April 13, 2024

New research reveals full killer whale diversity as two species appear off Pacific coast

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Aerial image of Southern Resident killer whales taken in the Salish Sea on southern Vancouver Island during the SR3 SeaLife Response, Rehabilitation and Research health survey. Images of John Durban and Holly Fearnbach using a non-invasive drone authorized by research permit 22306 issued by the US National Marine Fisheries Service. Credit: Research License SR3/NMFS 19091

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Aerial image of Southern Resident killer whales taken in the Salish Sea on southern Vancouver Island during the SR3 SeaLife Response, Rehabilitation and Research health survey. Images of John Durban and Holly Fearnbach using a non-invasive drone authorized by research permit 22306 issued by the US National Marine Fisheries Service. Credit: Research License SR3/NMFS 19091

Scientists have resolved one of the outstanding questions about one of the world’s most recognizable creatures, identifying two known killer whales in the North Pacific Ocean as distinct species. The research is published in the journal Royal Society Open Science.

Killer whales are one of the most widespread animals on Earth. They have long been considered a worldwide species known scientifically as Orcinus orca, with different forms in various regions known as “ecotypes.”

However, biologists have increasingly recognized the differences between resident whales and Bigg’s killer whales. Resident killer whales maintain close-knit family groups and prey on salmon and other marine fish. Bigg’s orcas roam in smaller groups, preying on other marine mammals such as seals and whales. (Orcas actually belong to the dolphin family.) Bigg’s orcas, sometimes called transients, were named after Canadian scientist Michael Bigg, the first to describe telling differences between the two types.

He noted in the 1970s that the two animals did not mix even though they occupied many of the same coastal waters, which is often a sign of different species.

The discovery recognizes the accuracy of the listing of southern resident killer whales as a distinct population segment that warranted protection under the Endangered Species Act in 2005. At the time, NOAA described the distinct population segment as part of an unnamed subspecies of southern resident killer whales. North Pacific.

Now, a team of scientists from NOAA Fisheries and universities has gathered genetic, physical and behavioral evidence. The data distinguishes two of the North Pacific coastal killer whale ecotypes – resident and Bigg – as separate species.

“We started asking this question 20 years ago, but we didn’t have a lot of data and we didn’t have the tools we have now,” said Phil Morin, an evolutionary geneticist at NOAA Fisheries’ Southwest Fisheries Science Center and lead author of the new paper. “Now we have more of both, and the weight of evidence says these are different species.”


Differences between two types of orcas in the North Pacific Ocean that new research recognizes as the first separate species of orcas. Killer whales have long been known as a worldwide species. Credit: NOAA Fisheries/Uko Gorter

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Differences between two types of orcas in the North Pacific Ocean that new research recognizes as the first separate species of orcas. Killer whales have long been known as a worldwide species. Credit: NOAA Fisheries/Uko Gorter

Genetic data from previous studies revealed that the two species likely diverged more than 300,000 years ago and come from opposite ends of the killer whale family tree. This makes them as genetically different as any killer whale ecotype around the world. Subsequent studies of genomic data confirm that they evolved as genetically and culturally distinct groups that occupy different niches in the same Northwest marine ecosystem.

“They are the most different killer whales in the world, they live close to each other and see each other all the time,” said Barbara Taylor, a former NOAA Fisheries marine mammal biologist who was part of the scientific panel that assessed the status of the southern residents. . “They just don’t mix.”

Recognizing new species

The Marine Mammalogy Society’s Taxonomy Committee will determine whether to recognize the new species on its official list of marine mammal species. The committee will likely determine whether to accept the new designations at its next annual review this summer.

Scientists proposed scientific names for the new species based on the first published descriptions in the 19th century. Neither will retain the globally ubiquitous nickname, orca. The team proposed calling the resident killer whales Orcinus ater, a Latin reference to their dominant black coloring. Bigg’s killer whales would be called Orcinus rectipinnus, a combination of Latin words for erect wing, probably referring to their tall, sharp dorsal fin.

The names of both species were originally published in 1869 by Edward Drinker Cope, a Pennsylvania scientist known more for unearthing dinosaurs than for studying marine mammals. He was working from a manuscript that California whaling captain Charles Melville Scammon had sent to the Smithsonian Institution describing the marine mammals of the West Coast, including the two orcas. Although Cope credited Scammon for the descriptions, Scammon took issue with Cope for editing and publishing Scammon’s work without telling him. (See attached story.)

The Smithsonian Institution shared Scammon’s work with Cope, and a Smithsonian official later apologized to Scammon for what he called “Cope’s absurd error.”


The neotype skulls of Bigg’s killer whale, Orcinus rectipinnus (left), and the resident killer whale, Orcinus ater (right). The skull of Bigg’s killer whale is more robust and has a wider rostrum (beak), which are presumably adaptations for feeding on larger prey such as marine mammals. Credit: NOAA Fisheries/Southwest Fisheries Science Center

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The neotype skulls of Bigg’s killer whale, Orcinus rectipinnus (left), and the resident killer whale, Orcinus ater (right). The skull of Bigg’s killer whale is more robust and has a wider rostrum (beak), which are presumably adaptations for feeding on larger prey such as marine mammals. Credit: NOAA Fisheries/Southwest Fisheries Science Center

Species reflect the ecosystem

The contested question of whether southern residents were distinct enough to merit endangered species protection initially motivated much of the research that helped differentiate the two species, said Eric Archer, who leads the Marine Mammal Genetics Program in the Southwest. Fisheries Science Center and is co-author of the new research paper.

The increasing processing power of computers has made it possible to examine killer whale DNA in ever greater detail. He said the findings not only validate the protection of the animals themselves, but also help reveal different components of the marine ecosystems that whales depend on.

“As we better understand what makes these species special, we learn more about how they use the ecosystems they inhabit and what makes those environments special as well,” he said.

The new research synthesizes early reports of killer whales off the Pacific coast with modern data on physical characteristics. They also use aerial imaging (called photogrammetry) and measurements and genetic testing of museum specimens at the Smithsonian and elsewhere.

Although the two species appear similar to the untrained eye, evidence shows that they are very different species. They use different ecological niches, such as specializing on different prey, said Kim Parsons, a geneticist at NOAA Fisheries Northwest Fisheries Science Center in Seattle and co-author of the new research.

Recent drone surveys and accurate aerial photos have helped differentiate Bigg’s orcas as longer and larger. This could better equip them to pursue large marine mammal prey. The residents’ smaller size is probably better suited for deep dives after their salmon prey, said John Durban, associate professor at Oregon State University’s Marine Mammal Institute. He leads drone research on killer whales with SR³ researcher Holly Fearnbach.

The different prey of the two species may also help explain their different trajectories. Southern residents are listed as endangered, in part due to a scarcity of their salmon prey. Bigg’s orcas, on the other hand, multiplied as they fed on numerous marine mammals, including California sea lions.

Although orcas represent some of the most efficient predators the world has ever seen, Durban said science is still unraveling the diversity among them. The identification of additional killer whale species will likely follow. One of the leading candidates could be the “Type D” killer whales identified in the Southern Ocean around Antarctica.

Other orcas in Antarctica also look very different from the more familiar black and white orcas. This reflects greater diversity within species, said Durban, who has used drones to study killer whales around the world. “The more we learn,” he said, “the clearer it becomes to me that at least some of these types will be recognized as different species in due time.”

More information:
Phillip A. Morin et al, Revised taxonomy of eastern North Pacific killer whales (Orcinus orca): Bigg and resident ecotypes deserve species status, Royal Society Open Science (2024). DOI: 10.1098/rsos.231368

Diary information:
Royal Society Open Science

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