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Study finds mule deer struggling

Posted: Monday, Oct 25th, 2010

The population of mule deer in the Pinedale Anticline gas field has declined 36 percent in the last nine years, triggering mandatory mitigation, according to a recent monitoring report.

The 2010 report, prepared by Western Ecosystems Technology Inc. (WEST), is on the agenda at the Bureau of Land Management (BLM) Annual Wildlife Planning Meeting Wednesday.

The report’s findings are significant for two reasons.

First, the 300-square-mile Pinedale Anticline south of Pinedale contains a plateau called the Mesa that is the wintering grounds for one of the state’s biggest mule deer herds and second, the Anticline is one of the biggest natural gas fields in the nation – capable of producing 25 trillion cubic feet of gas and billions of dollars in profits.

To manage the conflict between those two resources, the BLM drafted a monitoring and mitigation matrix in its 2008 Pinedale Anticline record of decision (ROD). That matrix has “triggers” that mandate mitigation for the Mesa’s mule deer herd if its numbers decline by 15 percent in one year or cumulatively since the winter of 2005.

The WEST report says the 2005 population was 2,894 deer. In 2008, it reached a high of 3,850 but in 2009, the number fell to 2,088 – a 28-percent decrease. What’s more, the 2009 population plummeted by 1,700 animals.

According to WEST, those changing numbers are enough to trigger the matrix.

“Given the magnitude of the observed changes between winters 2008 and 2009,” the report reads, “the 15-percent threshold appears to be


At the same time, the number of mule deer in the Ryegrass area – west of the Mesa – has nearly doubled from 1,000 to 2,000 since 2006. During the middle of winter, the two herds rarely mingle.

Both herds move to their wintering grounds to escape deep snow in the surrounding mountain ranges.

Decline and fall

The study postulates three reasons for the Mesa’s mule deer decline between 2008 and 2009.

The first is a series of mild winters that might not have pushed the deer all the way to the Mesa. The second is a new law prohibiting antler gathering before May 1. The report says the new law reduced winter ATV traffic in the Ryegrass area; previous traffic could have pushed mule deer to the Mesa. The last cause could be the Mesa’s natural gas development, particularly after the 2008 ROD allowed energy companies to drill during winter months.

“It is possible,” the study says, “that this increased winter disturbance affected fawn survival or adult reproduction.”

The WEST report also cites a Wyoming Game and Fish (G&F) population estimate that found that overall, the Sublette mule deer population declined by 21 percent from 2001 to 2009.


Wednesday’s meeting will be coordinated between the BLM and the Pinedale Anticline Project Office (PAPO), an interagency organization that manages a $36-million monitoring and mitigation fund, which is collected from the Anticline’s three main gas operators: Ultra, Shell and QEP.

According to the ROD, the PAPO fund is responsible for financing mitigation when the matrix is triggered.

In the spring, Anticline gas operators criticized the PAPO board – consisting of the Wyoming state directors of the BLM, G&F, Department of Environmental Quality, Department of Agriculture and Sublette County Commissioner Joel Bousman – for depleting the fund with conservation easements, which are legally binding agreements that prevent certain development on private land.

In April, the operators cited $6 million spent for an easement west of the Mesa when they asked the PAPO board to conserve money for future mitigation projects, such as projects mandated by the ROD if the matrix were triggered.

According to the ROD, those mitigation projects have four components. One is on-site mitigation that enhances habitats in the core development area. Another protects the so-called “flank” areas outside the core development area. Yet another is off-site mitigation such as habitat enhancements and conservation easements.

After allowing sufficient time for those mitigations to work, the final step would be a change in the pace of Anticline


Wednesday’s meeting is scheduled for 8:30 a.m. at the BLM office in Pinedale.

For the complete article see the 10-26-2010 issue.

Click here to purchase an electronic version of the 10-26-2010 paper.

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