Role of summer nutrition on elk habitat use in western Oregon and Washington
Distribution of elk in much of the western United States has shifted from public to private lands, leading to reduced hunting and viewing opportunities on the former and increased crop damage and other undesired effects on the latter. These shifts may be caused by increasing human disturbance (e. g., roads and traffic) and declines of early‐seral vegetation, which provides abundant forage for elk and other wildlife on public lands.
Understanding nutritional resources and habitat use of large herbivores like elk can benefit their management across a variety of land ownerships and management regimes. To provide managers with tools to predict how nutritional resources, elk productivity and performance, and elk distributions respond to management actions, researchers with the U.S. Forest Service, WEST Inc., NCASI Inc., Oregon Department of Fish and Wildlife, Muckleshoot Indian Tribe, Oregon State University, U.S. Fish and Wildlife Service, Washington Department of Fish and Wildlife, University of Illinois at Urbana-Champaign, Quileute Tribe, Makah Tribe, Greenbelt Land Trust, and the Lower Elwha Klallam Tribe recently completed a model of elk nutrition and habitat use across summer range forests of western Oregon and Washington. Results of this effort were published in a paper in Wildlife Monographs in late 2018.
Researchers developed and evaluated an elk nutrition model that estimated regional nutritional conditions for elk on summer ranges and used the predicted elk nutrition data to develop a summer habitat‐use model that integrated the nutrition model predictions with other covariates to estimate relative probability of use by elk. The primary hypothesis behind this effort was that elk habitat-use during summer is driven by a suite of interacting factors related to energy acquisition (e g., nutritional resources, juxtaposition of cover and foraging areas), and energy loss (e g., proximity to open roads, topography). Researchers used 25 previously collected data sets from 12 study areas (primarily work completed by NCASI researchers Drs. John and Rachel Cook) to develop and test candidate models.
The elk nutrition model predicted levels of digestible energy in elk diets in summer. Researchers used the nutrition model to develop a dietary digestible energy map across western Oregon and Washington. Model performance was evaluated by comparing predicted dietary digestible energy to nutritional resource selection by elk and to population‐level estimates of autumn body fat and pregnancy rates of lactating elk. Predicted values of dietary digestible energy were then used as a covariate in an elk habitat-use model. Habitat-use model results confirmed elk preference for areas that contained relatively high levels of dietary digestible energy, far from roads, close to cover‐forage edges, and on gentle slopes. Changes in slope were most important in predicting habitat use, followed by dietary digestible energy, distance to forest edge, and distance to open road.
Through this highly collaborative effort, researchers demonstrated how nutrition data collected at fine scales with captive elk can be used to predict nutritional resources at large scales. Further, these predictions were found to directly relate to habitat use and performance of free‐ranging elk across the Westside region. Results illustrate importance of managing for nutrition in combination with other important factors (e.g., roads, slope, cover‐forage edges) to achieve desired distributions of elk.
Rowland, M. M., M. J. Wisdom, R. M. Nielson, J. G. Cook, R. C. Cook, B. K. Johnson, P. K. Coe, J. M. Hafer, B. J. Naylor, D. J. Vales, R. G. Anthony, E. K. Cole, C. D. Danilson, R. W. Davis, F. Geyer, S. Harris, L. L. Irwin, R. McCoy, M. D. Pope, K. Sager-Fradkin, and M. Vavra. 2018. Modeling Elk Nutrition and Habitat Use in Western Oregon and Washington. Wildlife Monographs 199:1–69. https://doi.org/10.1002/wmon.1033