The mountain lion that passed through Greenwich a year ago is an indication, however extreme, that the big cats are spreading out from the western United States into the Midwest and the Canadian provinces, according to a new study.

For Paul Rego, wildlife biologist with the state's Department of Energy and Environmental Protection, it isn't a surprise that mountain lions, also known as cougars, are moving back into the Midwest.

"To me it is actually not news," he said of the study's findings, which are detailed in the June edition of the Journal of Wildlife Management. "It has been an increasing trend in the Midwest, the expansion of their territory."

One of the study's authors, Michelle LaRue, a Ph.D. student at the University of Minnesota, said mountain lions are rebounding dramatically after a century of decline.

"The cougar population declined dramatically from 1900, due to both hunting and a lack of prey, leaving the remaining population isolated to the American West," LaRue said. "Here we present the hard evidence that the Western population has spread, with mountain lion populations re-establishing across the Midwest."

Three main mountain lion populations exist in the Midwest, centered around the Black Hills in South Dakota, however, cougars are venturing far outside of this range, according to the study.

One male mountain lion from the Black Hills was found to have traveled more than 1,500 miles through Minnesota, Wisconsin and New York, before ending up in Greenwich last June. The mountain lion, which trekked more than twice as far as the longest dispersal pattern ever recorded for the species, was seen and photographed at the King Street campus of Brunswick School.

The mountain lion is believed to be the same one killed when it was struck on the Wilbur Cross Parkway in Milford on June 11, 2011.

Even with the spread of mountain lions, the chance of another Western one traveling to Connecticut is remote, Rego said.

"I'd say in Connecticut probably not in my lifetime," he said. "That was just phenomenally exceptional."

The chance of a mountain lion population developing in Connecticut is even more unlikely, said Rego, who has a quarter-century of experience as a state wildlife biologist.

Denise Savageau, the Greenwich conservation director, also said the mountain lion's presence in the region was a rare event. She, like Rego, agrees with the study's finding that cougars are branching out from their Western redoubt.

But Savageau, who cautioned that her expertise is not in wildlife management, said there could be another reason for mountain lions' dispersal -- humans' effect on the animals.

"Their habitats are being decreased," she said. "They might not have our scale of development (in the West), but they still do have it."

Familiarity with humans may be another reason for more sightings, Savageau said.

While wild animals tend to avoid human contact, centuries of living next to and among humans may make mountain lions feel slightly more comfortable being near them, she said.

It doesn't mean the animals will boldly come up to humans, she said, but it could mean they are more comfortable staying relatively close.

Working with scientists from Southern Illinois University and the Cougar Network, LaRue and Clay Nielsen, assistant professor at Southern Illinois University, analyzed mountain lion sightings since the 1990s.

The study's results reveal 178 cougar confirmations in the Midwest, with the number of confirmations steadily increasing between 1990 and 2008. Approximately 62 percent of confirmed sightings took place within 12 miles of habitat that would be considered suitable for mountain lion populations.

Of the carcasses recovered, 76 percent were male. As the Connecticut example shows, males are capable of traveling long distances. This finding suggests males are leading a stepping-stone dispersal of the cougar population, according to the study.

"This evidence helps to confirm that cougars are re-colonizing their historical range and reveals that sightings have increased over the past two decades," LaRue said. "The question now is how the public will respond after living without large carnivores for a century.

"We believe public awareness campaigns and conservation strategies are required across these states, such as the mountain lion response plans already in place in Nebraska and Missouri."