On mountaintop glaciers of Alaska, Washington and Oregon, billions of tiny black worms are tunneling upward to the barren, icy surface. What lures them, and how do they survive the frozen depths?

Transcript

STEVE INSKEEP, HOST:

We take you now high into the mountains of the Pacific Northwest. It's a good season to stroll on a glacier, wouldn't you agree? You can feel the cool air now. NPR's Nell Greenfieldboyce did just that, and she returned with a story of a tiny creature, an ice worm whose very existence is hard to grasp.

NELL GREENFIELDBOYCE, BYLINE: Mount Rainier in Washington is the tallest peak in the Cascade Range. Fortunately, to see ice worms, you don't have to go to the very top. We're going to Paradise Glacier - over 7,000 feet up. From the trailhead, it is a long upward slog through snow.

(SOUNDBITE OF SNOW CRUNCHING)

GREENFIELDBOYCE: Scott Hotaling has made this trek many times.

SCOTT HOTALING: Ice worms essentially changed my life from the first time I saw them.

GREENFIELDBOYCE: He's a researcher with Washington State University and a kind of ice worm evangelist.

HOTALING: I have no shame in promoting ice worms.

GREENFIELDBOYCE: He says many people who spend lots of time on Mount Rainier and other Pacific Northwest mountains have never seen one or didn't understand what they were seeing.

HOTALING: They're very obvious once you notice them. But it's so beyond your expectation when you're in a glacier environment that there will be worms.

GREENFIELDBOYCE: The worms only venture out onto the surface of a glacier at certain times, like late summer afternoons. Hotaling says these worms are the most abundant beast that lives up high on these mountains, at least when it comes to animals you can see with your eyes.

(SOUNDBITE OF SNOW CRUNCHING)

GREENFIELDBOYCE: Trudging along beside us is Peter Wimberger from the University of Puget Sound. He got interested in ice worms about 15 years ago when a student said he wanted to study them. Wimberger thought the guy was pulling his leg, that it was a prank.

PETER WIMBERGER: And he realized I didn't believe him. And all of a sudden he pulled out this little, small stack of papers, and he said, damn it, they're real.

GREENFIELDBOYCE: It was a small stack of scientific papers because hardly anyone has studied them. After some more hiking, Hotaling bends down and scoops up some snow.

HOTALING: Here's an ice worm.

GREENFIELDBOYCE: I would never have guessed that was a worm.

HOTALING: Yeah. Eventually, you get good at spotting them.

GREENFIELDBOYCE: It looks like a moving piece of thread, about an inch long, thin and jet black. It's wet, and its dark body sort of shimmers and glistens as it writhes in between ice crystals, going pretty intently and gracefully. Hotaling says finding one on the surface is a good sign.

HOTALING: That suggests to me that they're starting to come up.

GREENFIELDBOYCE: We keep going, ever higher. The sky is bright blue. We see other snow-topped peaks in the distance - Mt. Adams, Mt. Hood, Mount St. Helens. When we stop for breaks, I ask questions about ice worms; the answer is almost always the same - no one knows. Hotaling guesses they can live under 30 feet or more of snow, down where seasonal snow meets the older snow of the glacier. They may not need much to survive.

HOTALING: I've kept them in my fridge in my home for physiology experiments for a year or more without adding anything to their system, and they're fine.

GREENFIELDBOYCE: Winters here are brutal, but that may be when living is easy for ice worms because when they come out onto the glacier surface at the start of summer, they're actually fatter than they are at the end of the summer season. They're thought to eat algae and bacteria. But, again, who knows? And here's the most surprising thing about ice worms, which, after all, have ice in their name.

HOTALING: They can't handle even the slightest bit of freezing.

GREENFIELDBOYCE: Hotaling says the worms live at 32 degrees Fahrenheit, but lab tests he and a colleague did show that if temperatures dip even slightly below that, like just one degree, the worms die. Meanwhile, other tests show that the worms shrug off shockingly high levels of harsh ultraviolet light, which is a good thing for them because the sun up here is intense.

HOTALING: And I actually think they are coming looking for the sun a bit because they want to have some of that heat energy to drive their biochemical reactions.

GREENFIELDBOYCE: We cross over a ridge and onto Paradise Glacier.

HOTALING: Did you see them? It's happening. And so now you can start to see - like, you can just look out a little further, and you can sort of see them just dotting.

GREENFIELDBOYCE: Thousands and thousands of ice worms have appeared. As we watch, their numbers rapidly grow and grow until there's dark flecks everywhere on the snow.

HOTALING: There's no hint of them trying to blend into their surroundings.

GREENFIELDBOYCE: You don't want to step on them, but it's impossible not to. Hotaling thinks these worms must have some kind of impact on the world around them because a single glacier is estimated to hold more than 5 billion.

HOTALING: There are so many. Like, from where we're standing right now, I can see five, six, 10 glaciers, and if every one hosts that density of ice worms, like, that is just a massive amount of biomass that's in a place that is generally biomass poor.

(SOUNDBITE OF DIGGING IN SNOW)

GREENFIELDBOYCE: A grad student named Jordan Boersma shovel snow from some rocks and sets up a wildlife camera. It's one of several the researchers are putting up here to understand to what degree wildlife uses these glaciers. Already they've spotted birds like ravens and rosy finches chowing down on ice worms. The worms could be a critical food resource for some species. Hotaling points out that climate change is making glaciers like this one melt. This habitat is rapidly changing.

HOTALING: What goes away when a mountain glacier is lost? I don't think we have any real answer to that question.

GREENFIELDBOYCE: Ice worms might even speed a glacier's melting. Their bodies darken the glacier's surface, potentially making it absorb more heat. Hotaling thinks this is worth investigating. He says when it comes to ice worms, there are more mysteries than answers.

HOTALING: Ice worms are an extraordinary example of a bit of biodiversity on our planet that most people don't know about. And in this case of, like, Seattle and the Northwest, it's in the backyard of millions of people.

GREENFIELDBOYCE: And when they look at snow-capped peaks like Mt. Rainier, most don't realize they're gazing at the realm of the ice worm.

Nell Greenfieldboyce, NPR News.

(SOUNDBITE OF VUREZ'S "GLORIOUS CRYSTAL GLEAM (MMX2 - CRYSTAL SNAIL STAGE)") Transcript provided by NPR, Copyright NPR.

Tags: melting glaciers  high altitude  glacier  extreme cold  biology  climate change