Cinder blocks scattered around standing on end should slow them down on the snow mobiles.
If you can find out who did it you can legally prosecute them for destroying your property and farm crop. Even if it is only for feeding ducks and turtles. Get enviro activist nutty on their *** and claim it is a food source for indigenous wildlife.
Is the property posted as per the local laws regarding "Posted"???
After you have it legally posted as per local laws:
Even if you dont know who did it, immediately schedule an appointment with the Sherrif or Police Sergent. Fill out a report about the:
1 trespassing and criminal mischief
2 intentional or willful destruction of private property including destroying cultivated soil and crops and your driveway
3 disturbing the peace and aggravated intrusion into your privacy.
4 destruction of your front yard or driveway
Come equipped to the PD with a written summary of the stuff they did including date time, a summary of the land, crops, driveway, or anything which was disturbed or destroyed, and include the necessary repairs needed to fix what they destroyed. the nesessary ammound of damage estimated in dollars to fix the physical damage.
If the Police are not interested in taking care of you, let them know that you will be immediately contacting as many environmental groups and government agencies necessary to get the attention needed to deem the property as being damaged by the trespassing.
You have to get this on record to legally handle it.
Otherwise you can just shoot rock salt at them like mentioned above (not sure if that is legal) and put up fences, piles of boulders and cinder blocks, moats full of pissed off alligators, flaming scarecrows, pyrotechnics, remotely controlled catapults loaded with bags of flaming cow crap.
I like the rock salt, rpg and claymore idea also although I am not certain they sell that stuff at Walmart any more.
