Current Bison Research

Bison running through trees
Bison graze in the meadows of the North Rim of the Grand Canyon, but retreat to forests if they feel threatened. (NPS Photo)
The National Park Service will, in the next three to five years, reduce the size of the House Rock bison herd through capture and relocation and lethal culling. The EA, FONSI and other reference documents can be found on the NPS Planning Environment and Public Comment (PEPC) website here.

Operational details of herd reduction are being worked out and more information, including volunteer opportunities, will be announced at a later date through a news release. The information will also be available on our bison hotline 928-638-7900 and on the park web site:

The History of Bison on the Kaibab Plateau

Released into the wild after a failed ranching endeavor in House Rock Valley, bison have only been resident on the Kaibab Plateau in Northern Arizona since the early 1900s.

During the 1990s, bison, originally from the House Rock herd, began venturing southwest into the high country of Grand Canyon National Park's North Rim. In recent years, they have been spending their time within the park, affecting ecological and cultural resources, including: native vegetation, seeps and springs, and archeological sites.

Since 2008, a research team of biologists from Grand Canyon National Park, Arizona Game and Fish, and the US Forest Service have been researching the impact of the North Rim bison, and creating a strategy for managing the herd.The first priority of the research was to identify the number of bison found in the park. While they often graze in meadows, bison quickly escape into the thick forests of the North Rim when threatened, making them difficult to track and monitor. The most recent surveys estimate the herd to be between 400 and 600 individuals.

The biologists' second priority was assessing the impact that these large animals have on the vegetation, hydrology, and archeological sites on the North Rim. Since 2010, research groups have been studying the impact that bison have on the vegetation at watering holes they frequent.

The researchers found that as bison use increases, the amount of exposed soil at a given spring increases, while the amount of vegetation decreases. Between 2010 and 2014, vegetation cover at research sites decreased, indicating that the impact of bison on the North Rim was increasing. In addition to reducing the amount of vegetation in grazing areas, bison also reduce the number of plant species found, reducing the habitat and food sources for other species.

In addition to monitoring vegetation at springs, park biologists also studied the impact that bison have on water quality in the Grand Canyon. The drinking water in Grand Canyon National Park comes from Roaring Springs, a spring in the canyon that is fed by rain and snowmelt on the North Rim. Monitoring has indicated increased levels of E. coli bacteria in standing water associated with bison grazing areas.

Park biologists have also been researching ways to limit impacts by controlling the bison population within Grand Canyon National Park. A preliminary report estimated 80-200 bison as the sustainable population that can live on the North Rim and surrounding National Forest lands.

In 2014, biologists performed an experimental capture to determine how easily bison could be captured and relocated to more suitable habitat. 45 bison were captured in a corral, and 19 bison were successfully relocated outside of the park. The remainder were released from the corral.

During 2016 and 2017, the National Park Service (NPS) prepared an Initial Bison Herd Reduction Environmental Assessment (EA) which evaluated management actions that would reduce the herd. NPS Intermountain Regional Director Sue Masica signed a Finding of No Significant Impact (FONSI) authorizing the Park to proceed with the selected action which is designed to quickly reduce bison population density.

Multiple agencies are involved with bison management on the Kaibab Plateau and this EA was prepared in collaboration with the Arizona Game and Fish Department, the U.S. Forest Service, the Bureau of Land Management, and the InterTribal Buffalo Council.

Partner organization goals and objectives for bison management were considered in development of the EA and the Park and partner organizations are now actively developing specific operational guidelines for herd reduction.

An announcement of opportunities and a process for tribal members and members of the public to participate in volunteer culling will be made once operational guidelines for herd reduction are in place.

The FONSI is located here.

Last updated: September 12, 2017

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