There are many poorly understood links in the food web, often referred to as trophic relationships. Out in East Antarctica, a previously unconfirmed link between sea snails and Adélie penguins might reveal more than meets the eye for the Southern Ocean ecosystem.
When the option is to adapt or starve, animals are no stranger to getting scrappy in the face of climate change. Researchers conducted fieldwork in East Antarctica and revealed an underdocumented link in the food web of the Southern Ocean: Adélie penguins and their shelled pteropod consumption. Shelled pteropods, specifically Thecosomata, a suborder of free-swimming sea snails. The study aimed to better understand Adélie penguin foraging behavior and, in doing so, provided the first clear video evidence of Adélie penguins actively feeding upon shelled pteropods during their foraging sessions was acquired.
Researchers published their results in Marine Biology on March 16, 2026
The suborder Thecosomata are key components of the Southern Ocean's food chain, providing an abundant source of food for consumers in the environment. Theocosmata are also vulnerable to ocean acidification, a consequence of large-scale fossil fuel usage. Very little direct evidence of higher predators preying on Thecosomata is available, however necessity can often lead to unconventional behaviors.
Researchers found eight chick-rearing Adélie penguins, four female and four male. The penguins were equipped with time-delay, saltwater-activated cameras featuring a maximum of 12 hours of recorded video capacity along with a GPS sensor recording data every 10 seconds.
Over 86 hours of video footage were manually analyzed after the penguins' dive. Of the eight birds, seven of them were confirmed via video to consume the shelled pteropods, mostly Clio pyramidata and Limacina rangii, from what can be identified. For two of these individuals, over 60% of the prey consumed were shelled pteropods.
Reasons for this rate of consumption could range from preference, the energetic condition of the individual or prey availability. It was found that when dense areas of shelled pteropods were encountered, the penguins opportunistically consumed more, possibly due to availability but the influence of experience is not to be unconsidered.
However, this data does not suggest the Adélie penguins primarily choose shelled pteropods. In fact, most of their diet on the observed foraging dive consisted of krill as the dominant food type, followed by pteropods, then the rest filled in with other oceanic prey items suitable for a penguin. Krill and fish are the most energetically "profitable" for the penguins, though the rate of pteropod consumption can suggest a possible emerging food source.
"Our findings reveal that pteropods can serve as an opportunistic yet substantial prey for Adélie penguins, highlighting an overlooked but potentially significant trophic pathway," said Hina T. Watanabe, corresponding author and researcher of the study.
Some limits do apply to this study, though they do not underscore the importance of this discovery. Limitations include only studying a single colony for a single season and being limited to just the first half of the video evidence for the foraging trips, as foraging trips can be up to 34 hours long.
"Our next step is to examine whether this trophic link is persistent across years and colonies, or only occurs under specific conditions," said Watanabe.
Capturing video evidence of Adélie penguins actively consuming shelled pteropods highlights an underrepresented link in trophic relationships. While this direct observation answers some questions, researchers are more interested in what the larger scope of this relationship can mean for the Southern Ocean food web and the changes that might occur under climate-driven pressures.
Hina T. Watanabe and Akinori Takahashi of the National Institute of Polar Research with Hina T. Watanabe, Akiko Kato, Léo Marcouillier, Frédéric Angelier and Yan Ropert-Coudert of the Centre d'Etudes Biologiques de Chizé at La Rochelle Université with Léo Marcouillier and Thierry Raclot of the Université de Strasbourg, and Akinori Takahashi of the Polar Science Program at the Graduate Institute for Advanced Studies contributed to this research.
The WWF-UK, the National Institute of Polar Research, JSPS KAKENHI and the Institut Polaire Francaise Paul-Emile-Victor made this research possible.
