Several creatures of Pern are known to have multi-faceted eyes that exhibit the ability to change colour depending on the mood of the creature. This was first observed in the fire lizards, and later the Dragons and Whers who were genetically engineered from them. It is not clear whether all of Pern’s native species - such as Tunnel snakes or Wherries - exhibit this ability, or whether it is exclusive to the recent evolutionary tree of the fire lizards.