The saga began in August 2002, when Ramey proposed to test whether the Preble’s mouse truly qualified as a unique subspecies. The idea elicited a lukewarm response from the Fish and Wildlife Service, but in December, Ramey received a letter from the governor of Wyoming informing him that the state would fund his study. Wyoming had been a reluctant partner in Preble’s mouse protection, and state officials jumped at the chance to poke holes in the designation. Eventually, the Fish and Wildlife Service, along with the Denver Museum of Nature and Science, also kicked in money for the study.

Before he began, Ramey laid out the criteria he would use to determine whether Preble’s qualified as a subspecies. He would look for distinctness in its physical traits, in its ecology and in its genes. The mouse need not turn up uniqueness in all of these areas, Ramey said, but it should prove distinct in the majority of them. One by one, the team pitched these criteria to the mouse. And one by one, the mouse began to miss.

Ramey’s colleague, Lance Carpenter, measured the skulls of museum specimens to test Krutzsch’s assertion that the Preble’s mouse skulls were smaller than those of other meadow jumping mice. Carpenter measured nine characteristics of the Preble’s skulls, and found that they were smaller in only one. The morphological differences noted in Krutzsch’s monograph were merely "unsupported opinion," Ramey would write in his report. Strike one.

Likewise, when Ramey’s team scanned the scientific literature for evidence of ecological differences between the Preble’s mouse and other nearby subspecies, they found none. Ramey argued that if, during the 100-plus years the mouse had been classified as a subspecies, no one had published evidence that the mouse possessed unique ecological or adaptive traits, it was reasonable to conclude that they didn’t exist. Strike two.

Finally came the genetic work. Genetic testing didn’t exist in Krutzsch’s day, but by the time Ramey met the mouse, scientists had developed high-tech tools for peering into DNA and detecting even minute genetic differences. This has become the gold standard for determining whether populations are distinct.

Ramey’s team compared DNA from the Preble’s mouse to that of several nearby jumping mouse subspecies. The researchers examined two types of DNA — one found within the nucleus of cells, the other from organelles called mitochondria, which are passed from mothers to their offspring. Mitochondrial DNA evolves more quickly than nuclear DNA, so if the Preble’s mouse was starting to evolve separately from other meadow jumping mice, this shift would be expected to turn up in the mitochondrial DNA first.

But the Preble’s mitochondrial DNA sequences also turned up in the Bear Lodge meadow jumping mouse, a subspecies found in Wyoming, North Dakota, South Dakota and Montana. The nuclear DNA showed only small differences between the Preble’s mouse and the Bear Lodge mouse, the kind of variation that Ramey says you would expect to find in any normal population of a single species.

With three strikes against it, Ramey concluded that the Preble’s mouse was simply a population of the Bear Lodge meadow jumping mouse. He recommended that the two be lumped together as one subspecies.

When Ramey went public with his study in December of 2003, the crowd on both sides of the ballpark went berserk. The state of Wyoming, which had funded Ramey’s work, wasted no time filing a petition to remove the Preble’s mouse from the threatened species list. A coalition of builders, businesspeople and agricultural interests calling itself Coloradoans for Water Conservation and Development co-signed the petition. The Fish and Wildlife Service estimates that the Preble’s listing alone costs developers and landowners as much as $18 million a year; developers put the cost much higher.

Politicians seized on Ramey’s work as proof that the Endangered Species Act was protecting a mouse that had never existed in the first place. Senator Wayne Allard, R-Colo., called for the creature’s immediate delisting. House Representative Tom Tancredo, R-Colo., introduced a bill that would have delisted the Preble’s mouse and forbidden it from receiving any future Endangered Species Act protection.

Meanwhile, environmental groups pointed to delisting efforts as evidence of political tampering with science — accusations that grew more shrill when Ramey signed on as a consultant for the Interior Department, and testified before Congress in favor of Endangered Species Act reform. "If the Bush Administration really cared about good science, as they are so fond of claiming, and if they had any respect at all for the law, their decision would be a no-brainer," the Center for Native Ecosystems, a Denver-based environmental group, wrote on its Critterthink blog. "Alas, we all know this was never about the science or the law. This is about politics and money."

When the Fish and Wildlife Service asked 14 scientists to review Ramey’s report and verify his conclusions, their results did little to quell the debate.

Geneticist Keith Crandall of Brigham Young University was thoroughly convinced by Ramey’s argument, calling his conclusion "robust" and "strongly supported by all forms of data examined." Others, such as Gary White of Colorado State University, felt that Ramey’s work was insufficient to overturn a long-standing subspecies classification. Ramey’s conclusions, White wrote in his review, "are an example of basic statistical misinterpretation."

What everyone did seem to agree on, however, was the need for a more definitive answer. So the Fish and Wildlife Service commissioned U.S. Geological Survey geneticist Tim King to conduct an independent genetic analysis of the Preble’s and several other meadow jumping mouse subspecies.

A quiet man who shuns the limelight, King works at the Leetown Science Center in Kearneysville, W. Va. He conducted a genetic analysis of Atlantic salmon that was cited in the decision to place the fish on the endangered species list. He was chosen in part because he had never worked with the Preble’s mouse, and was not a stakeholder in the debate.