Both in Yellowstone and elsewhere. Some of these populations are quite small (For Example in Allegheny County Pennsylvania, whose County Seat is Pittsburgh Pennsylvania, had for decades the largest Bison herd East of the Mississippi River, about 15-20 Bison). Since the last time I read about that herd in the 1980s, "Buffalo Meat" has grown in demand and thus the widespread raising of Bison throughout the US. Thus between the huge number of Bison in Yellowstone and the numbers outside of Yellowstone it is NOT endangered as that term is used under the law.
On the other hand, Wolves are rare. Predators typically have a need for much larger territory han grazing animals, and thus the number of predators per square mile is low compared to grazing animals. Thus the Elk and Bison of Yellowstone are NOT endangered do to the large number of both inside Yellowstone, wolves and grizzly bears ARE endangered do to their much lower numbers do to the need for each to have much larger territory.
Endangered Species List:
http://www.fws.gov/endangered/wildlife.htmlThe Wood Bison (The only surviving Bison, the larger Plains Bison was wiped out in the late 1800s), is endangered and is listed, but as I said above, the population of wood Bison is quite large compared to wolves, thus the Feds have permitted Wyoming to kill any Bison that wanders out of Yellowstone. That is Wyoming's management plan for Bison. The Feds have found that acceptable given the huge number of Bison in Yellowstone, but the same can NOT be said of Wolves.
Allegheny County's (Pittsburgh) Bison Herd:
http://www.post-gazette.com/neigh_south/20030903sbison0903p2.asp The "war" about Yellowstone's Bison:
http://www.pbs.org/buffalowar/war.htmlhttp://www.cr.nps.gov/history/online_books/bison/chap6.htmhttp://www.billingsgazette.net/articles/2006/03/23/news/state/30-bison.txthttp://www.forwolves.org/ralph/bisonrpt.html