Your excellent question relates to the way in which the possession of the pearl gradually effects Kino more and more, turning him into something that he definitely was not at the beginning of the story before the pearl entered his life. The fact is that the pearl produces a malicious, bad and evil change on its bearer as Steinbeck uses it as a central image of how wealth can corrupt. One way in which this is demonstrated throughout the story is through the use of animal imagery to describe Kino and his actions as he fights to protect the pearl from those around him. One of the best examples of this from the novel comes at the beginning of Chapter Five, when Kino responds to his wife's attempt to dispose of the pearl and the evil it has caused them:
Kino looked down at her and his teeth were bared. He hissed at her like a snake, and Juana stared at him with wide unfrightened eyes, like a sheep before the butcher. She knew there was murder in him, and it was all right; she had accepted it, and she would not resist or even protest.
Note the way in which Kino is directly described as a wild animal, with his teeth "bared" and with his hiss that is "like a snake." He is shown to be losing his humanity through his greed for the pearl, and the fact that he is compared to a snake, a symbol of evil and temptation, is highly significant.
Not being innapropriate but kino strips naked to camoflauge between the rocks and not to be noticed by the trackers in the night that signifies a predator camoflauging on its prey.