Highly pathogenic avian influenza (H5) has killed more than 13,000 southern elephant seal pups on Heard Island, an Australian external territory in the Southern Ocean. Researchers estimate this figure represents over 75% of the island’s pup population. The findings, published in the scientific journal BioRxiv, mark the first time the virus has been confirmed in an Australian territory, raising concerns about the potential for further spread across sub-Antarctic regions.
Why are elephant seals so vulnerable to H5 bird flu?
Southern elephant seals are disproportionately affected by the virus because of their specific breeding behaviors. According to the research report, these seals return to the same dense, crowded colonies every year. Because they are unlikely to abandon these infected sites, they become trapped in disease hotspots. This behavior facilitates the rapid transmission of H5, potentially leading to recurring annual outbreaks if the virus persists in the local environment.

Researchers used drone technology to conduct 120 flights over 54 hours to gather this data. This allowed them to survey remote areas inaccessible by foot, covering 1,600 kilometers of terrain compared to just 8.8 kilometers covered by ground teams.
How does this outbreak compare to previous global events?
The devastation observed on Heard Island mirrors patterns seen in other parts of the world. Data from Argentina in 2022 showed a 96% mortality rate among elephant seal pups, with only one-third of the adults returning to breed the following year. Similarly, in South Georgia, the number of breeding females dropped by 47% between 2022 and 2024. These precedents suggest that the impact on population numbers often extends beyond the initial mortality event, affecting future breeding cycles.
What is the risk to the Australian mainland?
There is currently no evidence of H5 bird flu on the Australian mainland or Tasmania, according to the federal government. Environment Minister Murray Watt confirmed that the government has invested $113 million in preparedness efforts, with an additional $11.2 million allocated in the latest budget to support at-risk species. While the virus has reached sub-Antarctic territories, officials maintain that planning and monitoring are ongoing to detect any potential incursion.
Pro Tip: Monitoring Wildlife Health
Conservation experts emphasize that the best defense for native wildlife is maintaining strong, healthy populations. Reducing environmental stressors and monitoring for unusual mortality events are critical steps in managing the long-term resilience of species vulnerable to avian influenza.
Frequently Asked Questions
- Is bird flu currently in Australia? No, the virus has not been detected on the Australian mainland or Tasmania.
- Which species are at risk? While the mass mortality was observed in southern elephant seals, the virus was also detected in king penguins, gentoo penguins, Antarctic fur seals, brown skuas, and South Georgia diving petrels.
- Why is this outbreak considered “catastrophic”? Researchers warn that the high density of breeding colonies in the Southern Ocean creates ideal conditions for rapid viral transmission among vulnerable, threatened species.
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