How do civs gain familiarity with a given creature? Is it a guaranteed thing that if the creature is nearby and PET/PET_EXOTIC, then it will be tamed, or is it a chance/probability thing, or does it rely on historical figures to take a hand in the process?
Will Fort knowledge flow back to the civ in some way? Such that a fort that manages to tame a dragon will be able to impart some measure of knowledge back to the civ, so that if a subsequent fort also catches a dragon it will be easier to tame.
How does this alter the PET_EXOTIC tag? Is it obsolete, or does it signify a creature more difficult to domesticate than another? Speaking of, are some creatures more difficult to tame than others? I imagine if a civ has roughly equal numbers of wild dogs and, say, honey badgers in the area, the dogs would be more readily domesticated. Not that I pretend to any knowledge of what makes a creature easy/difficult to domesticate.
RE: DM disappearance, I'm not that sad. Sure, his idiosyncrasies were cool and all, but I'd rather dorfs be able to figure things out for themselves instead of relying on arbitrary nobles to teach/unlock things. It might be cool to have a Beast Master type noble similar in function to the Chief Medical Dwarf, where the Beast Master would be the guy who takes first crack at the more dangerous animals (thus ensuring that your most talented trainer is on the most valuable job,) but that kind of functionality shouldn't be associated with a random migrant.
I'm halfway tempted to ask if the DM getting the axe is a portent of things to come for the other absent/useless nobles (*coughPHILOSOPHERcough*,) but I suspect that's a bit farther afield than the near term releases.