Why have these twelve animals been chosen for the Zodiac?
There are various legends surrounding this question. One Japanese legend says:
Once upon a time, on a day near the end of the year, God told all the animals: “You must come to see me for New Year’s greeting on the morning of the New Year. I will make the first twelve the champions of all the animals for the following twelve years.”
All the animals were determined to get first place and waited eagerly for New Year’s Day. The cat, however, forgot which day he should visit God, and asked the rat, who lied and told him that it was the following day.
On New Year’s Day, the Ox set out on his way even before dawn, as he walked slowly. Watching the Ox leaving the cattle house, the rat who lived in the loft secretly jumped on the back of the ox. Unaware of the rat on his back, the ox arrived at the gate of God, but no other animals had arrived yet. So, he was pleased and waited, believing that he was the first.
When the gate opened, however, the rat jumped off his back and ran through the gate. This is why the rat is the first year, followed by the ox. The tiger, rabbit, dragon, sheep, monkey, bird, dog and bore arrived shortly after. The cat arrived one day late, so did not make it into the list. The story goes on to say that this is why cats always chase rats.
In another legend it was Buddha who called the animals to him. Other versions of the story include the rat “forgetting” to wake the cat on New Year’s Day hence it never made it on the list. Even with such variances in legends all animals arrive in the same order with the years named accordingly.