I had one encounter with animal people. They hanged out in woods on my way to cave entrance to underground.
At first I walked with my companions. They charged them as any other group of alike animals (but not animal people!) to kill them. I charged them too. They had same symbol as the animals too, I think. However the animal woman I was chasing started to screaming "Help me!". A little like a wounded Night Creature screaming "Help me!", when my peasant dwarf gets close and personal with steel ax and his legendary ax skills. However animal woman stopped running away, not seeing my companions. So I stopped too. I talked with her and she was talkative, until my companions arrived and she took off in panic again.
On returning way I decided to spring forward, getting slowly away from companions. I run into this group of animal people again. When I saw them I shouted my introduction and entered conversation with them. Strangely enough my companions didn't attack these animal people again. Maybe, because my shouting conversation? Anyhow they had nothing on them. No cloths, no tools, no nothing, so I decided to give them the simple stone axes I had with me for trading. Then I wished them farewell and took off with my 6 companions following closely behind.
I felt kind of pity, they just camped around without any wagons, any cloths (maybe they don't need, but how about armor), any tools. I wondered, if in future versions, maybe such gift of stone axes could spark a animal people tree-village (alike elvish one) and maybe even an animal civilization.
For now animal people are like wild animals in woods. Just another animal group, randomly spawned at front of you, to slow you down walking and if you walking same path repetitiously... to overpopulate this path to make it slow in fps and sometimes to crash your game to desktop. However killing entire group of animals, without crouching and stalking and with noisy 6 companions in metal armor... is impossible. DF needs
"DE-SPAWN THE DARN ANIMALS!!!"-procedure, which will be implemented in sectors of land, you left behind you.