Elk monitoring in Lewis and Clark National Historical Park: 2008-2012

Griffin, Paul; Jenkins, Kurt; Cole, Carla; Clatterbuck, Chris; Boetsch, John; Beirne, Katherine

Maintaining elk (Cervus elaphus roosevelti) herds in Lewis and Clark National Historical Park (LEWI) is central to the park purpose: preserving historic, cultural, scenic, and natural resources associated with the winter encampment of the Lewis and Clark expedition. Elk were critical to the Lewis and Clark expedition, providing food and hides and sustaining the expedition in the winter of 1805-06. Today, elk are a key component of interpreting the Lewis and Clark story to park visitors. In 2008, the US Geological Survey, LEWI, and the North Coast and Cascades Network, developed a protocol to monitor change in the magnitude and spatial pattern of elk use in and adjacent to LEWI. Objectives were to measure trends in 1) relative winter use of the Fort Clatsop unit by elk; 2) proportion of area where elk sign is present in the Fort Clatsop unit in winter; and 3) frequency of elk sightings from roads in and around the Fort Clatsop unit. This report synthesizes results of the first 4 years of monitoring elk in LEWI, 2008-2012. We also present data from FY2012 (Appendix A), in lieu of an annual report for 2012. We used fecal pellet group surveys to monitor trend in relative use of Fort Clatsop by elk and proportion of area where elk sign was present at the end of winter. We estimated pellet group density with data collected from fecal pellet plots distributed systematically throughout the unit. We developed a double observer sampling scheme to estimate detection bias and improve accuracy of pellet group density estimates. We computed the estimated detection probability for observed pellet groups as a function of pellet group size and stage of decay, lighting and vegetation conditions, and number of observers. We used the probabilities to adjust raw counts of pellet groups to account for groups that likely went undetected. We used results from the late winter fecal pellet surveys to quantify proportion of area where elk pellets occurred (PAO). We used weighted linear regression and spatial variation of pellet group densities over time to assess temporal trends in pellet group density and PAO for 2008-2012. We completed late winter fecal pellet surveys at 61-66 plots annually. We cleared fecal pellets at survey plots in late October/early November and returned in late February/early March to count pellet groups left by elk over the winter. Average pellet group density ranged 0.58-0.93 pellet groups/3-m radius subplot. Pellet group density declined ~8.8%/year but was not statistically significant. Proportion of surveyed points used by elk ranged 0.44-0.53. Estimated PAO declined 2.6%/year but trend was not statistically significant. Through simulation modeling we determined 2 more years of pellet group surveys would be needed to reveal a statistically significant trend. Relative use by elk during winter was greatest in the southeast part of Fort Clatsop. Spatial pattern in pellet group densities across Fort Clatsop was consistent across all 4 years. There was a slight shift in distribution of elk use in Fort Clatsop over the 4 years. We conducted roadside elk surveys 3-5 times/month in February, April, June, August, October and December. During surveys, we searched for elk along 4 routes totaling 32 km. Average number of elk groups seen/ survey ranged 0.75 (February) - 1.95 (June). Average total number of elk seen/survey was less variable.

Elk monitoring in Lewis and Clark National Historical Park: 2008-2012

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