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Researchers have reported a new and potentially more effective way of tracking penguin and other marine animal migrations throughout Antarctica.

Recording the movements of animals via GPS tracking devices has become a common technique among scientists, but the technique can be expensive, and sometimes invasive to the animal.

Now, a team including researchers from Louisiana State University, NOAA Southwest Fisheries Science Center, Oxford University and the Instituto Antártico Argentino have taken a play from the forensic science playbook to test a potentially better way of recording animal migrations.

They used a technique called compound-specific stable isotope analysis of amino acids--a high-resolution forensic analysis method to determine the chemical composition of something--in this case, penguin tail feathers.

First, the researchers attached geo-tags to 52 adult Chinstrap and Adélie penguins at their breeding colonies on the South Shetland Islands, located about 75 miles off the coast of Antarctica. The team returned a year later to retrieve the tags, but they also took a single tail feather from each of the 52 tracked penguins, plus feathers from 60 other penguins from the same group that had not been tracked.

They found that the data from the tags matched the chemistry of the penguins’ feathers, which allows the researchers to accurately determine where the penguins traveled, and what they ate.

"You can say, penguins 'are where they eat,' because a geochemical signature of their wintering area is imprinted into their feathers," said Michael Polito, lead author of the study and assistant professor in LSU’s Department of Oceanography & Coastal Sciences.

Chinstrap and Adélie penguins belong to the family of “brush-tailed” penguins, thanks to their 15-inch-long tail feathers. The birds shed all of their feathers after each breeding season, and before they migrate to their oceanic wintering grounds. But their tail feathers keep growing during the winter season while they are at sea.

The krill the penguins feed on have their own chemical signature of the ocean they live in, which also gets absorbed penguins’ feathers. Through the forensic analysis technique, the researchers can pinpoint where the penguins stopped to feed.

This method could be just as reliable as GPS tagging, while also being less invasive and inexpensive.

"This novel approach could be applied to different tissues from a wide variety of marine animals that migrate over long distances including seabirds, sea turtles, seals and whales," said Polito. "Using stable isotope forensics to increase the size and scope of animal tracking studies will help us to better understand these charismatic species and ultimately aid in their conservation."

The work was published today in Biology Letters.

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