Why does Buck create a mutiny among the members of the dog sled team in The Call of the Wild?
The dog/protagonist of Jack London's Call of the Wild, Buck does not care for the sled team leader, Spitz, and he realizes that the two will eventually battle it out to the death. Spitz has tried to kill him on several occasions, so Buck keeps a wary eye on the smaller dog at all times. Spitz is also a brutal leader, ready to attack and kill his mates when necessary. Buck is stronger and more intelligent, and his friendlier disposition toward the other dogs will also gain their confidence when Spitz is eliminated. So, when the two finally fight it out and Spitz is left with broken legs, the other dogs are more than happy to tear him to shreds just as he has done other dogs.
Buck creates a mutiny among the members of the dog sled team because he does not like having Spitz as the leader of the team. Buck feels that he has earned that right by now. This happens in Chapter 3 -- "The Dominant Primordial Beast."
Buck has hated Spitz ever since Spitz laughed when Curly got killed earlier in the book. But up to now he has not felt he knows enough to be the leader. So in Chapter 3 he starts to undermine Spitz by protecting the other dogs from him. The more he does this, the less the other dogs fear and respect Spitz.