Plate Nº 29 · recorded October 3, 2026
Biology & EvolutionReported finding
Baby Whales Are Washing Up Dead in Argentina, and Scientists Are Racing to Find Out Why
Southern right whale calves are dying in unusual numbers off Argentina. Scientists suspect gull-inflicted wounds let lethal marine bacteria in, but the cause remains unconfirmed.
By Priya Raman3 min read684 words
In brief
- Scores of southern right whale calves have washed up dead around Peninsula Valdes, Argentina, in an event researchers call unusual based on 23 years of population monitoring.
- The leading hypothesis is that kelp gull injuries allow marine bacteria to infect calves; bacteria have been found in tissue samples, but researchers are still culturing them to confirm the cause of death.
- Researchers declined to give a death toll; a clear count is expected only after the season ends around late November.
Dozens of baby whales are washing up dead along Argentina's Patagonian coast, and investigators are racing against time and decomposition to find the cause.
The carcasses of southern right whale calves have been appearing in unusually high numbers around Peninsula Valdes, a major breeding ground in Argentina's Chubut province. The whales, hunted to the brink of extinction in the 19th and 20th centuries, now gather in the peninsula's sheltered waters to give birth and nurse their young. Bodies have washed ashore around the gulf city of Puerto Madryn, some near the central waterfront, where they alarm residents and tourists.
"We're looking into the whale calf deaths based on 23 years of monitoring that we have of this same population. That's what allows us to say that this is an unusual event," said Marcela Uhart, a veterinarian with the One Health Institute at the University of California, Davis, who leads the investigation as head of the Southern Right Whale Health Monitoring Program.
Birds may be opening the door to infection
The leading hypothesis, according to Uhart, is that the calves are suffering infections from marine bacteria that enter their bodies through wounds inflicted by kelp gulls.
The mechanics of the problem are well documented. For decades, these seabirds have pecked at whales surfacing to breathe, gorging on their skin and blubber. Adult whales have learned a workaround: they surface with only their heads exposed, keeping their backs underwater and out of the birds' reach. Calves cannot perform that maneuver. That leaves their skin exposed and vulnerable to repeated attacks.
In theory, the resulting injuries could give bacteria a route into the young animals' bodies. Bacteria have already been detected in tissue samples collected from the dead calves. But detection alone does not settle the question. Researchers are still culturing samples at a veterinary school in the city of Tandil, farther north, to identify the specific microbes and determine whether infection actually caused the deaths, Uhart said.
Even if bacteria turn out to be the killer, a deeper question remains: why have they become so deadly this year?
A possible 'perfect storm'
Uhart points to changes in marine conditions, such as warming sea temperatures, potentially linked to climate change or El Niño, as factors that could contribute to what she calls "this perfect storm where this bacteria is powerful enough to overcome the immunity of the babies and cause their deaths."
"So to the extent that we can, we'll try to identify at least what factors may be triggering this event and making it so massive," she said.
For now, the scale of the die-off remains uncertain. Residents have reported hundreds of carcasses, but researchers declined to give a death toll. A reliable count, they say, will only become clear after the season ends around late November.
Grueling fieldwork
Uhart and a team of biologists, veterinarians and park rangers have been scouring the region for dead calves from the shore and with boats, planes and drones. The work is grim. They photograph and examine the bodies, collecting skin and organ samples before decomposition destroys the evidence.
Why these whales matter
Right whales got their name from whalers who considered them the "right" animals to hunt: they swam slowly, stayed close to shore and floated when killed, according to the International Whaling Commission, a global body that regulates whaling.
Southern right whales have gradually rebounded since gaining international protection in 1935, even though illegal hunting continued into the 1970s. Their recovery remains fragile, threatened by the same pressures facing whales worldwide: declining food supplies, entanglement in fishing gear, oil spills and ship strikes.
A die-off on this scale, if it recurs, could slow the population's recovery. That is why pinpointing the cause matters beyond this single season. By understanding what is killing the calves, researchers hope to find ways to protect a population still climbing back from near-extinction.
"If the cause relates to something that we are doing as humans, then we need to change that," Uhart said. "We don't want to endanger these whales again."
via Phys.org Biology (Source)
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Senior reporter covering industry trends and analytics at SciBeat.
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