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
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
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