MUMMIFIED penguins have been found littering the ground in Antarctica. The birds seem to have died during two bouts of extreme weather over the past 1000 years. Such conditions are expected to become more common as a result of climate change, making mass die-offs more likely.
The birds were found on Long Peninsula, in east Antarctica, by researchers led by Liguang Sun at the University of Science and Technology of China in Hefei.
It isn’t unusual to find dead penguins, but those on Long Peninsula – mainly chicks – are especially numerous, with up to 15 per square metre and hundreds overall. “They consist of well-preserved dehydrated mummies,” the researchers write in a paper.
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All are Adélie penguins (Pygoscelis adeliae), which only live in Antarctica. They currently breed in the Antarctic summer at about 250 sites, forming huge colonies near the coast.
To find out what happened on Long Peninsula, Sun’s team used carbon dating to estimate the ages of the corpses. They also studied sediments, which contain excrement and nest material.
They found that penguins have lived there for at least 3900 years, but most of the deaths occurred in two periods, about 750 and 200 years ago. The colonies were abandoned afterwards each time, as little new sediment was laid down in later centuries.
The cause seems to have been unusually heavy snow or rain over several decades. The team found evidence of floods that carried sediment and corpses downhill, and signs of erosion (Journal of Geophysical Research: Biogeosciences, ).
Rain is a lethal threat, says Yan Ropert-Coudert of the French National Centre for Scientific Research. “The chicks especially are not made for wet weather,” he says. Hypothermia is a risk. Meanwhile, snow makes it hard for parents to find pebbles to make nests, and if it melts the meltwater can drown chicks.
The cause of the wet weather was probably a shift in the Southern Annular Mode, a pattern of winds in the Southern Ocean that can send extra damp air to east Antarctica. Climate change is likely to make this more frequent.
Adélies are widespread, so can handle occasional disasters, says Steven Emslie at the University of North Carolina Wilmington. But they face increasing pressures. In April, Emslie published a study of the largest modern Adélie colony, at Cape Adare. “Sea level rise is going to displace hundreds of thousands of penguins there and at Cape Hallett within the next 30 to 50 years, as those beaches are gradually inundated,” he says.
Ropert-Coudert has detailed the disastrous 2013-14 breeding season, when no chicks survived in a major colony on Petrel Island in east Antarctica. Unusually heavy snowfall killed them, combined with weak winds that failed to break up the sea ice, preventing adults from catching enough food. And it wasn’t a one-off. “In 2016-17 we had a second massive breeding failure in the same place,” he says.
According to the International Union for Conservation of Nature, Adélie penguins are at low risk of extinction. But Ropert-Coudert says repeated breeding failures on Petrel Island are a bad sign. The solution is to limit climate change as much as possible, he says. We could also set up protected areas to “prevent other threats from superimposing on the climate ones”.
This article appeared in print under the headline “Graveyard is a bad omen for penguins”
