The first chapter contains a lot of references to animals - pigs, roosters, doves, goats, and also the scorpion which becomes the emblem of evil when it attacks the baby Coyotito. The effect of this is to emphasise the natural surroundings of Kino and his family, and indeed the whole Mexican Indian community.
In fact, Kino's whole race is regarded as being animal-like by the Spanish who have colonised and oppressed them for hundreds of years.
He could kill the doctor more easily than he could talk to him, for all of the doctor's race spoke to all of Kino's race as though they were simple animals. (chapter 1)
This quote serves to highlight the vast gulf between the races; there is simply no meaningful communication, far less any understanding and sympathy, between them. The Spanish view the Indians as being primitive and devoid of reason, the Indians resent the Spanish imposition.
On a more individual note, there is a striking use of animal imagery in relation to Juanita after the baby has been bitten:
She looked up at him, her eyes as cold as the eyes of a lioness. (chapter 1)
This comparison shows the strength of Juanita's maternal instinct. To save her baby, it is implied, she will do anything; she can turn dangerous if required.
Steinbeck utilizes animal imagery in the first chapter to illustrate Kino's natural environment and foreshadow events. Animal imagery is also used to characterize individuals and groups throughout the story. As was mentioned in the previous post, Steinbeck depicts roosters, pigs, and birds to illustrate the natural setting where Kino and his family live. In the Indian settlement where Kino resides, it is commonplace for goats and dogs to wander around and interact with humans. The indigenous people are associated with the wilderness, nature, and innocence. Steinbeck also uses animal imagery to symbolize Kino's plight. In the first chapter, Kino watches as a dusty ant frantically attempts to escape from a trap that an ant lion had dug. The dusty ant's tragic situation reflects and foreshadows Kino's struggle to escape from the oppressive Spaniards. Kino and the other Indians are also viewed and treated like animals by the ruling Spaniards. Additionally, Steinbeck uses the scorpion to symbolize the arbitrary evils that exist in the world after it stings Coyotito.