Southern Elephant Seals in Danger: Avian Influenza Triggers Devastating Die-Off in Patagonia
A deadly outbreak of avian influenza has wreaked havoc on a flourishing colony of southern elephant seals in Argentina’s Península Valdés, delivering a severe blow to a community previously hailed as a success in conservation. This outbreak, driven by the virulent H5N1 virus, began in 2023 and has already significantly diminished the population of adult seals while wiping out the latest generation of pups. Conservation experts now caution that this disaster might have regressed the population’s growth by nearly a century, with serious ramifications for marine biodiversity and ecosystem health.
A Once-Stable Population Falls into Despair
As per a recent study published in the journal Marine Mammal Science, scientists from the Wildlife Conservation Society (WCS) Argentina, the National Scientific and Technical Research Council of Argentina (CONICET), and the University of California Davis have been tracking the elephant seal colony for many years. Their long-term observations had painted an optimistic picture: from 2000 to 2022, the population enjoyed stable growth of approximately 0.9% annually. By 2022, the colony was estimated to have around 18,000 adult females and was regarded as a conservation achievement, with no major threats foreseen.
That changed dramatically in the spring of 2023.
Field teams monitoring the breeding season in 2024 discovered alarming declines in seal numbers. In traditionally high-density birthing locations, the count of reproductive females fell by 67%, dropping from 6,938 in 2022 to merely 2,256 in 2024.
“With decades of positive growth, the southern elephant seal of Península Valdés was a robust population and a highlight of incredible natural events,” stated Valeria Falabella, director of coastal-marine conservation at WCS Argentina and co-author of the study. “Until the avian flu of 2023 claimed thousands of calves and left us heartbroken.”
A Wide-Scale Avian Flu Outbreak
Avian influenza—historically affecting bird populations—has increasingly spread to marine mammals. The highly pathogenic H5N1 strain that impacted Península Valdés is thought to have originated in wild bird populations, spreading through environmental contamination or close contact among animals. Investigators recorded alarming fatality rates among the youngest seals: mortality among newborn pups soared to nearly 100%.
While initial fears were directed at the pups, researchers have since confirmed that adults were also severely affected. Data from the 2024 molting season—a period when adult seals shed their skin and fur while gathered on land—strongly indicates extensive adult fatalities, particularly among pregnant females.
Recovery Timeline: A Grim Outlook
Utilizing demographic models, researchers predict possible recovery scenarios. If only the pups had been affected, the population might realistically return to pre-pandemic levels within 6 to 29 years—young seals usually face high mortality rates, and populations tend to be somewhat resilient to losses in pups.
However, the outlook becomes considerably bleaker when accounting for adult mortality. In the likely scenario of a significant loss of reproductive females, scientists estimate that the population will not return to 2022 levels until around 2091.
More discouraging models—including further mortality among adult males or future outbreaks—shift the anticipated recovery into the next century.
“The significant effect that infectious diseases can have on wildlife populations has never been clearer,” remarked Dr. Marcela Uhart, Latin America Program Director at UC Davis and co-author of the study. “And with climate change advancing, such impacts are expected to occur more frequently and intensely.”
Why This Matters: Resilience and Threats in a Warming World
The southern elephant seal colony at Península Valdés has historically been a key indicator of oceanic and ecological health. This Atlantic breeding ground—home to one of the world’s most extensively studied colonies—was once believed to be shielded from the threats faced by other marine mammal populations.
Yet, as Dr. Claudio Campagna, WCS Argentina senior advisor and co-author, emphasized: “Only resilient populations with healthy numbers and broad distribution may withstand these threats and remain safe from many mortality causes linked to human activities—such as high-impact fisheries, extensive agriculture and mining, and pollution.”
This outbreak highlights just how swiftly disease can dismantle years of conservation achievements. Once thriving, the Patagonian southern elephant seal has now shifted from a symbol of recovery to a cautionary example of the susceptibility of even “safe” species in a time of changing climate, increasing human influence, and emerging pathogens.
An Urgent Call for Ongoing Conservation
While the long-term future of the Península Valdés elephant seals remains in doubt, the research team emphasizes that continuous monitoring, disease surveillance, and ecosystem-based management are vital for assessing the efficiency of any resilience or recovery strategies.
The extensive historical and demographic data gathered by WCS Argentina and its collaborators underpin this troubling forecast—proof