Puerto Madryn, Argentina – A bacterial infection is believed to be responsible for the deaths of hundreds of southern right whale calves along Argentina’s Patagonian coast, according to marine experts. Since June, dozens of deceased young whales have been found washed ashore in the southern Chubut province, raising concern among scientists and local authorities.

Mariano Coscarella, a researcher at the Marine Mammals Laboratory of Conicet, Argentina’s national research council, confirmed that the mortality rate among calf whales this season is notably high. Based in Puerto Madryn, a key whale-watching hub on the Atlantic coast, Coscarella indicated that veterinarians suspect an outbreak of erysipelas, a bacterial disease commonly present on the skin of these marine mammals. While the cause appears to be natural, he did not rule out potential impacts from human activities.

The government of Chubut province stated on Wednesday that it is collaborating closely with scientific teams to investigate the cause of the unusual die-off. Preliminary findings pointed to a common marine bacteria as the likely agent behind the deaths. The affected area, including Puerto Madryn and the nearby Valdes Peninsula, serves as a vital breeding ground for the southern right whale, a species known to reach lengths of up to 17 meters and weigh around 40 tonnes.

In 2025, local authorities recorded a record 2,110 southern right whales in the region, with approximately 800 calves among them. This year, officials counted 1,375 whales, including nearly 400 calves, highlighting a decline potentially linked to the ongoing calf mortality. Despite the losses, Coscarella emphasized that the current mortality rate does not pose a medium-term threat to the local whale population, given the species’ average lifespan of about 60 years.

The southern right whale population in this part of Patagonia remains under close observation as researchers continue their efforts to understand and mitigate the factors contributing to the young whales’ deaths.