In the last reproductive season of the species, a catastrophic event was recorded: a sharp decline in elephant seals in Península Valdés. The only continental and temperate latitude grouping of the species is located on the coasts of Chubut.
This was due to the highly pathogenic avian influenza virus. It killed 97% of the pups (around 17,000 individuals) and an “uncertain number” of breeding adults.
A census was carried out during the peak week of the reproductive season, this time to assess the impact of the epidemic on the Valdés population.
The decline in the elephant seal population
The census work team was composed of 20 members from different institutions: WCS Argentina, CESIMAR-CONICET, Universidad San Juan Bosco, University of California-Davis, Fundación Vida Silvestre Argentina, Conservation Department of the Municipality of Puerto Madryn, park rangers from the Ministry of Tourism and Protected Areas of the Chubut Province, and rangers from the National Parks Administration.
Southern elephant seals are one of the iconic species of the coastal landscape of Península Valdés and adjacent areas. They are distributed along 300 km of coastline.
Elephant seals: why the population decline.
This grouping maintained a slight growth rate during the last decades, with a total of 18,000 pups born in 2022.
However, in 2023, a mass mortality event was recorded. The information was published on Monday in Nature Communications, marking a significant change for the population.
“It was an unprecedented event that devastated a healthy population and decades of conservation efforts. It was the first global record of mass mortality of the species due to avian influenza,” said Valeria Falabella, Director of Marine Coastal Conservation at WCS Argentina.
The organization has been working in Argentina for 60 years and has been monitoring elephant seals since 1980.
Possible consequences
To assess the consequences, a small team of scientists has been recording the development of the reproductive season in specific sectors of Península Valdés since August.
In the first week of October, they also used drones to fly over for a complete count of the colony in the peninsula and adjacent areas.
The preliminary results are conclusive: the total number of individuals present on the coasts decreased between 16% and 66% depending on the analyzed sector. Specifically, the number of adult females decreased between 30% and almost 70%.
Compared to the 2022 count, the number of weaned pups showed an 82% reduction.
The number of pups born in 2024 has not been calculated yet, as hundreds of drone-taken photographs from areas inaccessible by land need to be processed. However, the preliminary results show that the 2023 avian influenza outbreak had a strong impact on a previously healthy population.
“Decades of reproductive seasons and molting on land without disturbances will be required, as well as pelagic stages with abundant food, for the population to recover and return to pre-2023 values,” stated Falabella.
Elephant seals: the importance of respecting the reproductive season
The sharp decline in the elephant seal population.
The uncontrolled public use of beaches where elephant seals are found can also have an impact. The transit of off-road vehicles and the proximity of fishermen, visitors, and pets affect the behavior of the animals.
Disturbances sometimes have undesirable consequences at key moments in their life cycle, such as the abandonment of the pup when the mother feels threatened, or energy-consuming displacements considering they fast on land.
“This species feeds in the sea where it spends most of the year, and only comes to the coast for relatively short periods. The most important one, between September and October, is for reproduction,” explains Julieta Campagna, Valdés Landscape Coordinator at WCS Argentina.
“And for molting from November to March, first the juveniles of both sexes, then the adult females, and later the large males,” she adds.
“The most important distribution area in Chubut is the Protected Natural Area of Península Valdés, although animals are also found between Punta Ninfas and the coast in front of Isla Escondida, where there is no protection,” emphasizes the specialist.
“Each female gives birth to a single pup, which she cares for and feeds for 3 weeks, a period during which it is necessary to take extreme measures to avoid disturbances affecting them,” she indicates.
In the last month, cases of elephant seals being present in unusual coastal areas were reported, such as Mar Chiquita, Mar de Ajó, Villa Gesell, Mar del Plata, and even Santa Catarina, Brazil. Therefore, it is essential to have information on how to behave when encountering these animals.
Recommendations for those visiting beaches with elephant seals
- Stay more than 30 meters away from the animals.
- Do not throw stones at them to make them move.
- Prevent dogs from approaching them.
- Never stand between the animals and the sea.
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