Experts probe into mass deaths of southern right whales in Argentina

Scientists are using boats, aircraft and drones in a race against time to investigate the deaths of whale calves that are washed up along Argentina's Patagonian coast in unusually high numbers.

Preliminary assessments detected infection from tissues collected from the corpses' skin and organ samples, pointing to an outbreak of a marine bacteria.

Locals and tourists around Peninsula Valdes in Chubut province, Argentina, recently reported a grim trail of calf carcasses lining the coasts.

The peninsula is a critical reproductive santuary for the southern right whales, which have been hunted to the brink of extinction in the 19th and 20th centuries.

A scientist who is leading the probe as head of the Southern Right Whale Health Monitoring Program says investigators are trying to solve the mystery of whale calf deaths based on 23 years of monitoring that they have of this same population.

Veterinarian Marcela Uhart with the One Health Institute at the University of California says: "Our leading hypothesis right now is that because of some evidence that we're seeing in the animals, which includes some very characteristic square-like lesions on their skin, especially on their backs, that suggests an infection with a bacteria that is called Erysipelothrix."

"It's got a complicated name, but it is a pathogen, a bacteria that is described in causing death on cetaceans in other parts of the world. And then it is also a bacteria that exists naturally in the marine environment," she says.

For decades, kelp gulls have pecked at whales for food when they surface to breathe. While adults have adapted by exhibiting a defensive surfacing behaviour with only their heads exposed, baby whales lack such capability, thus the open lesions serve as a direct entry points for pathogenic bacteria.

Uhart goes on to say that experts are still culturing samples to identify the microbes and determine whether infection was the cause of death.

She notes the "perfect storm" of climate factors, like warming sea temperatures, potentially exacerbated by El Nino, may have amplified the potency of this bacteria while simultaneously overcoming the immunity of the calves.