The Parandrus, or Tarandrus, is a creature described in medieval bestiaries as a beast that can change its appearance at will.
The Parandrus is said to be able to conceal itself by altering its physical appearance so that it can blend in with its surroundings. It is colored like a bear, but is the size of an ox and has long hair. It has the head of a stag with branching horns, and has cloven hoofs.
Pliny The Elder
In Natural History, Book 8, 52, Pliny mentions a beast from Sythia called Tarandrus that can change color.