I would say that one of Buck's most prevalent trait is his loyalty. Buck is extremely loyal to Judge Miller and represents obedience to his master at the start of the work. Yet, throughout his being kidnapped and abused, he is exposed to the very worst of human action. It would make sense that he would completely distrust people throughout such an ordeal. However, he demonstrates the utmost of devotion and loyalty to Thornton, remaining with him and not fully going with the wolf pack. At the end, when Thornton is killed, Buck cuts off all ties with human beings, as exposed to the absolute cruelty humans can do. His loyalty is still present, when each year he visits Thornton's grave. The idea in Buck of loyalty and devotion to a higher good is evident throughout London's work.
Buck is the strongest, most powerful and most fearless sled dog in all of the Klondike in Jack London's novel, Call of the Wild. A part-St. Bernard and part-Scottish shepherd, Buck weighs about 150 pounds. Stolen from his home in California, Buck is shipped to Alaska, where he is trained as a sled dog. He is whipped into shape by his masters and comes to fear and honor the club they use to beat him. Far larger than any of the other sled dogs, he quickly becomes the leader of the team. He learns his trade quickly, and he learns to fight and feed himself however possible. He is fair with the rest of the dogs, and they, in return, respect Buck far more than the previous leader, Spitz. After surviving several attacks from Spitz, he eventually kills him and becomes the lead dog. His team makes one run in record time, and his owners proclaim him the finest dog they have ever seen. When he later becomes the property of John Thornton, he earns even greater renown when he pulls a 1000 pound sled for 100 yards--even breaking the sled from the ice. He comes to love Thornton, the only master to treat him as a pet, and Buck idolizes his final master. When Thornton is killed by Indians, Buck furiously attacks and kills several of them. The call of the wild eventually lures him to join a wild wolf pack, which he quickly leads after fighting off their own attacks. He becomes a legend to the Indians, who fear the ghost dog that vengefully kill those who murdered his master. Surely, Buck is the greatest dog in all literature.