H5N1 Avian Flu Outbreak Poses a Long-Term Threat to Southern Elephant Seal Population
A recent avian influenza outbreak has severely impacted the southern elephant seal colony at Península Valdés in Argentine Patagonia. According to a 2025 study published in Marine Mammal Science, the H5N1 high pathogenicity avian influenza virus killed nearly all newborn elephant seal pups and an undetermined number of adults during the 2023 breeding season.
How Long Will It Take the Population to Recover?
Researchers estimate that under the best-case scenario—where only pups were affected—the colony could rebound to 2022 levels (around 18,000 adult females) as early as 2029 or as late as 2051. This is because pup mortality is naturally high among southern elephant seals.
However, if the virus significantly affected reproductive females, the recovery could be delayed until 2091. In the worst-case scenario—where both adult males and females died, reducing breeding potential, or if future outbreaks occur—the population may not return to its former size until the mid-22nd century.
2024 Breeding Season Offers Grim Confirmation
The first test of these predictions came during the 2024 breeding season, where researchers observed 67% fewer reproductive females on key beaches (down from 6,938 in 2022 to just 2,256 in 2024). The decline strongly points to high adult mortality, rather than delayed arrivals or redistribution.
Conservation Status Now Considered Vulnerable
Before this outbreak, the southern elephant seal population at Península Valdés was stable, facing no significant conservation threats. Now, the scenario has dramatically changed. The species is considered vulnerable, and climate change could worsen the spread of infectious diseases like avian flu, making future outbreaks more likely.
“With decades of growth, the southern elephant seal of Península Valdés was a healthy population… until the avian flu of 2023 left thousands of dead calves and our eyes in tears,” said Valeria Falabella, WCS Argentina’s Director of Coastal-Marine Conservation.
Experts Call for Enhanced Monitoring and Prevention
Dr. Marcela Uhart, Director of the Latin America Program at the University of California, Davis, emphasized:
“Avian influenza has starkly demonstrated the devastating impact that infectious diseases can have on wildlife populations. These effects are likely to intensify under current and projected climate change conditions.”
A Warning for Biodiversity Worldwide
According to Dr. Claudio Campagna, senior advisor at WCS Argentina:
“Only resilient populations with healthy numbers and wide distribution can withstand such threats. Global warming, ocean acidification, and human activity continue to push biodiversity toward potential extinctions.”
Why Continued Research and Conservation Funding Matters
Long-term monitoring by WCS Argentina and CONICET has been crucial in understanding the epidemic’s impact. Experts stress the urgent need for increased funding and support to track vulnerable species and protect marine ecosystem integrity.
Source and Citation:
Study Title: Predicting Population Consequences of an Epidemic of High Pathogenicity Avian Influenza on Southern Elephant Seals
Authors: Claudio Campagna et al.
Journal: Marine Mammal Science (2025)
DOI: 10.1111/mms.70009
Provided by: Wildlife Conservation Society