Kansas City, Mo. ? Two conservation groups have sued the Environmental Protection Agency for its decision to register pesticides that curtail prairie dogs, the main source of food for the endangered black-footed ferret.

The lawsuit, filed in federal court in Washington, D.C., by Defenders of Wildlife and Audubon of Kansas, says the chemicals threaten other species, and that in issuing registrations for their use, the EPA is violating the federal Endangered Species Act, the Migratory Bird Treaty Act and other federal laws.

The lawsuit claims the EPA failed to heed warnings from the U.S. Fish and Wildlife Service that registrations of the chemicals chlorophacinone and diphacinone “be disapproved or rescinded because of known and potential impacts to wildlife.”

It seeks an injunction against the registration in 10 states of Rozol, which contains chlorophacinone, and the local use of Kaput-D, which contains diphacinone. The chemicals cause internal bleeding.

EPA spokesman Dale Kemery said the agency planned to release a federal register notice next week related to the lawsuit.

“We are treating this request as a petition to suspend this use of Rozol,” he said in an e-mail Tuesday. “The docket will include the risk assessments as well as letters from other parties expressing similar concerns.”

Kemery said the EPA issued a similar notice about Kaput-D earlier this month.

“Once we receive and evaluate public comment on these notices, we will determine the future course of action,” he said.

The lawsuit, filed Sept. 23, takes issue with EPA’s decision in May to approve the use of Rozol to target black-tailed prairie dogs in Kansas, Colorado, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas and Wyoming.

“According to FWS, use of these rodenticides in these states could damage ferret recovery efforts and impact other federally-protected species,” the lawsuit said.

According to the lawsuit, the Fish and Wildlife Service requested that the EPA consult with it over use of both Rozol and Kaput-D “because the range of the black-tailed prairie dog overlaps with the black-footed ferret, one of the most critically endangered mammals in the United States.”

In a letter dated Sept. 8, Bryan Arroyo, the assistant director for the Fish and Wildlife Service’s Division of Fisheries and Habitat Conservation, told the EPA that his agency recommended the EPA withdraw its registration for Rozol and withhold registration for Kaput “until EPA completes a formal consultation with the Service on the use of these rodenticides to control black-tailed prairie dogs.”

Valerie Fellows, a Fish and Wildlife spokeswoman, said Tuesday that consultation has not occurred.

Arroyo said the agency earlier determined that prairie dog poisoning was a “major factor in the decline of the ferrets, through both decline of the prairie dogs and inadvertent poisoning of ferrets.”

He also said the agency was “especially concerned about potential mortality of migratory raptors due to the use of Rozol and Kaput.”

The black-footed ferret relies on prairie dogs for survival, said Ron Klataske, executive director of Audubon of Kansas.

“You have to have some places with prairie dogs to have ferrets,” he said.

Klataske said his group prefers the use of zinc phosphide to control prairie dog populations, which can compete with livestock for forage, because it “doesn’t result in a chain-reaction secondary poisoning.”

Black-footed ferrets were thought to be extinct until 1981, when a colony was found in Wyoming. The species has since been reintroduced in several western and midwestern states.

Pete Gober, who coordinates black-footed ferret recovery efforts for the Fish and Wildlife Service, said there are about 500 breeding black-footed ferret adults in about 18 sites in North America. The goal is to have about 3,000 of them scattererd across 30 sites, he said.