Some variants you could consider...
Use only the white result as a joker for the black dice. You can't use the color of an ostrich that already finished as a joker. As a result it is more difficult to put a spell on an ostrich and you'll there is a bigger chance you'll have to move an ostrich.
The lion starts out of the board, he will come to play when all ostriches have crossed the first terrain tile (without taking into account the Start tile). When this circumstance takes place, place the lion token in the Start space. At the end of each player turn, the player will have to move the lion towards the nearest ostrich. If there are two or more ostriches, the player chooses towards which one the lion is going to move. After that, the rear-most ostrich or the rear-most ostriches, if there are more than one, get one free movement point to move towards the Finishing Line. But, if the rear-most ostrich is spelled... He doesn`t get any movement point! The lion is coming! If lion reaches the space occupied by an ostrich, he will stop and have “lunch”. This ostrich is automatically last and you have to remove the lion token, because he is sated. The race continues on the common way.