Sunday, November 17, 2013

Happy feat on ice

Adelie penguins
Adelie penguins drift on ice floe in the Southern Ocean off the Australian Antarctic Territory. Picture: AFP Source: AFP
THERE could be more adelie penguins in Antarctica than ever before. 
A survey covering about 5000km of the East Antarctic coastline by a team of Australian Antarctic Division seabird ecologists has confirmed that adelie penguin populations have increased by close to 50 per cent since the 1950s.

The exhaustive survey, which involved several years of penguin observations from the ground and from the air, also found that adelie penguin colonies had spread over greater areas.

The penguins use pebbles, which are small enough to carry in their beaks, to build nests for rearing chicks during summer on exposed rocky parts of the continent.

Team member Colin Southwell said possible contributors to the adelie boom included:

ITS coincidence with a rapid decrease in sea ice cover, from the 1950s, which could have made it easier for the adelie penguins to forage for krill.

THE slaughter of whales, almost to extinction by the mid-20th century, which meant that fewer whales were eating krill, leaving more for the adelie penguins.

Dr Southwell said it suggested adelies thrived when sea ice coverage was just right, but suffered when there was too much or too little. He said the team's latest survey found that East Antarctic adelie penguin numbers had begun to plateau.

Dr Southwell said the impacts of sea ice variations on larger emperor penguins were harder to observe because the emperors nested on sea ice during winter, in the dark for much of the time.

Another team from NSW's Griffith University has concluded that penguins first appeared as a species about 20 million years ago. The scientists looked at the DNA from the 11 penguin species alive today and developed a "molecular clock" -- to calculate how species evolve on the basis of mutations in DNA.

This measure shows the forerunner of all penguins lived 20.4 million years ago (rather than 41 million-51 million years ago as previously thought) and they evolved into separate species at the same time as a decline in Antarctic temperatures.


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