A ways back, when my ex and lived in a garden apartment, a rat wandered inside. I believe it was a young one, looking for a home. About 3 seconds after it passed the threshhold, our larger cat [about 20 lb but NOT fat] attacked it. Shortly thereafter, there was one dead rat and one very proud cat. My input was staying out of the way and cheering him on.

Of course, Chongo Chimp would also fill this ecological niche.