Large rodents. I trapped for a guy, way back in high school. Guy had 3 ponds built, filled & stocked. Good sized ponds with old growth trees along the waters edge. He was in the truck with some DNR people, looked at me and I quote "leave the beavers alone, you trap a beaver & I find out....you're done." So, I let the beavers be. That fall they fell 3 large trees...into his field. I didn't say anything. That next fall I see more trees laying down & the top pond spillway had been plugged, it flooded around one end & ended up washing out & draining that pond. He said "trap every beaver that you can".