How does Buck react after John Thornton's death?

After John Thornton's death, Buck experiences profound devastation and a deep sense of loss. Thornton represents the epitome of kindness and loyalty in Buck's life, and his death signifies the loss of a bond that was not only based on mutual respect but also love. Buck's emotional response is a testament to the strong connection they shared; it highlights his capacity to form deep, meaningful relationships. This reaction emphasizes the themes of love, loyalty, and the impact of loss on one's life, particularly in the harsh setting of the wilderness. Buck’s mourning illustrates his transformation throughout the story, where he moves from being a domesticated pet to embracing his primal instincts while still cherishing the memories of those he loved.