Bird flu kills thousands of baby seals on remote Australian island

Lead

More than 13,000 southern elephant seal pups have died from bird flu on Australia's remote Heard and McDonald Islands, according to new research that paints a grim picture of the virus's impact on subantarctic wildlife.

The findings, based on surveys conducted in October 2025 and January 2026, estimate that 13,359 pups died out of a total population of 17,364 on Heard Island — a mortality rate of about 76%, with some areas experiencing up to 97% pup mortality, as reported by ABC Australia, BBC, and The Guardian.

The islands, located approximately 4,000 kilometers south-west of mainland Australia, are a critical breeding ground for seals and seabirds, with over a million breeding animals, according to the BBC.

Coverage Comparison

The story has been covered by multiple outlets, each offering slightly different details and perspectives. ABC Australia, the country's public broadcaster, focused on the devastating impact on Australian territory, emphasizing the federal government's financial preparations. The BBC highlighted that Australia remains the only continent free of H5N1, according to the Australian government, while The Guardian quoted expert reactions and provided additional context on the virus's likely origin.

All three outlets agree on the core figures: the number of dead pups, the high mortality rate, and the detection of the H5N1 strain. However, there are minor discrepancies in the reported mortality rate (75% vs 76%) and the exact number of affected species (six in all reports, but with slight variations in the list). These differences likely stem from the same underlying data presented with slightly different rounding or interpretation.

Key Claims

• Mass Mortality: More than 13,000 southern elephant seal pups died on Heard Island, with an average mortality rate of 76% and up to 97% in some areas. This is compared to a typical annual pup mortality of below 5%, according to Dr. Jarrod Hodgson, a senior research scientist and co-lead author, as quoted by The Guardian.

• Species Affected: Six species tested positive for the H5N1 strain, including southern elephant seals, king penguins, gentoo penguins, Antarctic fur seals, and South Georgia diving petrels, as reported by ABC, BBC, and The Guardian. Mass mortality was only observed in southern elephant seals, though elevated deaths were noted among king and gentoo penguins, with several hundred adult king penguins found dead.

• Virus Introduction: The virus likely reached the islands in August 2025 via infected wildlife, possibly from the French subantarctic Crozet Islands, approximately 1,800 kilometers away, according to multiple sources. This is a plausible route, though not definitively confirmed.

• Monitoring and Preparedness: Drones were used for data collection, completing 120 flights and covering 1,600 kilometers, according to a single source. The Australian government invested $113 million to prepare for the virus's arrival, with an additional $11.2 million for at-risk species resilience, as reported by ABC and The Guardian.

• Ongoing Threat: Researchers noted that mortality was still ongoing when they left, suggesting the figures may be an underestimate, according to Dr. Hodgson. The Australian Antarctic Program will continue monitoring for signs of bird flu in other Australian territories.

Perspectives

Dr. Michelle Wille, an expert quoted by The Guardian, described the survey results as "really devastating" but consistent with impacts observed elsewhere in the subantarctic. This context is important: while the numbers are alarming, they reflect a broader global pattern of H5N1 spreading through wildlife populations.

The Australian Antarctic Program's wildlife veterinarian, Dr. Tristan Burgess, noted that the impacts on elephant seals align with other outbreaks in the southern hemisphere, according to The Guardian. This suggests the Heard Island event is part of a larger ecological crisis.

The research has been published as a preprint in the journal BioRxiv and has not yet been peer-reviewed, a caveat noted by multiple outlets. This means the findings are preliminary and subject to further scrutiny.

As the world watches this unfolding event, the scientific community emphasizes the need for continued surveillance. Australia's status as the last continent free of H5N1 may be under threat, and the lessons from Heard Island could inform conservation strategies globally.