What is one primary struggle Buck faces while adapting to his new environment?

Buck's primary struggle in adapting to his new environment is indeed his longing for his previous home. As a domesticated dog used to a life of comfort and familiarity in California, the drastic shift to the harsh conditions of the Yukon during the Gold Rush places him in a completely different world. This sense of loss and nostalgia for his former life serves as a significant emotional barrier that he must overcome.

While concerns such as finding food and dealing with other dogs are certainly challenges Buck encounters, they are secondary to the emotional struggle of coming to terms with his displacement. The pain of missing his home illustrates a deeper inner conflict as he transitions from the life of a pet to a wild creature, signaling his journey towards embracing his instincts and the wildness within him.