“Op-Ed: Rats bigger than cows? Could be.” Evolution may be adjusting to fill areas and some species may go the way of the dinosaurs. I don’t think this will be happening right away, but think about the ramifications if rodents did become bigger. I might have to arm the technicians with rifles, no – not going to happen. I didn’t realize that the largest rodent was the size of a bull and weighed over 2000 pounds. Can you just imagine that?