My batmen got names, too... I think it just happens if creatures like that stick around for 3 or 4 years. I think I started with 6.
One got "overfriendly", and managed to fly into my fort's open doorway in my first year, and flew into a cage trap. Trying to move him accidentally wound up releasing him (should have built cage, not moved to a new cage), and led to quite the runaround, and killed one of the mayor's pet cats. (The only female I had imported, although she had JUST given birth, so there was a female kitten.)
The rest have been basically decorating my minimap's far northwest or southeast corners, generally around 10 floors above ground level, causing no problems.
Then this summer's human caravan showed up, and they shot down two of my poor batmen. (I actually watched that...)
In relation to things I only realize when I look at engravings, all I really get are tons and tons of failed elven seiges of the nearby goblin fortress. (You'd think they'd run out of elves eventually, but legends say that elves are willing to throw out dozens of sacrifices annually.)
I did, however, get surprised to find out that butchering the absurd number of puppies I get will actually show up as an engraving, which prevented me from slaughtering more (I just slaughter higher-value unicorns, and cows, now... working on getting high enough 'gator, bear, and giant jaguar populations to slaughter those, too).
I also used Dwarf Companion to look up a training accident that happened early on in my fort - turns out that my dwarf died because the then-highest trained axedwarf in my fort had put an unqualitied copper (no silver at that time) axe STRAIGHT THROUGH THE HEART of her sparring partner, taking out a lung and spleen, as well. No wonder he only left two tiles of blood trail behind him before bleeding out. (My first knowledge of the event was the "has bled out" message, and you can't check wounds on a corpse)