*Edit* No it isn't! Ignore the post that follows, turns out the attack() method detects the mobs.

I have a melee turtle sitting at the bottom of a standard 23-blck gravity drop mob trap, in a loop doing "if turtle.detect() then turtle.attack() end". The documentation says that turtle.detect() does not detect mobs, and yet the turtle only attacks when there are mobs there. Could this be to do with the stone pressure plate? Is the pressure plate detecting as a block only when it is pressed by a mob?