Cicero, On the Nature of the Gods
1.27.77 (tr. H. Rackham):
Do you suppose that there is a single creature on land or in the sea which does not prefer an animal of its own species to any other? If this were not so, why should not a bull desire to couple with a mare, or a horse with a cow? Do you imagine that an eagle or lion or dolphin thinks any shape more beautiful than its own?
an putas ullam esse terra marique beluam quae non sui generis belua maxime delectetur? quod ni ita esset, cur non gestiret taurus equae contrectatione, equus vaccae? an tu aquilam aut leonem aut delphinum ullam anteferre censes figuram suae?