Oct 22 2012 11:00am

Monster of the Week: Trolls

The science behind trolls

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 hulking, 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.

Troll Beauties
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, who mimic 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—weekly 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.

Image source: Magnet Films

Originally published at HSW: Monster of the Week: Trolls

Robert Lamb is a senior staff writer at and co-host of the Stuff to Blow Your Mind podcast and blog. He is also a regular contributor to Discovery News. Follow him on Twitter @blowthemind.

Iain Nicholas Mackenzie
1. Iain Nicholas Mackenzie
You'll find many a troll under a bridge in the Northwest region of the USA. During the day, they are simply large stone sculptures but after dark...
Alex Bledsoe
2. alexbledsoe
I live in the Troll Capital of the United States (Mount Horeb, WI). We even have a Trollway, with wooden sculptures of the beasties all over town. I have yet to encounter one practicing the sort of aggressive mimicry you describe, though. And believe me, I've looked.
Iain Nicholas Mackenzie
3. Wodan
Anyone who hasn't seen Trollhunter, you're missing out. It's available on Netflix.
Brian R
6. Mayhem
Don't forget Robert Asprin, who gave us the highly educated and erudite smashing machine that is the male Troll and their stunningly beautiful female counterparts the Trollops.
Iain Nicholas Mackenzie
7. lorq
What Wodan said. What a delightful film!
Lisamarie LiGreci-Newton
8. Lisamarie
@2, I live by Mount Horeb, I was going to mention that :D

PS - the Grumpy Troll is probably my favorite brew pub ever :D
Lisamarie LiGreci-Newton
9. Lisamarie
Regarding the article, I was not aware of the possible difference between the genders. I suppose this explains a bit how Hagrid's father is able to mate with a troll ;) Although I cant' recall if we ever meet any full blooded troll females.

I hate to burst your bubble, but we do NOT absorb vitamin D from sunlight. UV energy causes a reaction between in certain compounds already present that causes it to convert to vitamin D. So, if trolls are sensitive to vitamin D, it would be because they also carry out that reaction.
Mouldy Squid
10. Mouldy_Squid
Don't forget the infamous tanntrollene (tooth trolls) which often make an appearance during late October, particularly in countries that practice Hallowe'en.
Iain Nicholas Mackenzie
11. Innbranna
As a native Norwegian, I feel a certain obligation to point out that female trolls are just as huge and monstrous as male trolls, only they wear skirts and don't have beards. The beautiful redheads are a different breed altogether, namely the huldra ( - though I think both trolls and huldrepeople have been known to have cow tails.
Iain Nicholas Mackenzie
12. Soleil Bleu
Just to clarify, mammals don’t ‘absorb’ vitamin D from sunlight, but synthesize it from cholesterol in the presence of sunlight. Sunlight is just ... light. It doesn’t contain a complex chemical for anyone to absorb.
Birgit F
13. birgit
I suppose this explains a bit how Hagrid's father is able to mate with a troll

Hagrid's a half giant, not a half troll.
Lisamarie LiGreci-Newton
14. Lisamarie
OMG, you are totally right. I had a total brain fart there and mashed up the two representations of them in my head, as well as with the trolls in the Hobbit (which I think in general are portrayed as a bit more intelligent than the ones in Harry Potter, at least the one we see in the first book).

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