Adélie penguins poop pink guano. It’s so bright, you can see it from space.

The Adélie penguins that live across the coast of Antarctica and nearby islands love to eat tiny pinkish crustaceans called krill. They eat so much krill that it turns their guano (that is, their poop) a vibrant pinkish-red color. That poop stains the ground and, well, just about everything. Even their bodies.

The poop is so bright and so abundant, you can even see it from space. Which is helpful for scientists who want to count the Adélie all the way down in one of the most remote places on Earth.

“We don’t see individual penguins in the satellite imagery,” Heather Lynch, an ecology professor at Stony Brook University, said at the American Geophysical Union conference this week. “But we do see this pinkish stain left on the landscape by their guano. And we can work out from the area of the guano stains how many penguins must have occupied that site.”

Here’s what it looks like from space. In the red circle, you can see a brownish smudge. That’s penguin poop, an important indicator that penguins inhabit the area. And you thought those stains on your white underwear were bad!

Here’s another location with some prominent penguin poo.

Using this method, Lynch and her colleagues have been able to discover whole new — and massive — colonies of Adélie penguin, like a group of 1.5 million of them in the remote and aptly named Danger Islands. It’s also allowed them to go back into the satellite record and create a timeline, a history, of Adélie populations throughout the Antarctic.

The Adélie are actually useful for monitoring the Antarctic environment as a whole. That’s because while these birds live on ice-covered surfaces, they need to breed on exposed land. It means they’re sensitive to changes in both icy and rocky environments. So they can be a “canary in the coal mine” species.

It’s this longitudinal data that can help scientist better understand the long-term health of the species. “While the population of the Adélie islands is massive, it was even larger in the past,” Lynch says. She believes the penguins have been slowly, steadily declining since the 1990s, though they’re unsure of exactly why. “We want to be able to protect [this population], and that involves trying to understand why the populations changed.”

Scientists have been able to correlate the precise color of the guano stains with changes in the birds’ diets over time. In the photo below, you can see ecologist Casey Youngflesh preparing penguin guano for color analysis. “Penguin guano almost has the consistency of a wet tuna salad,” he says. “The guano has a pungent fishy scent and is definitely not pleasant. It’s something you just have to learn to cope with.” (Seems like a fun job.)

Knowing what the penguins are eating helps gauge the health of this species as climate change distorts the landscape, and as commercial fishery operations go after krill for fish oil supplements. Like so many species that live near the poles, all the species of penguins in the Antarctic face habitat loss.

And scientists have already noted the penguin population losses in the regions of Antarctica most impacted by climate change. (Though, in other places on the continent, penguin populations appear to be growing.)

If you’re really interested in the health of this species, you, too, can monitor penguin poop from space. On her lab website, Lynch has posted Google Earth satellite image files for anyone, anywhere, to help in the hunt to identify new penguin populations or changes in existing ones. “Look for the pink or brown stains in the snow, and keep in mind that colonies will always be close (max 1 - 3km) to water,” the website explains.

“We continue to discover new penguin colonies from satellite imagery every time we look,” Lynch says. “And I’m sure there are more out there.”