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Pronghorn, sage grouse still above matrix triggers

Posted: Monday, Nov 7th, 2011

Based on the Pinedale Anticline Project Area’s (PAPA) Wildlife Monitoring Matrix – which shows local mule deer populations struggle to regain numbers – pronghorn antelope and sage-grouse are doing slightly better and have not yet hit their matrix “triggers.”

Those reports were also part of the PAPA annual wildlife meeting agenda on Oct. 26 at the Pinedale Bureau of Land Management (BLM) building.

The Pinedale Anticline Project Office (PAPO gathers and distributes monitoring information and funds from Anticline operators’ oil and gas development areas – as required by the BLM’s 2009 supplementary environmental impact statement (SEIS) record of decision (ROD).

The PAPO sponsored those wildlife reports covered at the Oct. 26 meeting and also to be mentioned Tuesday Nov. 8, at the Pinedale Anticline Working Group (PAWG) meeting at the BLM offices.

“Matrix species” include mule deer, pronghorn antelope and greater sage-grouse on the Anticline; each has a different “trigger” where mitigation efforts must be stepped up by cooperating agencies such as PAPO, the BLM and Wyoming Game and Fish (G&F).

For mule deer, the trigger is a 15-percent decline in any one year or cumulatively over all years when compared to the “reference area,” in this case the Sublette mule deer herd unit as estimated by G&F.

For pronghorn on the Anticline, the trigger is also a 15-percent decline in one year or cumulatively compared to the Sublette pronghorn herd unit, also counted by G&F biologists.

For sage grouse, the trigger is a 30-percent decline in the total number of active leks or a 30-percent decline in the number of leks in a single complex, including the Mesa, Duke’s Triangle and Yellow Point.

Ryan Nielson, of WEST, Inc., gave an update at the Oct. 26 meeting and noted GPS units weren’t due to fall off last winter’s collared pronghorn until last week so he could only provide 2010 winter data. His draft report is due to the PAPO in April.

Nielson described aerial surveys for winter 2009-10 as the “first attempt to estimate pronghorn abundance in the PAPA and Cottonwood area,” leaving nothing to compare.

“Because we have only one year of abundance estimates for the PAPA and Cottonwood Creek area, a comparison of trends or changes in numbers between the study areas and the Sublette herd unit is not possible,” he said. “ … Mitigation triggers defined in the WWMM require at least two years of data for comparison. Because this report represents the first year of data collection we cannot assess whether abundance or avoidance thresholds have been exceeded at this time.”

During the aerial surveys if a group appeared to have more than 50 animals, high-definition video and computers were used to double-check counts. Researchers “catch one snapshot where they’re all in a group” and then confirm counts because it is more precise than a visual estimate, according to Nielson.

“It’s easy to underestimate small group sizes but it’s also easy to overestimate large group sizes,” he said.

In the Cottonwood area in January, 2,683 pronghorn were counted in 26 groups and on the Anticline, 775 were counted in 14 groups. In February, Cottonwood held 2,802 animals in 28 groups and the Anticline, 2,291 in 24 groups. A March aerial survey was cancelled to bad visibility.

With only one or two flights, it might appear there are “significant declines but it could be variable” at different times of winter, he explained, but add up to the same numbers.

“It highlights the need for conducting surveillance flights multiple times a year,” Nielson said of pronghorn counts.

He also reported of the antelope does collared in the Cottonwood and Anticline areas, 10 of 13 survived from Cottonwood for a 78.6 percent rate and on the Anticline, 13 of 14 survived for a rate of 92.8 percent. Data showed Anticline pronghorn on the average preferred elevations of 2,300 meters with a 5 percent slope, more low-density sagebrush and south and east-facing aspects. As distance from a well pad increased, the level of habitat use decreased; more than half in both areas showed “clear” seasonal migrations with the rest “nomadic or nonmigratory.”

Pinedale BLM field manager Shane DeForest recapped the pronghorn data: a 15-percent decline was found in reference areas compared to treatment areas with a higher survival rate on the Anticline than reference areas.

The 15-percent decline could lead to the matrix triggering further mitigation next year, he said.

Therese Hartman of the Game and Fish reported sage-grouse data. The numbers of active leks in reference area complexes are compared to the 2007 baseline, she explained.

There were six active leks in the Mesa complex, two in Duke’s Triangle (and three in 2008, now back to two) and eight at Yellow Point, which now has six. In treatment areas, there were 16 total leks; now there are 14 for a 12.5 percent


The peak numbers of active males in reference areas were 555 in 2011, down from 2009-10’s count of 616. Other counts were delayed by snow depths and lack of access due to bad weather and closed roads, she said.

Later, discussing the BLM’s decisions regarding matrix species, DeForest concluded, “So pronghorn and sage grouse, we haven’t yet hit a matrix trigger. … It’s still just mule deer for the trigger.”

Of sage grouse numbers, he said a decline doesn’t trigger the matrix and called it “interesting” that declines are greater in reference areas than treatment areas.

Pygmy rabbit counts have declined for three consecutive years, he added; PAPO has two years of data and 2012 will be the third under the matrix. Whitetail prairie dogs also do not have three years worth of data but he noted “little change” between 2009 and 2011.

Raptors had more active and more productive nests this year, DeForest noted, with 910 total nests and 142 of them active (with 36 inhabited by non-raptor species).

For more information, visit http://www.blm.gov/wy/st/en/field_offices/Pinedale/anticline.html.

For the complete article see the 11-08-2011 issue.

Click here to purchase an electronic version of the 11-08-2011 paper.

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