Blue Mountains elk herd: Juvenile recruitment and mortality monitoring

Washington’s Blue Mountains elk herd is an important natural resource that provides ecological, consumptive, aesthetic, and economic value. The Washington Department of Fish and Wildlife (WDFW, the Department) has been focused on this population since the 1980s due to concerns about productivity, poaching, predation, and nutrition in the herd (Zahn, 1992; WDFW, 2001; Myers et al, 1999; McCorquodale et al. 2011; WDFW, 2020). While the population grew steadily from 2000 – 2016, it declined to an estimated 4,396 elk in 2017 – 20% below WDFW population objectives - following a severe winter after two years of drought. The herd has been unable to rebuild to desired population levels, and was estimated at 25% or more below its population management objective of 5,500 elk in 2019, 2021, 2022, and 2024. In 2020, the population trended modestly up to 4,614, although this increase can be attributed to sampling variance (as discussed in “Methods”). Overall, the Blue Mountains elk herd population remains below the management objective and does not show evidence of rebounding. The Department has implemented actions to promote elk population growth, like reducing recreational and damage antlerless elk harvest and modifying cougar and black bear harvest regulations, while continuing long-standing habitat enhancement projects and protecting critical ranges on public lands.

Population declines motivated the Department to conduct an “at-risk” assessment of the Blue Mountains elk herd (WDFW 2021; see also WDFW 2015-2021 Game Management Plan). The assessment designates the Blue Mountains population to be “at-risk” and identified insufficient recruitment - juvenile survival to one year of age - as a primary factor limiting population stability or growth. This is especially true in the northern portion of the herd’s core range (the northern core), made up of Game Management Units (GMUs) 162, 166 and 175. The assessment noted marginally sufficient recruitment for stability across the southern portion of the herd’s core range.

In 2021, WDFW initiated juvenile elk survival and cause specific mortality monitoring in the northern core herd area (WDFW, 2021) to better understand what factors were limiting elk recruitment.