After 30 years, researchers are taking another look at the decline of Antarctic penguins such as the chinstrap penguins.
Credit: Wikimedia
WASHINGTON: Young Antarctic penguins may be dying because they are having a tougher time finding food, as melting sea ice cuts back krill populations, U.S. researchers suggested.
Only about 10% of baby penguins tagged by researchers are coming back in two to four years to breed, down from 40-50% in the 1970s, said the 30-year study in the Proceedings of the National Academy of Sciences.
"It is a dramatic change," lead researcher Wayne Trivelpiece of the National Oceanic and Atmospheric Administration's Antarctic Ecosystem Research Division, said. "There are still two to three million chinstrap pairs in this region but there were seven to eight million two decades ago," he said.
Population restricted to one area
Chinstrap penguins, known for their characteristic head markings that resemble a cap with a black line just under the neck, are the second largest group in the area after the macaroni penguins, and are at particular risk because their population is restricted to one area, the South Shetland Islands.
"There is some concern now. We need to follow these animals and track them," said Trivelpiece.
The study included chinstrap and Adelie penguins in the West Antarctic and tracked the abundance of their main food source, krill, which are the small shrimp-like crustacean mainly eaten by whales, seals and penguins.
Populations affected by environment
Trivelpiece was a co-author on a study published in 1992 that suggested penguin populations were surging and subsiding according to changes in sea ice - with the chinstrap doing better in warm years and the Adelie thriving in cold years.
Chinstrap penguins eat and make their nests away from the snow and ice and so are considered ice-avoiding animals, unlike their Adelie counterparts who feed in icy habitats and are seen as more vulnerable when there is less ice.
However, Trivelpiece and his co-authors now believe that krill are the real culprit for the disappearing penguin populations, and the damage affects both types of penguins.
"Unlike many other predators in this region, Adélie and chinstrap penguins were never directly harvested by man; thus, their population trajectories track the impacts of biological and environmental changes in this ecosystem," the authors wrote in the paper.
