More than 13,000 southern elephant seal pups died on Heard Island due to bird flu, according to corroborated reports. The outbreak involved the H5N1 strain and occurred on the sub-Antarctic island located approximately 4,000km southwest of Perth. The total pup population on the island was 17,364, with estimates of the proportion lost differing: one source states 76%, while another states nearly 80%. According to GDelt, the bird flu strain was detected for the first time on Heard Island in October, and the death toll was documented in a study published in BioRxiv. GDelt also reported that the strain has been found in king penguins, Gentoo penguins, Antarctic fur seals, and a South Georgia diving petrel, with elevated mortality observed in the penguin species. 7news.com.au reported that the outbreak on Heard Island was preceded by bird flu deaths on nearby French territories, Kerguelen and Crozet islands, and that Australian scientists from the Antarctic Program conducted field research on Heard Island in October and December, observing a mass-mortality event upon arrival. Mercopress reported that the outbreak occurred on both Heard and McDonald Islands. GDelt stated that mainland Australia is free of the H5 bird flu strain, and that the strain is present on all other continents. The Australian Antarctic Division observed a mass-mortality event upon arriving at Heard Island, according to 7news.com.au.