I've never seen a link mention that gliders don't always crab from fear. Very long, loud crabbing, yes, but there are shorter bursts of fussing that simply seem to indicate annoyance. I only get these from one of my gliders, and it happens when I disturb him while he's sleepy. He's not ready to wake up and gets upset I'm bothering him, but I highly doubt he's scared since he never does this when he's fully awake.
Has anyone else experienced this or is it just Xor?