It's not more hunters, the alfalfa farmers have been more aggressive managing the rats. Bait stations are standard now, but most effective, they've been ripping the top two feet of dirt every few winters. Only takes a couple days per pivot, and completely wipes out the hibernating rats.
You might scout Dinsdale Farms in northern Lake County. Sign in at the office on Arrow Gap Rd, a bit north of the junction with Christmas Valley Hwy. Dinsdale rules: 22LR only (no 17HMR, 22mag or centerfire) and rats only (no badgers or coyotes). When we scouted Dinsdale fields in May, the pivots near the office seemed most promising. We guide on Simplot pivots, more rats, all calibers OK, and long range rifle steel for when rats gets shy.