Guessing Game

My son is nine years old and does his own homework. Sure I look it over, but other than basic spelling and grievous grammar errors, I try to let him hand in work that is really his. Here is last night's.

Can you guess who my boy is writing about?

It lives in Africa.
It is six metres long.
It is a shiny coat with spots.
They are for neck fighting.
In order to pump blood to its head.
It eats leaves and shoots from trees.
So that it can be immortal against attack.

An immortal, blood pumping neck fighter that eats leaves and shoots from trees?

It can only be a deadly ninja giraffe!