The mountain goat population within the Olympic Mountains of Washington state has grown by more than 100 animals to roughly 344 since 2004, according to a U.S. Geological Survey population study, which adds that the population could double in 15 years if the rate of growth stays constant.
Not since the 1980s has there been a documented population increase in the park's mountain goat population, according to officials.
The data is contained in Mountain Goat Abundance and Population Trends in the Olympic Mountains, Washington, 2011, which was released this week by the park.
"Anyone who has ever attempted to search out animals in rugged terrain can attest to the challenges of finding elusive wild animals," USGS Director Marcia McNutt said in a statement accompanying the report. "This new census is based on the latest scientific understanding of population sampling to yield a statistically valid estimate of the number of animals present."
Being able to accurately estimate mountain goat populations is a key issue throughout Washington, including Olympic National Park. Mountain goats are not native to the Olympic Mountains and are a long-standing management concern at the park. In October 2010 a hiker on the Klahhane Ridge in the park was fatally gored by a goat that rangers later killed. (A wrongful death lawsuit is pending in the matter.)
Last summer's mountain goat survey entailed a new counting method, one the USGS maintains allows biologists to more accurately estimate the population. The new method, now in use throughout all of Washington State’s mountain goat range, was developed from 2005 through 2008 through a partnership between the USGS, National Park Service, and the Washington State Department of Fish and Wildlife.
“Accurate and up-to-date information is critical to making sound management decisions, and we appreciate the partnership that led to both the improved counting technique and this most recent goat census,” said Olympic Superintendent Karen Gustin. "The National Park Service is currently seeking funding to carry out an environmental analysis of mountain goat management options for Olympic National Park."
At the USGS, Kurt Jenkins, the lead author of the population report, said “We are keenly aware of the park’s interest in accurately monitoring the abundance of mountain goats. It’s not easy to do because of the extremely rugged nature of the terrain in which the goats live and highly variable weather conditions. In 2011, we used two new advances in survey methods to improve the estimates.”
One of the two advances adjusted mountain goat numbers to account for mountain goats that are present but not seen by the aerial survey crew due to terrain, tree cover, or other factors. In addition, the boundary of the areas surveyed was modified in so as to encompass all lands used by mountain goats during the summer. These two improvements were based on the 2005-2008 research that improved the accuracy of mountain goat surveys throughout western Washington. (More information about this previously published research is available at http://fresc.usgs.gov/research/StudyDetail.asp?Study_ID=487).
As in previous surveys, trained observers in helicopters searched a random sample of areas for mountain goats. They worked from mid to late July to target the period when mountain goats are in high-elevation habitats for the summer but before hot temperatures make it dangerous for helicopter flight at high altitude.
Because of changes to the survey methods it is not possible to directly compare the current population estimates with estimates from previous surveys. However, comparison of the “raw” counts, without adjusting for the unseen animals, indicates that mountain goat populations reached a peak density in the early 1980s. From 1981 through 1989, Olympic National Park conducted a live capture-and-removal program, resulting in the removal of 407 mountain goats in that period.
Surveys conducted between 1990 and 2004 indicated that mountain goat abundance remained relatively stationary at low densities for several years following the population reduction. Scientists factored in differences in survey methods when they concluded that the population increased by about 40 percent since 2004.