CHICAGO (CBS) — The city says complaints about rats are up 30 percent from November to February (9,207) compared to the same period one year ago (7,080).

Dept. of Streets and Sanitation Commissioner, Charles Williams, says it is largely due to the unusual weather. “We had a very mild winter; in fact, it was almost a record winter. So yes, that’s going to create more rodents. Often times, if you have a very bad winter, the younger rodents in those burrows don’t survive.”

It’s also thought that more complaints might be due, in part, to new posters the city put up in outreach efforts. One poster reads, “Don’t Feed The Rats! If rats can’t feed, they can’t breed.”

Chicago had to stop using dry ice, which is a method used to suffocate rats by placing it in burrows.

According to Streets and Sanitation, using dry ice to kill rats is on hiatus because it was not approved on federal Environmental Protection Agency (EPA) officials list of rodenticides for any city, yet. They started using this method in August of 2016 and stopped in December of 2016.

Williams said this method doesn’t work everywhere, but that it is effective in park settings. And added that he thinks using dry ice is humane, saying, “You’re putting the rats to sleep permanently.”

The city of Chicago is working with the Illinois Dept. of Public Health and state EPA to get an application in for registration with the EPA to use this method again. Williams said he hopes this happens, as the only way to control the rodent population is to kill them.

Another poster featured ways to help eliminate the rat problem in the Chicago area:

  • Keep garbage contained within closed bins
  • Ensure dog waste is disposed in sealed containers
  • Keep pet food indoors
  • Remove old tires, lumber or other piles of debris
  • Maintain fruit and vegetable from gardens
  • Maintain bird feeders

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