Dec. 3 (UPI) -- Penguins that only eat krill are more vulnerable to impacts of climate change, according to a new study.
Krill, small shrimp-like crustaceans, are a vital resource for penguins, seals and whales in Antarctica. But new research suggests some are more partial to the mini arthropod than others.
When researchers from Canada and the United States plotted penguin population changes over the last several decades, they found gentoo penguins are thriving, while chinstrap penguin numbers continue to decline.
By analyzing the nitrogen isotope values of amino acids in penguin feathers collected over the last century, scientists were able to track the diets of gentoo and chinstrap penguins. The data, detailed this week in the journal PNAS, showed the gentoo penguin's diet has become increasingly varied over the last few decades, while the chinstrap penguin continues to rely almost exclusively on krill.
Because the chinstrap penguin's diet is so picky, the species is especially vulnerable to the impacts of climate change and human activities.
"When seal and whale populations dwindled due to historic over-harvesting, it is thought to have led to a surplus of krill during the early to mid-1900s," study co-author Michael Polito, researcher at Louisiana State University, said in a news release.
Scientists theorized that the abundance of krill spurred an explosion of the gentoo and chinstrap penguin populations.
"In more recent times, the combined effects of commercial krill fishing, anthropogenic climate change, and the recovery of seal and whale populations are thought to have drastically decreased the abundance of krill," Polito said.
As krill numbers declined, isotopic data showed gentoo penguins began eating more and more fish and squid. Chinstrap penguins failed to make the same adjustments. As a result, their numbers have suffered.
"Since the 1930s, human activities have reduced the population of chinstrap penguins by 30 to 50 percent. That's accompanied by increases in the gentoo population of up to 600 per cent in some locations," said University of Saskatchewa researcher William Patterson. "This has implications for future populations, where the specialists are more likely to be endangered by human activities and variability in the natural environment."