University of Otago geologist Assoc Prof Ewan Fordyce
examines a fossilised penguin wing bone that shows signs of
a grooves heat-retention mechanism. Photo by Jane Dawber.
Most people think of penguins as cold-water or polar
birds, but latest research linked to the University of Otago
sheds new light on that traditional view.
A research paper published last week in British-based journal
Biology Letters also offers new insights into the
evolutionary development of penguins.
The paper's first author is Dr Daniel Thomas, a New Zealander
who is a postdoctoral fellow at the University of Cape Town,
South Africa.
His recent Otago doctorate was supervised by Associate Prof
Ewan Fordyce, who heads the Otago University geology
department.
Prof Fordyce, who also contributed to the paper, said it had
long been believed that penguins thrived by adapting to
increasingly cold conditions, including in the now largely
ice-covered Antarctic.
This region, which had earlier been semi-tropical, became
glaciated about 34 million years ago.
However, the paper points out that, much earlier, about 49
million years ago, penguins lived in much warmer conditions,
when some ocean surface temperatures were about 25degC.
And it was at that stage that penguins evolved a key
heat-retention mechanism that effectively pre-adapted them to
thrive in later, much colder, conditions, including in the
Antarctic.
It seemed ''counterintuitive'' for such mechanisms to evolve
at a time of global warmth, but researchers suspected that
the evolutionary change occurred then ''to allow penguins to
forage for food in cool depths, far below the warm surface
waters'', Prof Fordyce said.
Faced with a ''constant threat from hypothermia'' in deep,
cold waters, penguins had developed a ''counter-current heat
exchanger'', which managed the flow of blood along the wing
and significantly improved heat retention and energy
efficiency.
Wings were used to help propel the birds through the water.
Prof Fordyce said grooves in fossilised wing bones showed
evidence of this mechanism.
By the mechanism, warmer blood that was being moved out to
the wings was also used to heat the cooler blood coming back
from the wings before it re-entered the penguin body core.
Dr Thomas was a ''very, very good researcher'' and the study
highlighted the ''power of fossils'' to show how animals had
evolved, Prof Fordyce said.
- john.gibb@odt.co.nz
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