Yellowstone National Park Natural Resource Vital Signs, 2011

In 2008, Yellowstone National Park released its first report on the status of important natural resource vital signs. The selection of these indicators and development of a method to communicate their status and trends to scientists and managers represented a true advance in the synthesis of monitoring data for ecosystem management. The Park is grateful to Tom Olliff, Chief of the Yellowstone Center for Resources from 2006 to 2009, for his commitment to and vision for developing the 2008 report and framework for communicating science to managers. This report, Natural Resource Vital Signs, 2011, presents recent data that are available to help managers gauge the health of the Greater Yellowstone Ecosystem. A number of noteworthy highlights have emerged from this year’s report, including: Earthquakes: The University of Utah’s seismic stations detected 3,274 earthquakes in the park during 2010, the largest number since 1985. Most were too small to be felt by people, but they included a swarm of about 2,400 quakes from mid-January to mid-February northwest of Old Faithful. It was the largest swarm since 1985. Grizzly bears: The estimated Greater Yellowstone Ecosystem grizzly bear population reached 602 in 2010, the largest number since the recovery program began in 1975. About 150 bears occupy ranges partly or entirely within the park. For a short time from 2007 to 2009, the grizzly bear was removed from the endangered species list; however, it was re-listed as threatened in consideration of the potential threats caused by climate change and loss of whitebark pine. Wolves and elk: The decline in Yellowstone’s wolf population to 97 in 2010, the lowest since 1999, is attributed in part to a drop in the northern range elk population by more than two-thirds since the mid-1990s, which is attributed in part to predation by wolves, the growing bear population, hunting, and possibly drought-related effects on elk pregnancy and survival. However, the wolf population in Wyoming and the greater Yellowstone area overall has continued to increase. The gray wolf was removed from the endangered species list in Idaho and Montana in May 2011, but it remains on the list for Wyoming. Bison: The state of Montana has expanded the area outside the park’s north boundary where bison are allowed to use winter range. This increased tolerance for bison prevented the need to send to slaughter hundreds of bison that crossed the boundary when last winter brought an aboveaverage snowpack. The estimated summer population is 3,700, down slightly from 2010. Native fish: The Yellowstone cutthroat trout population in Yellowstone Lake has declined substantially since the 1980s as a result of low water flows during drought years, predation by nonnative lake trout, and whirling disease. Nearly 550,000 lake trout have been removed from the lake since 1994, including about 146,000 in 2010. The number of lake trout caught per 100 meters of net has been rising since 2002, suggesting that the lake trout population has been increasing faster than the fish are being removed. Over the next year, the Yellowstone Center for Resources, along with our partners, will reexamine this suite of vital signs with special emphasis on developing desired conditions for many of the indicators. This will enhance the value of these indicators by helping to establish management targets.

Yellowstone National Park Natural Resource Vital Signs, 2011

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