Pinedale Mesa deer population drops
A mule deer buck, with swollen neck signifying the fall rut, traverses the sagebrush habitat of the Pinedale Anticline in this November 2009 file photo. (Cat Urbigkit/Star-Tribune correspondent)

PINEDALE -- Mule deer on the Mesa near Pinedale have declined 60 percent in 2009 compared to 2001, and the animals' numbers are 28 percent lower in 2009 than in 2005, according to the most recent research on the matter.

The Mesa hosts the Pinedale Anticline natural gas field, and the deer decline has been tracked as part of an ongoing research project that has continued for more than a decade, paid for by industrial companies developing energy resources in the region.

Hall Sawyer with Western Ecosystems Technology Inc. explained the most recent research results to a work session of the Pinedale Anticline wildlife annual planning meeting Wednesday. The long-term deer decline result was also compared to Wyoming Game and Fish Department population estimates, which indicated Mesa mule deer numbers declined at a higher rate than the region's overall deer population.

The Bureau of Land Management's wildlife monitoring and mitigation matrix for the Pinedale Anticline Project Area mandates that a 15 percent cumulative change in mule deer abundance requires additional mitigation and monitoring.

Not included in the report, but evident to Sawyer in evaluating data, was a change in the mule deer survival rate on the Mesa. Hall reported that the average annual survival rate for adult females in most deer populations is 85 percent, and the annual survival rate on the Mesa has been about 80 percent. But this year, the survival rate dropped to less than 70 percent, and most of the radio-collared deer in the study that died did so during the first two weeks of May. He noted that the timing of deaths is "indicative of poor body condition" going into spring.

"Survival is as low as we've ever seen it," Sawyer said. "It certainly raises a red flag."

Shane DeForest of the Pinedale BLM Field Office reported that since "the matrix threshold has been reached," additional mitigation measures must be undertaken, as well as monitoring of those measures.

The BLM's record of decision for the energy development project details mitigation measures that must be undertaken, with emphasis on on-site mitigation including habitat enhancements and protection of important areas from disturbance; on-site and off-site mitigation such as conservation easements or property acquisition; and modification of energy operations.

DeForest reported the number of new projects undertaken in the past two years that fall under the list of increased mitigation, which include everything from winter range closures and deferment of development, to various habitat enhancements and the completion of the Sommers and Grindstone Ranch conservation easements.

"It's been a very short amount of time since we've implemented these things," DeForest said. He noted that the monitoring program for the Pinedale Anticline has been long-term and ongoing, but many of the mitigations are new projects.

"That is the definition of adaptive management, I suppose," DeForest said.

DeForest noted that the environmental impact statement for energy development acknowledged "habitat impacts will be substantial due to full field development." But DeForest said it's important to note that the mitigation response is early enough to assure both effective mitigation responses and a fluid pace of development. The goal of the program is to identify impacts to wildlife so that they will be addressed before consequences become severe or irreversible, he said.

Scott Smith of the Wyoming Game and Fish Department agreed that habitat enhancements are a good place to start. He noted that the weekend before the meeting, a sagebrush fertilization project was undertaken on the northern end of the Mesa, and the 468-acre treatment is one of the first on-site habitat enhancement projects undertaken.

Such a project is a logical place to start, Smith said, but there are challenges to enhancements in sagebrush habitat. In the past, habitat enhancement in sagebrush country has generally meant killing off the sagebrush first, Smith said, and the question now is to learn whether it is possible to enhance sagebrush productivity without killing the habitat first. One of the habitat goals should be to get deer on a better nutritional plane during their third trimester of pregnancy, Smith said.

Noting the recent habitat work and other mitigation measures undertaken, Shell's Tim Murray urged the group not to overreact to the research. He noted that there was a great deal of industrial activity in installing the liquids gathering system on the Mesa, and that could have caused localized impact in the northern portion of the Mesa during the construction. Now that the system has been completed, that activity has concluded, and the benefits of the system should follow.

Continuing monitoring is needed, Murray said. "Let's see what the results are before we start reacting too much to what could be naturally caused variation," he said.

Smith agreed to the monitoring, but added, "We've hit the threshold, and I hope we don't get caught up in cause and effect. … We've got to be proactive."

BLM High Desert District Manager John Ruhs agreed that "aggressive and positive action" is needed at this time.


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