A herd of thirty to sixty million could hardly be killed out by human predation even with modern rifles considering the harvest could hardly have been more than a million a year. And that is a generous estimate on the kill. Need to look for another cause. There are plenty of accounts of dead bison covering the landscape. Indians died of introduced European disease. Bison overpopulated. Domestic cattle were introduced and driven into bison territory. Most likely cause was something like Texas tick fever or anthrax. Hunters couldn't have very well killed more than the natural reproduction.
Your numbers are wrong. By the time the market hunting started the numbers had already dwindled to much less 30-60 million which are just estimates anyway.
Those figures are estimates that include the tall grass prairies as well as the short grass. The tall grass herds were gone long before the railroad ever pushed into the short grass prairies.
Know one knows the real numbers.Woodland herds were the first to go in places like Kentucky circa 1700s, Next were the tall grass herds in the early 1800s. Next the Southern short grass herds. Then the northern short grass herds were the last to go.
Hunters can easily kill more than natural production. There was natural predation going on at the same time. The herds were already in balance. Indians, wolves, bears and natural causes were also taking animals. The market hunting was on top of that, The government intentionally killed the herds to starve the wild Indians.
The disease scenario does not hold water because the big herds were not around cattle. The cattle did not come into the short grass until the Indians were passified and the herds were gone.
