Plans by Yellowstone National Park officials to remove roughly 1,000 bison from the park's herds are drawing criticisms and protests from groups that say the slaughter is unnecessary.

A month ago Yellowstone officials announced the culling plan, which Defenders of Wildlife officials say will be "the largest in seven years" if it achieves the goal of removing 1,000 bison. In addition to the 500-600 bison that head outside the park and into Montana being removed by park staff, it is anticipated that public and tribal treaty hunting in Montana will remove 300 to 400 bison. Park crews began rounding up bison Thursday.

"America's last wild buffalo are right now being trapped for slaughter along Yellowstone's northern boundary. These capture for slaughter operations are happening even as state and treaty hunters are shooting buffalo that migrate into Montana," the Buffalo Field Campaign wrote on its website. "Such management actions are driven by Montana's bison-intolerant livestock industry, intolerance that is codified in the statute: MCA 81-2-120, a law crafted by the livestock industry that needs to be repealed."

At Defenders, the group said "(T)his capture and slaughter program, implemented by the National Park Service, is meant to keep the Yellowstone bison population below an arbitrary cap of 3,500, imposed decades ago as part of a settlement with the state of Montana for now discredited concerns over brucellosis and carrying capacity."

The wildlife advocacy group also said a poll of Montana residents last month found that 67 percent of those contacted support relocating Yellowstone bison to start herds elsewhere in their state.

"(Montana) Governor (Steve) Bullock and the National Park Service need to move quickly to bring bison management into the 21st century," the group's release said. "They need to expand the tolerance zone around Yellowstone, finish their environmental assessment of the quarantine and relocation program and kick-start plans to update the 14-year old Interagency Bison Management Plan, the document that sets guidelines for managing Yellowstone’s wild bison."

Jonathan Proctor, Defenders' program director for the Rockies and Plains, said that, “(B)ison are wildlife and should be managed as such. Wholesale slaughter of these genetically valuable animals simply because they leave Yellowstone National Park looking for food is archaic and driven by policies that treat them like livestock. Rather than working towards Montanans’ goal of wild bison restoration, this shipment to slaughter program kills the bison that could, instead, be the beginnings of new restoration herds.”

“We’ve proved that bison restoration from Yellowstone to Montana’s public and tribal lands is viable, making this shipment to slaughter wasteful, unacceptable and unnecessary. Recent polls also clearly show that the majority of Montanans want wild bison restoration. So, why are the National Park Service and Montana’s Department of Livestock continuing to implement this unnecessary and expensive slaughter program? It’s a waste of taxpayer funds, and a waste of prized Yellowstone wild bison.”