By Ella Davies
Earth News reporter
'Gay' king penguin pairs do not stay together
King penguins do not form long-term homosexual pairs despite same-sex "flirting", one of the first evidence-based studies has revealed.
Researchers found that over a quarter of the birds in one colony displayed in same-sex pairs, yet only two pairs bonded by learning each other's calls and both were later seen caring for eggs in heterosexual pairs.
The scientists suggest that these same sex displays could be caused by an excess of males or high levels of testosterone.
Researchers from the Centre for Functional and Evolutionary Ecology in Montpellier, France studied king penguins on the Antarctic island of Kerguelen to better understand their mating behaviour.
During the mating season king penguins displayed with potential partners: closing their eyes, stretching their heads skyward and moving them in a half-circle to "take peeks" at one another.
To successfully pair bond the penguins learned one another's calls to stay in contact in the breeding colony.
The scientists did not set out to measure rates of homosexuality in king penguins.
Instead, they came to their conclusions after studying the birds' behaviour and crucially, sexing individuals.
In doing so, they ended up with the first evidence-based study of homosexuality among king penguins, and one of the first among all penguins.
In their study, published in the journal Ethology, the researchers found that 28.3% of the birds studied displayed to penguins of the same sex.
"Of course, it took DNA sexing to work this out since males and females look so similar," said Director of Research, Professor F Stephen Dobson.
In the past, it was claimed that penguins could not discern between the sexes because they looked alike.
However, Professor Dobson debunked this theory when his results did not meet "random" projections.
'GAY' PENGUIN PARENTS
In New York's Central Park zoo a male-male pair of chinstrap penguins hatched and reared an "adopted" egg. One of the pair later bonded with a newly introduced female
In Germany's Bremerhaven zoo, a male pair of Humboldt penguins were given a fertilised egg to nurture and successfully reared the chick
The San Francisco zoo was home to a homosexual male pair of Magellanic penguins who also raised a chick. One male bonded with a neighbouring female in the following breeding season
"I found that the rate of homosexually displaying pairs was significantly lower than one would expect by chance," said Professor Dobson.
Of the displaying pairs, he observed, only two bonded: "Among 75 bonded pairs, we found one male-male pair and one female-female pair that had learned the song of their partner."
"So these [homosexual] pairs can bond. But, bonded pairs can split up if one finds a more preferred partner," Professor Dobson explained.
The four homosexually-bonded penguins were later observed raising eggs in the breeding colony, suggesting they had left their same-sex partners and formed heterosexual bonds.
The primary aim of the study in Kerguelen was to record patterns in penguin attraction in order to understand the subtleties of their appearances.
Researchers recorded the condition of the penguins to gauge their age and relative experience but found no similarity of characteristics amongst the homosexually displaying birds.
The evidence showed that the displays were not limited to young or inexperienced birds who were displaying to same-sex partners by mistake.
Professor Dobson theorised that an excess of males in the colony (1.65 to each female) could explain the male-male "flirting".
He also pointed to previous findings that male king penguins returned from the sea with high levels of testosterone, making them highly motivated to display.
This does not explain the female-female bonded pair however.
King penguins are second only in size to emperor penguins, standing at up to one metre tall with both males and females sporting recognisable yellow breast and orange beak and ear patches.
The flightless birds do not nest but take care of eggs and chicks on their feet, meaning breeding colonies are mobile.
This movement raises the importance of communication between partners who cannot rely on recognising a location to find their family.