::shrug:: There are a lot of animals that are capable of doing things that could be considered "evil" or "bad", that we can't just pass off as their nature. For example, I heard about an elephant that was kept in a cage away from the public at a zoo because he was so dangerous. A woman sneaked in one night to see him because she felt sorry for him. The elephant proceeded to kill and eat her. Normally, elephants don't EAT people, that I know of. They might attack and kill you, though. Is that evil or is it just the nature of the elephant to do that?
Also, one of my cats is bipolar and VERY smart, from everything I've ever seen. He's perfectly capable of doing malicious things. My wife has told me many stories of stuff he did before we met (she had him for about 5 years before we met) like pooping in an old boyfriend's shoes because he (the cat) didn't like him, scaring the crap out of one of her old roommates by hiding in his room and jumping out at him, etc. I suppose you could say he's evil in some ways. He's a very friendly cat once you gain his trust, though.
I've also heard of chimps ganging up and killing other chimps for sport. Not to mention, what about black widows? They kill and eat their mates.