Estimates show decrease in 200 bison since last summer
Weekly Wire Services

Yellowstone National Park has
completed its annual summer bison
population monitoring.
The population is estimated to be
3,700 bison. The estimate is based
on a series of aerial surveys. There
are an estimated 2,300 bison on
the Northern
Range this
summer, with
1,400 in the
Central Interior
herd.
Winter mortality
was estimated
at 500 bison.
There were 583
calves of the year
observed
in a June aerial
survey.
The population was estimated at
3,900 bison last summer. The peak
population estimate of 5,000 bison
was recorded in the summer 2005.
The observed rate of population
change this past year is within
the natural range of expectation
for wild bison. The rate at which
wildlife populations increase is a reflection
of the combined effects of
reproduction and mortality, and is
heavily influenced by age structure
of the population, and environmental
conditions.
This 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 based on this
estimate.
The IBMP is a cooperative
plan designed to
conserve a viable, wild
bison population while
protecting Montana’s
brucellosis-free status.
The 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, the Montana Department
of Fish, Wildlife and Parks, the Inter-
Tribal Buffalo Council, the Confederated
Salish Kootenai Tribes, and the
Nez Perce Tribe.