The mass strandings of dolphins in Argentine Patagonia have sparked concern and curiosity for years. However, new scientific research is beginning to shed light on the causes of this phenomenon.
A study published in Royal Society Open Science analyzed episodes recorded on the coast of Río Negro and found evidence that these events may be associated with pressure from natural predators.
In particular, the work focused on the cases that occurred in Bahía San Antonio and the Golfo San Matías, two key marine areas of the Patagonian ecosystem.
The results indicate that, under certain circumstances, dolphins move towards shallow waters to escape attacks, which increases the risk of becoming trapped near the coast.
Recent episodes that raised alarms
The mass strandings of dolphins in this region are infrequent. However, between 2021 and 2023, two significant episodes were recorded that prompted detailed investigations. The first occurred in September 2021 in the province of Río Negro, when 52 common dolphins died after becoming stranded on the coast.
During that event, researchers performed necropsies on 38 individuals to identify possible causes related to diseases, pollution, or human activity. Subsequently, in April 2023, an even more shocking episode was recorded. Nearly 570 dolphins were trapped in very shallow waters in the same region.
However, on that occasion, the quick intervention of volunteers, fishermen, and authorities allowed all the animals to be returned to the sea. This rescue operation included the use of kayaks and small boats to guide the dolphins to deeper areas before they became permanently trapped in the sandbanks.
Orcas and dolphins: a natural dynamic that explains the strandings
Research conducted by scientists from the Centro de Investigación Aplicada and Transferencia Tecnológica en Recursos Marinos Almirante Storni and the Universidad Nacional del Comahue points to an explanation based on the natural interaction between species.
According to the analyses, strandings occur when large groups of dolphins try to escape the presence of Orcas, one of the most efficient marine predators. Before both episodes, scientists and local observers confirmed the presence of these cetaceans in the area.
In response to the danger, the dolphins tend to swim in compact formations and move quickly to shallow areas seeking refuge. However, this defensive strategy can become a trap.
The coastal geography of the bay, combined with sandbanks and strong tidal variations, increases the probability of the animals becoming trapped near the shore.
Scientific evidence on stress caused by predators
The necropsies performed on the dolphins that died in 2021 provided key information to rule out other hypotheses. The analyses revealed that the animals were in good physical condition and showed no signs of serious diseases or injuries caused by fishing nets or pollution.
No signs of malnutrition, severe infections, or parasites capable of explaining the event were detected either. These results reinforced the idea that the main trigger was the stress generated by the presence of predators.
In highly social species like dolphins, collective behavior amplifies the effect of panic. When part of the group flees towards the coast, the rest of the individuals tend to follow, which can lead to mass strandings.
A natural phenomenon that poses new challenges for marine conservation
The study forces a review of some previous interpretations about cetacean strandings. For years, these events were mainly associated with pollution, diseases, or human disturbances.
However, the evidence obtained in Patagonia shows that natural ecological factors can also play a determining role. Understanding this dynamic allows for improved rescue protocols and more accurately guiding conservation actions.
Additionally, constant monitoring of the orca and dolphin populations in the Golfo San Matías becomes essential to anticipate new episodes.
In this context, scientists warn that the interaction between predators and prey is part of the natural balance of the ocean, but it can also generate unexpected situations for marine fauna in sensitive coastal areas.
