Source: The Mercury, 16 January, 1997, p.67
By ROGER ATWOOD Torgersen Island Antarctica Research is revealing some surprising and, at times, un- savoury secrets about penguins, those elegantly-feathered symbols of Antarctica. They steal each other's eggs and come close to pecking each other to death to defend their territory at remote, windswept nesting sites such as tiny Torgersen Island. The new research also suggests penguins' pugnacity at their nesting sites could be linked to testosterone, the male hormone that rages through penguin blood early in the mating season and which, in humans, is popularly associated with aggressive behaviour. The difference is that in penguins, hormonal secretions are all calibrated by natural selection to give the birds' fluffy, grey offspring the best possible chance at surviving in a harsh environment, researchers said. "The thing that most impresses me about the penguins is how attached they are to their young and to their nesting sites," said Carol Vleck, an Iowa State University zoologist. Blood samples from Adelie penguins taken by Vleck hint at a hormonal drive behind the eccentric, at times violent behaviour of penguins early in their breeding cycle, followed by a more nurturing phase when chicks hatch and testosterone levels crash. "It's extraordinary to see how much personality they have," Vleck said, standing among hundreds of jabbering, wide-eyed penquins on the island near the US National Science Foundation's Palmer Station research site. "They make a sudden shift from aggression and defending their territory early in the breeding season to raising and nurturing their chicks later on. And you can see hormonal changes behind that shift." The Iowa State study is one of several on little- understood aspects of penguins, who are notoriously hard to study because they spend most of their lives at sea and breed in a tough climate. Recent research into an- other species, the Emperor penguin, has shown that males incubate the eggs for nine weeks in temperatures ranging down to minus 60 degrees during winter and the penguins can dive to 630 metres making them possibly the world's deepest-diving birds. The Adelie penguin's breeding cycle starts in October when the winter ice pack starts melting and the male and female come ashore to court and stake out territory. The female lays two tennisball-sized eggs in a nest made of pebbles and heads out alone to the open sea to fatten up on krill, a shrimp-like crustacean. The male, meanwhile, stays at home to keep the eggs warm and protect them from skuas, hawk-like birds that terrorise nesting sites. When the female returns, the male, who has been fasting for up to a month, leaves to feed and the two then alternate every couple of days in incubating the eggs until the chicks hatch by late December. By March, when winter starts its onslaught, the young are ready to fend for themselves. The penguins few months on land, when daylight lasts about 22 hours and food is abundant, give researchers a brief look at how they live and interact, not always in a positive way. Penguins have been known to steal eggs from their neighbours or usurp another's nest, take over the chick and raise it: odd behaviour since "it makes no evolutionary sense at all," Vleck said. Males and females constantly defend their territory or try to expand it at neighbours' expense, sometimes violently. Vleck once saw penguins peck a neighbour nearly to death to try to carve out more nesting territory. One of the attacking birds was found to have unusually high levels of testosterone. Penguin parents cannot leave their offspring alone for a second lest they be eaten by skuas or their territory stolen by neighbours. They nest in extremely close quarters, apparently because a closer concentration makes it harder for flying predators to grab eggs and chicks. A 50-square-metre plot can have hundreds of nesting pairs and there is fierce competition among penguins for the best sites. Not all penguins manage to find a mate. Those that do not "just kind of wander around looking forlorn", while others make a nest and go through all the motions of incubating eggs even though there are none, a practice that "could be some kind of practice for next year," Vleck said. She sees all this behaviour as part of a kind of internal programming to raise young, a genetic automatic pilot that keeps them sitting on the nest for days even if the eggs have been eaten by a skua or stolen by a neighbour. She and her research team draw blood from about 300 penguins each season, catching them with nets and drawing bright-red blood from the bird's neck. Studies of penguin populations could give crucial data into climate changes in Antarctica. For example, a decline in Adelie penguins and an increase in another species, the Chinstrap, could be an indirect result of a slight warming in the Antarctic over the past 30 years, said William Fraser, an ecologist from Montana State University and chief scientist at Palmer Station. Adelie penguins prefer to spend the winter on pack ice, which has become scarcer as the climate warms, while Chinstraps prefer open water, potentially giving them an advantage in the race for food, he said. Reuter
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