Polar Meltdown
Is the heat wave on the Antarctic Peninsula a harbinger of global climate change?
As early as the mid-'80s, researchers at Palmer could see the local Adelie population dropping. At the same time, chinstrap penguins, almost unknown here before the late 1950s, were (and are) prospering, sometimes walking right into Adelie rookeries and setting up housekeeping flipper to flipper with their cousin species. And while krill may be down, both penguins eat them, so a food shortage seemed an unlikely way to explain their differing fates. Except for a dark line under their beaks, chinstraps look a lot like Adelies. And for a long time scientists knew of no significant behavioral differences between the species that would explain why one might do better than the other. A big clue came in the coldest, darkest months of 1988. That year the U.S.-chartered research vessel Polar Duke explored the Weddell Sea on the east side of the Antarctic Peninsula. The expedition, with Fraser on board, found the winter ice pack swarming with Adelie penguins. By contrast, the open sea glittered with chinstraps. Until then nobody knew that Adelies depend on sea ice to get through the winter, feeding on krill around its edges. In recent years, as sea ice has become scarcer around Palmer, it became apparent why the region's Adelies were struggling while the chinstraps flourished.
But that's not the Adelies' only problem. By nature, Adelies are hard-wired for a narrow and inflexible range of behavior, as an anecdote from several winters ago illustrates. The icebreaker encountered perhaps 2,000 Adelies marching along single file. As the ship pulled even with the marchers, the lead bird reached a gap in the ice perhaps a foot across. It hesitated, hopped over, tripped on a small bump, fell flat on its face, popped up, and kept going. "Damned if every single penguin didn't jump at exactly the same place and do a face plant exactly like the first one," Fraser recalls. "Bam, bam, bam." Not one Adelie thought to cross just 5 inches to the left or right. "That says something about the intelligence of Adelies," Fraser said.
This is more than a humorous story to Fraser. It demonstrates that, even more than many other penguins, this species has evolved very inflexible habits. "That is a boon in a fragile and tough environment where, once one finds a good niche, it pays off to stick with it," Fraser explains. "But it is a behavioral flaw in times of climate change."
Creatures of habit. Around Palmer, he sees evidence on every visit to the rookeries of the Adelies' inability to adjust to surprises. The birds live a dozen years or longer and mate for life. Once a pair establishes a nesting site--most commonly on the same island where they were born and often in the same colony--the couple usually returns to the exact same nesting place year after year.
But warmer air holds more moisture, and in this still-cold place, that means more snow. Prevailing winds here pile snow deepest on the southwest-facing sides of the small islands where the penguins nest. The birds there seem incapable of recognizing, in the deepening snow, that it is time to set up housekeeping somewhere else. When spring arrives in September and October, the Adelies often--and stubbornly--pile pebbles atop snow 2 feet thick or more to build their nests. Later, frigid meltwater kills eggs and newborn chicks by the score. By contrast, chinstraps seem a bit more flexible in where they nest, choosing sites based more on their immediate suitability.
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