HBOAs u/Justzxcvbnm explains: "I saw this theory some time ago but I didn't care at the time. But after I saw the Ep 5 promo, I started to think... This theory says that in the fifth season, when Drogon spends almost a whole season gone, he's actually laying eggs and is in fact a female. That's why he was burning fields full of sheep, goats, etc. He's the only one who disappeared, the only one who drove herds and took them all like roasted sheep."

Source: The Irish Daily Star May 09, 2019 19:30 UTC