Just what is it about a full moon that affects a werewolf? Is it the light? Is it just that werewolves are on a 28-day cycle that always syncs with the Moon?

If it were light, then just keeping a werewolf out of the light would prevent them from changing.

Is there something specific about the full Moon that forces the change?

  • 3
    Are you interested in the werewolves in some particular piece of fiction? Because werewolves don't exist in the real world, and the answers might be different in different pieces of fiction. Jan 30 '12 at 1:55
  • 1
    @DJClayworth: Answers may differ, but I work with archetypes in my writing, which includes different views and, honestly, there's useful information if people answer about one mythos, or several, or all known. As to in the real world, well, if they were in the real world, it wouldn't be science fiction or fantasy, would it?
    – Tango
    Jan 30 '12 at 2:04
  • 1
    Note that this question was closed, yet there is no clear consensus as to whether closing it is appropriate. Please see this meta discussion. Voting to reopen, as closing it was premature without an appropriate meta consensus.
    – Beofett
    Jun 8 '16 at 13:16
  • 2
    @Beofett: as the asker and someone who just found out this was closed, I don't see a solid reason for closing this. I've left my reasoning in an answer in that discussion. The short version is I think a lot of times users and mods are too pedantic and have their heads up their hindparts and are just eager to do something that makes them feel like they can make decisions and do things.
    – Tango
    Aug 3 at 18:21
  • 1
    @Beofett: Yes, and it seems to me, in that discussion, one person is pretty much doing a good job of making my point by demonstrating the kind of closed or convergent thinking I was saying was the issue. Quite busy saying, "This doesn't make sense," and yet being just the kind of person I'm talking about.
    – Tango
    Aug 9 at 15:32

The effects of a full moon on a werewolf can vary greatly from story to story (including actual folklore). Some of the numerous lunar werewolf mechanics I have seen include:

  • Only being able to transform under a full moon.
  • Being able to transform at will, but being forced to transform under a full moon.
  • Sleeping with the full moon's light on your face being a requirement for becoming a werewolf.

The association with the full moon and werewolves likely originated in the association with a full moon and insanity. This is called the Lunar Effect.

  • 1
    Speaking of the Lunar Effect, I remember when I worked in a psych hospital, every time we had a unit shutdown or a half shutdown, it was during a full moon. I know all the stuff about statistics that say it doesn't seem to be a real effect, but there was never a shutdown in the 2 years I was there that wasn't during a full moon.
    – Tango
    Jan 30 '12 at 2:03
  • @TangoOversway - that's how crazy stories got started back in the day. Crazy people during a full moon? MUST BE A MAN TURNING INTO A WOLF! Jan 30 '12 at 2:08
  • I think that was part of it, but I remember reading something about rabies and rabid activity (including foaming at the mouth and the disease being transmitted by biting another) was part of it. I think there was another part that played in, too, but I can't remember that.
    – Tango
    Jan 30 '12 at 2:12
  • Rabies almost definitely had something to do with the werewolf myth. Like a lot of folklore, a lot of circumstantial evidence got lumped together to form a big ball of crazy. People are afraid of things they dont understand and see connections that aren't there. Jan 30 '12 at 2:22
  • Yes, and when I ask these questions (werewolves, vampiers, etc), often any answers are useful because they help me see how the myth is perceived. For my work, that's as useful as hours of research. So the folklore and roots is helpful, but so is seeing what is commonly believed now.
    – Tango
    Jan 30 '12 at 2:23

I don't think I've ever heard a physiological explanation for moonlight or the Moon itself doing anything, but in all stories I can remember, it is the moonlight itself that causes the transformation, so keeping them inside ought to keep them safe. Including Harry Potter:

A cloud shifted. There were suddenly dim shadows on the ground. Their party was bathed in moonlight.

Snape collided with Lupin, Pettigrew, and Ron, who had stopped abruptly. Black froze. He flung out one arm to make Harry and Hermione stop.

Harry could see Lupin's silhouette. He had gone rigid. Then his limbs began to shake.

"Oh, my --" Hermione gasped. "He didn't take his potion tonight! He's not safe!"

Although that brings up the question of why Lupin had to go to the shrieking shack/curl up under his desk instead of hanging out in the dungeons...


While there has already been an accepted answer, I thought I might contribute a bit.

During the full moon, since there is even more light reaching the area from which the full moon is visible, the ambient energy is much greater. Several vineyards are actually getting positive results from synchronising their harvest with the cycle of the moon, claiming that letting the grapes grow during a period of high energy makes them sweeter.

So, even in the dark, one might consider that the increased ambient energy is triggering the transformation.


The interpretations vary. While the mythos is certainly linked to lore surrounding the moon, I'd like to suggest the answer from Being Human.

In the show, while there is a supernatural aspect, there's also an attempt at a scientific approach. They link the effect of the moon on tides to that on werewolves, even managing to negate (or delaying) the transformation by putting the (would-be) werewolf in a hyperbaric chamber. In that universe, it's all about gravity and pressure.


Tidal effects, if wanted werewolves to be science based the gravitational pull of the moon cause it same way as sea tides.

  • Can you add a little more explanation on your answer? May 12 '14 at 16:10
  • You know the grational pull of the moon causes seas tides to rise so the same could apply to werewolves.
    – user26156
    May 12 '14 at 16:14
  • But that is due to the water being "lighter" than the Earth, hence the water would be pulled easier. that way a werewolf would always be transformed/never transform
    – Oak
    May 12 '14 at 16:35

Not the answer you're looking for? Browse other questions tagged or ask your own question.