Answer:
The call of the wild is an amazing story about Buck's life, I guess. Buck at the start was a bit aggressive, more so, scared. Then at the middle, Buck calmed down, aware and ready, sharp and unwilling- but got used to this. At the mid-end, Buck finally got used to this treatment, and was even somewhat protective. He was still aware, but less, and more willing. At the end, Buck at softened - strong as he was, but loyal, willing, protective, aware, and sharp to others.
Please comment if you have a specific question about the Call of the Wild novel.