We have rat breeding animals, now we only need rat killing animals to complete a rat powered animal farm. I know thereis already the kill animals option for rats, but the rat will just kill every single animals in that option, so I suggest a upgrade that make rats leave behind some adult animals for breeding, if the number of adult animals in the radius exceed that amount, the rat will kill extra animals. The upgrade should have the ability to config the animal inside the game, like the miner upgrade. This upgrade is an upgrade to the killing animals options so rats will work with this upgrade in that mode, that mean they wont pickup items and can have a looting tool for killing.