Hundreds of southern right whale calves have been washing up dead on the coastline of Peninsula Valdés, Patagonia, since June this year and experts are desperate to find out why.
“The record of an unusually high number of dead southern right whale calves off the coast of Peninsula Valdés has generated deep concern throughout the community,” says the Whale Conservation Institute in a statement.
- Watch: Humpback whale rescued from fishing gear after being tangled for nine days
- Why this huge frozen whale in Alaska has got scientists so confused
Mass mortalities of young whales have been seen in this region before but this one may be even bigger than past events. “113 calves were killed in 2012, the highest number documented so far for the species, both locally and globally,” adds the Whale Conservation Institute. “Preliminary records from this year would indicate that it could be an event of an even larger scale.”
Further study is still needed to solve the mystery but some have suggested the culprit might be a bacterial infection. The potential cause is gruesome.
Experts suspect the young whales may have died from infection caused by seabirds pecking at their skin and eating them alive.
Kelp gulls are known to land on the back of southern right whales, peck holes in their skin and feast on the skin and blubber. The whales’ calorie-dense blubber is a fantastic source of energy for the seabirds.
Scientists first noticed this behaviour around the 1970s and it just got worse. “The percentage of mothers and calves with lesions caused by gulls increased from 2% in the 1970s to 99% in the 2000s,” write the authors of a 2023 paper in Biology Letters.
The birds also increasingly went after young whales rather than adults. “Initially, calves were rarely attacked by gulls but, since the mid-1990s, calves have become the main targets of attacks and their average wound severity has increased,” write the study authors.
When they try to swim away from the birds’ harassment, the whales use up vital energy that should fuel their journey to the feeding grounds.
- How to help a beached, stranded whale or dolphin - and help save its life
- "Their lipid- and protein-laden bodies create unique, nutrient-rich ecosystems that may sustain creatures of the abyss for decades…"
The open wounds can also get infected. In a 2016 study in the journal Diseases of Aquatic Organisms, scientists found evidence that nasty bacteria can get in through the lesions made during gull attacks. “During the 2013 whale season, several calves were reported showing kelp gull injuries with a swollen area surrounded by rhomboid-shaped raised edges,” the authors write in the paper.
When the researchers analysed samples taken from the wounds, they detected bacteria called Erysipelothrix rhusiopathiae, which can cause skin disease and sepsis in whales and dolphins. These can sometimes be fatal.
This 2016 study was the first evidence that “these wounds may act as an entry route for pathogens,” they write.
Researchers are now wondering if this new wave of deaths could be to do with gull-inflicted injuries that have become infected.
Getting to the bottom of what’s going on will take time because scientists need to collect and analyse samples as well as looking into other potential factors that could be affecting survival rates.
“Studies are needed in the waters of the Nuevo and San José gulfs to investigate environmental conditions that could affect the whales' survival and welfare,” writes the Whale Conservation Institute. “It is also essential to systematically survey the coasts to establish how many dead animals are recorded, avoid duplications and characterise the event spatially and temporally.”
Spellbinding footage captures critically endangered whale with her baby off the New England coast
What's the world's fastest whale? Clue - it can swim at a staggering 37kph, despite weighing a hefty 70 tonnes
Top picture: Southern right whale mother and calf. © Gerard Soury/Getty
