I've noticed that I often have animals in my dreams: usually threatening ones. The most common are bears and sharks! I wonder what my subconscious is trying to tell me? Note to self: If you see a shark or bear outside of a zoo or TV, do a RC. You're dreaming sucka!
Fear itself is a huge dream sign for many people. I used it myself to start lucid dreaming as a kid, I've also had nightmares about bears ever since I was a kid but somehow they've never made me realise I'm dreaming...