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.
Best Answer
"Do Thresher Maws have a "nest" zone where they stay and don't venture from?"
Yes, they typically occupy an area, if you drive over that area, they will try to pop up and either do a spit attack or melee the mako if they are close.
"Do I have to keep rolling around that zone for them to continue engaging me?"
No, but I highly recommend staying on the move as they can 1 shot you with their melee attack if they pop up near the mako. And as you noticed, if they pop up under you, you will instantly die.
As to how to identify the nest zones, the wiki entry has some great suggestions.