Bacterium suspected in deaths of young whales
Researchers suspect a bacterial infection among hundreds of whale calves in Patagonia, but the cause has not yet been definitively established.
Young southern right whales have washed ashore again in Argentina’s Chubut province. Researchers suspect a bacterial infection may be involved, while the regional government and scientists continue to investigate the precise cause.
The deaths among southern right whale calves, also known as southern right whales, have been under investigation since June. Dozens more young animals were found this week on beaches around Puerto Madryn. According to Mariano Coscarella of the marine mammal laboratory at research institute Conicet, this is an unusually high level of mortality for this stage of the season.
Veterinarians suspect an outbreak of erysipelas, a disease caused by bacteria. According to the researchers, the bacterium is more commonly found on the skin of marine mammals. However, finding a bacterium does not prove that it explains all the deaths. The laboratory analysis and further fieldwork have not yet been completed.
The government of Chubut province says it is working with scientists and specialised research teams. According to the regional authorities, preliminary information points to a common marine bacterium. According to Coscarella, human influence has still not been completely ruled out. There is therefore still no definitive conclusion about what caused the deaths.
The coast around Puerto Madryn and the Valdés Peninsula is an important breeding ground for southern right whales. In the 2025 count, 2,110 whales were recorded there, including approximately 800 calves. In the first count of 2026, researchers recorded 1,375 animals, of which 409 were calves.
The difference between the counts cannot be directly translated into a mortality rate. The counts take place at different times and the population changes during the season. In addition, it has not yet been established exactly how many animals died in the recent event.
Coscarella told AFP that the current mortality does not pose a medium-term threat to the population as a whole, partly because southern right whales live for a long time. That assessment concerns the population as a whole and does not diminish the exceptionally high mortality among young animals. The investigation must establish whether the event is a one-off outbreak or part of a broader pattern.
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The article explicitly presents the bacterial cause as a hypothesis and avoids giving an exact mortality figure that the sources do not provide. The population counts were checked against AFP and CENPAT-Conicet.
- confirmed Elevated mortality among young southern right whales in Chubut has been under investigation since June. — Reported by AFP, based on statements from a Conicet researcher. source
- confirmed Researchers suspect erysipelas or another bacterial infection. — The source describes this as a preliminary suspicion, not an established cause. source
- confirmed In 2026, 1,375 whales were counted, including 409 calves. — Mentioned by CENPAT-Conicet. source
- confirmed In 2025, 2,110 whales were counted, including approximately 800 calves. — Reported by AFP. source
- confirmed According to Coscarella, the mortality does not pose a medium-term threat to the population. — This is attributed as the researcher’s assessment. source
Editor's note
The high mortality and the bacterial hypothesis were reported by AFP, based on a Conicet researcher. The cause has not yet been peer-reviewed or definitively established; the counts provide context, but not an exact mortality figure.Sources
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