Adelie penguins target jellyfish with prominent gonads for a tasty meal, research from Antarctic "penguin cams" suggests.
Footage shows the penguins occasionally feeding on jellyfish with visible sex glands, even when their preferred food of small shrimp-like crustaceans known as krill are available, the study backed by conservation charity WWF found.
The findings, revealed in a new publication by scientists from the French and Japanese national Antarctic programmes, come from research conducted by fitting penguins with tiny cameras to see what they got up to under the sea ice.
The cameras weighed between 15g and 22g - less than an ounce - and were retrieved when the birds returned to the nest.
Footage filmed by the penguin cams was released last December when it became an internet sensation, WWF said.
It is thought the penguins, the smallest and most widespread in the Antarctic, target the jellyfish with prominent gonads because the carbon and protein content of the reproductive organs is greater than any other part of the creature.
Jean-Baptiste Thiebot from the National Institute of Polar Science, Japan, said: "We were surprised to see the penguins go for jellyfish and it raised the question: is this new behaviour for Adelie penguins, possibly developed because they had a hard time finding food during this year of very unusual sea-ice conditions, or is it simply newly revealed by using this video approach to study their diet?
"To clarify this, we will need to see comparisons across different penguin species and different ocean regions.
"But these observations already reveal one more piece of the puzzle in the oceans' food web."
Information gathered from the research is being used by the wildlife charity to help create marine protected areas around Antarctica, to protect species such as the Adelie penguin, which is affected by fishing in the region and climate.
Rod Downie, WWF polar programme manager, said: "A year on from the release of the penguin cam footage, it's clear that we still have a lot to learn about Adelie penguins and other ice species.
"The results give us a better understanding of how they might respond to climate change and related shifts in the Antarctic food web."
Studies such as the penguin cam research will help international efforts to protect the "amazing waters" around Antarctica, he said.
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