Endangered Australian Sea Lion Dies of H5 Bird Flu

South Australia has confirmed the first death of an endangered Australian sea lion from H5 bird flu, raising critical conservation concerns for a species already facing steady population declines. Authorities reported that the animal was discovered dead at Seal Bay on Kangaroo Island, which houses the species’ third-largest colony.

South Australia Environment Minister Emily Bourke stated on Sunday that the sea lion had been monitored for three months while recovering from a shark wound. Laboratory testing returned a strong positive result for H5 bird flu, leading officials to conclude the virus was the cause of death rather than the shark injury, though officials noted the animal’s recovery state may have heightened its vulnerability. No other sea lion deaths from the virus have been identified at Seal Bay, but monitoring across the site has been increased.

Threat to a Vulnerable Population

Estimates for the remaining Australian sea lion population vary across studies. Authorities note that roughly 12,000 animals remain, though a more recent estimate places the total population at fewer than 10,000. South Australia is home to approximately 85% of the global population, with the remainder residing in Western Australia. Prior to the detection of bird flu, the population was already shrinking at a rate of 2% annually.

Scientists warn that the virus could spread rapidly through colonies because sea lion habitats sit in close proximity to wild seabird populations. John Woinarski, a mammal scientist at Charles Darwin University, warned last month that the virus could cause significant conservation impacts due to the species’ low population base. Global outbreaks of H5 bird flu have previously caused heavy mortality among marine mammals in sub-Antarctica and South America, including a reported 75% reduction in seal pup numbers on Heard Island and up to 95% mortality in other impacted regions.

Vaccine Exploration

There is currently no commercially available bird flu vaccine produced for marine mammals. However, Bourke noted that experimental trials conducted on monk seals in Hawaii yielded positive results following earlier applications in United States cattle. South Australian officials are working with the Australian federal government to assess participation in potential local vaccine trials to protect the remaining population.

Background

H5 bird flu strains have caused extensive mortality in wild bird populations and marine mammals globally in recent years. South Australia recorded the country’s first confirmed case of H5N1 in a mainland mammal in August, after a dead long-nosed fur seal tested positive at Beachport on the Limestone Coast.