No, no, no, you've got the solution all wrong. First you bring in a feral cat to eat the feral rat, then you bring in a feral dog to chase off the feral cat that ate the feral rat, then you bring in a feral tiger to chase off the feral dog that chased off the feral cat that ate the feral rat, then you bring in a feral elephant to stomp on the feral tiger that chased off the feral dog that chased off the feral cat that ate the feral rat.

Then you have a feral elephant problem. Easy.