1974 Cooperative Agreement

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1974 Cooperative Agreement

• 1. Historic Population Level Averages
• 2. Winter Range Carrying Capacity
• 3. Cost of Supplemental Feeding
• 4. WGFD Objective Levels for Jackson Hole

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Simulates ungulate forage intake under a range
of elk population sizes and during a range of
climatic conditionsThe impacts of different
levels of utilization of winter forage on
ecosystem processesWhat are the effects of
food shortages on elk mortality?
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Carrying capacity is a complicated ecological
concept.
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Model Conclusions

• Forage utilization rates of 50 or greater on
  winter range
• at all elk population levels
• during all winter severities
• may not negatively affect, and may enhance,
  future soil fertility and plant production

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• In average winters with average pre-winter
  precipitation
• 16,000 elk can find forage and not incur forage
  deficits on the Greater Teton Ecosystem
• 5,000 elk can find forage on the National Elk
  Refuge without deficits

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• Winter snow severity
• negatively affects forage availability at most
  elk population levels.
• Severe drought
• reduces forage production to 45 of the mean
• increases forage deficits for all winter
  conditions and all elk population levels

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• Effect of increasing the number of bison on
  forage deficits
• mild effects in the Greater Teton Ecosystem
  during average winters (with avg. pre-winter
  precipitation)
• stronger effects under more severe climatic
  conditions
• greatly exacerbated deficits on NER

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• Cattle grazing negligibly affects forage
  deficits.
• Supplemental feeding overcompensates forage lost
  due to NER fence.

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• Adult animal starvation expected at relatively
  low levels (5)
• If severe winters occur when the elk population
  is large (18,000), mortality could rise to as
  high as 30

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• EIS alternatives manipulate 5 variables that
  affect forage deficits
• elk numbers
• bison numbers
• winter feeding
• willow availability on the NER
• irrigation on the NER

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