Free: Contests & Raffles.
I think the only way this stops is if there's enough bait to bring them out, catch in the act, then have a good talk with them. They obviously don't care about law enforcement, with the lack of, or the current court systems that favor criminals.
I haven't tried any of the trackers but would seriously consider it if I had an ATV.https://www.amazon.com/LandAirSea-Waterproof-Magnetic-Personal-Location/dp/B06XVZ6Y4T/ref=sr_1_3?crid=35BN7U2CS51IB&keywords=gps+tracker+for+vehicles&qid=1643301228&sprefix=gps+tracker%2Caps%2C167&sr=8-3Pretty cheap but you would have to recharge the battery on this one often. Knowing me I would try to wire it to the vehicle's power.
$20 a month on top of the purchase price. Might be better options, that's just the one I saw.There are other trackers that use bluetooth but you would obviously have to be pretty close to it.If they were only being stolen when used it wouldn't be bad to pay for a month during hunting season but it sounds like a bunch disappear out of back yards so you would have to pay all year.