I've installed camera to catch a recording of rats breaking through from next door's garden. Last night a rat came through but the camera wasn't activated, I was pure luck that I was looking at the time, I just caught the the action halfway through. 

I have the detection set at 10, the zone in the right place and set for pets etc. It records if one of our dogs goes near it. The rest was about 6 inches long and the camera is only about 3 feet from the action. Any ideas why it doesn't start recording when the rat appeared?