After laying eggs, a female travels across the ice and out to sea to feed on krill, fish and squid that she regurgitates to feed her young. The male keeps the eggs warm until she returns. But when the sea ice is extensive, the female may be gone for months. The male eventually gives in to his hunger and abandons the egg or chick.
Caution Against Generalizations
Thus, as the scientists note in their paper in Nature, extensive sea ice poses a trade-off for emperor penguins. In population terms, its nutritional advantage, which favors higher survival and further reproduction, "outmatches its physical disadvantage of reducing fecundity," they write.
Despite the findings that show a negative effect of global warming on emperor penguin populations, Weimerskirch cautions against making generalizations about the impacts of climate change on wildlife. For example, a reduction in the amount of sea ice is favorable to Adelie penguins, he said. On the other hand, elephant seals and some albatross species were also negatively affected by the prolonged warming period in the 1970s.
Climate scientists believe that Earth's polar regions are harbingers of the effects of global warming and play a major role in regulating global climate. The Antarctic circumpolar wave, for example, is tied to episodes of drought and deluges of rain in Australia.
The science, however, is still evolving. "We are progressively understanding how environmental variability affects populations," said Weimerskirch.
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