The bonnacon is a beast with a head like a bull, but with horns that curl in towards each other. Because these horns are useless for defense, the bonnacon has another weapon. When pursued, the beast expels its dung which travels a great distance (as much as two acres), and burns anything it touches.

Pliny the Elder [1st century CE] (Natural History, Book 8, 16): The bonasus is found in Paeonia. It has the mane of a horse but otherwise resembles a bull. It has horns that curve back so they are useless for fighting; when attacked, it runs away, while releasing a trail of dung that can cover three furlongs. Contact with the dung burns pursuers as though they had touched fire.

