I re-read Robert Bartlett’s The Natural and the Supernatural in the Middle Ages today and came across the following:
For there are animals called dragons and these animals fly in the air, swim in the water and walk on land, and sometimes when in the air they become aroused by lust, whence they often emitted semen into springs and rivers and because of this a deadly year ensued. So a remedy was found for this, that a fire should be made of bones and thus the smoke would drive these animals away.
-John Beleth, Summa de ecclesiasticis officiis (12th century), quoted in Bartlett, 71-72.
Yikes, as if dragon-fire wasn’t perilous enough!