A zebroid (also zedonk, zorse, zebra mule, zonkey, and zebmule) is the offspring of any cross between a zebra and any other equine: essentially, a zebra hybrid. In most cases, the sire is a zebra stallion. Offspring of a donkey sire and zebra dam, called a zebra hinny, or donkra, do exist but are rare. Zebroids have been bred since the 19th century. Charles Darwin noted several zebra hybrids in his works.