In June 2015, scientists identified 337 dead sei whales on Gulf of Penas along Chile’s southern coast.
The team’s analysis showed that all whales died within the same event, around March 2015, researcher says.
Researchers are looking at all natural causes, but cannot reveal their conclusions before the paper is peer-reviewed and published.
In April 2015, Vreni Häussermann, Director of the Huinay Scientific Field Station in Chilean Patagonia, and her team, discovered nearly 30 dead sei whales on the Gulf of Penas along Chile’s southern coast while surveying the region’s marine fauna. Sei whales (Balaenoptera borealis) are members of the baleen whale family, and can reach lengths of 50 feet and can weigh around 100,000 pounds (~45,000 kilograms).
On returning to Puerto Montt, a port city in southern Chile, Häussermann notified the Chilean National Fisheries Service about the beached whales. Officials of the Fisheries Service then undertook a study to assess the situation, and in an official statement released in May, said that around 20 whales had beached along Chile’s southern coast.
While whale beaching, or stranding, is not uncommon along Chile’s coast, Häussermann was convinced that the scale of deaths was larger than the official study had revealed.
So supported by a grant from National Geographic Society’s Waitt Foundation, Häussermann, and Carolina Simon Gutstein of the Universidad de Chile and Consejo de Monumentos Nacionales in Santiago, set out on a four-day expedition in a small four-seater plane, and surveyed the area around Gulf of Penas.
Using high resolution aerial and satellite photos, Häussermann and Gutstein identified 337 dead sei whales within the area they surveyed. The team’s analysis showed that all the whales had died around March 2015, within the same event. This, according to the scientists, is the largest known whale beaching event to have occurred within such a short duration.
“We were all shocked by this finding,” Häussermann told Mongabay. “It was an apocalyptic image, and none of us had seen anything like this before.”
Häussermann declined to comment on the potential causes of the mass die-offs, though.
“We are looking at all natural causes, but I cannot reveal our conclusions before the paper is published since this has to be peer-reviewed by colleagues first,” she said.
However, Häussermann did reveal that her team had finished analyzing more than 10,000 photos, several hours of video and other data that they had gathered during the expedition.
One reason for the whale deaths, Häussermann and other experts speculate, is red tide—toxic algal blooms that have been blamed for poisoning and mass whale stranding in the past.
“For baleen whales mass mortalities are uncommon because they normally do not aggregate as toothed whales do,” Häussermann said. “This is a very unusual event, and the largest one at one place and time for baleen whales.”