Yea, forgot about the .50-70 Sharps.
It wasn’t until we moved to Wyoming that we learned firsthand just how early the herds were destroyed - the slaughter really was getting going as early as 1870. The southern herd was largely destroyed by 1872 or so.
It really didn’t take long to destroy the herds. But there were a lot of hunters. Hides were at a premium and it created an industry for awhile.
The military also encouraged it because it took their main source of food away from the Indians, prompting them to accept treaties and go on the reservations.
The Native Americans were working on destroying the herds long before the paleface arrived. The paleface just used more efficient tools and the Injuns were too few in number to affect the herds significantly.
A common fallacy is that the Native Americans never killed more than they needed and were careful to preserve the herds of wild animals. In fact, they had absolutely no concept of animal management whatsoever.