Why does Shakespeare use so much animal imagery in Othello?

Like the repeated references to plants, these references to animals convey a sense that the laws of nature, rather than those of society, are the primary forces governing the characters in this play. When animal references are used with regard to Othello, as they frequently are, they reflect the racism both of characters in the play and of Shakespeare’s contemporary audience. “Barbary horse” is a vulgarity particularly appropriate in the mouth of Iago, but even without having seen Othello, the Jacobean audience would have known from Iago’s metaphor that he meant to connote a savage Moor.