• Steam rises off of the colorful Mammoth Hot Springs Terraces. Photo courtesy Jacob W. Frank


    National Park ID,MT,WY

Yellowstone's Summer Bison Population Estimate Released

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Date: October 15, 2007
Contact: Al Nash, 307-344-2010
Contact: Stacy Vallie, 307-344-2012

National Park Service
U.S. Department of the Interior

Yellowstone National Park
P.O. Box 168
Yellowstone National Park, WY 82190
October 15, 2007     07-100   
Al Nash or Stacy Vallie (307) 344-2010 or 344-2012


Yellowstone’s Summer Bison Population Estimate Released

Yellowstone National Park has completed the 2007 summer bison population estimate.

The summer population is estimated to be 4,700 bison.  The estimate is based on a series of aerial surveys conducted in July and August. 

The late-winter population was estimated at 3,600 bison in February. The population was estimated at 3,900 bison last summer.  This increase is within the historical rates of the herd’s annual population increase during the summer.  

This summer’s population estimate remains below the peak of 4,900 bison recorded in the summer of 2005.

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 -

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