The austral spring usually finds Antarctica's Adélie penguins paddling in from the sea to begin their breeding season. But this year all is not well. When biologist Lyn Irvine, who staffs Australia's Antarctic Mawson base, traveled to the penguins' two island colonies on 25 November, she found dozens of dead animals and others that were listless and inert. At last count some 100 birds were dead among the population of 15,000.
Mawson scientists have monitored the Adélie penguins for 12 years to determine whether harvesting of krill--small shrimplike animals--hurts their breeding success. But never before have the scientists seen so many dead birds.
The cause may be some sort of disease. "We have no idea what it is," says Knowles Kerry, a biologist with the Australian Antarctic Division, headquartered just outside Hobart, Tasmania. Kerry can recall only one other mass death, in 1972, when he happened upon a Mawson penguin colony whose chicks were dying. The latest deaths underscore how little is known about the diseases that strike Antarctic wildlife. "We're only just starting [to find out]," says Kerry. "We expect that like any wild population there will be natural cycles."
However, finding out will have to wait until the supply ship Polar Bird brings pathology samples of the dead penguins to Hobart for analysis on 27 December. Till then the Mawson researchers are doing all they can to make sure they do not spread the disease. Trips to the colonies are restricted and footwear and clothing are sanitized before and after visits to each island.
"We can't stop the outbreak," says Kerry. "Our goals are to find out what it is, to make sure we're not spreading it, and to try to prevent it from confounding our study on the effects of krill harvesting."