The rat problem is city-wide and with warmer weather on the way, the population is expected to multiply.
They can grow to be a foot long and squeeze through a hole the size of a quarter.
"The colder it is, they try to find a way inside of a house or building to keep warm," said Lee Fondern, A-1 Pestmaster technician.
At A-1 Pestmaster, the calls have been coming in non-stop with homeowners reporting a rat invasion and technicians laying rat poison in one corner after another.
"They'll reproduce, they'll eat anything," said Carolyn Bowman, A-1 Pestmaster. "They can chew through pipe. They can tread water for three days. They are the amazing rodent."
At least one alderman has seen enough.
"We do have a problem, let's acknowledge it," said 2nd Ward Alderman Bob Fioretti. "Let's try to find a way to deal with it and then make sure it's effective."
Fioretti now wants Chicago to take a page out of New York City's rat playbook and hire a company that's devised a way to sterilize rats with a special liquid.
"There's nothing wrong with taking an idea from another city, maybe building it up, putting it into the problems that we have here in this city," he said.
"If you can control the breeding process, you can control the problem," Bowman said.
The city's preferred method is to poison the rats and during this harsh winter, officials say they've increased preventive measures by 20 percent compared to last winter.
Last month, the Chicago Streets and Sanitation commissioner was confident they had a handle on the problem.
"The young rats have a difficult time surviving, so that we should see fewer rats on the streets and certainly fewer rats in the spring," said Commissioner Charles Williams.
The city says calls to 311 about rats are actually down this winter.
But Thursday, Mayor Rahm Emanuel said he'd explore the use of that rat sterilizer the Big Apple uses.
"I'm always interested in new ideas to address an old problem," Emanuel said.
The company that produces the rat sterilizer said its product has led to a 40 percent reduction in the rat population in some parts of New York City and Thursday Emanuel confirmed that Streets and Sanitation officials have a meeting scheduled with that company.