Well someone can correct me if these are wrong but here goes:
AMBUSHPREDATOR -> Like giant cave spiders.
BENIGN -> Determines whether creature can show up on "tame" maps (includes elephants), which will generally avoid dwarves, although they may chase and/or attack them if they get too close).
BUILDINGDESTROYER ->Allows a creature to destroy furniture and buildings. (Giant Cave Spiders have this at 1, but most other creatures have it at 2. The difference between these values is unknown.) So 2 for destroy stuff, 1 is unknown at the moment.
CURIOUSBEAST -> I think this makes them steal items/ changes behavior, the wiki says you can add an _ITEM or _GUZZLER for items and alcohol.
NEUTRAL/EVIL/GOOD -> Only affects maps if I recall correctly, all animals attack if provoked EVIL can let goblins use them in sieges.
LARGE_ROAMING/LARGE_PREDATOR -> Predators attack without provocation roaming don't.
MEANDERER -> Means when moving they meander, instead of going straight, will not go straight to fortress.
PATTERNFLIER -> I'm not completely sure but it seems to be on all the flying animal men, might effect there behavior/ make them seem more intelligent, this is the only thing I'm not sure on.
(Most from the wiki, check harder next time.)
[ April 27, 2008: Message edited by: Corpze ]