Blue Mountains ELK NUTRITION AND HABITAT MODELS

Transcription

1 USFS Pacific Northwest Blue Mountains ELK NUTRITION AND HABITAT MODELS Second generation models for management Managing for elk requires compromises among economic, ecological, and recreational objectives. To help state and federal agencies and local communities make these decisions, an interagency modeling team has developed new habitat and nutrition models that predict elk use and nutritional conditions in the Blue Mountains. Based on recent research incorporating data from large-scale radiotelemetry studies and elk nutrition patterns, new nutrition and habitat models offer updated science in a user-friendly format to inform land management planning across the Blue Mountains region. The models allow landowners and public land managers to think strategically about emphasizing (or deemphasizing) elk habitat according to management objectives. With their flexibility for multi-scale analyses, the models are useful for cooperative planning across ownerships. The nutrition model predicts the nutritional value (dietary digestible energy) of late-summer forage for elk across the landscape a key driver of elk habitat use and population health across the region. The habitat model predicts the level of elk use in a given area by using estimates of late summer nutrition from the nutrition model combined with other variables that affect elk use: open roads, topography, and vegetation composition. To connect with practitioners and solicit their feedback, the modeling team held a workshop on April 25, 2012 in Pendleton, Oregon. Over 140 land managers, planners, and biologists from a variety of agencies and organizations joined the team for a day of presentations and discussions about the models and their applicability. This briefing paper presents workshop highlights as well as feedback from participants. September

2 Model context and validation The study area includes the Blue Mountains of eastern Oregon and Washington. Model training and validation sites include the Sled Springs and Starkey areas. What is the new elk habitat selection model appropriate for? Summer range Late summer nutrition needs Hunting season Large regional landscapes (20,000 to 150,000 acres) Yes No Multiple land ownerships Integrated management strategies Forest plan revision guidelines Validation with independent data sets showed a good fit with our draft habitat use model, with predicted use by elk closely matching observations of elk from GPS locations. 2

3 One of our biggest problems is not elk numbers, but their distribution. With the help of these models, elk distribution can be managed effectively between ownerships. Mike Wisdom Can management change elk use? YES. Management implications The best habitat model for predicting elk use on the landscape contains four variables: dietary digestible energy (DDE), distance to open roads, vegetation composition, and slope. These variables were selected by a rigorous model selection process. Variables were considered for inclusion based on their consistency and ease of calculation, but also for their relevance to management. Other than slope, all of the selected variables are responsive to management actions and can be altered to affect elk use on the landscape. Distance to open roads was the strongest predictor of elk use of all the model variables. Travel management and strategic control of access and human disturbance will have strong effects on the patterns of elk use on the landscape. For example, keeping human disturbance lower during early spring can benefit elk, since the limitations of late summer nutrition increase the importance of the high-quality forage available in early spring. However, the nutritional bottleneck for Blue Mountains elk in late summer does not easily lend itself to management solutions. Seasonal precipitation patterns, typically resulting in dry soil conditions by August, greatly limit options for improving forage quality in drier vegetation types. Higher elevation forests tend to be wetter and thus have more potential to provide nutritious forage in summer. Opening these stands by reducing overstory, particularly through uneven-aged treatments, can improve elk habitat. If you have elk on your land, these models can predict where they will be during summer and what nutritional resources are like. There are interacting issues managers must weigh to identify where the bottlenecks are in a specific area, such as summer forage or human disturbance. The models simply illustrate the underlying conditions that affect elk use in late summer, allowing practitioners more information to apply their professional judgment as they make decisions. As one practitioner said, This is a good tool to use in conjunction with what you already know. Caveat. Land managers, policy makers, biologists, and land owners in the Blue Mountains region face a number of elk management concerns in the area, some of which can be addressed by the nutrition and habitat models, and some of which we lack the data to fully assess. Issues such as livestock grazing, predator pressure, and crop depredation are outside of the scope of the models. Because of a data void, we can t fully assess the effects of cattle on elk distributions. It s an essential and unmet need for evaluating elk summer range. 3

4 Data and information products Potential information products for users Maps of elk nutrition on summer range across all lands of the Blue Mountains Supporting GIS files ArcGIS programs Users guide What would be most useful to you? Contact us with your feedback. The model provides a reliable, science-based foundation for ranking habitat and using that information to predict herd performance. New models offer updated science Including the importance of summer nutrition Late summer forage conditions create a nutritional bottleneck for elk. This concept challenges traditional perceptions that competition for scarce winter resources constrains herd health and reproductive success. The nutrition work conducted by the modeling team has shown that female elk body fat levels in the spring are a function of their body fat levels from the previous fall, not how severe the winter was. In fact, every variable measured in their studies calf growth, yearling growth, adult fat levels, adult pregnancy rates, breeding time, and winter survival was correlated with summer nutrition. This means that if we have information on summer forage quality, as displayed using the new nutrition model, we can predict nutrition-based aspects of herd performance. The nutrition model provides information about nutrition resources on summer range across all Blue Mountains ownerships. How you can help. Telemetry data. For additional model training and validation, we would like to bring in more telemetry data sets. We are looking for information that includes unique animal identification with each location, date, and the number of elk and locations in the data set. Feedback. Although the model is predicting elk use very well, it is still a draft. We still have some tweaking to do. Please send your suggestions and questions. Beta testing. Do you manage land for elk? Do you have GIS experience or access to an analyst? Betatesters will get hands-on training and early access to the models. The nutrition limitations of summer range is a new idea to me. We always thought that winter conditions were the big management issue. workshop participant 4

5 Model application Collaboration. These models work well for planning at the landscape scale and across ownerships, which are particular challenges with elk. We can use these models to understand how to think strategically about emphasizing elk habitat in some areas and discouraging their use of other areas. Weighing trade-offs. Elk habitats can benefit from active forest management. The two models can be useful in making decisions about combining habitat improvements with other objectives, such as travel management plans or thinning treatments. Flexibility for multi-scale analyses. The models were built to depict elk nutritional conditions and probability of use for every 30-meter pixel across a given landscape. Both the nutrition and habitat models can be applied on very large areas, even the entire Blue Mountains region. Users can evaluate these large landscapes, including information from all landowners, and then drill down to the smaller areas to evaluate specific, local management issues. Local projects can easily be addressed in this manner. Forest plan revision and more. The models are intended for use as a regional analysis tool to meet whatever objectives are established among landowners. The models could be particularly helpful in creating standards and guidelines for land management planning, but this guidance needs to include all land owners within a given area where management of elk use is of strong interest. Oregon and Washington Departments of Fish and Wildlife can also apply these models in their wildlife units, and tribal nations can use them to evaluate their reservation and ceded lands. The models are not intended to be used solely in Forest Service or Bureau of Land Management land use planning. Where this tool will really be useful is in coordination with other landowners, said one workshop participant. As one Forest Service biologist said, A forest plan revision is coming. We need standards for elk because they are going to be indicators for all kinds of species. There are people working on this every day at the district level. They need help and information to get this right. 5

6 Questions from workshop participants Can these models be used during hunting season? No. These models were developed for late summer (August 1-20) only, when nutritional resources for elk are at their lowest levels in the Blue Mountains. They will not be accurate in the hunting season, or for spring or winter. However, separate models for hunting season or spring would be possible to develop with the data we have. What about the effect of: specific treatments such as herbicide application? prescribed burning? livestock grazing? predator pressure? hikers? We don t have continuous fine-scale data on specific treatments, grazing, predation pressure, or recreational use across the regional landscapes we are modeling. One of our goals is to make sure these models are user-friendly, which means we need to be conscious of the availability of the data required. Why do you truncate habitat type classification in the nutrition model down to only four types? Doesn t this ignore a lot of variation? A more detailed classification system might explain a little more variation, but elk are such good high-graders while foraging that it takes a big difference in plant communities for that variation to come into play. Our categorizations are based on decades of nutrition studies, and despite having only four broad categories of potential vegetation and the corresponding equations for nutrition, we are still able to accurately predict elk nutritional conditions. Why don t you include agricultural lands in the model? The distance-to-nearest-agricultural-land variable fell out early in the model selection process. However, agricultural lands are included in the model through the estimates of DDE in the nutrition model, which then feed into the full habitat use model. Is quality of forage related to vegetation structure? Are you predicting elk use based on structure? No. We are not modeling variation in forest structure. People sometimes mistakenly assume we are saying that elk are seeking cover. Elk are seeking sites that provide security and nutritious forage. Regardless of low or high canopy cover, elk are selecting for a composite of vegetation conditions, not just stand condition. 6

7 Questions from workshop participants Travel management is an important issue for elk because of human disturbance from roads and trails. Can you analyze the interaction between cover and distance to road? Or forage value and distance to road? It is a good idea to test the relationship between hiding cover and distance to road. We will also look into the link between forage conditions and human disturbance. Why did you take location data over a 24-hour period rather than looking at peak foraging times? We could look into this by running models on peak foraging times, assigning coefficients, and then seeing if the results become stronger. We developed the model to be a general habitat use model for elk, not a foraging model. How do existing elk habitat effectiveness index (HEI) models compare to these new models? The original (1979) Blue Mountains summer range evaluation methods included cover/forage ratios, density of roads open to motorized vehicles, and distance between forage areas and cover. These variables were each tested during our model training, but none were strongly supported by the elk telemetry data we used for the August analysis period. Most likely, elk are selecting strongly for larger blocks of forest vegetation types, perhaps because they can forage more efficiently in these areas. These models represent the first time mapping of habitat resources has been used to predict performance of an elk population. John Cook Management to benefit elk nutrition is likely to benefit herd performance. 7

8 Timeline Westside introductory workshop Corvallis, OR Westside beta test results workshop Portland, OR Beta testing Westside model development Blue Mountain model development Beta testing SW Oregon model added Blue Mountain introductory workshop Pendleton, OR Blue Mountain beta test results workshop Sponsors: National Fish and Wildlife Foundation Boone and Crockett Club Rocky Mountain Elk Foundation Sporting Conservation Council USDA Forest Service Bureau of Land Management Collaborators: USDA Forest Service, Pacific Northwest Region USDA Forest Service, PNW Research Station Oregon Department of Fish and Wildlife Washington Department of Fish and Wildlife National Council for Air and Stream Improvement WEST, Inc. Oregon State University Oregon State University Extension Service Contact: Mary M. Rowland Research Wildlife Biologist USDA Forest Service 1401 Gekeler Lane La Grande, OR (voice) Mike Wisdom Research Wildlife Biologist USDA Forest Service 1401 Gekeler Lane La Grande, OR (voice) Workshop summary prepared by Rachel White, USFS PNW Station. 8