Wednesday, July 14, 2010

Penguin courtship tests devotion

Adelie penguins
PHIL REID/Dominion Post
CALL OF THE WILD: Adelie penguin mating calls 'sound like a cross between a donkey and a stalled car'.
New Zealand academics have shown the female penguins in some species use courtship to decide which males are likely to be devoted dads, with fatter males their more probable choice.
Auckland University researcher Dr Emma Marks said in a study in published a science journal, Behaviour, that penguin calls hold clues to a male's paternal potential.
Adelie penguins team-parent to successfully raise a family in Antarctica: males and females take turns incubating the eggs and guarding the chicks while their mate hunts.
Males claimed a territory and built a nest, and when the females arrived, the males threw their heads back, pointing their beaks to the sky, and emitting a series of hoarse trills and squawks.
"They're not musical calls - they sound like a cross between a donkey and a stalled car," Dr Marks said in a statement from the National Evolutionary Synthesis Centre in North Carolina, USA.
The courtship calls told females how fat a male was and what kind of father he'd be, said her co-author, Associate Professor Dianne Brunton of Massey University. Fatter males made better fathers because they had good energy reserves and were less likely to leave the nest and desert their chicks.
"A fat male is a good choice for a female because males do so much of the offspring care," said Prof Brunton. "They're able to incubate the eggs for longer and use up their fat stores, while skinny males aren't able to do that."
Dr Marks spent three months of her summer near Scott Base, with half a million Adelie penguins.
She weighed dozens of males and recorded their calls, then noted how successful they were at attracting mates and raising chicks.
The researchers found that steady frequency over the longest part of the call - an extended chattering in the middle of the male's display - best predicted male buffness and mating success.
"It's as if females are listening to the stability of the call," said Dr Marks.
Males with more consistent pitch were snatched up. These males were also heavier and more successful at raising chicks.
"The fat surrounding the male's voice box changes what his call sounds like," said Prof Brunton.
"We don't yet know the physiological mechanism for call production, but body fat appears to stabilise their calls," Dr Marks said.
After choosing a mate the female laid two eggs and returned to feed at sea, leaving the male on the nest until she returned to take the next shift. Father penguins could lose more than 20 percent of their body weight over breeding season, the researchers said.
"It's a pretty arduous task, especially for the males," said Dr Marks. "If a male doesn't have enough fat to last these fasts, he may have to abandon the eggs ... it's imperative that the female pick a male in good condition."


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