A bacterial infection is suspected of causing the deaths of hundreds of southern right whale calves in Argentina’s Patagonia region, where dozens of dead young whales washed ashore again this week, continuing a trend that began in June. Researchers are investigating a possible outbreak of erysipelas, a serious bacterial disease commonly associated with bacteria found on the skin of the mammals. Scientists have not yet established the cause conclusively, while authorities continue working with researchers to investigate the deaths.
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Southern right whale calves continue washing ashore
Dozens of dead southern right whale calves washed up on beaches in southern Chubut province again this week, continuing a pattern that began in June. Mariano Coscarella, a researcher at the Marine Mammals Laboratory of Argentina’s National Scientific and Technical Research Council (CONICET), told AFP that the mortality rate among young whales has been particularly high this season.
The deaths are occurring in an important breeding area for southern right whales. Puerto Madryn and the nearby Valdes Peninsula are major breeding grounds for the species, which can grow up to 17 metres long and weigh about 40 tonnes.
Researchers suspect a bacterial infection
Veterinarians suspect an outbreak of erysipelas, a serious disease caused by bacteria commonly found on the whales' skin. The Chubut provincial government said preliminary research indicated that the deaths may be linked to a “common marine bacteria” and that it was working with the scientific community to investigate what is happening.
Coscarella said the deaths appeared to have a natural cause, while adding that the possible influence of human activity could not be completely ruled out. The suspected bacterial infection therefore remains part of an ongoing investigation rather than a confirmed explanation for all of the deaths.
Nearly 400 calves counted dead this year
The scale of the calf deaths comes as researchers continue monitoring the southern right whale population around Patagonia. AFP also reported that a record 2,110 whales were counted in the area in 2025, including about 800 young whales.
This year, authorities have counted 1,375 whales, including nearly 400 calves, according to figures revealed by Coscarella. The figures come as researchers record an unusually high mortality rate among young whales during the current season.
Scientists continue investigating the unusual number of deaths
Authorities in Chubut are working with scientists to determine what is causing the unusual number of deaths. While a bacterial disease is currently suspected, the investigation has not established that it is definitively responsible for all the whale deaths.
Coscarella also said that the recent mortality does not constitute a medium-term danger to the area's whale population, noting the southern right whale's long lifespan. Local authorities estimate that the species can live for around 60 years.
