Garcia Marquez uses animal imagery to highlight certain character traits. Santiago is young and naive, described by his friend as a falcon chasing a "warlike crane," the experienced prostitute Maria Alejandrina Cervantes. Santiago's friend warns him that his ill-advised pursuit of Maria can only lead to a lifetime of pain.
Animal imagery is also used to foreshadow the death of Santiago Nasar. On the day of his death, he wakes up, as he puts it, feeling "completely spattered with bird s***." Rabbits are used as ill omens throughout the story, and on the morning of Santiago's death Victoria Guzman treats the rabbits the way she'd like to treat him—removing their entrails and feeding them to the dogs. Surely enough, Santiago's grisly death reflects that of the rabbit, ending up with "all his intestines exploded out."
Then there are the dogs. When the Vicario brothers leave the pigsty with their murder weapons, the unwrapped knives, the dogs start making a huge noise. Their barking is a premonition of the terrible events that are about to follow. Also, the dogs become agitated by the smell of death after Santiago's body is laid out in the center of the living room. It's almost as if they're lamenting his death with their insistent howls.