The giraffes tongue is well adapted to its feeding habits. Its tough as leather, which protects it from the thorns of the acacia tree. Its very long around 45cm in length, making it easier to reach as high as possible and in between the thorns when trying to get at the very nutritious and moisture filled acacia leaves.
Being so tall has its obvious advantage of being able to reduce competition with other browsers and the added advantage of reaching the highest leaves which are generally the juiciest and most nutritious.
Males are taller than females in height and this reduces competition between the sexes and reduces pressure on the tasty acacia.
Interestingly the Acacia also defends itself from the feeding giraffe. After a period of having their leaves gobbled on by the giraffe, the acacia tree it lets of a bitter and foul tasting tannins so the giraffe reluctantly stop feeding. The acacia also warns its neighbors downwind who amazingly pick up a scent and begin releasing tannins in defense before any giraffe has thought about touching its leaves.
So off the giraffe head, ambling upwind to find some unsuspecting acacia who have not yet been warned by their neighboring acacia friends.