In the first Mass Effect, I've had several times where I heard the rumbling and screaming of a Thresher Maw appearing, but when I wheeled around my Mako and got ready to fight, there was simply nothing there. It seems they pop up, but I'm already out of their range (or it's a bug, that's always possible).
My question is this: do Thresher Maws have a "nest" zone where they stay and don't venture from? Do I have to keep rolling around that zone for them to continue engaging me? And if there are such zones, how can I tell where they begin and end? I want to fight those things, they're fun battles, and give a ton of experience points.
If you're feeling super generous, some tips on how to prevent trivial deaths would be helpful too. I have had a few times where, during one of these fights, the Maw suddenly appeared right under me and I died instantly. Needless to say those kind of deaths are less than satisfying.