Scientists have warned that an endangered population of Australian sea lions could be wiped out if a deadly strain of bird flu spreads through the country’s colonies, the Australian Associated Press reported on Tuesday.

The warning came days after Australia confirmed its first case of bird flu in a mammal after a long-nosed fur seal found in South Australia tested positive for the virus.

Authorities are now testing a second marine mammal suspected of carrying the virus.

The Pages – which covers two small islands between Kangaroo Island and the mainland – was the site of a mass mortality event among birds, likely due to the H5 strain, last week.

It is a key breeding site for the endangered Australian sea lion, which has a population of fewer than 12,000.

“If the virus were to reach that species, we could see a huge mortality event that could threaten the species with extinction,” Antarctic ecologist Jane Younger said.

Curtin University associate professor Bill Bateman warned that Australia should expect a “mass die-off” of marine mammals due to the spread, similar to those seen in South America and Heard Island.

“This is a very worrying development,” he said.

Australian waters are home to three types of pinnipeds that breed in Australian waters: the long-nosed fur seal, the Australian fur seal and the endangered Australian sea lion.

In 2023, H5N1 killed more than 17,000 southern elephant seal pups in Argentina, and drone surveys detected more than 13,000 dead southern elephant seal pups on Australia’s Heard Island in 2025 and 2026.

There have now been 298 positive H5 bird flu cases recorded in Australia since the outbreak, with 194 of those in South Australia.