What is Reepicheep's Tail?

Reepicheep looses his tail in battle. Reepicheep wants his tail to be restored by Aslan, claiming that the tail of a mouse is his glory. When Aslan refuses, the other mice following Reepicheep begin to cut off their own tails, explaining that they won't have such an honor if it is denied to their leader. Because of their love for Reepicheep, Aslan grants the request.