Capuchin monkeys are the smartest monkeys in South America. And they are pretty violent.

I volunteered in an animal rescue centre in the Amazon and the alpha female hated women and blonde women in particular. I wasn't paying attention one day and she almost scalped me. Then on another day one of her boyfriends came after me and I had to hide behind one the male volunteers in the first cage bit (since there's mulitple cages so they can't escape).

Good times!