1,000 Cats Released from Shelter to Tackle Chicago Rat Problem The city of Chicago has a rat problem. A big one. And the Tree House Humane Society thinks they have a solution. And honestly, I'm thinking it's pretty brilliant. The Humane Society's "Cats at Work" program is being used to combat the massive rodent issue in what they are calling an "environmentally friendly, feline solution." Since 2012, the program has released 1,000 feral cats into the city for rat control. The cats are humanely caught, and then spayed and neutered before they are released back into areas that are experiencing a problem. And it seems to be a win-win solution for the stray cat AND rodent population that has seemingly spiraled out of control.