natureNaturenaturecreepy crawlies

Ice Worms Emerge From Glaciers In Summer. Why? Nobody Knows

What are the ice worms plotting?


Rachael Funnell


Rachael Funnell

Digital Content Producer

Rachael is a writer and digital content producer at IFLScience with a Zoology degree from the University of Southampton, UK, and a nose for novelty animal stories.

Digital Content Producer

ice worms emerge

There are billions of ice worms on a single glacier, but without adequate snow cover, they could disappear. Image credit: Southwick3 - Own work via Wikimedia Commons, CC BY-SA 3.0

A curious phenomenon can be spotted on the glaciers of north America in the summer. That is, if you’re looking closely. In the late afternoon during the warmer months, these mysterious little black ice worms emerge from their frozen home, but nobody really knows why.

The peculiar ice worms (Mesenchytraeus solifugus) are around 1 centimeter (0.4 inches) long and dark brown to black in color. They look like loose pieces of string strewn across the snow on glaciers and emerge in such large numbers that it can be hard to avoid stepping on them when going for an evening walk on certain glaciers.


What makes the ice worms extra baffling is that they appear to exist on a knife edge. Their glacial homes are 0°C (32° F), but if ice worms are exposed to temperatures any colder than that they die. 

They’ve been found to contain anti-freeze proteins that stop them from turning into icicle worms on the frosty glacier, explained the North Cascade Glacier Climate Project. There are actually many species that have evolved to resist freezing in this way, but unfortunately, humans aren’t one which is why we probably couldn't ever survive being frozen like a popsicle in cryonic preservation (something we explored at length in our free e-magazine, CURIOUS).

Curiously, they seem to enjoy a kind of reverse hibernation as they emerge after winter fatter than they are by the end of summer. Exactly what they get up to in the winter months when they burrow further down into the snow is just one of many mysteries surrounding these animals.

Another is their reproductive cycle, as nobody really knows how and when baby ice worms emerge.


"Early in the summer you tend to see more smaller ice worms, suggesting that at some point before that, their little eggs hatched and baby ice worms popped out," said Peter Wimberger of the University of Puget Sound to NPR, "but we don't know."

ice worms
The wiggling ice worms look like bits of string from a distance. Image credit: Dick Culbert from Gibsons, B.C., Canada - Mesenchytraeus solifugus, Ice worms, CC BY 2.0

These animals are remarkably understudied when you take into account how many of them there are, with estimates putting it at around 5 billion ice worms per glacier. Unfortunately, despite their numbers, there could still be bad news on the horizon for the world’s ice worms.

The climate crisis has seen snow melting and glaciers retreating across the planet, and as the precious snow cover disappears it’s been found so too do the ice worms. If warming continues at its current rate, it could be that the ice worms disappear before we have a chance to crack all the secrets to their existence.

[H/T: NPR]


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