Earlier this year, off the remote Patagonian coast of Chile, researchers made a chilling discovery. Littering the isolated fjords and bays of the pristine landscape were hundreds of sei whale carcasses. In what could be the largest ever standing of whales reported, researchers have been working tirelessly over the past few months to try and figure out its cause, which they will reveal early next year.

“We found all together 337 whales of which 32 were bones only,” explained Vreni Häussermann of the Huinay Scientific Field Station, who first reported the strandings in April and conducted the follow up research with Carolina Gutstein from Consejo de Monumentos Nacionales, to IFLScience. “We have since then done the analysis. We have been gathering data on the red tide throughout all Patagonia, on all types of diseases of whales, and we’ve been gathering information on currents and winds of the area.”

A group of dead whales, all of which are thought to be sei whales. © Vreni Häussermann.

Along with oceanographers from the Scottish Association of Marine Science, Häussermann has been working on drift models to allow them to backtrack from where the whales were found to where they could have died at sea. Whilst Häussermann can’t disclose exactly what they have found, the results of this analysis as well as their conclusions as to the likely cause of the mass stranding will be published in a scientific journal in a few months’ time.

Häussermann first found the whales by chance, when out on a separate research trip in the remote region between the Gulf of Penas and Puerto Natales, along the southern tip of Chile. Very few boats pass through this region, which is made up of a maze of inaccessible inlets and fjords. She first spotted 25 whales in one location, and then another five 200 kilometers (125 miles) further south. This suggested that some sort of mass mortality event had occurred over a vast distance, and after finally managing to get funding from National Geographic, Häussermann was able to take a chartered flight with Gutstein to establish the true extent of the stranding.

Two of the carcasses spotted from the flight over the remote region. © Vreni Häussermann.

“It was definitely a really shocking event, I mean we’ve never seen something like this,” says Häussermann. “We were convinced we would find more dead whales when we went on the flight, but we expected maybe two or three times more than the 30 I had found, but we were not prepared to find ten times more.” The addition of 32 skeletons to the 305 carcasses suggest that this is not the first time a mass mortality event has happened in this region, though clearly not on the same scale.

The numbers counted by Häussermann are shocking, but they could represent only a fraction of the true mortality event. Earlier research focusing on gray whales in the Pacific suggest that only between five and 10 percent of whales that die at sea get washed up on the beach. Finding the true number of whales to have died is something the researchers are interested in exploring further. “One of our thoughts is to go back into the area in the future with a remotely operated vehicle and look on the sea floor and search for whale falls,” says Häussermann.

Worryingly, this is not the first mass stranding reported from the Pacific this year. In August, over 30 whales were reported to have been washed up off the coasts of Alaska and British Columbia, with the reason behind that event equally uncertain. Häussermann has been in contact with those working on the strandings, and admits that it’s not clear just what is going on or if these events are connected.