Comparative
Studies of Sympatric Bighorn Sheep and Mountain Goats in the Greater
Yellowstone Ecosystem
The Greater Yellowstone Ecosystem of
Montana, Wyoming, and Idaho comprise an important region for bighorn
sheep in North America. However, there has been a gradual
increase in the abundance and distribution of non-native mountain goats
in this region during five decades. High densities of mountain
goats could negatively affect bighorn sheep because their ranges now
overlap substantially. Also, the limited information available
indicates potential for dietary overlap in some seasons and dominance
of goats over sheep when foraging in the same areas, which suggests
that bighorn sheep may be sensitive to inter-specific
competition. In addition, bighorn sheep are well known for their
sensitivity to a variety of diseases that can cause episodic die-offs
that result in substantial population reductions. Though mountain
goat populations do not appear to be susceptible to disease die-offs to
any appreciable extent, mountain goats are effective hosts for a
variety of parasites and pathogens that also infect bighorn sheep.
Thus, information regarding potential competition, disease transfer,
and/or displacement of bighorn sheep by mountain goats is a key issue
for natural resource managers in this region.
Temperatures across western North America
have shown a pronounced warming over the past 50 years and contribute
to decreased snow levels and increased drought. Mountain
ungulates may be sensitive to these changes in climate through
influences on forage availability and quality in alpine and subalpine
areas. For example, warmer temperatures could speed up the rate
of snow melt and cause the wave of growing vegetation to occur at
higher elevations than it would under cool conditions for corresponding
times of the year. Also,the peak of forage quality (~30 days
after snow melt) could occur over a narrower elevation band under a
warmer climate than it would under otherwise similar but cooler
conditions. In turn, these changes could influence the abundance
of mountain ungulates, their migration patterns, the degree to which
they transmit diseases, and the extent and outcome of competitive
interactions.
Objectives:
- Undertake an in-depth, scientific review
of the current state of knowledge about mountain goats and bighorn
sheep in the Greater Yellowstone Area, including (1) herd maps and
demographic data, and (2) syntheses of competition (spatio-temporal
overlap, diet overlap, behavioral interactions), movements and
spatio-temporal distribution, disease/health, and metapopulation
dynamics.
- Review and synthesize data on observed
trends of climate variables, with a focus on temperature, snow pack,
and vegetation phenology trends at select habitat sites for mountain
goats and bighorn sheep in the Greater Yellowstone Area.
- Develop and implement recommended study
plans for investigating broad-scale spatial patterns of bighorn sheep
and mountain goat occupancy to identify areas of current and potential
sympatry, evaluate and refine existing habitat suitability models, and
provide foundational knowledge for understanding metapopulation
dynamics.
- Develop recommended study plans and sites
for conducting comparative analyses of multiple sympatric bighorn sheep
and mountain goat herds in the Greater Yellowstone Area, including
competition, movements and spatio-temporal distribution,
disease/health, and metapopulation dynamics.
- Develop recommendations for assessing the
influence of landscape by climate interactions on bighorn sheep and
mountain goat vital rates and movements and predicting effects of
climate change on distribution and foraging behavior.
Collaborators:
Montana State
University – Bozeman
Bob Garrott, Professor, Ecology Department
Jay Rotella, Professor, Ecology Department
Megan O'Reilly, M.S. Graduate Student
Jesse Devoe, Lead Project Technician
Mike Sawaya, Database Contractor
Mike Zambon, GIS Contractor
National Park Service
P.J. White, Yellowstone
National Park, Mammoth, WY
Sarah Dewey, Grand Teton National Park, Moose, WY
Wyoming Game and Fish Department
Doug Brimeyer, Wildlife Biologist,
Jackson Hole, WY
Kevin Hurley, Bighorn Sheep Coordinator, Cody, WY
Doug McWhirter, Wildlife Biologist, Cody, WY
Montana Fish Wildlife and Parks
Julie
Cunningham,
Wildlife Biologist, Bozeman, MT
Tom Lemke, Wildlife Biologist, Livingston, MT (retired)
Karen Loveless,Wildlife Biologist, Livingston, MT
Justin Paugh, Wildlife Biologist, Big Timber, MT
Shawn Stewart, Wildlife
Biologist, Red Lodge, MT
Idaho Department Fish and Game
Hollie Miyasaki, Wildlife Biologist, Idaho Falls, ID
Dale Toweill,
Wildlife Program Coordinator, Boise, ID
U.S Forest Service
Jody Canfield, Wildlife Biologist, Gallatin National Forest, Bozeman, MT
Andrew Pils, Wildlife Biologist, Shoshone National Forest, Cody, WY
Dan Tyers, Wildlife Biologist, Bozeman, MT
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