Don't bother petting these cats -- they're working

About five years ago, Chicago resident Paul Nickerson turned to a trio of cats to deal with a rodent infestation after higher-tech pest-control methods failed. He figured he had nothing to lose.“It got to the point where my neighbors and I couldn’t walk out of our back doors to throw the garbage out at night because rats would be running over our feet,” Nickerson said.The cats came from a Tree House Humane Society program that places animals that aren’t suited for life as