Young emperor penguins brave icy, winter waters in their first year

Only months after their first ocean swim, young emperor penguins are braving Antarctica’s treacherous winter seas. GPS trackers strapped to 15 young penguins showed the birds venturing north to warmer waters beyond Antarctica’s pack ice in December 2013, and returning a few months later as the waters chilled.

That finding surprised some scientists, who thought the inexperienced juveniles might play it safe closer to the Antarctic sea ice’s edge rather than risk freezing or drowning in the choppy open sea. After all, “they just learned how to dive a few months beforehand,” says marine ecologist Sara Labrousse at the Woods Hole Oceanographic Institution in Massachusetts.

But within a few weeks of being on their own, at around 5 months old, these plucky penguins were already diving to depths of around 100 meters, like adult penguins do, the researchers report January 17 in Marine Ecology Progress Series. That’s just after they had shed their fluffy down, and before they had built up an insulating fat layer.

The tracked birds then headed more than 1,000 kilometers north to open, ice-free waters, in some cases reaching points roughly halfway between Antarctica and Australia. Data from more than 62,000 dives indicate the emperor penguins (Aptenodytes forsteri) made mostly shallow dives there, likely hunting fish and krill that feast on floating algae, the authors say.

In March or April, when the birds were about 8–9 months old, the fattened youngsters returned south and ventured back to Antarctica’s sea ice for winter.

Scientists don’t yet know why the penguins return to the ice, Labrousse says, suggesting it could be to feed on krill that eat algae attached to the bottom of ice. Learning more about these early behaviors helps scientists understand how lost sea ice and other changes could affect the penguins — a task that’s becoming more important amid climate change.