An acrobatic mouse is threatening Bush administration efforts to give Western developers an upper hand over endangered species.

The Preble's meadow jumping mouse is in fact a unique creature with "distinct evolutionary lineages that merit separate management consideration," says a U.S. Geological Survey study presented Wednesday to senior Interior Department officials.

"Those populations facing demographic challenges should be afforded high conservation priority," the study says.

That finding contradicts research touted by Interior Secretary Gale Norton last February when she proposed removing the mouse from the government's endangered species list. Critics say it also undercuts the administration's claim that it uses the best science available in promoting fewer protections for imperiled wildlife.

The previous study, which was done by a biologist since hired by Norton's department, concluded there was no genetic difference between the Preble's meadow jumping mouse and the much more common Bear Lodge meadow jumping mouse.

Listed by the government as a threatened species since 1998, the Preble's meadow mouse stands in the way of any project that could damage its habitat, a broad swath of Colorado and Wyoming, from Colorado Springs north through Denver and Fort Collins and reaching to Laramie.

The 3-inch mouse uses its 6-inch tail, and strong hind legs to launch itself a foot and a half into the air, where it can abruptly switch directions in mid-flight.

It prefers to roam by night, scurrying and jumping along streams through undisturbed grasslands. There it dines on insects, spiders, fungus, moss, willow, sunflower, grasses and seeds, hibernating each winter from mid-October to early May.

Nearly 31,000 acres were designated as critical habitat to be conserved for the recovery of the Preble's meadow mouse, which has dwindled to an average of 44 mice per mile of stream because of urban sprawl.

A year ago, developers welcomed the findings of biologist Rob Roy Ramey of the Denver Museum of Nature and Science and the Interior Department's conclusion, based on his findings, that the Preble's meadow mouse no longer needed federal protections.

Ramey was later contracted as a science adviser to the Interior Department in its attempt to reclassify several species whose endangered status is blocking developers.

The new study was conducted by Tim King, a USGS conservation geneticist based in West Virginia, and peer-reviewed by academic experts outside government.

One of the reviewers, Eric Hallerman, a professor of fisheries and wildlife science at Virginia Tech, said King's study debunks Ramey's work.

"It contradicts it fairly strongly," Hallerman said.

"The Preble's jumping mouse is distinct from other jumping mice," he added. "Which means that the Preble's mouse should have protection under the Endangered Species Act and development may have to be controlled in some way in the critical habitat areas."

Ramey studied the mouse's genetic code by analyzing tissue samples and museum specimens of several of the 12 subspecies of meadow jumping mice that range across the country to come up with his findings, which also were peer-reviewed. He repeated some of the original 1954 research that helped establish the Preble's mouse as a subspecies of its own.

For King's taxonomic analysis, USGS field crews collected genetic samples from more than 140 meadow jumping mice at several sites across the Northern Great Plains. They also trapped mice in the Black Hills and Bear Lodge Mountains to assess those populations.

King's study says Ramey's conclusions "should be considered questionable."

Hallerman said Ramey's work reflects the Bush administration's intrusion of politics in its scientific research.

"It seemed to me from the get-go, he wanted to find that this was not a taxonomically valid subspecies," Hallerman said.

After others raised similar doubts, Interior officials agreed to revisit Ramey's work by commissioning King's study.

The Interior Department's Fish and Wildlife Service said King's study results "raise significant questions" about Ramey's study.

The agency said it will convene an expert panel and study the mouse for at least another six months before deciding whether to change or keep its endangered status.

"I would think that would be one of the options," King said in an interview.

Ramey, reached in Baja, Mexico, where he is counting bighorn sheep for a conservation group, said his study had a "clear-cut" hypothesis and critical tests that allowed for "no wiggle room," while King's study "relied on interpretation."

He acknowledged having strong views about endangered species.

"You cannot make everything a top priority and expect to accomplish anything, in terms of preserving species," Ramey said. "If we focused on conservation of fewer genetically unique populations and pooled our resources, we might accomplish more for conservation."