BILLINGS, Mont. (AP) — Large numbers of migrating Yellowstone National Park bison are likely to face slaughter for at least the next couple of winters as officials weigh changes to a 15-year-old agreement that drives the practice.

Most of the bison removed from America's first national park are captured and sent to slaughter over concerns they may transmit disease to Montana livestock. Yellowstone Superintendent Dan Wenk told The Associated Press he's hopeful the slaughters eventually will be phased out and replaced by hunting. Wenk says that's not feasible in the short term with a near-record population of about 4,900 park bison.

Montana State University wildlife researcher Robert Garrott says Yellowstone's bison recovered dramatically from near-extinction over the past century. But Garrott says that success is overshadowed by the widely-criticized slaughters used to control bison numbers.