Marko, like me (but in no wise in an imitation of me), does a Monday-morning weird-search roundup, and he had this seriously choice (bordering on prime) item this week:
conservation of mass and werewolves
Werewolf fiction that respects the law of conservation of mass works around the rule that the mass in a closed system remains constant. For werewolves, that would mean that a 120-pound person would be a 120-pound wolf no transforming into some hulking 600-pound monster. Werecritter stories that respect the law of conservation instead of just waving the “It’s Magic!” wand tend to center around critters that are roughly similar in mass to adult humans: wolves, jaguars, leopards, cougars/mountain lions, and so on. No werebears or weretigers, since a 600-pound weretiger or 1,200-pound weregrizzly would be incredibly obese in human form.
Closest I’ve ever come to this premise was back in the fall of ’06, as follows:
A few eons ago, Sheri S. Tepper wrote of Mavin Manyshaped, one of a clan of shapeshifters, who, once her powers develop, flees from the family compound, lest she be abused like the other women in the clan. Mavin takes her younger brother with her; to speed the process along, she assumes the shape of a horse.
So far, this is a fairly routine fantasy concept, but Tepper is never routine. If you think about it obviously she did the Mavin/horse is going to have to eat, and eat a lot, during a long journey like this, and once she returns to human form, well, what’s going to happen to all that bulk she was carrying as an equine?
Yep. Don’t go there if you can help it.