What are some examples of Kino acting like an animal in The Pearl?

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.