You're seeing them make noises in one direction and track you because they likely do use some form of echolocation like bats... and they're still not going to be able to take over the world or be "tamed" into helping us in our fight against the Thalmor. I'm pretty sure if it moves and wasn't with them before the fight started that the Falmer kill it, end of. I've found dead Falmer in caves where only Falmer are, as if to suggest they even kill eachother.
And yeah, there's a cart outside of Dragon Bridge and down to the junction where you can find Falmer arrows and an obvious looting scene. They're definately venturing above ground.
A guard at Whiterun will give you a quest to go investigate if you don't get the radiant quest from the Companions. He says he saw the ugliest little creature outside that cave that he's ever seen. Charus?
anyway... yeah... I don't think they're a reliable resource. I think they'd like us all to go home now and we're not going, so... we'll slowly wipe them out one cave settlement at a time until there aren't enough of them to repopulate.
btw... anyone seen YOUNG Falmer? or GIRL Falmer? just a curiosity.
