Schweitzer signed an executive order to prohibit the importation of park bison into Montana for 90 days. That effectively blocks all potential routes out of the park to slaughter plants in Montana and neighboring states.
The Democratic governor told The Associated Press that he was worried the shipments could spread brucellosis to Montana livestock. And he said he was sending a message to federal officials in Washington, D.C. to rein in a diseased bison population that regularly spills out of the park and into Montana.
In the interim, Schweitzer suggested the park bring in loads of hay to feed 525 bison captured so far this winter after trying to migrate out of the snow-packed park in search of food at lower elevations.
"More than anything else, this is a direct signal to the Department of Interior in Washington, D.C. to get their hat screwed on right and manage this bison population," Schweitzer said. "Their plan is, when there gets to be a lot of snow, buffalo will go into Montana and then somebody else will have to deal with it."
Caught off guard by the governor's action, park administrators scrambled Tuesday to craft a response.
Yellowstone spokesman Al Nash noted that the slaughter plan was agreed to last month by the Montana Departments of Livestock and Montana Fish Wildlife and Parks. He said past bison shipments did not lead to brucellosis infections in cattle.
"I don't know what the governor was trying to address," Nash said.
The disease causes pregnant cattle, bison and elk to prematurely abort their young. It has been confined largely to Yellowstone's wildlife after a decades-long eradication effort by the cattle industry, although periodic transmissions occur between elk and cattle.
No bison-to-cattle transmissions have been recorded.
More than 200 of the recently captured bison have tested positive for exposure to the disease. They are being held in corrals just inside the Yellowstone's northern border. The slaughter shipments were slated to begin two weeks ago but were put on after wildlife advocates asked a court to intervene.
For years such shipments have been carried outs with state backing. That includes three years ago when more than 1,400 bison were rounded up by park workers and state livestock agents and subsequently sent to slaughter. Before the slaughters began last decade, Montana livestock agents had shot bison leaving the park.
In halting this year's shipments, Schweitzer is treading a fine political line. On one side are wildlife advocates and conservation groups vehemently opposed to slaughter. On the other, a ranching industry anxious to protect its cattle from disease.
For years the two sides have deadlocked over the park's estimated 3,700 bison.
Tom Woodbury with the Western Watersheds Project - which has a pending request for a court order to stop the slaughter before the 9th Circuit Court of Appeals - said Tuesday's executive order puts the burden on federal officials to break that impasse.
But John Youngberg with the Montana Farm Bureau said the governor was taking away the only method of population control available to the park. He said the governor was "throwing the baby out with the bathwater" by eliminating the only effective means to reduce bison numbers.
"The one way they had to do that was when they come out of the park, they get slaughtered and removed," Youngberg said.
The initial request by Woodbury's group and others to halt the slaughter. was denied on Monday by U.S. District Judge Charles Lovell, who characterized the slaughter program as a distasteful but ultimately necessary way to manage the animals.
Lovell also weighed in against feeding the animals as Schweitzer is proposing: "Promoting population expansion by supplemental feedings would likely lead to more problems for the herd," the judge wrote.
Feeding Yellowstone bison was a common practice for much of the last century.
After hunting by early European settlers reduced the total number of bison in the park to just 25 in 1901, park officials began to closely manage the species to bolster their population. From the 1920s through the late 1960s, that included supplemental feeding, periodic culling and the exporting of "excess" bison to other parts of the country.
The practice was dropped when the park adopted a policy of "natural regulation" - allowing wildlife populations to rise and fall according to climate conditions or food supplies.
But by the early 1980s, the bison herds had expanded to more than 2,300 animals and were increasingly pushing beyond the park's boundaries. To guard Montana livestock, more than 3,100 bison that crossed outside the park's northern or western boundaries over the next two decades were killed, many of them shot.
An agreement signed by five state and federal agencies in 2000 was designed to pursue alternatives to killing, but wildlife advocates and members of Congress have been critical of the little progress made to date.
That has left Yellowstone's bison mired in a vicious cycle: the population outgrows the park's capacity, large numbers of bison are slaughtered attempting to leave, and then within a year or two the population starts to increase yet again.