A herd of pronghorns graze near a natural gas drilling rig, Pinedale, Wyoming (Image: Joel Sartore/NGS/Getty Images)

Meet the latest player in the fractious debate over “fracking” for natural gas: the pronghorn. Disturbance from drilling is causing the fleet-footed ungulates to vacate their prime wintering grounds in Wyoming.

In winter, pronghorn (Antilocapra americana) migrate from higher ground to the Upper Green River basin – which in recent years has experienced a boom in gas drilling.

To study the effects of this development, a team led by Jon Beckmann, of the Wildlife Conservation Society, based in Bozeman, Montana, put GPS collars on 125 female pronghorn and tracked their movement.


Between 2005 and 2009 the researchers documented a five-fold decline in the use of habitat patches predicted to be of the highest quality, as the animals avoided areas disturbed by drilling. “We are seeing the abandonment of crucial winter range,” says Beckmann.

Pronghorn populations haven’t yet begun to fall, but a parallel study of the area’s mule deer (Odocoileus hemionus), a more sedentary species, doesn’t bode well: its numbers declined by 50 per cent over the same period.

By 2009 more than 3300 wells had been drilled in the Upper Green River basin, many of which are fracked, and thousands more are expected to follow. The researchers want the federal Bureau of Land Management, which must approve drilling operations, to minimise wildlife disturbance. That could be done by concentrating wells onto fewer drill pads, and using “directional drilling” techniques to extend the wells horizontally.

Journal reference: Biological Conservation, DOI: 10.1016/j.biocon.2012.01.003