In the books
In the A Song of Ice and Fire novels, zorses are striped black-and-white equine native to Essos who are known to be fierce and foul-tempered. They were originally created by breeding horses with a striped, horse-like animal found in southern Yi Ti and Leng, but later came to be bred as their own species. They are supposedly capable of surviving for many months on weed and devil grass and travel over long distances without food or water.
Members of the Brave Companions, the sellsword company led by Vargo Hoat, likely transported to Westeros as their personal mounts when they were brought over by Tywin Lannister. Hoat ties Jaime Lannister and Brienne of Tarth to the pommel of his saddle and drags them around the fortress with his zorse.
Zorses seem to be unknown in Westeros even among the most well-educated. Arya Stark, who sees the Brave Companions riding them at Harrenhal, is unfamiliar with them despite having a good education and being well acquainted with horses. However, Maesters are aware of them.
Daenerys Targaryen sees zorses being sold in the Eastern Market of Vaes Dothrak. She is later given one as a gift by the Jogos Nhai in Qarth, though she sells later sells it along with other gifts in order to gather enough wealth to petition the Pureborn.
In the real world, zorses are specifically the offspring of male zebras and female horses, and like most hybrid species, are infertile can cannot reproduce.
Animals and Plants of the Known World
Basilisks · Bears · Cats · Dogs · Direwolves · Dragons · Horses (Dornish sand steed) · Lions ·
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