Mystery of killer whale swallowing 7 otters

A female killer whale may have died from an otter carcass stuck between her mouth and esophagus after eating six other otters.

Intact otters were removed from the belly of a stranded female killer whale. Photo: Sergey V. Fomin

Scientists in Russia discovered seven perfectly preserved otters in the stomach of a stranded killer whale ( Orcinus orca ), according to a study published on September 28 in the journal Aquatic Mammals. The carcass of the unfortunate killer whale was located far from its usual hunting grounds, raising questions about what it was doing there. The female killer whale was found in 2020 on the coast of the Commander Islands, off the coast of Russia’s Far East in the Bering Sea.

The team conducted an autopsy and found not only seven otters ( Enhydra lutris ) weighing a total of 117 kg (250 pounds), but also 256 cephalopod beaks. One otter was stuck between its mouth and esophagus, which could have led to the killer whale's death. There were a few things about the killer whale that puzzled the researchers. "The situation was very unusual because killer whales don't usually eat otters," said Olga Filatova, a marine mammal researcher at Moscow State University.

Instead, they prey on seals, sea lions, dolphins, and even other whales. Regardless of the species, they don’t swallow the animal whole, but always tear it apart and eat only the tastiest parts, Filatova said. Swallowing an otter whole would likely be difficult for a stranded killer whale, since adult otters can grow to 5 feet (1.5 meters) in length. The researchers think the killer whales may do this because they are starving.

The researchers also analyzed the killer whale’s DNA and determined that the individual belonged to the Bigg’s killer whale population, which has a large range that stretches from the Aleutian Islands and the Gulf of Alaska to coastal California. This is the first time a member of this population has been found in the western Pacific , leading Filatova and her colleagues to hypothesize that the animal learned its hunting tactics elsewhere. Foraging tactics are often passed down from mother to calf.

While the orca stranding raises some questions, it may help answer many others. The otter population between the Aleutian Islands and the Gulf of Alaska is declining. While some scientists suspect that orcas are behind the decline in the region’s otter population, this is the first direct evidence of the behavior.

An Khang (According to Live Science )

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