They were climate change "winners," the authors write. About 15,000 to 20,000 years ago, the retreating ice exposed expanses of bare ground that the penguins could build nests on, allowing them to expand their populations.
This historical perspective is helping researchers to understand the penguins' current situation in western Antarctica. (See "West Antarctic Glaciers Collapsing, Adding to Sea-Level Rise.")
The warming that researchers are now measuring on the Antarctic Peninsula is approaching the limits of what these penguin species experienced in the past, says Gemma Clucas, a doctoral student at the University of Southampton in the United Kingdom and lead author of the new paper. "We're seeing a very different response [from them now.]"
Genetic analysis of 249 gentoo, 166 chinstrap, and 122 Adélie penguins showed that all three populations expanded after the last glacial maximum—when the ice sheets were at their greatest extent—the researchers report today in the journal Scientific Reports. But only gentoo penguins seem to be holding their own against current warming trends in the western Antarctic. The other two species are in decline.