Thanks for the input guys! All things seem to point to predators, though. Mauser, good point about pesticides. I never thought of that. Ususally, the plows don't destroy the holes because they mostly burrow under and around boulders imbedded in the field and create mounds. Alsoaround stumps and wood lines. Plows & harvesters avoid them.If you spot a bump with tall grass in the middle of a field, 9 out of10 times you will find chuck there. As far as crop rotation, the fields I hunt are mostly pasture for cattle & livestock...grass & clover. One of my usual hunting farms was sold last year & the new owner flipped everything to corn & planted orchards. No good. But that's the exception in my case. The only other variable could be pesticides, which I could understand. I guess it's time to start knocking on doors again.