Hmm, I was about to post an entire new thread about animals going aggro based on vengence, how many monsters of that breed killed, e.t.c
You kill 40+ forest wolves and you\'re now hunted by them whenever you enter their particular \"territory\", or are relentlessly chased by them and their more powerfull bretheren when in combat with them. A little unreasonable, as I wouldn\'t ever want to kill more than 10 of the same animal over and over, monotony in MMORPG\'s are a major turn off for moi.
Again, you kill a bunch of lizardmen lets say, now this is a bit more exciting! Not only are you marked as an enemy by the lizard men, you suffer trading penalties with lizard merchants, you are bounty to their \"Lizararman Mercenaries\" , and are a favored target in the city raids, or caravan raids.
Same against a tribe of sorcerers, or any other sentient being.
Animals, would be afraid of you, and wouldn\'t befriend you much after a couple massacering of their kind. Though, killing in their presence might make them aggro if they were not otherwise.
This goes with my preference of not killing animals unless they are for game like pelts or meat. But of course, barbarian-like tribes of lizard men are xp cows!