Yellowstone National Park has an estimated 4,600 bison roaming within its boundaries.
The park counted the bison during its annual summer bison survey.
The aerial survey found about 3,200 bison in the Northern herd and 1,400 in the Central herd this summer.  There were about 700 calves-of-the-year observed in a June aerial survey.
This year's count represents an increase of 8.75 percent over last year's survey. 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.