Category: Wildlife Research
Published: December 2016
Author(s): Brock Hoenes, Sara Hansen, Richard Harris, and Jerry Nelson
In the Game Management Plan July 2015-June 2021, the Washington Department of Fish and Wildlife made the commitment to assess ungulate populations that have the potential to be held below a desired population level due to predation. This document represents that assessment; it uses only data and information presently available.
The Washington Department of Fish and Wildlife is responsible for the management of white-tailed deer, mule deer, black-tailed deer, Rocky Mountain elk, Roosevelt elk, moose, bighorn sheep, mountain goats, and pronghorn. The Department coordinates management of the Columbian white-tailed deer with the U.S. Fish and Wildlife because it is both federally and state listed as an endangered species.
Depending on location, the suite of predators occurring in the state of Washington that prey upon ungulates may include gray wolf, cougar, black bear, grizzly bear, coyote, bobcat, and lynx. Increasingly conservative management of hunting seasons and harvest opportunities for cougars and black bears, since they were designated as big game species in 1966 and 1969 respectively, has resulted in sustainable populations of both species which are hunted annually. Gray wolves began recolonizing Washington during the mid-2000s and the Department confirmed the first documented wolf pack in 2008. The distribution of recolonizing wolves does and will continue to overlap with black bear, cougar, and coyote populations. This development, as it has in other states, has elevated interest in knowing more about the impact on prey populations when an additional apex predator establishes itself in an ecosystem. Both lynx and grizzly bears occur in low numbers and have limited distributional range in Washington; thus, we have not considered either in this assessment.
This assessment covers white-tailed deer, mule deer, black-tailed deer, Rocky Mountain elk, Roosevelt elk, bighorn sheep, and moose. The remaining ungulate species in Washington are unique enough in their distribution, abundance, natural history, and management that except for rare instances we considered their populations unlikely to be affected by predation.
The intensity of management and the available data differ among ungulate species in Washington. We used existing available data from a number of sources. Not all data were deemed appropriate for this assessment. In this assessment, we considered population estimates obtained from aerial surveys; composition counts that provide minimum-known-alive counts and age and sex ratios that were conducted either from the air or on the ground; harvest; hunter numbers; and hunter effort depending upon the available information for each population. We also looked at the results of ungulate research conducted both in and outside Washington by a number of different entities. In some cases, these provided herd-specific vital rates (i.e., survival, productivity, recruitment), but in most cases, our assessments were necessarily based on indirect measures. In the Wolf Conservation and Management Plan and also reiterated in the recent Game Management Plan, the Department defined an at-risk ungulate population as one that falls 25% below its population objective for two consecutive years, and/or one in which the harvest decreases by 25% below the 10-year average harvest rate for two consecutive years. These measures were also used in the assessments.
Using the data at our disposal, none of the ungulate populations in this assessment appear to show clear signs of being limited by predation. However, the limitations of some of these data might preclude the ability to detect impacts of predation on a specific ungulate population. One subpopulation of moose that is currently suffering low recruitment and is the subject of active research requires additional resources to better understand the population impacts of predation.