They don't really have any; few predators will risk injury by attacking a fully grown raven as they tend to be feathery balls of murder! Raven's beaks and claws are robust and sharp, and they are highly aggressive in the defense of their young. read more
Great Horned owls have been known to kill ravens (and other birds) as they roost at night, but it is not very common. Skunks, raccoons, and various types of snakes will invade the nests of ravens and eat their eggs and young, and Magpies have been known to do the same. read more
Plus, most predators just don’t catch and consume scavengers like ravens and vultures as they only land on the ground if there is already a fresh kill to feed from. This minimizes the chance of putting themselves on the menu, and everyone gets to eat their fill. read more
If it wasn’t such a misguided and ultimately dangerous sentiment I might just ¯\_(ツ)_/¯ whenever folks claimed that crows and ravens have no natural predators because those of us who spend even a small amount of time observing them in the summer will know this is anything but true. read more