Spitz and Buck see huskies chasing after a bunny.
Spitz and Buck start chasing after the bunny with the other huskies.
Spitz goes on a shortcut, Buck and the ret of the huskies follow the bunny.
Spitz gets there before Buck because of the shortcut he took and kills the bunny.
Buck gets mad at Spitz for killing the bunny before he did because Buck wanted to taste the killing. So Buck gets in a fight with Spitz.
The after the fight, Spitz gets killed. This all relates to survival of the fittest because Buck is fit and wants to survive so he kills off Spitz to be dominate and show power so he is not taken down. Spitz wanted to kill the bunny and Buck for the same reason, he wants to have power so he is fit to survive.