KALISPELL (AP) - Roman Biek's been tracking cougars the hard way _ one molecule at a time. He has no hounds, hasn't even been out in the woods.

Instead, Biek's been in his genetics lab _ first at the University of Montana, then at Emory University _ using a tiny virus to follow the big cats across the modern landscape. He's even tracking cats generations dead and gone.

"It's really very interesting," the researcher said. "The virus can teach us things about cougars that the cougars themselves could never teach us."

The wildcat hunt began for Biek back in 1999. He was looking for a doctoral program in wildlife ecology _ hopefully one with an emphasis in genetics _ when he received a call from Dr. Mary Poss.

Poss is a UM researcher, and at the time was wondering whether a species-specific virus might not act as a "genetic tag," allowing scientists to track the history and distribution of animal populations.

"It was Mary's idea," Biek said, "and I just signed up to follow through."

The notion was simple: Animal genetics change very slowly, but viruses evolve with remarkable speed. Perhaps by picking apart virus DNA, researchers could untangle the recent history of host animal populations.

Throughout North America, Biek said, most of the landscape-level changes that might affect animals have occurred in the past few decades. That's nowhere near enough time for impacts to show up in the DNA of big critters.

But if a single virus was specific to a single host species, then perhaps changes to the virus could point to those emerging impacts.

"Cougars were a good choice," for the study, Biek said, because they are relatively common, are available locally and, perhaps best of all, are hunted.

They also tend to carry feline immunodeficiency virus, or FIV, and FIV evolves fast.

For funders such as the Yellowstone to Yukon Conservation Initiative and the Wilburforce Foundation, the implications were obvious _ study the distribution of the virus, and perhaps you could determine whether barriers had fragmented the landscape, creating obstacles to genetic flow.

"We wanted to know whether recent changes in (cougar) population history can be detected using viral genes," Poss said. "This is important because processes that are likely to impact wildlife populations occur in the recent past, before we can see a change in the genetic makeup of the animals themselves."

"The question was, how to get those cougar samples," Biek said.

Enter the hunters.

Biek got together with the Montana Department of Fish, Wildlife and Parks, with houndsmen and with outfitters, and roped them all into the service of science.

He shipped out sampling kits and then he waited.

Over three winters _ 2001, 2002 and 2003 _ he collected 365 blood samples from 365 different cats, mostly in Montana but stretching from Alberta to British Columbia to Wyoming.

And from that blood, he said, he collected DNA from feline immunodeficiency virus.

The virus evolves quickly _ a rate of about one-half percent over 10 years means that of 1,000 samples, five should look distinctly different in just one short decade.

"We took the genetic sequence," he said, "and we found individual viral lineages. Then we looked at how each lineage fit into a family tree. Essentially, we created a genealogy of cougar FIV virus."

Eight separate lineages emerged, he said, each "distinct, easily genetically differentiated."

The random and fast-paced genetic change in viral DNA provided Biek and Poss a molecular clock of sorts, a timepiece with which they could look back and determine how long each lineage had been separate _ how long since they all shared a common ancestor.

Turns out, they were in fact of one parent, a virus that thrived within the past 100 years.

The researchers knew that before bouncing back, cougars had been hunted to near extinction in the early part of the 20th century _ Montana bounty hunters collected on 170 cats in 1908, then zero by 1929.

And so they confirmed that the virus, like the cats, had recently expanded.

Turns out, the most widely distributed lineage is the earliest, providing a "signature of population expansion for the virus," Biek said.

FIV diversified from that early variation, with lineages spreading across the country as the cats dispersed.

As hoped, the molecular clock showed FIV expansion at precisely the same time state wildlife records showed cougar expansion.

Tracking the virus had in fact enabled them to track the cats through both time and space, revealing much about cougar population structure in the very recent past.

The fact that some individual virus lineages were widespread also revealed much about how the wild cats continue to use the landscape.

It appears, Biek said, that they continue to range broadly, passing genetic stock across vast areas during the past 80 or so years.

"Cougars are still moving through the landscape very effectively," he said, which is the beginning of an answer about how habitat fragmentation might, or might not, affect at least one species.

It is a population dynamic, he said, that could not be tracked any other way, because cougar DNA evolves far too slowly.

"By studying the virus, we were able to obtain more information than we could from the host animal's genetic data alone," Poss agreed.

In January, Biek and Poss, along with computer scientist Alexai Drummond, published in the prestigious journal "Science," detailing their new methodology that could unlock secrets to countless wildlife species.

With time, he expects the various FIV lineages to spread out evenly across his map, as animals continue to disperse and share infection. If they do not, then he'll have a strong indication that some barrier is in the way of cougars' travels across the landscape.

Remarkably, the fast-evolving virus could show him that change in just one decade.

"And I think we're only scratching the surface for infectious agents out there," Biek said. "There are lots more out there we can use."

The implications, too, reach far beyond cougars, even far beyond wildlife biology. Currently, Biek works as a postdoctoral researcher at Emory University, where he continues his research into animal viruses.

One avenue he's exploring has taken him down the dark corridor of ebola, a virus deadly to people, and one he believes moves from human population to human population by way of a wildlife host. His work could help medical researchers understand the viral spread.

"We want to know how these viruses move through the landscape," Biek said, "and DNA is an incredible tool for doing that."