My experience...the little ones are the ones to watch out for. They don't show fear. I had a little 2 footer rattle at my work truck when I was in college, and I was sitting there idling. I've also heard the young ones don't "know" to hold back some of their venom so they deliver everything they have with one strike. In my experience, the grown ones high tail it out of there if they know you're coming. I stepped on one as I stepped up onto a culvert one day, and I'm not sure who was more rattled, I didn't know until I felt something squishy in the grass under foot, and it hightailed it into the culvert. Anytime we ever tried to kill one, we would have to run after them and tap them with the shovel before they would coil up and rattle to where we could chop off the head with the shovel. Most times they put their head under their coils as they rattle so you have to work to get the head out.