Nature in The Call of the Wild is a force to be reckoned with. In the frozen terrain of northern Canada, Buck experiences starvation, exhaustion, and, of course, bitter cold. But the natural world isn’t purely antagonistic; it also stimulates the dogs, shapes them, and molds them into stronger, more powerful beings. The wild is an antagonist and a guide at the same time.
Buck adjusting to the wild around him is ultimately representative of his accepting the wild within. These internal adaptations are far more important to this character's change than the external, physical changes he undergoes.
While Buck gains much by adapting to the wild, he loses important aspects of his original persona, such as morality and domesticity.