Climate change and penguin physiology

Adelie penguins
Photo credit: Charles Sturt University

ANTARCTICA - What can penguin physiology tell us about how these birds are affected by climate change? As part of a multi-national team studying Adélie penguins, ecologist Dr Melanie Massaro from Charles Sturt University in New South Wales, Australia, is finding out the answers to that question.

Dr Massaro's research trip to Cape Crozier on Ross Island in January this year was her 12th visit to Antarctica. She started as a lecturing scientist on Antarctic cruise ships, before making her first journey as a researcher in 2007. Since 2009, she has been part of a team that includes researchers from the USA, New Zealand and France studying Adélie penguins in the southern Ross Sea. 

The New Zealand researchers study the penguins at Cape Bird and the US team conducts research at Cape Crozier and Cape Royds, where the southern-most colonies of Adélie penguins are located.

"The big, overall project is a meta-population study trying to figure out climate change effects on Adélie penguins," said Dr Massaro.

"My part of the project focuses on how penguins may respond to challenging environmental conditions by studying penguin physiology."

To do this, the researchers attached devices called accelerometers to known-age penguins, with the oldest birds being 17 years old. To follow individual birds through their life, researchers have banded several thousand birds since 1996.

"But only a small percentage of them return," said Dr Massaro. "At Cape Crozier we would encounter about 1000 banded birds per season among this big colony of 200,000 pairs."

"It takes quite a lot of searching to find these banded birds but we do have the GPS coordinates of their nests from previous year. The birds tend to return to a similar area where they nested previously so we go back there looking for them."

Adelie penguin
Photo credit: Charles Sturt University

After the accelerometers are attached to the penguins, they are returned to their nests and chicks. When the birds' partners return, the ones with the device then go out to sea for several days to find food for their young. The devices are removed when they come back.

"The device gives us detailed information on how much and far the penguin moves; how deep they dive and how many dives they do; and how much energy they use," said Dr Massaro.

The researchers also take a blood sample "which tells us all sorts of things but mainly we are looking at corticosterone levels, which is a stress hormone".

When the chicks are bigger and begin to moult they are banded.

"There used to be colonies of Adélie penguins on the Antarctic Peninsula [the northern-most part of Antarctica] but they are moving south," said Dr Massaro. "But our penguins are at the southern-most colony, so they can't go any further south."

The warming effects of climate change are still impacting the Ross Island penguins. Huge icebergs are breaking off the Ross Ice Shelf and these giants of glacial ice block off McMurdo Sound.

"This affects our colonies as the penguins can't return to some of their colonies anymore," said Dr Massaro.

Adélie penguins migrate each winter. When the Ross Sea near their breeding colonies freezes they migrate north to the edge of the sea ice.

"The Cape Royds colony had a big crash several years ago. There used to be over 4000 pairs and now there are only about 1600 pairs."

Dr Massaro said it is still too early to draw conclusions from her project regarding stress levels.

"It's hard to tease apart climate change effects from other factors influencing the penguins," she said.

"We do know the penguins at Cape Crozier are struggling to raise their chicks.

"For some reason there may not be enough food in the ocean where they feed which may be linked to human activities such as climate change, which can change prey abundance and distribution; or it might be because of competition as the Crozier colony is very large and the penguins are depleting their resources.

"We've found that they start depleting their resources close to the colony and then they have to move further and further afield to forage for food as the season progresses."

This lack of resources may also explain why the penguin chicks at Cape Crozier are small, unlike the "huge, fat chicks" at the much smaller colony at Cape Royds.

"Cape Royds is the riskier place to be at the beginning of the season because the adults really have to work hard to get to the colony because of the extended sea-ice early in the season," said Dr Massaro.

"But once the adults survive the incubation period and the ice breaks up, Cape Royds is the better place for raising big healthy chicks."

Source
Good, bad and ugly for Antarctic penguins [media release] by Wes Ward, 8 May 2014, Charles Sturt University