The color of penguin poo: Satellites reveal the chilling truth of global warming’s impact on an iconic polar species
Scientists study poop patterns of Adélie penguin colonies across all of Antarctica over a 30-year span using Landsat satellite images, a first for capturing food-web and population trends at continental and decadal scales relative to climate change
image:
Nesting Adélie penguins on Antarctica's King George Island
view moreCredit: Michael Polito, UC Santa Cruz
SANTA CRUZ, Calif. – Scientists from a handful of universities across the country have made innovative use of satellite images from NASA: to determine the diet of Antarctic Adélie penguins across the continent by studying their icy feces with the fidelity and frequency that could only be captured by space technology.
The team, whose new study appears in Current Biology, found satellite images to be an ideal way to study colonies across the continent and over the span of decades to figure out what the mid-sized, tuxedo-patterned seabirds eat. This provided measurable insights into how their diets and population correlate to climate-change impacts like shrinking sea ice.
What they found is a concerning trend where global warming is once again threatening an iconic polar species: Over a 30-year period, Adélie penguins in places with more sea ice ate more fish. In years and places with less sea ice, they relied more heavily on krill.
The study also found that diet was linked to long-term changes in penguin populations. Colonies with more krill-based diets were more likely to be declining than colonies with more fish-based diets. Previous research has shown that chicks fed more fish tend to be larger and have better survival prospects than chicks fed more krill. In areas where fish are less available because of a decline in sea ice, penguins may be forced to rely more heavily on krill.
“Antartica has experienced rapid environmental change in recent decades, and this approach gives us a new and powerful tool to learn how it has affected penguins,” said co-author Michael Polito, a professor of ocean sciences at the University of California, Santa Cruz. The study, titled “Space-based monitoring of penguin diet links sea ice, food webs, and population change,” was led by Clemson University in collaboration with researchers from Stony Brook University, UC Santa Cruz, NASA, and other institutions.
“It’s exactly what it sounds like,” Polito said. “We spied on penguins from space by using satellite images to figure what they eat all around Antarctica to help explain their diet and population response to recent climate change.”
Decoding guano to map diet patterns
In the study, the researchers used the spectral signature—essentially, a quantitative measure of color across visible and infrared wavelengths—of guano to infer what the penguins had been eating. Based on the color of the guano, the team reconstructed Adélie penguin diets across nearly the species’ entire global range from 1984 to 2013.
Clemson researcher Casey Youngflesh collected samples at penguin colonies in the field and then analyzed the spectral properties in a lab. Polito then used stable isotope analysis of these same guano samples to determine where the penguins’ diet fell on a spectrum from krill to fish. Those data allowed the team to build a model connecting guano spectra to diet and apply that model to satellite imagery from Landsat, a long-running NASA Earth-observing program.
Youngflesh, an assistant professor of biological sciences at Clemson, said the study is the first use of satellite observations to capture food-web dynamics at continental and decadal scales, adding that this work points to a broader future for satellite-based wildlife monitoring.
“Satellites enabled us to do something that would otherwise be impossible,” Youngflesh said. “The innovation wasn’t the satellite technology itself, but the ability to leverage these decades of satellite imagery with modern geochemical, statistical and computational tools. No one intended for these satellites to be used to monitor penguins, but now we’re able to use them in these novel ways.”
The wide distribution of Adélie penguins and the relative ease with which they can be monitored from satellites make them useful indicators of broader Antarctic ecosystem change.
The challenges of Antarctic research
Until now, studying that process across the entirety of Antarctica has been difficult because the continent is vast, remote, and logistically challenging to work in. Researchers can visit some penguin colonies, collect samples and monitor populations, but it is not feasible to sample every colony repeatedly across decades.
Adélie penguins are one of the most numerous predators in Antarctica, but they depend on a relatively small number of prey species to survive. During the breeding season, their diet consists primarily of Antarctic silverfish and krill, a small, shrimp-like crustacean. Besides being less nourishing than fish, Polito said krill itself is becoming less abundant in some parts of Antarctica because of climate change and increased consumption by recovering seal and whale populations.
In the years since the end of this study period, large-scale declines and record lows in Antarctic sea ice have been observed. If those declines continue, Adélie penguins may have to shift toward more krill-dominated diets across larger parts of their range.
“Adélie penguins are an iconic species breeding all around the continent of Antarctica,“ Polito said. “They act as a ‘canary in the coal mine’ and our study illustrates how recent warming has disrupted the Antarctic marine food web they rely on to the detriment of many of their populations.”
Satellites link sea ice to Antarctic food webs and penguin population change
Clemson University researcher Casey Youngflesh spreading out guano samples in preparation for analysis.
Credit
Casey Youngflesh, Clemson University
Journal
Current Biology
Method of Research
Observational study
Subject of Research
Animals
Article Title
Space-based monitoring of penguin diet links sea ice, food webs, and population change
Article Publication Date
7-Jul-2026
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