Adelie Penguins Poop So Much, Their Feces Can Be Seen From Space
Satellite images of the Adelie penguin’s pink guano shows how their colony size and diet have changed over the last 4 decades
Typically, humans have sent satellites into space to hunt for the most otherworldly and mysterious objects: black holes, quasars and exoplanets. But at least one NASA-funded team is using our eyes in the sky to study one of the most worldly and least mysterious objects: they’re using satellites in space to monitor massive penguin poop stains.
The krill-heavy diet of Adélie penguins, which live on the coast of Antarctica and the remote islands nearby, turns their guano a striking pink color. When contrasted with surrounding snow, the guano shows up pretty well in LandSat images. Brian Resnick at Vox reports that researchers at the American Geophysical Union conference recently explained how they are using those images to find remote penguin colonies and even reconstruct the diet and history of the colonies over time.
The satellite images don’t show individual penguins, since they are much too small to be seen. But the immense accumulation of bright pink poo is relatively easy to spot, which allows researchers to calculate the colony's size.
“Male and female penguins take turns incubating the nest. The guano left behind builds up in the same areas occupied by the nests themselves,” co-investigator Heather Lynch, an ecologist at Stony Brook University says in a NASA press release. “We can use the area of the colony, as defined by the guano stain, to work back to the number of pairs that must have been inside the colony.”
Yasemin Saplakoglu at LiveScience reports that the team spent 10 months poring over clear satellite image of Antarctic islands to create a global survey of the species. The team thought they’d done a thorough job, but once they started using an algorithm to help them find poop-peach colored pixels, they discovered they’d missed quite a few of the waddling birds. In particular, they’d overlooked a massive 1.5 million strong colony on Heroina Island in the remote Danger Islands. When a team traveled to the suspected roost, they found the computer was indeed right and the island was teeming with the birds.
“We thought that we knew where all the [Adélie] penguin colonies were,” Lynch said during a new conference. “We, I think, had missed it in part because we hadn't expected to find them there.”
The team is reviewing satellite images dating back to 1982 to learn about the population rise and fall of individual Adélie colonies. They’ll also examine the color of the massive skid marks to learn about the penguins’ diets over time. When the penguins are munching on fish, their guano tends to come out white, but the more krill they eat the pinker the waste becomes.
To test their idea, the team collected guano from the colonies, which it turns out is not as fun as it might sound.
“Penguin guano almost has the consistency of a wet tuna salad,” co-investigator Casey Youngflesh, a postdoc at the University of Connecticut, tells Resnick. “The guano has a pungent fishy scent and is definitely not pleasant. It’s something you just have to learn to cope with.”
After powering through the stench and analyzing the guano, the team found that their diet estimates from the satellite images correspond pretty closely with what the penguins are actually eating. However, when they compared the diet data with fluctuations in colony size, they were surprised to find there was no strong connection.
“It is interesting that no obvious trend in diet was seen over time, despite changes in the physical environment,” Youngflesh says in the press release. “This was a big surprise, since the abundance and distribution of Adélie penguins has changed dramatically over the last 40 years and scientists had hypothesized that a shift in diet may have played a role.”
In fact, some colonies have seen dramatic population crashes, while others have remained stable or grown larger, and researchers would like to understand these changes better. Getting a handle on the size of the colonies and their natural fluctuations over time is the first step to understand what is happening. That will help researchers manage and protect the penguins as more man-made threats, including climate change and krill fishing, which harvests the tiny crustaceans for the health supplement industry, put more pressure on their nesting grounds.