DENVER -- Some people think of mice as pets.

Some people feed mice to their pets and some people are creeped out by mice.

Experts at several major pest control firms tell 7NEWS they've seen a large increase in the number of calls for mouse and rodent control, up about 40 percent over last year.

The calls are coming from all over the metro area, including Denver, Thornton, even Cherry Hills Village.

"Yeah, I saw a mouse last week," said Gennadiy Ketslakh, who lives in southeast Denver. "He or she ran along here (front wall of his house) then disappeared down this hole." Ketslakh pointed to an opening for a utility wire conduit leading into his crawl space.

Ketslakh's neighbor, Larry Gray, has seen mice recently, too.

"Mice have been right out here on the grass," Gray said. "They try to get in through holes or dark spaces and then into the house or crawl space."

Gray said his dogs chase them back out.

John Davis, president and general manager of Moore Pest Control Service, attributes the increase in mice to Mother Nature.

"There has been no real deep enough freeze in the last couple of years," Davis said, "so there's been no mortality for the inside rodents and for the voles, or meadow mice."

Keith Kohler, service manager at Moore Pest Control, said another likely reason more mice have moved into the metro area is that development on the fringe of the city is tearing up their normal habitat.

Davis told 7NEWS that a mouse can crawl through an opening measuring 1/4 inch by 1/2 inch.

He said homeowner can keep mice out of their homes by sealing up the openings using steel wool and glue.