While searching Antarctica’s rocky Cape Irizar, US biologist Steven Emslie stumbled upon ancient remains of penguins, along with some that looked quite fresh.
There were decaying carcasses – mostly of chicks – complete with feathers, as well as guano stains, implying recent use of the site. Old pebble mounds identified them as Adélie penguins, which use pebbles to build their nests.
“We excavated into three of these mounds, using methods similar to archaeologists, to recover preserved tissues of penguin bone, feather, and eggshell, as well as hard parts of prey from the guano – fish bones, otoliths,” Emslie says.
“The soil was very dry and dusty, just as I’ve found at other very old sites I’ve worked on in the Ross Sea, and also had abundant penguin remains in them.
“Overall, our sampling recovered a mixture of old and what appeared to be recent penguin remains implying multiple periods of occupation and abandonment of this cape over thousands of years.”
The problem is, there are no records of an active penguin colony at the site – located just south of the Drygalski Ice Tongue in the Ross Sea – in the nearly 120 years since Robert Falcon Scott and his colleagues first explored the region.
And Emslie’s further investigations have confirmed that. When he took samples back to the University of North Carolina Wilmington for radiocarbon analysis, he discovered there were at least three occupation periods of the cape by breeding penguins, but the last ended around 800 years ago.
The best explanation, he suggests in a paper in the journal Geology, is that when the last occupation ended, the remains on the surface were covered in snow and ice and preserved intact until recent exposure from snowmelt.
Global warming has increased the annual temperature in the Ross Sea by 1.5 to two degrees Celsius since the 1980s, and satellite imagery over the past decade shows the cape gradually emerging from under the snow.
So Emslie’s “fresh” remains are in fact about 800 years old.
“In all the years I have been doing this research in Antarctica, I’ve never seen a site quite like this,” he says.