As redditor 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. to feed the baby dragons. He's the only one who disappeared, the only one who drove herds and took them all like roasted sheep."