June 2021 - 16

IN THE FIELD
Bighorn sheep forage under a net as part of the Elk Mountain heard sightability study in northeast Wyoming. The sheep were netted so researchers could place radio collars on them. (WGFD photo)
Game & Fish develops aerial
bighorn sheep counting method
Wildlife managers strive for a more accurate count
of northeast Wyoming's Elk Mountain herd
By Game and Fish staff
W
yoming Game and Fish Department
biologists are developing
a bighorn sheep population
survey that should give wildlife
managers a more accurate count of the
animals found in the Black Hills in northeast
Wyoming. The survey, called a sightability
estimate, will be conducted by helicopter and
account for the hard-to-see bighorn sheep
biologists may miss when they do their annual
counts.
The Elk Mountain bighorn sheep herd
resides on the Wyoming-South Dakota border
southeast of Newcastle, and has been
managed jointly by Wyoming and South
Dakota for 18 years.
16 | June 2021
The herd was created with reintroductions
near Hell Canyon by South Dakota Game,
Fish and Parks in 2001, but the sheep took
up residency along the state line instead. After
several large fires burned Elk Mountain in the
early 2000s, the habitat changed to benefit
bighorn sheep and their numbers increased. By
2008 the herd was estimated at 100 animals,
enough for a hunting season.
Accurate bighorn population numbers are
difficult to obtain because it is not possible to
count every animal on the landscape, especially
in the rugged terrain.
For example, in thick vegetation or rocky
outcroppings, a biologist may observe eight animals
while three others are hidden from view.
Game and Fish Wildlife Biologist Joe Sandrini
said there are ways to predict the number of
unseen animals so biologists can get a more
reliable estimate of the total population.
" The goal of this new project is to develop
a helicopter-based model to estimate bighorn
sheep numbers in the Black Hills, specifically
on Elk Mountain, that compensates for variations
in topography and vegetation, which
results in sheep not being detected, " Sandrini
said. " Our hope is once it is developed, the new
technique will give us a very accurate approximation
of the population and require just one
survey flight per year. "
Two previous survey methods have already
been tried with limited success. One was a
ground-based survey developed by a graduate
student in 2013, and the other was a
forward-looking infrared survey conducted
in 2018.

June 2021

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https://www.nxtbook.com/wyominggame/WyomingWildlife/December2020
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