In recent weeks, 21 dead whales were found in Argentina’s Valdés Peninsula, bringing the total to 71 so far in 2024. This sudden increase in fatalities is a red flag for right whales, the peninsula’s main visitors. Why is this happening?
This year’s whale mortality rate has doubled last year’s count of 30, and is a significant increase from 2022, which saw only 12 deaths. Peninsula Valdés, a UNESCO World Heritage Site, is one of the world’s most important breeding grounds for southern right whales. This unusual mortality event has raised serious concerns about the population’s future, prompting further investigation.
The Mortality Crisis in Valdés Peninsula
According to the Southern Right Whale Health Monitoring Program, a report released by the Government of Chubut noted that from October 19 to 29 alone, 15 adult cetaceans (12 females, 2 males, and 1 of unknown sex), 2 juveniles (1 female, 1 of unknown sex), and 2 male calves were found dead.
Before their deaths, it appeared that adult and juvenile whales had been feeding on algae from a harmful algal bloom in Golfo Nuevo. This toxic algae is a potential cause of poisoning, especially concerning as whales typically fast for months and may have ingested more than usual during their return for breeding season.
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Authorities are now actively removing the whale carcasses from the coast with the help of the Directorate of Flora and Fauna, the Provincial Highway Administration, and the Administration of the Peninsula Valdés Natural Protected Area.
What Is Causing These Deaths?
Local researchers suspect that a paralytic toxin in zooplankton—part of the whales’ diet—may be responsible. Initially, they considered the possibility of a red tide, but experts clarified that this toxin differs from that found in typical red tide events. Gabriela Bellazzi, president of the Puerto Pirámides Deliberative Council and member of the stranding network, suggests this toxin is naturally occurring, though likely exacerbated by climate change.
These toxins are found in oceans worldwide, but warming seas may be increasing their frequency. Zooplankton feed on toxin-containing algae, accumulating these toxins in their bodies. When whales consume large amounts of zooplankton, they ingest the accumulated toxins, which can lead to death. This subtle effect of global warming demonstrates how even the smallest environmental changes impact vulnerable species.
As protection measures are reinforced on the Chubut coast, scientists continue their investigation, hoping to find solutions to protect the region’s whale population.
This article was originally written in Spanish by Perla Vallejo in Ecoosfera
