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Yellowstone’s Summer Bison Population Estimate Released

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Date: September 5, 2006
Contact: Nash, (307) 344-2010
Contact: Vallie, (307) 344-2012

Yellowstone National Park has completed the 2006 summer bison population estimate.

The summer population is estimated to be 3,900 bison. The estimate is based on a series of aerial surveys conducted in the month of August.

The population was estimated at 4,900 bison last summer. Going into this summer season, the population had dropped to 3,400 animals. This was due to brucellosis risk management actions, hunting outside the park, traffic deaths, natural mortality and predation.

The bison population decline did not impact the herd’s reproductive capability. There were about 500 calves born this year. This is within the historical rates of the herd’s annual population increase during the summer. It demonstrates the robust nature of the Yellowstone bison herd and the abundance of natural forage in the park.

The summer population estimate is used to inform adaptive management strategies under the Interagency Bison Management Plan (IBMP). Specific management actions may be modified based on expected late winter population levels as corroborated by the summer population estimate.

The IBMP is a cooperative plan designed to protect Montana’s brucellosis-free status while allowing for the conservation of a viable, wild bison population. Protecting Montana’s brucellosis-free status requires keeping bison from mixing with cattle grazing on land outside the park.

The five cooperating agencies operating under the IBMP are the National Park Service, the U.S. Forest Service, the Animal and Plant Health Inspection Service, the Montana Department of Livestock and the Montana Department of Fish, Wildlife and Parks.

- www.nps.gov/yell -

Did You Know?

Summer Crowd at Old Faithful.

At peak summer levels, 3,500 employees work for Yellowstone National Park concessioners and about 800 work for the National Park Service.