What lesson does Buck learn about loyalty?

Buck learns that true loyalty is not something that can be demanded; rather, it is a bond that must be earned and can be reciprocated. Throughout "The Call of the Wild," Buck's understanding of loyalty deepens as he encounters various characters and situations. Initially, he is loyal to John Thornton, who treats him with kindness and respect, showing Buck that loyalty can be a mutual relationship based on trust and care. This stands in contrast to his experiences with other masters who expect loyalty without providing any form of respect or affection in return.

The journey Buck undergoes illustrates that loyalty develops through shared experiences and mutual respect, rather than being a fixed trait that one simply extends without consideration for how one is treated. This lesson underscores the theme of survival in the wild, where respect and partnership might be the difference between life and death. It also highlights the fundamental changes Buck undergoes, moving from the domesticated pet he once was to a creature shaped by raw instinct and the realities of his environment.