December is behind us, but there’s still a lot icy-cold winter left in our part of the world. That means we’re surrounded by snowmen, sleds, and cute little images of penguins and polar bears. This season I’m seeing those penguins in a whole new light, thanks to research presented at the American Geophysical Union’s annual meeting last month.
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| Nesting Adélie penguin feeding a chick, Danger Islands, Antarctica. Image Credit: Michael Polito, © Louisiana State University. |
Adélie penguins live on the opposite side of the world from Santa, along the Antarctic coastline. They are adorable, with tuxedo-like coloring and white rings around their eyes. Adults are a little over 2 feet tall and weigh 8-12 pounds. During breeding season Adélies live in large, tightly-packed colonies. They return to the same spot to nest each year. They also poop a lot.
You might say that Adélies are a picky species. To breed successfully, they need ice-free land, open access to water, and a good marine food supply. Since the Antarctic is one of the most rapidly changing places on the planet, in large part due to climate change, many researchers call Adélie penguins “the canary in the coal mine.” In other words, by observing these cute animals we can learn a lot about how the climate is changing and the impacts of this change.
It’s tough to observe creatures in a place where 99% of the land is permanently covered in snow and ice. There are no cities or towns in Antarctica, only research stations and tourist-carrying vessels. The appropriately named Danger Islands, where some of the largest Adélie colonies are located, are surrounded by large fragments of ice. In fact, it was only four years ago—in 2014—that scientists even discovered there were large penguin colonies in the Danger Islands. Now we know there are about 1.5 million Adélies there.
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| Quadcopter aerial imagery of an Adélie penguin breeding colony on Heroina Island, Danger Islands, Antarctica. Image Credit: Thomas Sayre-McCord, WHOI/MIT. |
The colonies were discovered in pictures taken by Landsat 8, an Earth-focused imaging satellite. Since 1972, Landsat images have been used to monitor and study all kinds of things—including wildfires, glaciers, and forestry. Since the images are taken from 438 miles above the surface of the Earth, you can’t see individual penguins in them. But you can see their collective poop stains.
Penguin poop, or “guano” if you want to be dinner-table appropriate, is pink. Because the Adélies live in such close quarters during their breeding months and their colonies are so large, their nesting areas have a nice pink hue that’s visible from space.
After seeing this characteristic sign on Landsat images, an expedition team went out to the Danger Islands in December of 2015. While there, the team counted penguins, collected samples from nesting grounds, and did other things that biologists do. But as a physicist, what really caught my attention was their guano analysis.
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| Casey Youngflesh processes penguin guano samples aboard a ship in the Antarctic. Image Credit: Photo courtesy of Casey Youngflesh. |
At the AGU meeting, the University of Connecticut’s Casey Youngflesh talked about how he collected guano samples during the expedition and processed them to learn about the diet of Adélies (he was then a graduate student at Stony Brook University working with Heather Lynch). Adélies eat primarily krill, a type of crustacean, and fish. The researchers wanted to know how diets varied between colonies and over time.
Here’s where the cool physics connection comes in. The color of a penguin’s guano varies slightly depending on the relative proportion of krill to fish in its diet. The difference between one pink and another can difficult to tell by eye, but there’s a better way. We learn about stars and galaxies by analyzing their spectral fingerprint—the specific wavelengths that together compose their light signal. But spectrometers, the tools that break down a light signal into its component colors, aren’t just for astronomers.
By performing a spectral analysis and then a chemical analysis of guano samples, Youngflesh and the team mathematically correlated diet to the spectral fingerprint of guano. Then, they scaled up this relationship and applied it to Landsat images. The result? They can now identify differences in diet between Adélies colonies based on images taken from space! They were able to go back through nearly 40 years of Landsat images and look for changes (preliminary results show no noticeable changes on average), and they can monitor Adélie diets going forward. That’s especially important given the scale of climate change in this region.
Spectral imaging isn’t a new tool to biologists—it’s used in many different fields, but this application is a nice reminder of the power of light to connect and inform us. Whether you’re looking at a distant galaxy or a distant continent, a twinkling star or a guano stain, light is there for the gathering, offering information that can help us better understand, monitor, and protect our home.
For more information on this project and others areas of penguin research, and to search for undiscovered colonies of penguins via their guano, check out Penguin Map.
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| Adélie penguins jumping of iceberg, Danger Islands, Antarctica. Image Credit: Rachael Herman, Stony Brook University/ Louisiana State University. |
