Amid a growing chorus of complaints, the Environmental Protection Agency has initiated a review of at least one blood-thinning poison used to kill prairie dogs.

The review notice, published Wednesday in the Federal Register, stems from a protest filed June 5 by the World Wildlife Fund and a more recent request by the Montana Department of Agriculture.

Just two weeks ago, Defenders of Wildlife and Audubon of Kansas filed a lawsuit against the EPA over its decision to allow the general use of Rozol Prairie Dog Bait to target black-tailed prairie dogs in 11 states, including Kansas. The lawsuit also took aim at the EPA's decision to approve special local needs registrations for the use of Kaput-D to target prairie dogs.

Jason Rylander, the Defenders of Wildlife attorney who filed the lawsuit, doubts the review is coincidental, considering the WWF request was filed in June.

Rylander said he's been asking if the WWF would work as a petition to force the review.

"And I got no response until this week," he said.

Rylander said the lawsuit he filed will stand, despite the review, unless the EPA pulls the registration for both Rozol and Kaput-D.

Steve Forrest with the WWF said he was aware of the Defenders lawsuit, and knew the EPA planned to open the review on the poison.

Rozol contains the blood-thinning chemical chlorophacinone and was approved by the EPA for use on prairie dogs on May 13.

Kaput-D, which contains diphacinone, another blood-thinning chemical, was not included in the most recent move by EPA. The EPA did, however, initiate a review to add prairie dogs to a producing containing Kaput-D and a a flea-killing chemical.

The WWF's request for the review nearly parallels the lawsuit, other than it didn't include the latest letter from the U.S. Fish and Wildlife Service.

That letter, written Sept. 9, objects to the registration and asks EPA for "formal consultation" with FWS.

It did, however, point to a 2006 Nebraska Game and Parks Commission letter, objecting to the EPA's special local needs registration of Rozol for prairie dog control.

That letter took aim at the registration process, especially in Kansas, and the study that detailed Rozol's effectiveness. The study was conducted by Charles Lee, a wildlife damage specialist at Kansas State University. He has also served as the adviser for the Nature Conservancy in its quest to limit the number of prairie dogs on its Logan County ranch.

In August, the Wildlife Society also took aim at Rozol and Kaput-D.

Its letter detailed the agonizing death following ingestion of the blood thinners, and the risk of poisoning other animals -- including the highly endangered black-footed ferret and eagles and hawks -- that eat the dead and dying prairie dogs.

Nebraska's wildlife agency and the Wildlife Society both suggested that costs involving the use of Rozol could be twice that of zinc phosphide, a poison generally preferred by wildlife advocates because there's a reduced chance for secondary poisoning.