In genus Equus there seem to be 8 extant species, of which one - tarpan - is extinct in the wild. Out of these, 2 are classified as horses: tarpan Przewalski horse Tarpan and Przewalski horse famously have a different number of chromosomes (tarpan 64, Przewalski horse 66) and as famously produce fertile offspring with unpaired chromosomes. Now, 3 species of Equus are classified as asses: African ass Onager Kiang and 3 are classified as zebras: Grevy zebra Plains zebra Mountain zebra Now, while hybrids of tarpan and Przewalski horse are fertile, hybrids of tarpan and African ass are readily produced and even more famously sterile. The hybrids of African ass and onager have been mentioned to exist. Any details? Are they sterile (like ass/horse hybrids) or fertile (like tarpan/Przewalski horse hybrids)?