Simply mowing the grass becomes a dangerous game when the area is riddled with ground squirrel holes. People have injured their back when their mower hit a ground squirrel hole. Yes, people go out on disability because ground squirrels were considered a little nuisance.
Besides personal injury, mowers and tractors can be damaged and grass cutting blades dulled. Shakers will refuse to bring in the walnut crops when an orchard has too many holes because they need to protect their workers and equipment.
Another option is visiting me in person. If you need California DPR continuing education units, I'll be speaking at the upcoming PAPA Seminars:
7/11/18 San Diego