Sublette mule deer crash below matrix threshold

Mule deer on

the Pinedale Anticline’s Mesa suffered a severe

loss last winter, cutting that portion of the

larger Sublette herd almost in half.

And as an overall unit, the Sublette mule

deer herd dropped almost one-third – 28 percent

– triggering the Pinedale Anticline Project

Area’s wildlife monitoring and mitigation

matrix for the first time since 2009-2010 and


However, Wyoming Game and Fish and

Bureau of Land Management personnel had

no definitive responses about required mitigation

at the Pinedale Field Office’s April 26

annual wildlife planning meeting.

Western Ecosystems Technology, Inc. of

Laramie has monitored Sublette and Mesa

mule deer since 2001, switching to aerial infrared

surveys in 2018. WEST prepared the

2018 report and Wyoming Game and Fish

Coordinator Brandon Scurlock presented the

outcomes, saying WEST no longer has the

annual monitoring contract.

“Here we report monitoring results for

the winter of 2017-18, where population estimates

indicate that mule deer abundance has

decreased by 48 percent in the Mesa and 28

percent in the Sublette herd since the baseline

year,” said the WEST report overview.

The Pinedale Anticline Monitoring and

Mitigation Matrix states that mitigation measures

are triggered when the Sublette mule

deer herd hits a 15-percent relative decline.

In this case, the Sublette herd’s 28-percent

decline is subtracted from the Mesa’s 48-percent

decline to reach the relative 20-percent


That leaves an estimated 1,495 mule deer

wintering on the Mesa and 17,299 in the Sublette

herd compared to the baseline of 2,846 on

the Mesa and 24,165 in the Sublette herd unit.

Game and Fish has a Sublette herd population

goal of 32,000.

With a straight line leveling its ups and

downs, Ryegrass-Soapholes mule deer saw

“a slight decrease (that) was not statistically


“Long-term trends indicate that mule deer

have declined at higher rates in the Mesa portion

of the Pinedale Anticline Project Area

compared to the larger Sublette herd and

nearby Ryegrass-Soapholes area,” the 2018

monitoring report says.

The “sharp decline” in 2018 for Mesa and

Sublette mule deer “was an artifact of the unusually

severe winter of 2016-17, where adult

mortality was estimated at 35 percent and approximately

90 percent of the fawn crop was

lost,” the report continues. “This population

decline was not detected (in 2017) because the

survey was conducted early in the winter, January,

before most deer succumbed to the winter

conditions in late winter and early spring.”

Surveys for 2019 have not yet taken place,

according to Scurlock.

From the public, Linda Baker asked Scurlock,

“The threshold was exceeded – what is

your response to that decline?”

“The (wildlife) matrix spells that out,” he


BLM Pinedale Field Office Manager Caleb

Hiner added that with more than a 15-percent

decline, “more mitigation” will occur.

Baker pointed out “a lot of strategies have

been tried. What has been successful in terms

of mitigation?”

Scurlock said the Pinedale Anticline mitigation

team has done offsite fence modifications,

sagebrush mowing and many other

habitat projects: “I don’t know how to measure


BLM biologist Mark Thonoff said it can

be very difficult “to quantify” with a bad


“With a lot of mitigation measures our

long-term goal is to reinvigorate plant

growth, specifically sagebrush,” he said,

adding wildlife-friendly fences, long-term

conservation planning and private-land easements

are ongoing.

A severe winter usually causes deer numbers

to drop, he said. “Long and short, it’s

very difficult to correlate that to mitigation.”

Baker asked if the PAPO mitigation team

has collected data about its offsite strategies.

“I understand winter does have a significant

impact on a herd,” she said. “Do you

have any collective database to show effects?

If you put millions of dollars into it I would

think you would want to know the results.”

Scurlock replied, “The (Anticline 2008)

Record of Decision said there would be declines

in the (Pinedale Anticline). We can

only do so much to mitigate for lost mule

deer range.”


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