Scientists say an estimated 150,000 Adelie penguins have been wiped out on Antarctica's Cape Denison in the five years since a giant iceberg blocked their main access to food.
A study recently published in the journal Antarctic Science says the B09B iceberg crashed with the Mertz Glacier Tongue and got stuck in Commonwealth Bay, an area that was rarely covered by sea-ice, making it ideal for Adelie penguin colonies.
The B09B, with an area of about 2,900 square kilometres (1,120 square miles), blocked access to the penguins' natural feeding areas beginning in December 2010. The huge piece of ice forced the birds to walk more than 60 kilometres (37 miles) in search of food, gradually reducing the population to just a few thousand.
Not coming back
"We saw a lot of dead carcasses, particularly the young, which was terrible to see. But the really important thing is that the penguins are just not coming back to that area," Chris Fogwill, a co-author of the study, told The Associated Press on Monday.
However, a penguin researcher who wasn't involved in the study isn't sure the birds are actually dead.
"Just because there are a lot fewer birds observed doesn't automatically mean the ones that were there before have perished," Michelle LaRue, a penguin population researcher at the University of Minnesota in Minneapolis, told Live Science in an email interview. "They easily could have moved elsewhere, which would make sense if nearby colonies are thriving."
LaRue says that Adélie penguin colonies always have dead birds scattered around because the carcasses don't decompose in Antarctica's dry, cold climate.
The new survey was conducted in 2013-14 by Fogwill and other scientists at the Climate Change Research Center at the University of New South Wales in Australia along with New Zealand's West Coast Penguin Trust.
Adelie penguins can be found throughout Antarctica. They are known for being sociable and gathering in groups as well as for their appearance as the classic tuxedoed penguin.
Researchers say it is hard to know how long it will take the Adelie penguins to recolonize the Commonwealth Bay area. The worst case scenario is that without their natural breeding cycle and lacking new members, the colony could die out in about 20 years.