Just like humans give off indicators as to how they are feeling at the moment, animals provide cues to what they are thinking and experiencing as well. Here’s a few resources to help you interpret what’s happening:
Canine body language – This short document from the ASPCA Pro site provides you the basics of dog behavior. From what the eyes and mouth tell you, to what the ears and tail are indicating this is a short (4 pp) document that gives you the basics of dog behavior indicators.
Cat body language indicators – From the catster.com site, this short (3 pp) document gives you an explanation of what a cat is thinking by analyzing what’s going on with their ears and tail. There’s also some graphics that make it easy to see at a glance.
Rabbit body language – From the rabbitspeak.com site there are some great indicators of rabbits. If you are new to rabbits this document will help you understand what it means when a rabbit turns its back on you.