With the arrival of spring in the South Atlantic, the whales also arrive: the Valdés Peninsula area, in Argentine Patagonia, is the scene of an annual celebration, an incessant pilgrimage of tourists who want to see the great marine mammal with their own eyes. This year, however, the news is different, the unusual number of baby whales that appear stranded and dead on the coast.
"Particularly, during this season the mortality has been quite high," declared Mariano Coscarella, a researcher at the Marine Mammal Laboratory of the National Scientific and Technical Research Council (Conicet) in Puerto Madryn, the main city in the area.
In 2025, 2,200 whales were recorded in the waters of the Golfo Nuevo and 80 were found dead. This year, out of 1,200 right whales registered, more than 350 dead whales have already been counted on the beaches of the Valdés Peninsula.
The scientists' hypothesis is that a bacteria is responsible for the deaths. "There is a bacteria that produces erysipelas, which is a disease that can manifest itself in whale calves cutaneously, as diamond-shaped lesions," explained Víctor Fratto, a graduate in Environmental Management and a reference in the study of whales in Argentina.
The bacteria being studied is in the marine environment and associated with other species, Fratto added. "It is in the mucus that covers the skin of fish, crustaceans and mollusks. We do not know why this outbreak occurs this year. We are also not clear why it only affects the offspring. There are still many questions," he admits.
A study published in 2016 in Argentina detected the erysipelas bacteria in lesions associated with seagull attacks in two whale calves examined during the 2013 season. These wounds were considered a possible entry route for different microorganisms.
"The kelp gull, which is constantly pecking at the whales' backs, is the vector that is introducing the bacteria into the whale calf," believes Fratto.
Unfortunately, there is no health treatment to resolve these cases at sea: "It is very difficult to control this type of situation, because the whale calves are pecked by seagulls as soon as they are born."
Marine biologist Juan Cruz Martín considers that "so far there is no evidence that the mortality was caused by human factors," although "the samples taken from each animal continue to be investigated to determine the possible causes of their death," as he explained to this newspaper.
The samples taken were sent to Buenos Aires to be analyzed at the Malbrán Institute, the reference laboratory in the country, and experts hope to have more certainty at the end of this month.
"These types of scenes could continue to appear on the country's coasts, but it is very important that citizens understand that if they encounter dead animals on the beach, they should stay away and notify local wildlife guard representatives. The cause of death is not yet known, and direct or close contact could be dangerous," warns Cruz.
Fratto, for his part, highlights that what is happening in Argentina is not new: "Cetaceans have died from erysipelas in different parts of the world. It has happened in the United Kingdom, in the Netherlands, on the coast of California. Now it is happening to us here."
The appearance of such a high number of dead whales generates concern in the Puerto Madryn area, internationally recognized for hosting the largest reproductive group of southern right whales in the southwest Atlantic. Tourism is the great source of income in the Valdés Peninsula and nearby towns.
