Before he is kidnapped, Buck lives a “sun-kissed” life. London begins the first chapter of Buck’s tale by describing how Buck slowing descends into a more primitive society.
Buck certainly lived high on the hog at the judge’s house in the Santa Clara valley.
[He] was king—king over all creeping, crawling, flying things of Judge Miller's place, humans included. (chapter 1, enotes etext p. 4)
Buck lives a very civilized life until Manuel steals him. He does not expect to have to go into the primitive, where he will need to rely on his animal instincts to survive. Buck is surprised when the men put a rope around his neck and it is not removed when he asks.
But when the ends of the rope were placed in the stranger's hands, he growled menacingly. He had merely intimated his displeasure, in his pride believing that to intimate was to command. (ch 5)
Buck is used to getting his way. He has not yet learned how to survive in this survival of the fittest, law of club and fang world.
He had learned the lesson, and in all his after life he never forgot it. That club was a revelation. It was his introduction to the reign of primitive law, and he met the introduction halfway. (p. 8)
When Buck learns the law of club and fang, the law that the strongest survive, he is getting his first taste of the primitive, and he does not like it one bit. Yet Buck is strong, and he is adaptable. He learns quickly, and he will succeed.