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Predicting Future Forage Conditions for Elk and Mule Deer in Montana and Wyoming

Predicting Impacts to Elk of Changing Forage, Phenology, and Habitat Treatments
Principal Investigator
Tabitha Graves


Start Date
End Date
Release Date


Improving the quality of habitat for western big-game species, such as elk and mule deer, was identified as a priority by the Department of the Interior in 2018. Maintaining healthy herds not only supports the ecosystems where these species are found, but also the hunting and wildlife watching communities. For example, in Wyoming, big game hunting contributed over $300 million to the state’s economy in 2015. Yet as climate conditions change, the quantity, quality, and timing of vegetation available to mule deer, elk, and other ungulates, known as forage, could shift. It’s possible that these changes could have cascading impacts on the behavior and population sizes of many species. A key strategy used by managers to improve forage [...]

Child Items (3)


Principal Investigator :
Tabitha Graves
Funding Agency :
North Central CASC
Co-Investigator :
Jerod Merkle
Cooperator/Partner :
Jill Randall, Brent Jamison
CMS Group :
Climate Adaptation Science Centers (CASC) Program

Attached Files

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Mule deer and elk are important species for hunting, the cultural heritage of the west, and as an integral component of food webs. Significant changes in mule deer and elk behavior and population sizes could occur from changes in forage resulting from changes in climate and land use. Habitat treatments are an important tool that managers have for increasing forage and adapting to change, but the successful outcome of habitat treatments may vary under increasing climate variability and interacting effects of drought, changes in season length, shifts in forage green-up, and invasive species. Habitat treatments (e.g., prescribed fire, thinning, invasive weed treatments) are planned to counteract predicted declining mule deer habitat quality that is affecting mule deer population size in the Kemmerer-Cokeville area in southwestern Wyoming. Information on how forage is already changing given the context of climate variability, and the tradeoffs of the effect of treatments on forage and wild ungulates, given invasive species, is crucial now to ensure treatments are effective and meet the goals of helping mule deer and elk. This project has three objectives. First, we will quantify predicted changes in forage characteristics across Wyoming and Montana. This will provide baseline information about the direction, degree, and certainty of change in forage quality and timing. We will use a combination of historic remote sensing data and predictive models to describe how forage has and will change. Second, focusing on the habitat treatment area, we will use scenarios of likely outcomes of treatments to build maps of future forage. The scenarios will reflect weather variability and other influences on the success of treatments. For instance, because of the threat of invasive species that can negatively affect forage, we will map the current distribution of cheatgrass and along with the influence of either a cold and wet spring or a dry, hot spring, create predictive maps of forage characteristics. We will use the maps for our third objective, to evaluate the likely effects of treatment options on mule deer migration, fawning, and summer habitat areas and forecast the effects on elk calving, habitat use, and migration. Reports and maps will be co-produced with state and federal stakeholders. State and federal wildlife managers need this information to help prioritize treatment options and use of resources to best support mule deer and elk populations. This will assist them in meeting their multiple missions in this large and complex inter-jurisdictional landscape. Successful management supports multiple state and federal objectives to provide hunting opportunities for the public, healthy ecosystems, and recreational opportunities that feed into local and state economies. The proposed work directly addresses the Department of Interior’s recent directive to focus on mule deer, elk and other ungulate habitat use and migration in western states.

Project Extension

typeTechnical Summary
valueIn response to concerns about declining mule deer populations and recent research indicating the role of transitional ranges in supporting healthy populations, Wyoming Game and Fish Department (WGFD) is beginning a habitat treatment plan with the Kemmerer Field Office of the Bureau of Land Management (BLM) that seeks to improve habitat quality for mule deer and other animals. This proposed project will provide baseline information on changes in forage at regional scales, with science to inform structured decisions for the Kemmerer-Cokeville habitat treatment plan. First, we will assess and predict long term changes in forage important to supporting mule deer and elk in Wyoming and Montana that managers can use to direct resources regionally. At the local scale, we will predict changes in forage from planned treatments in aspen forests, mixed-mountain shrubs, and sagebrush communities, building on the baseline of change identified regionally and focusing on the likely impact on mule deer migration, fawning and summer ranges locations and elk calving, habitat use, and migration. This will add a multi-species perspective to specific habitat treatment decisions, including the role of invasive species. At the regional scale, we will evaluate changes in forage, specifically the timing of high quality forage availability during green-up, the quality of the forage, the quantity of forage, and spatial heterogeneity over the last 20-25 years. We will use remote sensing metrics shown to explain mule deer and elk fawning and calving locations, summer habitat use, and migration (NDVI, EVI, and derived metrics for IRG, start of spring, duration of spring, end of season, cumulative forage, and peak growing season). We will assess predictive models to evaluate the likely impact of continued changes in the absence of active management for forage metrics. Resulting reports and maps will summarize past and future changes in forage by watershed units, hunting areas and herd unit, and the associated uncertainty so that managers can evaluate forage changes most relevant to the components of ungulate ecology most important for their area. Second, for the focal treatment area, we will develop scenario-based predictions of the impacts on forage for combinations of preferred treatment alternatives and potential outcomes that address possible conditions such as drought, the range of variability in snow pack (e.g., early versus late start of spring, high versus low snowpack), and invasive species, and the likelihood of those conditions based on climate and forage predictive models. We will use an interactive approach with managers (at minimum WGFD and BLM) and other experts in phenology, sage systems, and ungulates to combine the best available models with local knowledge to focus these analyses to be useful for decision-making. Finally, we will use predicted forage to describe the effects of habitat treatment within areas important to mule deer fawning, seasonal use, and migration in the treatment area and to forecast the impacts to elk ecology calving, the movement and habitat use in seasonal ranges, and migration between seasonal ranges. We will use existing models describing these ungulate needs that connect predicted changes in forage to these components of mule deer and elk ecology. This joint project among USGS, WGFD, BLM, and University of Wyoming will serve as a framework for assessing the impacts of habitat treatment on wildlife. It will be an important example of an approach to assess vegetation treatments intended to help one species through the lens of climate change, invasive species and multiple species. Two reports and associate GIS layers will include 1) summaries by watershed, hunting area, and herd unit for past and future forage across MT and WY, 2) a map of cheatgrass in the treatment area, 3) maps and summaries of predicted treatment outcomes.

Budget Extension

typeAward Type
typeAward Number

Additional Information


Type Scheme Key
RegistrationUUID NCCWSC 95b92f15-cf0f-4cc7-98f8-30657359dbd5
StampID NCCWSC NC18-GT1344

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