Editing American bison (section)

=== Yellowstone National Park Bison Herd ===
[[File:Frosty bison in the road on a cold morning in Hayden Valley (53482547136).jpg|thumb|Bison in winter in [[Hayden Valley]].]]
The Yellowstone National Park Bison herd started with only 25 individuals, and there was evidence of two population bottlenecking events from 1896 to 1912, with a population ranging between 25 and 50 individuals during this time. In 1902, 18 female and 3 male bison from outside herds–the Pablo-Allard herd and Goodnight (TSBH) herds respectively–were introduced to the Yellowstone herd. After the addition of those individuals, the effective population size is estimated to have been N<sub>e</sub>=7.2 individuals. The Yellowstone herd was kept completely isolated from 1902 to around 1920, and these previously mentioned founders contributed between 60 and 70% of the genetics of the current bison population at Yellowstone.<ref name="Hedrick-2009" />

Similar to the Texas State Bison Herd, the introduction of new individuals into the population in 1902 likely was the savior of this herd, which now numbers around 5,900 individuals as of summer 2022.<ref>{{cite web |last1=Park |first1=Mailing Address: PO Box 168 Yellowstone National |last2=Us |first2=WY 82190-0168 Phone: 307-344-7381 Contact |title=Yellowstone Bison - Yellowstone National Park (U.S. National Park Service) |url=https://www.nps.gov/yell/learn/nature/bison.htm |access-date=2023-04-24 |website=www.nps.gov |language=en}}</ref>