A little more about the Great Chain of Being Metaphor System ---
The mapping between HUMANS and ANIMALS is one of the most productive metaphors in the system. This can be seen by reviewing the large number of animal proverbs and clichés that exist in the English language: “The early bird catches the worm,” “When the cat’s away the mice will play,” and “There are plenty more fish in the sea,” to name a few. In fact, ANIMAL for HUMAN metaphor is so prominent that the Center for the Integrative Study of Animal Behavior at Indiana University has devoted an entire web page to lists of animal proverbs and clichés. (http://www.indiana.edu/~animal/fun/wordplay/proverbs.html).
Another example of the prominence of animal metaphor is found in fables. The OED identifies the most prominent sense of a fable as “A short story devised to convey some useful lesson; esp. one in which animals or inanimate things are the speakers or actors; an apologue.”
Some of the best-known fables are those by Aesop which date back to the 6th century B.C., they include: The Ant and the Grasshopper, The Boy who Cried Wolf, The Dog and the Bone , The Goose that Laid the Golden Eggs, The Lion and the Mouse, The Tortoise and the Hare, The Wolf in Sheep's Clothing.