On our rural property , after getting pics similar to yours ( two dudes on 4 wheelers at 1:00 in the morning ) I added these words to our posted signs " this property is now booby trapped, travel at your own risk " ! It wasn't but problem solved.
Present day surburban property , another trail cam stolen about a month ago . Now there is one that is defective ( imagine that ) that has a tracking device in it , exactly like the ones worn in ankle bracelets, if the cam moves outof the 100 ft "fence " it is tracking ,,, all the way into their house step by step ,, Imagine when we get to knock on that door with an officer to ask for our camera back ?