Planetary temperatures warmed up naturally thousands of years ago, at the end of the last Ice Age. Some Antarctic penguin populations flourished under the changes. 11,000 years later, however, some Adélie and chinstrap colonies are turning from winners into losers: As temperatures around the western Antarctic Peninsula increase at some of the fastest rates on Earth, their population numbers are falling quickly, while gentoo penguins appear to holding their own.
What’s the difference between then and now?
Looking the past to learn more about how different species might fare under today’s anthropogenic climate change, researcher Gemma Clucas of the University of Southhampton, U.K., and her team collected samples of feathers and blood from 537 individual Adélie, chinstrap, and gentoo penguins, which live and breed near each other on the Antarctic Peninsula, and sequenced DNA from the samples.
By calculating the rate of genetic diversification revealed in the DNA, Clucas and her team were able to project how the different species’ populations changed over time, and draw some tentative conclusions about why. Their findings are published in the June 12, 2014 edition of the open-access journal Scientific Reports.
Their findings suggest that while a certain absence of ice is important to improving the welfare of penguins, too little can tip things against them.
During the last Ice Age, the amount of ice covering land and water around the Antarctic Peninsula limited the growth of these penguin populations, because all three species need access to the sea to feed, and ice-free land for breeding. When snow and ice cover on both water and land decreased, the penguins were able to get at increased amounts of krill, minute shrimp which feed on algae growing beneath the ice. There was also more ice-free land available for nesting and raising chicks. Gentoo, chinstrap, and Adélie penguins all appear to have flourished for thousands of years under these conditions.
But with sea-ice further melting over the last half-century, krill habitat has also decreased. Most colonies of chinstraps and Adélie, which have krill-heavy diets, are losing numbers fast, while gentoo penguins, which eat a wider array of fish and squid in addition to krill, seem to be showing greater resilience to the shifting environment. Clucas and her colleagues think the more varied diet is a key:
The researchers don’t want the findings to be taken as a sign that global warming is nothing to worry about, however. Says one report co-author in a statement, “We are not saying that today’s warming climate is good for penguins. In fact, the current decline of some penguin species suggests that the warming climate has gone too far for most penguins.”