Do you have any photos of the animals? Are you sure they are nutria and not muskrats or beavers? Nutria really do a lot of damage. It would be a good idea to let the Illinois Department of Natural Resources wildlife biologist know about the damage. In your area, the biologist is Ryan Swearingin. Ryan can be reached at (618) 462-1181 ext. 146. He can give you tips for trapping the nutria, but if it is another species causing the damage, he can issue a nuisance animal permit (the permit is free).