They may all waddle around in their tuxedolike feathers, but the penguins of the Antarctic Peninsula are not equal in their ability to adapt to a warming climate.

While the populations of the Adélie and chinstrap penguin species are currently declining, the gentoo species is increasing. But this hasn't always been the case, according to a recent study published in the journal Scientific Reports.

By tracing the genetics of the region's present-day penguins back about 12,000 years, a team of scientists from Oxford University, the U.K.'s University of Southampton and Woods Hole Oceanographic Institution (WHOI) found that the penguins' ancestors had flourished during the period of warming following the end of the last Ice Age.

"The populations of all three species of penguin during that time increased because the ice melted and provided them with more breeding space," said co-author Michael Polito, a WHOI postdoctoral investigator.

"Now, two of the three species are declining in response to current warming."

Why it's better to be a 'generalist'
So, what changed?

According to Polito, although the melting of the Antarctic Peninsula's sea ice has provided the penguins with more open land—and, in turn, better breeding sites—it has also reduced their main food source, krill.

The reason the gentoo species of penguin is able to flourish under these conditions, when the Adélie and chinstrap penguins are not, has to do with a contrast in diet. Gentoo penguins are not as dependent on the tiny, transparent crustaceans as the other two species, which also happen to rely on fish that eat krill.

"Gentoo penguins have a much more flexible diet than the other two species," Polito said. "Therefore, they may be better able to adapt to the shortage of krill."

Moreover, he added that, unlike the others, gentoo penguins live in small colonies and forage closer to shore. And their larger size allows them to dive deeper in the water, giving them access to more kinds of fish.

"Basic ecological theory would predict that specialists are more sensitive to environmental changes than generalists," he said. "By definition, specialists are little less flexible."

Commercial fishing of krill and the rebound of the region's krill-eating humpback whale population are also contributing to the reduction of the penguins' main source of prey, Polito said.

"We are not saying that today's warming climate is good for penguins," Tom Hart, a co-author from Oxford's Department of Zoology, said in a press release. "In fact, the current decline of some penguin species suggest that the warming climate has gone too far for most penguins."

"Penguins needs two things to be successful," Polito said, "a place to breed and food to eat."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500