Warmer temperatures forcing emperor penguins out of their traditional breeding grounds to make gravity-defying journeys up 100-foot ice wallsPosted by Jim at Sunday, January 12, 2014
9 January 2014 (Press Association) – Emperor penguins are having to struggle up 100-foot walls of ice as warmer temperatures force them out of their traditional breeding grounds, a study has shown.
The gravity-defying march of the penguins was spotted by British Antarctic Survey (BAS) scientists in satellite images of four colonies.
The birds normally breed on thin sea ice, close to easily accessible food sources. But ice forming later than usual in recent years has compelled them to move to much thicker floating ice shelves.
Experts believe the unusual behaviour could indicate that the penguins are adapting to environmental change.
Lead scientist Dr Peter Fretwell, from the BAS, said: "These charismatic birds tend to breed on the sea ice because it gives them relatively easy access to waters where they hunt for food.
"Satellite observations captured of one colony in 2008, 2009, and 2010 show that the concentration of annual sea ice was dense enough to sustain a colony. But this was not the case in 2011 and 2012, when the sea ice did not form until a month after the breeding season began. During those years the birds moved up on to the neighbouring floating ice shelf to raise their young.
"What's particularly surprising is that climbing up the sides of a floating ice shelf - which at this site can be up to 30 metres high - is a very difficult manoeuvre for emperor penguins. Whilst they are very agile swimmers they have often been thought of as clumsy out of the water."
The findings are reported in the online journal Public Library of Science ONE.
Because of their reliance on sea ice as a breeding platform, emperor penguins have been classified as "near threatened" in the IUCN's "red list" of endangered species. [more]
ABSTRACT: We describe a new breeding behaviour discovered in emperor penguins; utilizing satellite and aerial-survey observations four emperor penguin breeding colonies have been recorded as existing on ice-shelves. Emperors have previously been considered as a sea-ice obligate species, with 44 of the 46 colonies located on sea-ice (the other two small colonies are on land). Of the colonies found on ice-shelves, two are newly discovered, and these have been recorded on shelves every season that they have been observed, the other two have been recorded both on ice-shelves and sea-ice in different breeding seasons. We conduct two analyses; the first using synthetic aperture radar data to assess why the largest of the four colonies, for which we have most data, locates sometimes on the shelf and sometimes on the sea-ice, and find that in years where the sea-ice forms late, the colony relocates onto the ice-shelf. The second analysis uses a number of environmental variables to test the habitat marginality of all emperor penguin breeding sites. We find that three of the four colonies reported in this study are in the most northerly, warmest conditions where sea-ice is often sub-optimal. The emperor penguin’s reliance on sea-ice as a breeding platform coupled with recent concerns over changed sea-ice patterns consequent on regional warming, has led to their designation as “near threatened” in the IUCN red list. Current climate models predict that future loss of sea-ice around the Antarctic coastline will negatively impact emperor numbers; recent estimates suggest a halving of the population by 2052. The discovery of this new breeding behaviour at marginal sites could mitigate some of the consequences of sea-ice loss; potential benefits and whether these are permanent or temporary need to be considered and understood before further attempts are made to predict the population trajectory of this iconic species.