A while back I had the same problem. The little buggers ate the insulation off my fuel injector wires. Luckily no damage or electrical shorts. I thought it was squirrels, but figured they were probably chipmunks or mice instead. I have always found a few tree nuts sitting on top of the tranny and engine everytime I checked under the hood. I called the local animal exterminator to see what my options were. They were way too expensive. They told me putting mouse/rat poisen out for chipmunks was illegal. But if it was intended for mice/rat's and the chipmunks got into it then not a problem. I bought a couple rat poisen packs and added a little peanut butter. I placed the poisen packs in my engine compartment so anything large couldn't get to it like the local farm cats. The cats take care of most of the rodents (unfortunately birds as well), but I think those chipmunks may be too fast for the cats. I actually caught one of the cats stalking a chipmunk/mouse hiding under under my car. The chipmunk/mouse heard me open the car door and ran. The cat gave chase, but no luck. The rat poisen did seem to help though. I noticed a significant decrease in tree nuts in the engine compartment. None of the barn cats or neighbor's dogs died or went missing.