Climate change is putting picky penguin eaters at risk, according to a new study.
Chinstrap and Gentoo penguins live in close proximity to one another in the Antarctic Peninsula, especially during the summer breeding season. So in order to peacefully co-exist and avoid competition for food resources, they evolved different feeding strategies over time. Now, however, this seems to be backfiring on one of the two species.
Named for the black stripe under their chins, Chinstrap penguin populations are decreasing while Gentoo penguins, recognized by their bright orange beaks, are actually increasing in number.
"Our data shows Gentoo penguins have a more diverse and flexible diet than Chinstrap penguins, which forage farther offshore and preferentially feed on Antarctic krill during the breeding season," lead author Michael Polito, from Louisiana State University, said in a press release.
Thanks to climate change, the Antarctic Peninsula is the fastest warming region in the Southern Hemisphere, according to the British Antarctic Survey. Over the past 50 years, the annual air temperature has risen by about 5 degrees Fahrenheit (2.8 degrees Celsius).
"For a region that for most of the year hovers around the point of freezing, a few degrees plus or minus is the difference between freezing and melting, particularly of sea ice," Polito explained.
This isn't just bad for penguins, but for the Antarctic krill that they mainly feed on, which use sea ice for protection from predators. Krill also feed on algae that grow beneath these slabs of ice, so as temperatures warm the lack of sea ice means fewer krill are around for penguin species to eat.
Based on the laws of supply and demand, there isn't enough krill to go around - especially during breeding season when penguins have to worry about feeding their chicks. So Chinstrap penguins whose diet relies on Antarctic krill find themselves in a tough spot.
On the other hand, adaptable Gentoo penguins are doing just fine, even amongst rapidly changing environmental conditions. They are flexible in their diet and breeding location, and also likely ease the transition of their chicks into adulthood by feeding them for a longer period of time.
Researchers determined the species' feeding habits by examining their stomach contents, studying the ear bones of fishes to determine if the penguins were feeding nearshore or offshore, and analyzing breast feathers from fully grown chicks to see how much krill versus fish they were fed. The results showed two very different strategies.
"These may be the reasons why Gentoo penguins in the Antarctic Peninsula are benefiting from changes in climate and their populations are increasing, but Chinstrap penguins are decreasing," Polito said.
The results are described further in the journal Marine Ecology Progress Series.
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