Where do penguins go in winter?

Where do penguins go in winter?

20 May 2009

Penguins leave Antarctica after summer, but where they go in winter was a mystery. Now, thanks to a tiny location device, scientists discovered that macaroni penguins do not go sunbathing: they spend winter feeding in the cold southern oceans.
Macaroni penguin

The macaroni penguin.

Macaroni penguins are the most common penguin species and one of the top consumers of fish and krill in Antarctica. During the summer they nest in islands surrounding Antarctica, where their breeding and feeding habits are quite well known. But after the moult at the end of the summer, the macaroni penguins disappear from sight. So what do they do over the next seven months?

To find out, Dr Charles-André Bost and colleagues from the Centre d'Etudes Biologiques de Chizé (CNRS) in France and the British Antarctic Survey, headed out to the Kerguelen Islands, home to one of the biggest colonies of macaroni penguins. The team attached miniature global location sensors to the legs of 21 penguins at the end of the breeding season in March-April.

Six months later, the team returned to Kerguelen as the penguins were coming back from the winter migration. They caught 14 of the tagged penguins and managed to download data from 12 devices.

'To our knowledge this was the first time these penguins were followed outside the summer breeding season to their winter grounds,' says Bost. The penguins headed east as soon as they leave Kerguelen and travel long distances, swimming on average about 10,000 km, says the report published this week in Biology Letters. None of the birds came ashore during the six months of winter.

The macaroni penguins did not stay together but scattered shortly after departure. Some continued eastbound, while others turned south half way. 'The penguins did not disperse randomly and stayed within the Polar Frontal Zone,' says Bost. The zone, which has seawater temperatures between 1 and 5°C, is the northern limit of Antarctic waters.

It's not clear why some penguins prefer swimming east and others head south, 'maybe it's due to individual differences or variation of fitness,' suggests Bost. But the scientists found that south-bound penguins were in best physical conditions on the way back.

'Despite choice of routes, the penguins stay within the Polar Front waters,' says Bost. While macaroni penguins are not currently under threat of extinction, their global population is declining worldwide. 'It's useful to know where their winter feeding grounds are to have a proper understanding of their ecology,' adds Bost.

The penguin's position was calculated with light (about 6g) that did not hamper movement. The device measured sea water temperature and the levels of light every 10 minutes for six months. With this information, Bost and his team were able to tell the timing of sunset and sunrise, which they used to calculate the daily latitude. Longitude was estimated using the length of each day.

The paper: C. A. Bost, J. B. Thiebot, D. Pinaud, Y. Cherel, and P. N. Trathan. (2009) Where do penguins go during the inter-breeding period? Using geolocation to track the winter dispersion of the macaroni penguin. Biol. Lett. doi:10.1098/rsbl.2009.0265

Source:
http://planetearth.nerc.ac.uk/news/story.aspx?id=430