Fewer penguins

A yacht brought the researchers to Deception Island, a volcanic island of 137 square kilometers (85 square miles) in northern Antarctica. The researchers then continued their journey on foot, in often icy rain and heavy wind. The team was tasked with finding out just how many chinstrap penguins breed on Deception Island.

The German-American research team's mission was organized by Oceanites, a nonprofit organization committed to the protection of Antarctica. The researchers went from one penguin colony to the next, counting all the chinstrap penguins and their island nests. "The animals are not scared of people," biologist Thomas Müller from the Frankfurt-based Loewe Biodiversity and Climate Research Center told Deutsche Welle. "But they will occasionally snatch at your leg if you get too close."

Thomas Müller currently works at Maryland University in the U.S., and was a member of the team that did the penguin population census. "The biggest colony consisted of almost 50,000 animals," he said. "So of course you'll count wrong occasionally. That's why we always counted three times."

Half as many left

Chinstrap penguins can reach a size of almost 80 centimeters (31.5 inches), living in the sea and breeding in the ice-free zones of the coast. They are considered to be belligerent - a reputation Thomas Müller confirmed.

And their population has reduced considerably. Over a period of less than 10 years, their numbers have declined by almost 40 percent, the team's count showed. Due to their large habitat, chinstrap penguins are still not considered endangered. In addition to parts of Antarctica, they can also be found on islands in the South Atlantic.

The penguin colonies of Antarctica are becoming increasingly attractive to tourists, and Deception Island is within easy to reach by boat from Tierra del Fuego. Some say the increase in tourists is preventing the penguins from breeding, which is supposedly why their numbers have been declining.

But Thomas Müller doesn't agree. "If tourism had any kind of an effect, the population decline would be worse in penguin colonies that attract lots of tourists than in colonies that don't," he explained. "But that's not the case. Population decline is the same for all penguin colonies, no matter whether tourists go to see them or not."

Climate change to blame

Thomas Müller and his colleagues said they can't be 100 percent sure as to the precise reason for the dwindling population of penguins, but they believe climate change is the main cause. "Climate change is an obvious thing on Deception Island. In the course of a long term project I was able to see for myself how there's less ice and snow there every year," the biologist said.

The gradually receding sea ice is important for krill, the small crustaceans that sustain the chinstrap penguins, said Müller. "We assume the following: If the sea ice recedes, krill numbers decrease, which means important food resources for some penguins are on the decline. But that's difficult to prove."

Müller stressed that the findings of their study were limited to Deception Island, and that the situation of chinstrap penguins may be entirely different in other areas of Antarctica. "Climate change doesn't affect every region in exactly the same way."

Possible benefit for some species

But not all penguin species are hard hit by climate change - and some even benefit from it. Gentoo penguins, which also live in large parts of Antarctica, apparently prefer higher temperatures. "This species is not quite as good at dealing with ice," Müller explained.

Heather Lynch and her team of researchers from Stony Brook University in New York recently reported that gentoo penguins are expanding their habitat southward - into areas that previously were much too cold for them. Population numbers for this particular penguin species have been rising by some 2.4 percent every year. This is good news not just for the species, but also for conservationists: gentoo penguins are listed as "near threatened" on the early warning list of the World Conservation Union (IUCN).