The original woodcut, of course, represented the bull alone, illustrating the article De Tauro in the 1551 edition of the Historiae Animalium of Conradus Gesnerus. It was hand-colored, probably soon after the book was originally purchased. Some time later, a talented artist of the grotesque school, known for its combining of human with animal and vegetable forms, added the head in profile arising from the rearward parts of the animal.
What is the meaning of this unusual juxtaposition? Doubtless the artist meant to compliment his friend or patron by associating him with the power and nobility of the bull. Centuries later, we can no longer identify the subject of the portrait, but the intended compliment is legible to a wider audience than the artist could ever have imagined.