CHICAGO (CBS) — We’ve gotten used to seeing a lot of wildlife, such as deer, foxes and coyotes, closer to our homes.

But as CBS 2′s Bill Kurtis reports, there is something else, something more dangerous, which may be lurking nearby: cougars.

We’re used to seeing them here at the zoo.  But one night last October, Jane Stickney says she saw a large cat in her quiet Lake Forest neighborhood.  She was walking her dog when it popped out of the tall grass.

“It definitely was a big cat. I just couldn’t believe it,” she says.  “I could really see the outline of its head, the ears, the tail.”

Stickney’s sighting is unconfirmed. But on April 14, 2008, Chicago police definitely encountered a cougar in the Roscoe Village neighborhood.

The cat appeared ready to attack. Officers opened fire.  That cougar’s remains are now at the Field Museum.

“He’s quite a formidable predator,” says Bruce Patterson, a curator of mammals for the museum’s zoology department.

More and more of these big cats are turning up in the Midwest, according to Southern Illinois University wildlife ecologist Clayton Nielsen.  So, why are the cougars migrating eastward?

“Cougars are attempting to recolonize their former habitat in the Midwest,” Nielsen says.

Illinois has had three confirmed cougar sightings in the last 10 years.  Since 2008, Wisconsin has had even more confirmed cougar sightings.

“We’ve had at least six individuals identified in Wisconsin,” Adrian Wydeven, mammal ecologist with the Wisconsin Department of Natural Resources, says.

He discovered that paw prints found on a snowy Wisconsin farm belonged to the cougar killed in Chicago. The DNA analysis indicated the animal most likely originated from the Black Hills of South Dakota.

He also tracked another cougar killed in Connecticut last year. In 2010, it was captured on a Wisconsin trail camera. The animal was also photographed in 2009 by a police dashboard camera near Minneapolis.

In all, that cougar travelled 1,500 miles.

“It represented a longer distance movement than had ever been recorded for a cougar,” Wydeven said.

So can expect to see many more cougars?

“It seems almost inevitable that dispersing males and females will find each other and they can get families going,” Patterson says.

Cougars are already living and breeding near major cities like Seattle, Denver and Los Angeles.

And, closer to home, there have been many more confirmed sightings in Missouri and Iowa.

Experts say the cats can swim the Mississippi River. If you encounter one, the experts say you should stand your ground, act “big,” wave your arms and yell.