The non-native mountain goat population of the Olympic Mountains has more than doubled over the past 12 years, according to a U.S. Geological Survey report released today. The current population stands at approximately 620 mountain goats.

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"The population has now been growing for over a decade,” said U.S. Geological Survey’s Kurt Jenkins, a collaborator on the effort to monitor mountain goats in the Olympic Mountains for the past 19 years. “This information will be useful for park managers currently developing a plan for non-native mountain goat management in the Olympic Range."

Three successive surveys show that the population of non-native mountain goats in the Olympic Mountains increased at an average rate of eight percent annually from 2004-2016. If this rate of population growth were sustained, the population would increase an additional 45 percent over the next five years.

In July 2016, wildlife biologists from the National Park Service and Washington Department of Fish and Wildlife counted mountain goats from a low-flying helicopter, focusing on ice-free areas above 4,500 feet in elevation in Olympic National Park and adjacent areas of Olympic National Forest.

The survey methods were determined from previous studies of GPS-collared mountain goats conducted collaboratively by USGS, WDFW, and NPS. These methods, now used throughout Washington, account for sampling uncertainty and the possibility that not all mountain goats present are seen during aerial surveys. Therefore, the 2016 survey total of 623 mountain goats is an estimate, with the uncertainty of the estimate ranging from 561 to 741 mountain goats.

There were 230 mountain goats estimated from surveys conducted in 2004 and 350 estimated in 2011, yet differences in areas surveyed during survey years prevent a direct comparison of those estimates to the current estimate. Instead, researchers adjusted numbers of goats observed in each survey to comparable survey areas to deduce population trends.

The National Park Service, in cooperation with the U.S. Forest Service and WDFW, is preparing an environmental impact statement for managing the park’s population of non-native mountain goats. More information about this planning process is available online.

Mountain goats were introduced to the Olympic Mountains in the 1920s, before establishment of Olympic National Park, and have since colonized the entire range, with most of the population residing within the park.