diffusion alone is not sufficient to replace used air inside the burrow with fresh air. The way that a prairie dog builds the openings to its burrow, however, helps to harness wind energy from the windy plains and create passive ventilation through the burrow’s tunnels.

As air flows across a surface, a gradient in flow speed forms, where air moves slower the closer it is to the surface. The prairie dog is able to take advantage of this gradient by building a mound with an elevated opening upwind and a mound with a lower opening downwind. Over the elevated opening, wind velocity is faster than it is over the lower opening, creating a local region of low pressure (following Bernoulli’s principle). The result of this difference in pressure between the two openings is one-way air flow through the burrow as air gets sucked into the lower opening and flows out the elevated one. This is the mechanism behind a Venturi tube.

The mounds around the burrow openings serve additional functions for the prairie dog, like providing a perch to watch for predators. Other organisms use a similar arrangement of openings to generate passive flow, including sea sponges and limpets.

Image: Morgane Rae / Copyright © - All rights reserved
Last Updated July 2, 2020