Yellowstone National Park’s estimated bison population this summer is approximately 4,600 animals. That’s the figure biologists came up with after the annual summer aerial surveys. Park officials say approximately 3,200 are in the northern herd and another 1400 are in the central herd. Additionally, biologists say those surveys spotted about 700 calves-of-the-year. Altogether, the count represents an 8 ¾% increase over last year’s count. Still, that’s down from the Park’s record population in 2005 of an estimated 5,000 bison. Officials say the fluctuation is considered within the natural range of expectation for wild bison.