I would make a temporary cage type fence and tackle one ant hill at a time. They go after the stuff like crazy, they don't move away from it. They think it's food. Kind of sad really. Our ants never came back and we had the largest ant hills I've ever seen.While fencing ant hills is a good idea for this purpose and we did consider this, but it seems there are just too many to fence. We have over 15 ant holes...I do wonder if it is all the same colony, though. They are spread out throughout the yard, it would probably be a lot of fence =P