You've all seen it somewhere. Werewolves and their mortal foes the vampires. You'll often find those two beings side by side in fiction, usually at each other's throats. It makes logical sense, if you step ack and look at it. Fictional vampires and werewolves typically have a lot to fight about.
Hungry Werewolves, Hungry Vampires
Picture this: you're a beast-like creature that feeds on human flesh, hunting at night. You can also sire an heir, make a human into a werewolf, with a mere bite. Humanity is both food and reproduction to your kind.
There is another creature that feeds on humans. The vampires. They are undead creatures that drink human blood, hunting at night. They can sire heirs, make humans into vampires, with a mere bite. Humanity is both food and reproduction to their kind.
If you think you just read the same thing twice, then you're right. Werewolves and vampires share a prey species to almost every last detail. They occupy the same ecological niche. Of course there would be fierce competition. Every time a werewolf feeds, a vampire starves.
Protector Werewolves, Predator Vampires
What about the Twilight approach? There are many stories that feature werewolves as heroic. Why do werewolves and vampires fight in those stories?
The answer lies in the fact that the above situation, werewolves and vampires competing for food and breeding stock, has occured so much in fiction that it's difficult to steer away from the idea. It's certainly possible to have a werewolf story with no vampires, but how many could you name off the top of your head?
Werewolves against vampires is practically a staple of horror fiction, even if one of the two does not mean humanity harm. So what would you think if I told you that in the origins of the mythology, werewolves and vampires never fought with each other?
The Original Creature of the Night
The original mythology of the vampire was a creature that drank blood, avoided sunlight, and could transform into a bat or a wolf. In other words, the first vampire was also a werewolf!
Somewhere along the line, the two transformations got split, and today we have the feuding beasts we love to see in fiction.
There's many myths and legends about them. The full moon, a bite, a silver bullet. Beast-man monsters, wolves wearing the skin of humans. Werewolves plagued humanity in the middle-ages... and then, come modern day, it all changed. Attacks stopped. Monsters vanished. Humanity reigned supreme... while the monsters lived in the shadows, the edges of the modern world. Humans forgot, and the monsters struggled to survive in a world now stronger than they.
