What is a theme for survival in The Call of the Wild?

The main conflict in The Call of the Wild is the struggle between civilization and the wild. The novel traces Buck's gradual transformation from a domesticated dog to a wild one.

Buck has to learn to adapt to an entirely new way of life and code of conduct in order to survive. He must give up his life of leisure and his trusting nature. He learns "the law of the club and fang," meaning that those who have the greatest physical strength are the rulers. The chain of command is comprised of men with clubs; the lead dogs, who have achieved mastery by wounding or killing dogs that challenge them; and the other dogs, who do most of the work.

Buck starts out on the bottom of this hierarchy, but soon adapts to his new life. He begins to steal food, losing his moral nature. Most of all, Buck is fit, and his superior strength, conditioned by his experiences, allows him to be more aggressive. He challenges the lead dog and wins the coveted top position. His survival instinct leads him to refuse to lead the team any further when they travel on thin ice.

At this point in the narrative, Buck's consistent "development (or retrogression)," as London calls it, from civilization to the wild is halted. When Thornton becomes his master, he discovers a stronger bond - love - than any he has ever experienced. His risks his life for his master, in direct contradiction to the new ethos he has learned on the trail. With Thornton, Buck lives a domesticated life, but he continues to hear the call of the wild. Although he is torn between the two, he remains with Thornton, unable to break the bond between them. When Thornton is killed, he is released, finally able to fulfill his true nature and join the wolf pack. Only then is his transformation from domesticated dog to wolf-like wild one complete.