[quote=@Earnest Evans]
<Snipped quote by Orcus>

There is no canon mention of mules and donkeys being extinct. In Fallout, you can find a recently-dead mule. In Fallout 2, there is reference to mare's milk being in good supply. In Fallout New Vegas, the Dead Horses obviously know that horses exist. In real life, wild horses are still [i]astonishingly[/i] common out west. A nuclear apocalypse would cause some upheaval in their numbers, but if [i]dogs and cattle[/i] can survive, a horse could too. To think that [i]every single species of equid in America[/i] is extinct is, quite frankly, silly.
[/quote]

Chris Avallone comes straight out and says that while they might exist it would be like finding a unicorn, the man with the mule does imply that they did make it through, but in probably severely diminished numbers. Probably even worse than most animals, and NV breaks lore a lot but the dead horses could of found them in picture books man. Zion is after all a preserve.