Scotland's official national animal is the unicorn, a fictitious creature. The unicorn has been a Scottish heraldic symbol since the 12th century, when William I put it on an early form of the Scottish coat of arms.
When King James VI of Scotland succeeded Elizabeth I of England, uniting the two countries, the Scottish Royal Arms featured two unicorns supporting the royal shield. As a gesture of unity, James replaced the left unicorn with the English lion. This provides strong symbolism, as mythology paints the lion and the unicorn as enemies, vying for the crown of king of beasts; the unicorn rules through harmony and the lion by might.
The United Kingdom's Royal Coat still has the English lion on the left and the Scottish unicorn on the right. Scotland's Royal Coat of Arms has them reversed.