In The Call of the Wild, describe Buck's changes.
Over the course of the book, Buck gradually becomes reconnected with his true identity. Although his early life on the ranch was blissfully happy and carefree, there was always something unreal about it. Buck, like all domesticated animals, was ultimately dependent for his welfare on the whims of human beings. All it took was for one bad individual to come along and ruin everything.
But the Spaniard who kidnapped Buck also shows him another side to human beings, one that was hidden from him on the ranch. The negative impression Buck gains of the human animal is subsequently confirmed when he's unceremoniously shoved into a freight train headed north to the wilds of Alaska.
Yet the great hardships endured by Buck are character-building and allow him to develop a true animal identity, one that re-establishes a connection to his wolf ancestors. What does not kill Buck makes him stronger, and soon he comes to thrive among the frozen wastes. As the best sled dog in the business, he's found a role in life, albeit one still defined by human beings. But Buck's understanding of humans has changed to a very great extent. He knows that they will only treat him well if they respect him, and they will only respect him if he can continue to show his strength, hardiness, and leadership skills, the qualities of an alpha dog. In doing so, he can have the best of both worlds. His fate is no longer entirely in the hands of human beings; now he knows that he can, to a large extent, shape his own destiny.
I think that Buck changes because he learns to fully grasp the nature of human cruelty. Buck undergoes changes from a domesticated dog to a wild one as a result of all that is done to him. His abduction from Judge Miller was the result of human deceit and through this, Buck learns how to adapt in the wild. Buck's loyalty to Thornton is once again severed by human cruelty. This causes him to change into a being of the wild to forgeo the world of humans, fraught with disloyalty and dishonor. The notion of civilization being more uncivilized than any other domain helps to bring out the changes in Buck. He understands the rules of the wild as the dreive to survive is the only adversary. These rules are clear, while the rules that govern the world of humanity are far from clear and obscure, at best. The refined coat he has at the start of the narrative is replaced by one that is weathered more by survival and the wild. This helps to reinforce the emotional change that Buck undergoes, from one who enjoys what is deemed as luxury to a survival based existence where trial and challenge exist at every turn. The lure of the wild in terms of the hunt and the nature of "kill or be killed" is something of which Buck becomes a part, fully evolving into the "Ghost Dog," a being of the wild.