In a shaky, hand-shot video from 2010, Nimish Vyas of the United States Geological Survey pans across a field in Vernon, Colo. Vyas focuses on a dirt mound and then zooms in on a pale spot atop the dry, tawny grass. The spot twitches, and he zooms closer.

A black-tailed prairie dog lies on its side. Its belly is heaving, and its front and back legs twitch—a motion that at first appears similar to what a dog does while dreaming, only the twitching continues in a spasmodic, almost syncopated, manner. This prairie dog isn't dozing. It's dying.

Narrating the video, Vyas says that Rozol Prairie Dog Bait was applied to the colony 24 days ago. According to the label, animals should begin dying of internal bleeding within four to five days after eating it, and people should expect to survey the area for up to two weeks afterward to bury or remove the bodies.

Vyas points out that, while it's difficult to see the bodies from the ground, the twitching prairie dogs could easily attract predators flying above the grasslands.

What he doesn't say, though his video makes explicit, is that the prairie dogs suffer a cruel death—as do any other animals that eat the bait or the poisoned prairie dogs. And while a federal judge temporarily banned Rozol from New Mexico last year, if the US Environmental Protection Agency has its way, that ban could soon be lifted.

Manufactured by the company Liphatech, Rozol has a complicated history. What’s even more complicated, however, is the relationship between two federal agencies—one that permits the use of chemicals and the other mandated to protect endangered wildlife.

More than 20 years ago, the US Fish and Wildlife Service warned EPA that using Rozol to kill rodents could potentially put 21 endangered species at risk. But when people began using Rozol Pocket Gopher Bait "off-label" to poison prairie dog colonies, EPA worked with a number of states to develop special rules legalizing the practice.

Then, in late 2006, one month after the bait was applied to a black-tailed prairie dog colony in Nebraska, a bald eagle carcass was found. Scientists determined it had died from exposure to chlorophacinone, Rozol's active ingredient. EPA and FWS met to discuss endangered species protection, but three years later, EPA registered Rozol for use on prairie dogs in 10 states.

Over the next few years, conservationists filed lawsuits, and the FWS again requested that EPA consider how Rozol might impact endangered species, including black-footed ferrets—a rare species that lives near and preys on prairie dogs. Prairie dogs also create habitat for more than 150 species of amphibians, birds, mammals, plants and reptiles—few of which are protected under the Endangered Species Act. According to an FWS study, species declines due to the destruction of prairie dog habitat will result in "cascading effects" through the grassland ecosystem that extend beyond the poisoned prairie dog towns.

Last year, a federal judge sided with environmental groups, saying EPA had violated the Endangered Species Act by registering Rozol Prairie Dog Bait without consulting with FWS. US District Judge Ellen Huvelle banned Liphatech from selling it in all but the six states with "special local needs" rules until the FWS weighs in on how it affects endangered species.

Meanwhile, EPA anticipates that, once it finishes consulting with FWS, the judge will lift the ban. That's likely, but with restrictions. According to the FWS' 2012 draft biological opinion, using Rozol within the vicinity of eight known endangered species violates federal law. FWS' recommended ban will apply to a number of specific areas across the West, including within five New Mexico counties.

This may mean good news for endangered species, but it's still tough shit for prairie dogs.

George Dennis, aquatic ecosystems branch chief of the FWS' Ecological Services Field Office in Albuquerque, points out that Rozol is just one tool people use to kill prairie dogs. But since it is FWS' job to enforce the Endangered Species Act, its opinion only matters when rare species might eat the bait or when protected species—such as the bald eagles found in Nebraska in 2006 and again in 2011—die.

As for the squirrels and meadowlarks and other species exposed to the bait—not to mention the prairie dogs themselves—they're on their own. That is, until they're rare enough to be protected under the Endangered Species Act.