Northwest Colorado has been called “the deer factory” because its diverse mix of sagebrush flats, pinyon-juniper woodlands, and rocky draws provides critical winter habitat for one of the largest migratory mule deer herds in the continent. But the region and the underlying Piceance Basin also encompass one of the largest natural gas reserves in North America. Colorado researchers have now, for the first time, quantified the impacts of that collision, and shed light on how further gas development could reduce its harmful effects.

Gas production in the Piceance skyrocketed from 126 billion cubic feet in 2000 to 859 billion cubic feet in 2012. New drilling has slowed with a drop in gas prices in the last few years. Still, there are thousands of new well pads and miles of supporting roads that affect the region’s wildlife. Studies from Wyoming’s Pinedale Anticline region show migratory mule deer herds have been cut in half in some cases since the oil and gas boom started. But scientists haven’t yet teased out energy effects from other threats to mule deer, such as drought, disease and new residential development that have contributed to herd declines since the 1980s.

To assess the impacts of oil and gas development in the Piceance, starting in 2008, scientists and consultants used helicopters to trap mule deer and place GPS collars on 53 females to monitor their movements – and their hard-to-track behavior amid the sprawling gas patch. “This is one of the first mule-deer studies that allowed us to quantify how much critical winter range is impacted,” says Joe Northrup, a Colorado State University wildlife biologist and lead author of the study published in the journal Global Change Biology last week.

Northrup and his colleagues determined that gas development areas in the Piceance compromised between 25 and 50 percent of mule deer’s critical winter range. At active drilling sites, the deer stayed an average of a half-mile away, and were especially skittish at night, likely trying to avoid the bright lights and jarring noise of around-the-clock industry at the same time they’re trying to do their nightly foraging. “What stood out was how much of the range was impacted,” Northrup says.

But the researchers also found that the Piceance’s mule deer persevered within the basin’s diverse and rugged terrain better than herds around Pinedale, which has lots of sage along a high and open mesa but little else. They suggest the deer’s ability to use refuge areas near developed patches mitigated severe population decline. The diverse terrain allowed deer to avoid development yet still feed and withstand the winter.

“Now that we understand how the deer respond to different types of activities, that informs our planning process moving forward,” says Chuck Anderson, Colorado Parks and Wildlife mammals research section leader and another study co-author. “Energy development does inhibit the ability of (mule deer) populations to rebound, and that’s why we’re interested in development activity and how we can proceed in the future.”

Another study author, George Wittemyer, a Colorado State wildlife biologist, added, “We’re seeing evidence of how we can do this smartly if we can get ahead of the curve and do some landscape-level planning.”

The state and the Bureau of Land Management can both set stipulations on drilling, production and site reclamation that build on the study’s findings. Measures based on the study’s results could, for instance, prohibit nighttime drilling or encourage clustered well pads. Agencies could also try to establish landscape-level planning programs to coordinate where development occurs and avoid the most sensitive or important habitat areas. Such mitigation and planning isn’t groundbreaking, but it’s not common either.

Anderson says that companies working in the Piceance have collaborated and consulted with state wildlife officials, and he hopes the latest research will provide guidance for reducing wildlife impacts while accommodating ongoing development.

Joshua Zaffos is an HCN contributing editor. Follow him @jzaffos. (Disclosure: Zaffos is an adjunct professor in Colorado State’s Warner College of Natural Resources where both Wittemyer and Northrup work.)

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