In the book, Sharptooth wasn't just hungry, he also wanted to kill Cera and Littlefoot for the injury to his eye.
He also seems to be eviller there and may like killing for more than just to get food. He was near the Great Valley there and it said that he sniffed the air with evil joy or something when he was near the entrance to the Great Valley.
The book also has some of the cut scenes, like where they are at some oasis and the creatures there are so selfish that they'd rather die of hunger and thirst than share with other kinds.
I happened to have some of the books myself, but that was years and years ago, and I highly doubt I have them anymore.