Norway is troll country. Oh sure, the electronic music and pickled fish are nice too, but it's the region's indigenous populations of hulking, deformed hill monsters that captivate our imaginations and draw in millions of tourists a year. *
Generally speaking, trolls are huge, hairy repugnant brutes with a penchant for destruction and a lethal weakness to sunlight. By day, they rest up in their underground lairs and mountain caves. By night, they wander and rampage through the wilderness, occasionally encountering humans -- which they may eat, ignore or bestow with riches, depending on their temperament.
Beyond these generalities, however, troll physiology and behavior differs quite a bit throughout Scandinavia. For instance, male Norwegian trolls are exactly the sort of monstrous giant you'd expect, but their females look like beautiful human women with long, red hair (source: Rose). As you might imagine, this leads to all manner of inner-species complications between humankind and trollkind.
Scientifically, the existence of the redheaded she-troll hottie (visual approximation) is likely a situation of aggressive mimicry, not unlike that practiced by female Photinus fireflies, that mimics the mating dances of Photinus ignitus fireflies so as to lure them in and devour them (more on this here). So the female troll may appear as beautiful women as a means of attracting male humans, which their monstrous menfolk then brutalize.
Other accounts bear witness to the existence of troll wives that are suitably inhuman and hideous, suggesting that various female morphs may exist within the species, much like the African Swallowtail butterfly (Papilio dardanus). Either way, the trait would seem to be one somewhat complicated by the social advancements of not only humans but the Norwegian Troll itself, as some myths attribute the creatures with aptitudes for metal work, herbalist medicine and subterranean architecture.
Turned to Stone
Ah, but what of sunlight? Why does the light of day cause trolls to turn to stone or explode? The 2010 documentary "Trollhunter" sheds interesting light on this subject, as it discusses the biology of several species of Norwegian troll: jotnars, ringlefinchs, tosserlad and mountain kings. According to the film, the nocturnal troll can't convert vitamin D (which most denizens of the day-lit world receive from sunlight) into calcium. So when trolls absorb vitamin D from direct sunlight or UV rays, their bodies rapidly suffer from acute vitamin D toxicity.
In younger trolls, the excess vitamin D causes an intense and painful build-up for gas in the creature's stomach and veins, resulting in full-body fragmentation. In older trolls, however, the veins are too constricted, causing the expansion to occur in the creature's bones. This reaction causes the creature's entire body to calcify -- or "turn to stone" to use the language of folklore.
So when visiting Norway, beware strange scarlet beauties in the wilderness. Don't try and invite them out for an afternoon in the park, and it's probably best that you turn down any of their romantic invitations as well.
Monster of the Week is a - you guessed it - regular look at the denizens of our monster-haunted world. In some of these, we'll look at the possible science behind a creature of myth, movie or legend. Other times, we"ll just wax philosophic about the monster's underlying meaning. After all, the word "monstrosity" originates from the Latin monstrare, which meant to show or illustrate a point.
* While native to Scandinavia, trolls have been known to range as far as Greenland, Northern Canada and the Shetland and Orkney Islands in the UK.