I would say yes. Evil implies a choice, and animals have no choice in their actions. Their actions are predetermined by their instincts. An animal is no more evil than a rock that falls off a high place and lands on someone's head and kills them. The rock's action is predetermined by gravity. This is likely why we don't put insane people into prisons. They are like animals. Rationality is a requirement because a moral decision is just that, a decision.
Thats a very good point, but I have a question (A little bit off topic). Suppose we are not free beings, suppose our actions are totally determined and that our option to choose is unexistant, in other words, pure determination. Many people defend this, I personally don't, I think human beings are free, but if they were not...do you think we could blamne them for their actions? It would kind of bring the whole concept of justice down, but it's the idea I have every time I read the opinions of a determinist.