Scientists are normally pretty careful with their language, so this line from a pre-print research paper last November really caught my eye: “If the virus does start to cause mass mortality events across penguin colonies, it could signal one of the largest ecological disasters of modern times”.
In total, bird flu has killed around 10 species in the Antarctic region (most of them on the sub-Antarctic island of South Georgia) including fur seals and elephant seals, with hundreds of carcasses counted by researchers on the ground. Most recently tourists on a cruise ship told me they couldn’t reach Ernest Shackleton’s grave because of dead seals.
Although it has killed gentoo and king penguins, the losses have been relatively small. “There is cause for optimism. It’s not as bad as we thought it could be when we saw the first cases,” said Norman Ratcliffe, a bird ecologist at the British Antarctic Survey (BAS) who has worked on penguins and seabirds on South Georgia, a haven for Antarctic wildlife. Considering the virus arrived in the region in October last year, he was surprised it took this long to take hold in the penguin population.
Most colonies along the north coast of South Georgia would have come into contact with it via scavenging birds, says Ratcliffe. Densities of penguins, albatrosses and seals around the coastlines are particularly high. “It’s hard to imagine that they haven’t been exposed to the virus,” he said.
Macaroni penguins nest in high density colonies, and there is no evidence of any mortality. For gentoo penguins it has been “localised and brief”.
This is somewhat surprising given penguins were badly hit in South America and Africa. “There’s perhaps some genetic factor that makes these [Antarctic] species less vulnerable,” said Ratcliffe. Although they are in the same family, Antarctic species belong to a different genus (genus is the next level of classification up from species).
A reason penguins are vulnerable to bird flu is because they huddle extremely close together in spectacular colonies comprising hundreds of thousands of individuals. Yet, as the breeding season draws to a close, there is more space between individuals meaning less risk of it spreading between them.
Macaroni penguins are moulting now, so they will continue to huddle together in dense colonies for warmth until the end of March. After that they disperse, which is a circuit breaker for disease. “The risks diminish considerably if they can make it through the moult,” said Ratcliffe.
However, gentoo and king penguins will remain vulnerable over winter. Gentoo penguins tend to come on shore every night and group together. King penguins chicks are left on land in big huddles as their parents are out foraging. “That again, is a recipe for transmission because they have very close contact with one another,” said Ratcliffe.
It will be an uncertain few months.
“The only thing you can expect from this virus is that it does the unpredictable. I think it’s very difficult to gauge what it might do,” said Ratcliffe. “This virus is constantly changing and evolving very rapidly. So it’s uncertain whether there could be changes in the virus that suddenly meant that the different penguin species on South Georgia suddenly become susceptible as hosts for it.”
Generally, viruses try to evolve in a way that means they don’t kill their hosts – so they become less dangerous and more transmissible over time. “The rates at which that will happen is anyone’s guess,” he said.
Other than limiting movement of people in infected areas, there is not much that can be done to stop H5N1 in the Antarctic. Vaccinations and are impractical, as is carcass disposal, as it’s a huge area with very few people. Ratcliffe said: “You’ve just got to watch and see.”
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