Antarctic Adélie Penguins Enjoyed Favorable Foraging Conditions During Unusual Ice-Free Season
Adélie penguins in continental East Antarctica, covered more ground in less time by swimming instead of walking as they searched for prey during an unusually ice-free 2016-2017 breeding season, according to a new study. Without the need to locate cracks in sea ice for breathing, the penguins - considered a sentinel species that can warn of the environmental effects of climate change in continental Antarctica - were also able to conduct shorter dives while catching more krill. This higher foraging success led chicks to grow faster while increasing body mass in adult males and females. Although previous research has tracked various ways that Adélie populations have responded to interannual variations in sea ice, most of these studies have been correlational rather than experimental, and looked at population and breeding effects only - without examining how foraging behavior could account for links between environmental changes and breeding success. To track foraging behavior in detail across four breeding seasons within the past decade (2010-2011, 2011-2012, 2012-2013, and 2016-2017), Yuuki Watanabe and colleagues monitored 175 penguins in the Lützow-Holm Bay by tagging them with animal-borne GPS loggers, accelerometers, and video cameras. The 2016-2017 breeding season proved unusual since a large quantity of sea ice in the bay broke up and drifted away with currents, providing a natural experiment by which the scientists could observe penguins foraging in the absence of sea ice. The researchers found that the penguins may have expended an average of 15% to 33% less energy per trip compared with ice-covered seasons, putting that saved energy into growth and reproduction. Since climate models predict that the Antarctic will rapidly lose sea ice as the 21st century progresses, the results suggest that Adélie penguins may experience a population boom in the years to come. However, Watanabe et al. note that, according to previous studies, Adélie penguin populations that reside in warmer, sea-bordering regions (about 30% of the species) do not fare well when sea ice diminishes.