DENVER (AP) - Conservation groups trying to stop the poisoning of prairie dogs in South Dakota argued in federal court Wednesday that the plan could also derail efforts to protect the black-footed ferret, an endangered animal that eats about two prairie dogs a day.

The hearing on whether to stop plans to drop poisoned oats along the border of the Conata Basin in the Buffalo Gap National Grasslands ended without a decision. More arguments were scheduled for today.

The U.S. Department of Agriculture plans to start poisoning prairie dogs on federal land in four counties in southwestern South Dakota starting Oct. 11. Eight conservation groups object to including the Conata Basin in the plan since more than half of the 400 wild ferrets left in the country live there.

Jay Tutchton of the University of Denver's Environmental Law Clinic told U.S. District Court Judge Phillip Figa that the U.S. Fish and Wildlife's expert on reintroducing the ferret was not allowed to comment on the plan before it was announced.

Ranchers complain that prairie dogs have been moving onto their property and ruining livestock grazing land by destroying the grass.

Tutchton objected to the government's plan to move ferrets from the areas to be poisoned because the animals usually die when transported. He said that the loss of even one ferret could hurt plans to protect the animal.

"It's that close to the edge that all genetic diversity must be preserved," he said.

Assistant U.S. Attorney Amanda Rocque said prairie dogs are so plentiful in the area there would still be plenty for ferrets to eat. She said the government already takes ferrets from the area to help them reintroduce them in other areas.

If workers are unable to remove ferrets from any area, she said that there would be no poisoning there.

Rocque urged Figa to allow the project to move forward this fall, since snow and rain would prevent the action over the winter and poisoning isn't allowed during most of the summer since migrating birds could eat the oats.

After the hearing, Tutchton said the real reason the government is pushing to start killing prairie dogs is because of the upcoming election.

Both Democrats and Republicans in South Dakota have been taking credit for persuading Interior Secretary Gale Norton to remove the prairie dog from the list of candidates being considered for designation as endangered species last month, clearing the way for the poisoning plan.

"The hurry has nothing to do with anything other than they promised important people," Tutchton said.