The hook that holds the device in place does not grab it very well so it takes very little to set these off. I had all 4 set out and the next day when I came outside 3 of them had been set off but the "bait" wasn't disturbed. I reset them as I was doing yard work. There was a decent breeze blowing through at one point and it caused 2 of the traps to go off. I ended up throwing them away.