Assuming the vampire is the natural predator of the human, what is the natural predator of the vampire?

I asked this question awhile back on my Facebook page and got a wide variety of responses. Werewolves and witches were the most popular choices, Buffy was in there somewhere, one person even suggested killer owls, and a few put forth dhampirs, vampire/human hybrids, that only feed off vampire blood (that was probably my favorite).

Bram Stoker to Stephanie Meyer—one of the most common consensus among writers of vampire literature is that they do not get along with werewolves. They’re like Tolkien’s Elves and Dwarves—they hate each others guts into oblivion—but they seem too evenly matched to me. A true predator has a distinctive advantage over their prey. One might say the Werewolves have the edge of going out in the sunlight, but they are at their strongest under a full moon…