Wind-induced ventilation of the burrow of the prairie-dog,Cynomys ludovicianus

Summary Where a fluid flows across a surface, such as wind over the earth, the velocity gradient created provides a potential source of work. This gradient might be employed by one burrowing animal to induce air-flow in its long, narrow burrow. The burrow of the black-tailed prairie-dog constitutes a respiratory dead-space of extraordinary magnitude in which diffusion appears inadequate for gas exchange. But the burrow is arranged in a manner appropriate for wind-induced ventilation, typically with two openings at opposite ends and with mounds surrounding these openings of two forms (Fig. 3), with one form on each end. When a breeze crosses the mounds, air enters the burrow through the lower mound and leaves through the higher. The same unidirectional flow is evident with scale models of real mounds on a model burrow in a wind tunnel; flow inside the burrow is nearly a linear function of flow across the mounds (Fig. 4). Wind-induced ventilation in the model burrow could also be induced with model mounds differing in shape but not height. Mounds with sharp rims were more effective exits for air than mounds with rounded tops; in nature such shape differences complement the differences in height. This study was supported by the Duke University Research Council, NIH Biomedical Sciences Support Grant K-01-GM-1222, and NIH Research Grant HL-02228. We thank Knut Schmidt-Nielsen, William Bretz, and Marvin Bernstein for useful advice, Carl Mills for the use of a flow meter, Vance Tucker for the use of the wind tunnel, and LeRoy Smith for assistance in the field.