Winter is coming. And with the harsh winter conditions expected this season, experts are predicting that the herds of bison which roam freely in Yellowstone National Park may begin making the move in thousands toward Montana for their annual migration.

With the bison, unfortunately, also comes the potential for livestock to be contaminated with diseases which the wild bison may bring across the state borders due to their migration. Brucellosis, for example, is one of the leading causes of livestock death from disease transferred from bison. Various strains of the infection are seen in cows, pigs, sheep, coats, camels, dogs, and some strains can even transfer to humans.

Disease transfer is the basis of a controversial agreement made between the federal government and the state of Montana reached way back in 2000 to cull Yellowstone's bison herds by killing off hundreds of them to reduce their migration numbers.

According to reports, the plan for this year is to target up to 1,000 bison, mostly females and calves, in an attempt to reduce their reproductive rate. Although the agreement is met with much controvesy, Yellowstone National Park maintains that it must be done to maintain the balance of the park's bison population in relation to the park's area.

“Through the legal agreement the National Park Service has to do this. If there was more tolerance north of the park in Montana for wildlife, particularly bison as well as other wildlife, to travel outside the park boundaries, it wouldn't be an issue,” said Sandy Snell-Dobert, a spokerson for Yellowstone National Park.

Stephanie Adams from the National Parks Conservation Association added that despite bison being a hardy species, the lack of space for bison to roam around beyond the park boundary forces them to eliminate the numbers of bison which are becoming larger.

Park officials are scheduled to meet with the representatives from the state, Native American tribes, and other federal agencies to come up with a plan of action for culling the bison herd.

Huntsmen, along with native tribes whose hunters have treaty rights to capture animals in the Yellowstone area, are expected to kill at least 300 bison, while others are reportedly planned for capture to be used for research.