Why does buck and spitz fight in chapter 3?

In Chapter 3 of "The Call of the Wild," Buck and Spitz fight primarily due to a clash over leadership and dominance within the dog sled team. Spitz, the established leader, sees Buck's growing strength and confidence as a threat to his authority. Their rivalry escalates when Buck challenges Spitz's position, culminating in a brutal confrontation that signifies Buck's determination to assert himself and take control of the team. Ultimately, this conflict underscores the themes of survival and the struggle for power in the harsh environment of the Yukon.