Symbols are objects, characters, figures, or colors used to represent abstract ideas or concepts.
Mercedes loads the sled up with so many of her things that the dogs cannot possibly pull it; later, she herself gets on the sled, making the load even heavier. Her insistence on having all of her possessions with her emphasizes the difference between the wild, where the value of an object lies in its immediate usefulness, and civilization, where the value of an object lies in its ability to symbolize the wealth of its possessor. Material possessions and consumerism have no place in the wild, and it is at least partly Mercedes’ inability to recognize this fact that leads to her death when the overburdened sled falls through the ice.
The significance of Buck’s traces—the straps that bind him to the rest of the team—changes as the plot develops. The novel initially charts his descent from his position as the monarch of Judge Miller’s place in civilization to a servile status in which it is his duty to pull the sled for humans. But as he becomes more a part of the wild, Buck begins to understand the hierarchy of the pack that pulls the sled, and he begins to gain authority over the pack. After his duel with Spitz, he is harnessed into the lead dog’s position; his harness now represents not servitude to the humans but leadership over the dogs. Finally, however, John Thornton cuts Buck free from his traces, an act that symbolizes his freedom from a world in which he serves humans. Now a companion to Thornton rather than a servant, Buck gradually begins to enter a world of individual survival in the wild.
When Buck is kidnapped, he attempts to attack one of the men who has seized him, only to be beaten repeatedly with a club. This moment, when his fighting spirit is temporarily broken, along with the brutal killing of Curly by a group of vicious sled dogs, symbolizes Buck’s departure from the old, comfortable life of a pet in a warm climate, and his entrance into a new world where the only law is “the law of club and fang.”
In the closing chapters of the novel, Buck feels the call of life in the wild drawing him away from mankind, away from campfires and towns, and into the forest. The only thing that prevents him from going, that keeps him tied to the world of men, is his love for John Thornton. When the Yeehat Indians kill Thornton, Buck’s last tie to humanity is cut, and he becomes free to attack the Yeehats, killing a number of them. To attack a human being would once have been unthinkable for Buck, and his willingness to do so now symbolizes the fact that his transformation is complete—that he has truly embraced his wild nature.