I am fine with snapping turtles in my pond. They are a great clean up crew. They are not aggressive when in water. They rarely kill healthy fish. They taste good. And good luck keeping them out. My only real concern with them, is when the females migrate ashore to lay eggs, is that my dogs will mess with them, and end up getting bit in the nose. When I find them in the yard, I relocate them, would eat them at that time, but I don't want to prevent them from laying their eggs. Also most states have laws which do not allow you to kill them when they are gravid, and have certain dates when they are out of season. I have several that have learned when feeding time is, and seem to love Aquamax. Also about the frogs, though it is counter intuitive, bullfrogs, and green frogs, tend to migrate away from ponds in mid summer. I do not fully understand why, but have read it many times.
