H5 bird flu is decimating wildlife on Heard Island

Scientists from the Australian Antarctic Programme have published new findings on the spread of highly pathogenic H5N1 avian influenza on the remote Heard and McDonald Islands. The archipelago lies around 4,000 kilometres south-west of the Australian mainland and represents the first confirmed detection of the virus in an Australian territory.

During two expeditions in October 2025 and January 2026, the researchers investigated the impact of the disease on the local wildlife populations. Samples from nine vertebrate species were analysed, with six species testing positive for the globally widespread H5N1 strain. These included southern elephant seals, king penguins, gentoo penguins and Antarctic fur seals.

The young southern elephant seals were particularly hard hit. Analysis of drone footage revealed an average mortality rate of 76 per cent, rising to as high as 97 per cent in some colonies. Of the estimated 17,000 pups born, around 13,000 died. Increased mortality was also observed among king penguins; several hundred dead adult birds were recorded on the island.

In total, the scientists carried out 120 drone flights covering more than 1,600 kilometres, as well as numerous ground surveys. Drone technology made it possible to monitor even hard-to-reach coastal areas and breeding colonies without causing further disturbance to the animals.

Genetic analyses suggest that the virus was likely introduced by migratory wildlife from the French Crozet Islands, some 1,800 kilometres away, and is thought to have reached Heard Island in August 2025.

The findings highlight the continued spread of H5N1 avian influenza in the sub-Antarctic region and show that southern elephant seal populations, in particular, are at high risk. These genetic test results have been submitted to a scientific journal for consideration for publication but have not yet been peer-reviewed. A preprint is available on BioRxiv.

Heiner Kubny, PolarJournal