What instinct does Buck gradually develop throughout the story?

Buck's development of survival instincts is central to his transformation throughout "The Call of the Wild." Initially, Buck is a domesticated dog accustomed to a comfortable life on a California ranch. However, as the story progresses and he is thrust into the harsh realities of the wilderness and the brutal life of a sled dog, he learns to adapt to his new environment in order to survive.

Survival instincts encompass a variety of skills and behaviors necessary for enduring the challenges of the wild, including the ability to find food, protect oneself from threats, and navigate unfamiliar terrain. Buck's journey is marked by a gradual shedding of his domesticated behaviors and an awakening to the primal instincts that allow him to thrive in a brutal environment.

This transformation is evidenced by his increasing ability to work with the pack, respond to the dangers posed by other animals and humans, and manage the demands of a life dictated by the harsh conditions of the Yukon. His encounters with other characters, both human and animal, further shape these instincts, reinforcing the idea that survival in this new reality is paramount.