Spitz and Buck fight to the end as both of them followed the same prey. They met when they were hunting a night. Buck and Spitz fought to the end and Buck resulted victorious. Spitz was not able able to survive because in the primitive, the only rule is survival of the fittest.
JOHN THORNTON IS NO MORE
One day, Curly was trying to be nice to a husky. She acted all friendly with the husk, but not the husky with her. The Husky howled and his pack came. Soon huskies would have left nothing else than cuts and injuries. Soon Buck learned that you can't act friendly with others, or else they will think you are an enemy.
DAVE IS GONE
When Buck arrived at Seattle, he encountered a man with a red sweater. The man tore apart Buck's feelings and injured Buck physically too.. He taught him to follow the law of club. He also showed that the most prepared and strongest can survive.
Dolly has gone mad
John Thornton has now been attacked a Native tribe. He and his friends have been killed and Buck is now free from ownership. How ever, Now that John is dead, this shows that he was not strong enough to survive.
Dave is now on his last leg, he had an option to rest but decided to die with honor instead. When they reached their destination Dave got dragged to a forest area and from there there was a revolver shot. This showed that Dave was strong enough to live while his age allowed him to.
While Buck was walking towards his destination, Dolly came from behind and attacked him. This was caused because Dolly had rabies. At her last breath, she got executed. This showed that Dolly wasn't strong enough to live in the wild.