The big challenge that you face with this topic is deciding how to find your focus, either by focusing in on a specific animal and/or by focusing in on a specific cultural tradition.
As you can see, some of the animal Storybooks overlap with other topics, so you might want to take a look at some of the topics that lend themselves to stories with animal characters: Creation Stories, Jataka Tales, Bible Stories, Greco-Roman Mythology, Aesop's Fables, Native American Traditions, and Fairy Tales & Nursery Rhymes.
Online Resources: There are myths and legends from all over the world that feature animal characters, so by browsing through the Online Books, you can find literally hundreds and hundreds of animal stories. As you get ready to focus your research, you can search the Sacred Texts website for a specific animal, such as the wolf, or focus in on wolf stories at the Native American section of Sacred Texts, or the elephant in the African section, for example. You can also search the Andrew Lang fairy tales for different animals.