We have deer, of course, cayotes, fox, tons of hawks and literally a bazillion red cardinals flitting back and forth on the access lane and the pasture from yaupon holly clump to clulmp (it's tightly wrapped around every single tree trunk and cardinals love to nest in 5-7' dense vegetation like that). And they are everpresent year-round. So movement sensors would likely be sounding off the inside chime non-stop (from the cardinals alone) and we might go crazy with those. But we might have to pay that price to catch human intruders we DON'T want. We thought about cameras, but unless connected inside to rule out wild fauna activity, that, too might get to be problematic and we'd have to have SO MANY of them to protect the full perimeter of 42 acres.
Get one with adjustable volume, keep it turned down in normal times but if TSHTF turn it up dusk til dawn, Cameras have to be watched to catch bad people in real time. something that buzzes or dings is better. You could use the more developed Microwave and PIR combined detectors that can distinguish by size, which helps reduce false alarms. if TSHTF someone in the house is going to be on duty overnight anyway listening for the warning buzzer.