Adélie penguins colony crash may not be a die-off, expert
Tuesday, February 16, 2016, 12:18 PM - New research published last week suggests a grounded iceberg is responsible for a massive population crash of a penguin colony in eastern Antarctica.
Only 10,000 Adélie penguins remained out an estimated population of 160,000 in the two years after the iceberg cut the colony off from its food supplies in 2010.
However, at least one Antarctic researcher says while the penguins' numbers may have sharply declined, that doesn't necessarily mean they have all died off, as some media reports have suggested.
"To suggest that 150,000 birds died in two years because of this one iceberg, is a pretty big leap, in my opinion," Dr. Michelle LaRue, a University of Minnesota scientist whose research focusses on Antarctic mammal and bird populations, told The Weather Network. "We can’t really say that with the information at hand."
The original study, published in the journal Antarctic Research, noted that when iceberg, known as B09B, cut the colony's access to the open sea, it would have forced the penguins to make a detour of 60 km to find food, and seriously hampered their breeding cycles.
But while LaRue says she doesn't claim to know exactly what happened to the birds, she says many of them may simply have moved, or postponed breeding.
That's not mere speculation: LaRue points to another incident when iceberg B-15 put a Ross Sea colony in similar straits. Luckily, many of those penguins were marked for study, so scientists could see how they reacted.
"Turns out that they moved a lot more between colonies, rather than coming back to the colony [where] they were previously breeding," LaRue says. "This was because of extensive sea ice as well."
She noted the researchers mention another nearby colony not blocked off by B09B was found to be thriving, and says some of the members of the cut-off colony might have migrated there.
Image: Adélie penguins, NOAA/Wikimedia Commons
Adélie penguins prefer to return to the same place for breeding. LaRue says some of the ones who were trapped at Cape Denison may have been unable to adapt, but the species as a whole has proven flexible, especially when faced with a massive detour of dozens of kilometres.
"If it’s going to take that long to get there, why on earth would you go back? And if you did, why would you breed?," she says.
The original study uses dire language to describe the state of the colony. A widely-quoted release from the University of New South Wales does not explicitly say that all the missing birds in the "decimated" colonies have died off, but quotes one researcher's bleak description of the colony's remnant.
"The normally noisy and aggressive Adélie penguins were so subdued they hardly acknowledged our intrusion into their realm," Dr. Kerry-Jayne Wilson said in the release. "It was sad to walk amongst thousands of freeze dried chicks from the previous season and hundreds of abandoned eggs."
But LaRue, who has herself visited the Antarctic, says grisly scenes like that are not uncommon in penguin colonies.
"Having that be the only anecdote of the fact they could have died is pretty unimpressive," LaRue says. "If you go to a penguin colony, you can’t walk without stepping on them, they are all over the place," she said.
She says she hasn't spoken to the researchers, and is not criticizing their work, but wanted to respond to media reports suggesting the colony crash was due to a massive die-off.
In any case, the colony would only have accounted for a small proportion of the Adélie penguins' population, which numbered 3.79 million breeding pairs at last count.
"150,000, even lets just assume they did all die, that certainly is not apocalyptic," she says.