estimating the size of the herd

[Ross]

The article in the Herald Leader last Sunday said there would likely be a herd of about 700,000 deer this fall in Kentucky. For a long time I've been curious about how those estimates are reached. Could anyone comment on what the formula is for figuring out the size of the herd? Or point me to a good web site about it? (Actually I think this would be a good topic for a page on the KDFW web site.)

Thanks.