There has never been a closed season on state or private ground in SD. AS I said, federal and Indian reservations are another story, and the ranger was most likely referring to ederal lands, as that is in their jurisdiction. State conservation officers are whom you should reference questions regarding state and private lands to. The rangers on the National Grasslands have no jurisdiction over private lands, and likely aren't familiar with state laws regarding such things. The info he gave you may well have been accurate regarding federal lands. I have no reason to hunt federal land, as my family owns a ranch with a small resident prairie dog population (and smaller each year, as we poison the things to save pastureland and prevent their spread) and I can get my fill of shooting them there. Being a licensed "pesticide applicator" my father is well versed in the laws regarding prairie dogs.