A pod of more than a dozen orcas has disappeared after having thrashed in freezing Japanese waters for about a day trying to escape being trapped by drifting ice. It isn’t known what has happened to them, but there are fears they have died.
Fishermen near the island of Hokkaido first noticed the pod struggling in the thick slush early on Tuesday. Images and drone video show at least 12 orcas, including several juveniles, struggling in a tight space closed off by heavy drift of ice about 1 kilometre offshore.
As of Wednesday morning, the entrapment area was empty, which has given hope that the animals may have escaped into the Sea of Okhotsk’s open waters, stated Japanese news media NHK state.
But a group of 17 orcas was spotted trapped in an ice drift late Tuesday afternoon, 2 kilometres north-east of the original site, NHK report.
“Killer whales are not ice-adapted whales; they’re not comfortable in this area,” says Colin Galloway at the University of Manitoba in Canada. “So, they’d be certainly experiencing … stress from the confinement, and they’d be likely starving.”
Cetaceans that live full-time in Arctic areas, like narwhals (Monodon monoceros) and belugas (Delphinapterus leucas), occasionally get trapped in ice. Orcas (Orcinus orca), however, usually avoid heavy ice and thus entrapment.
Even so, the black-and-white marine mammals sometimes find themselves in icy waters at the wrong time. In a 2016 review, scientists found there had been 17 cases of a total of 100 orcas trapped in ice in the northern hemisphere – nearly half of which occurred in Japan’s Sea of Okhotsk – since 1840. Entrapments usually end in the death of the animals, says Galloway.
Scientists believe that even killer whales reported to have “broken free” after being trapped in ice probably die as they struggle through more ice drifts while trying to reach open water.
A 2019 study of ice-trapped orcas suggests that the mammals might live up to 50 days on body fat before starving to death during entrapments. It says sightings of orcas trapped in ice had become more common in recent years, as Arctic ice melts and curious orcas endeavour to explore new territories.
Global warming could certainly play a role, says Galloway, whose team is currently investigating the environmental effects of orcas’ gradual northward shifts. But entrapment cases might also simply appear more common because people are reporting them more.
“It’s really hard to disentangle with climate warming – which is one prediction – from us just being better at finding them and seeing them and writing them down, and just caring more,” he says.