Stony Brook University Researchers Use Satellites to Track What Penguins Eat from Space

STONY BROOK, NY-July 8, 2026-Researchers at the State University of New York at Stony Brook (Stony Brook University) are using satellite images of Adélie penguin colonies and their guano to determine what they eat and how changes in sea ice are affecting the Antarctic's food web. This study emerged from the research team led by Institute for Advanced Computational Science (IACS) Endowed Chair for Ecology & Evolution Professor Heather Lynch. The study, "Space-based monitoring of penguin diet links sea ice, food webs and population change," has been published in the journal Current Biology.

First author and Stony Brook University alumnus Casey Youngflesh, now an assistant professor at Clemson University, reconstructed Adélie penguin diets across nearly the species' entire global range using the color of their guano as seen in satellite imagery. Changes in diet were strongly linked to both changes in Antarctic sea ice and long-term penguin population trends.

"Satellites enabled us to do something that would otherwise be impossible," Professor Youngflesh said. "The innovation wasn't the satellite technology itself, but the ability to leverage these decades of satellite imagery with modern 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. "We're no longer restricted to just studying the colonies we can easily get to," said Professor Lynch, "and this provides a whole new perspective on environmental change in the Antarctic."

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.

Professor Youngflesh collected guano samples at penguin colonies in the field and then analyzed the spectral properties in a lab. The researchers then used stable isotope analysis 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 satellites, a long-running NASA earth-observing satellite program.

Professor Lynch's team has been pioneering the use of satellites to track the abundance of penguins through time, but this study is the first to use satellite imagery to capture food web dynamics at such a broad spatial scale.

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. In years and places with more sea ice, Adélie penguins ate more fish. In years and places with less sea ice, they relied more heavily on krill.

"As sea ice dynamics change through time, we expect those changes to cascade through the food web," said Professor Youngflesh.

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.

"Penguins can certainly eat krill," said Professor Youngflesh. "But there are likely fewer krill available now than there were previously, partially because there are more things competing with penguins for that resource, including humans."

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.

"The fact that we can figure out what something is eating from a satellite is pretty incredible," Professor Youngflesh said. "It illustrates the power, and to some degree the necessity, of these types of data resources for understanding how natural systems work and how they are changing over time."

The research was supported by NASA NESSF fellowship NNX16AO27H, a Sigma Xi Grant-in-Aid of Research, an Analytical Spectral Devices Goetz Award, NASA grant NNX14AC32G, National Science Foundation grant ANT-1443585 and a Stony Brook University Institute for Advanced Computational Science Postdoctoral Fellowship.