"When we started this project two years ago, we laughed about this being the Sasquatch of the East. But now we have some really hard evidence that we've got something more tangible," Dr. Stroeher said in an interview from her university lab in Lennoxville, Que., near Sherbrooke. "It's very exciting."

Once widespread across North America, cougars were hunted during European colonization and driven into three last strongholds: the Rocky Mountains, the Olympic Peninsula in Washington State, and the Florida Everglades. The last known eastern cougar was shot near the Quebec-Maine border in 1938. Since then, thousands of cougar sightings have tantalized Ontario, Quebec, the Maritimes and the New England states, but hard evidence of the cats has remained elusive.

On July 23, 1953, two employees of the Great Lakes Paper Company reported a tawny, 5 1/2-foot-long cat standing at the side of the TransCanada Highway about 50 kilometres west of Thunder Bay, Ont.

On April 13, 1954, an engineer and a fireman travelling on the Canadian National Railway between Thunder Bay and Atikokan, Ont., said they saw a cougar cut across the tracks in front of the train and leap on to a rocky promontory.

In the spring of 1990, Roger Noble of Waasis, near Fredericton, attempted to capture on videotape an animal he believed to be a cougar, but the fuzzy images allowed no independent identification.

There was hope of solving the mystery of the cat's existence when a cougar was shot on May 27, 1992, in front of a house in Saint-Lambert-de-Desmeloizes, in the Abitibi region of Quebec. But that turned out to be a South American cougar that had escaped after being brought north as an exotic pet.

Cougar tracks and scat found near Deersdale, N.B., in 1992 were tantalizing, but offered no evidence whether this was a wild cougar or another escaped pet.

Then, in 2000, a truck driver contacted Dr. Gauthier, a wildlife biologist at the small research company Envirotel 3000 in Sherbrooke, saying he had hit a cougar with his rig near East Hereford, in Quebec's Eastern Townships. He asked whether the scientist could identify the animal's origins: Was it another escaped zoo animal or a true eastern cougar?

To solve the puzzle, Dr. Stroeher began looking for molecular markers that uniquely characterize the DNA of cougars.

Meanwhile, Dr. Gauthier began setting up poles, scented with cougar urine, in the Gaspe region, the Eastern Townships and the Mont Tremblant area of Quebec to attract the cats. The poles were covered with velcro to catch the animals' hairs. If any cougars were out there, he hoped to capture evidence of their existence. The breakthrough came in August, when a hair sample collected by Dr. Gauthier in the Gaspe came up positive in Dr. Stroeher's lab.

"My student came in. He's a very serious student. He always has a furrow in his brow. He looks at me and he says: I've got an interesting result," Dr. Stroeher recalled. "He said: 'I've worked this up, I've done the reactions three times, and I keep getting a cougar.' We re-did the whole procedure from the hairs on, and sure enough. We definitely have a cougar."

Where did the Gaspe cougar come from? There are only three possible explanations, Dr. Stroeher said.

The first is that it escaped from a zoo or from an owner who kept it as an exotic pet.

The second is that cougars from elsewhere in North America are returning to colonize their old habitat in the East.

The third explanation is that the secretive eastern cougar never really died out. "It's possible they just hunkered in, somewhere north of here, and because we have such an expansion in prey, they're coming down again."

As she refines her molecular analysis techniques, Dr. Stroeher hopes she will eventually be able to tell the difference between cougars native to the Rocky Mountains, South America, the Florida Peninsula and eastern North America, based only on their DNA samples. That, together with Dr. Gauthier's research, could provide evidence about how many cougars are roaming through Eastern Canada and where they came from.