Australasian Science: Australia's authority on science since 1938

Penguins Retreat from Sea-Ice

By Stephen Luntz

For the first time, emperor penguins have been found nesting on ice shelves, sometimes 40 metres above the ocean rather than the much lower sea-ice they normally frequent.

It is unknown if this is a well-established behaviour that has not been observed before, or a response to global warming.

Although breeding colonies have been spotted on small islands, a paper in PLoS One notes: “Emperor penguins have previously been considered sea-ice obligate species”. However, the authors report that four colonies have now been spotted on ice shelves.

Two colonies are newly discovered and have only been observed on shelves, while another two have been seen shifting to ice shelves in years when sea-ice conditions are poor.

“Breeding on ice shelves may be an adaptation employed by emperor penguins when sea-ice conditions are poor, but this is only possible where emperor penguins have access to the top of an ice shelf. This is not the case at all colony sites,” says Dr Barbara Wienecke of the Australian Antarctic Division. Wienecke is not sure how some of the colonies travel between the ocean and their locations on high ice shelves, but in some cases snow bridges have been spotted that might provide access.

Emperor penguin colonies are remarkably mobile, with Wienecke describing movements in response to wind storms or “just because they can”. How colonies might choose a radically new location remains a mystery since Wienecke says: “Colonies have no leader. An individual just decides to move and the others choose to follow until another moves in a different direction.”

Late sea-ice formation can leave emperor penguins with less than the 5 months they need to breed and raise their chicks. Colonies have been known to skip a season in consequence, but Wienecke says that “it makes sense to use an inferior location rather than skipping a season entirely”.

While there are almost a quarter of a million breeding pairs of emperor penguins, the loss of sea-ice has caused them to be listed as of “near concern”. The paper reports hopefully: “This previously unknown and surprising behaviour recorded in such an iconic animal suggests that other species may also be capable of unpredicted or unknown behavioural adaptations in a future warming world.”