In the last decade, white orca sightings—once extremely rare—have increased, with between five and eight spotted in the western North Pacific. While the cause of the sudden uptick of white killer whales is unclear, scientists worry it's the result of inbreeding.

In August 2010, a group of whale researchers were watching and recording orcas off the coast of Russia, when to their "surprise and elation"—according to researcher Erich Hoyt, who organized the trip—they spotted a 6-foot white fin in the water near the Commander Islands. The fin belonged to a partially albino male who is known today as Iceberg, thanks to his white coloring.

As Hoyt and his colleagues explained in a recent study published in Aquatic Mammals Journal, Iceberg was one of the first white male orcas ever discovered. But he didn't hold the title for long: Just two days later, a second white whale made an appearance in the area. Since then, there have been at least five and possibly eight other white whales spotted in the western North Pacific.

Because genetic data has yet to be collected from any of these white whales, the cause of their appearance is unclear. What scientists do know is that the collection of white whales is an area-specific occurrence. No more than two white orcas have ever been spotted in any other single region. Meanwhile, Hoyt's team estimates that in the western North Pacificthere is possibly one white killer whale in every thousand.

“What we are seeing is strange. It’s a very high rate of occurrence,” Hoyt said.

At the time, the Far East Russia Orca Project, the group leading the expedition, thought Iceberg might be albino. Albinism is usually the result of inbreeding in mammals, but the population of orcas in the region is substantial enough to avoid inbreeding. Other areas have lower populations of whales and yet lack any white orcas.

“They are not what we would think of as the most inbred orca population,” said Hoyt. “Some populations in the eastern North Pacific contain just a few dozen individuals.”

Still, as New Scientist points out, another recent study shows that different regions have different whale cultures, and each type of culture is genetically distinct. Orcas are one of only two species whose evolution has been shaped by culture (the other being humans).

“Often these [cultural] populations are reproductively isolated from neighbouring populations, and often it’s not clear why this is,” said Andrew Foote, a researcher at the University of Bern, Switzerland, who conducted the study. “But it does lead to the populations being relatively in-bred."

Another clue might be Chimo, the white, female orca that was kept in captivity and did not have true albinism. Instead, Chimo had Chediak-Higashi syndrome, a condition that causes immunity problems and partial albinism. As a result, she only lived to age 4.

Researchers doubt Iceberg and his buddies have this disease because he's already 22 years old; if he had the condition, he likely wouldn't have lived this long. On average, male orcas live to be about 29 years old, but some can live as long as 60 years in the wild.

More studies will have to be conducted to see what the cause of this new trend could be and if it's indicative of the changing climate.

[h/t New Scientist]

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