For more than a century, killer whales have been understood to be just one worldwide species, Orcinus orca, with many types.
But now, after decades of work, scientists have determined the differences between the two types of killer whales that frequent the Salish Sea are so large, they ought to be designated separate species all together.
“It has been so long getting to this point,” said Phil Morin, of the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center.
Morin, of the center’s Marine Mammal Genetics Program, is the lead author of a paper published Tuesday night in the journal Royal Society Open Science, which officially proposes the new species designations to the international scientific community. Next, the Society for Marine Mammalogy’s taxonomy committee will vote on the proposal and could make the designations in the next few months, according to a NOAA spokesperson.
The two orca types include Bigg’s killer whales, which have a healthy, growing population and feed on other marine mammals, and residents, which encompass the endangered southern residents that feed on Chinook salmon and other fish.
Bigg’s would be known as Orcinus rectipinnus (Latin for recti, meaning upright, and pinna, meaning fin). Bigg’s should continue to be used as the common name for these whales, the scientists suggest. The name Bigg’s is intended to honor the late Canadian researcher Michael Bigg, who pioneered the study of this species.
The other proposed species is Orcinus ater, (Latin for black or dark). For now, scientists suggest continuing the common name already in use for this species, of northern and southern residents, depending on their home range. Meanwhile, local tribes are being consulted by the scientists proposing the new species designations for a fitting new common name for the residents, perhaps Blackfish.
The new species designations will be the first breakouts from the worldwide Orcinus orca since the species descriptions by Charles Scammon in 1874. A whaling captain and not a scientist at all, in his book with the remarkable title, “The American Whale-Fishery,” Scammon describes the ocean’s top predators with quite a bit of emphasis on what he regards as their bloodthirsty ways:
“… in whatever quarter of the world the orcas are found, they seem always intent upon seeking something to destroy or devour.
“Indeed, they may be regarded as marine beasts that roam over every ocean, entering bays and lagoons, where they spread terror and death …”
Scammon’s hand-drawn sketches and wildly incorrect understanding of killer whale biology are a window into the process of discovery by observation of animals which, back then, could only be glimpsed in passing.
Scammon didn’t understand the difference between marine mammal-eating orcas and those who eat fish, and thought killer whales with taller fins were a different species, when they were simply different genders.
But then, science is an iterative story, built generation by generation, that depicts an ever more accurate — but never complete — understanding of our world. And so it is that Scammon’s hunch that there might be more than one species of orca out there was correct — just not quite in the ways he thought.
How they differ
Scientists used to think that it took physical separation, or an inability to breed together, to produce separate species. But, it turns out, profound cultural traits can differentiate species, too. After all, Bigg’s and residents overlap in some of their range. And they could physically interbreed. But they have never been witnessed to do so in 50 years of scientific observation.
They do not interact, or even speak to one another. Yet they tick multiple boxes that indicate differentiation as species, both from one another, and all other killer whales, scientists argue in the paper.
Consider:
—Bigg’s eat marine mammals, while residents eat mostly salmon, especially Chinook. Never does either even sample the other’s diet.
—Bigg’s of both sexes are physically much larger than residents. John Durban, associate professor of fisheries, wildlife and conservation at the Marine Mammal Institute of Oregon State University, can measure killer whales to the centimeter using a camera on a drone, flown high over the whales. From these images has emerged the fact that Bigg’s killer whales are more robust than the residents. They are bigger and longer, by nearly a half a meter on average. The Bigg’s also have a different jaw structure. Both their jaw and bigger body size make sense for an animal that has to take on big prey.
—The Bigg’s dorsal fin is wider at the base, more triangular, and pointed at the tip, and the saddle patch — the marking behind the dorsal — is nearly all white. Resident saddle patches include black in their pattern.
—Bigg’s hunt by stealth, quietly and in small groups of two to six. Residents roll out in a big crew of as many as 18 whales, using echolocation to ping and track their prey and call to one another as they hunt. The residents’ sonar click sequences are produced on average six to 27 times more often and are twice as long as in Bigg’s whales.
—Residents’ seasonal movements have been linked to salmon species aggregations, while Bigg’s seasonal peaks are associated with the pupping season of harbor seals and the migration of gray whales.
—Modern genetic tools show just how long ago and how completely Bigg’s and residents separated themselves on the family tree, with no gene transfer between them since anywhere from 350,000 to as long as 700,000 years ago, scientists estimate.
Genome sequencing beginning in 2018 ultimately decoded the DNA of about 100 southern resident killer whales, living and dead. That opened a panoramic window into their nature. The findings, published in 2023, for one thing showed how inbred the southern residents are — yet another risk to their survival.
The genetics of the residents were once such a muddle, he noted, that NOAA rejected the initial petition for listing the southern residents as an endangered species in 2002, on the basis that the whales did not meet the criteria to be even a distinct population.
It took a district-court ruling to goad the agency into doing two things at once: determining the data it needed to understand the diversity of killer whales, and do it without traditional methods. “Most species live on land, or can be hauled into nets, and are set apart by differences in what they look like,” Morin said. “That wasn’t going to work here.”
Eventually the agency determined the residents likely were a distinct population from other killer whales. While the agency didn’t have all it needed to prove it, the legal requirement to rely on its best available science in making a determination tipped the scales in favor of finally listing the southern residents in 2005 as a distinct, endangered population.
Now has come the next step, of species designation.
“It’s an interesting story, a fascinating melding of scientific knowledge in the mid- to late 1800s with the very, very high-tech, gee-whiz research,” said Thomas Jefferson, an independent marine biologist based at NOAA’s Southwest Fisheries Science Center, and an author on the paper. “It is interesting it can be put together and make a cohesive story from such a wide range of information.”
You are what you eat
While it may seem obvious now that Bigg’s and resident killer whales are different species, the scientific detective work proving it was years in the making.
John K.B. Ford, the renowned Canadian marine mammal biologist, a reviewer of the paper, remembers the first time he began to think something was profoundly different among the killer whales he was observing as a young scientist for Canada’s Department of Fisheries and Oceans Pacific Biological Station at Nanaimo. Back then, in the 1970s, the so-called transients were called that because they were so rarely seen. Scientist Bigg also called them “oddballs,” Ford said. But with the legal protection of marine mammals, the transients’ numbers grew along with their prey. And that is when some of the key differences between the transients and residents started to emerge, suggesting there might be multiple species of Orcinus orca.
This was also during the capture era, when killer whales were netted for aquariums around the world. When two captive killer whales nearly starved to death rather than eat salmon, scientists began to realize killer whales had profound dietary preferences.
The Bigg’s, Ford noticed, also made very different sounds from either the northern or southern residents. “I was shocked at how different they sounded,” Ford said. “I made recordings and realized they all shared the same dialects, unlike the residents, where you have different clans, and pod-specific dialects.” These, he realized, were languages, passed on culturally, generation to generation, just like the residents’ emphatic dietary rule of eating only fish.
Once scientists could show just how different the Bigg’s and residents are from one another, another question emerged for scientists researching this paper. What to call the two species? That’s where a bit of skulduggery from the past surfaced, in Jefferson’s research into the history of the scientific names for these animals over time.
Scammon, the whaling captain, wanted to publish his descriptions of killer whales in a scientific journal — but as a nonscientist, he knew he needed help. He sent his write-up to the Smithsonian Institution, where it ultimately found its way to zoologist Edward Cope. He not only edited the manuscript, but unbeknownst to Scammon, Cope sent the manuscript — with his own, extensive narrative at the top — out for publication. So it is that Cope’s name, along with Scammon’s, is on the paper published in the Academy of Sciences of Philadelphia in 1869, with Scammon’s first descriptions of orcas as a species.
It is from that paper that the names suggested today for the new species come, under the scientific tradition under which whomever is the first to describe a species gets to name it. Hence, the scientific Latin binomials Orcinus rectipinnus, Scammon’s description of what turned out to be Bigg’s killer whales, and Orcinus ater, his name for the what we today know to be residents.
What’s in a name?
The new classifications are of more than academic interest. The deeper understanding that undergirds the species designations underscores that the residents are unique in the world — a special and distinct society all their own.
The southern residents that frequent Puget Sound are particularly at risk. There are only 73 left. They face many threats to their survival, including lack of adequate, readily available Chinook salmon, boat and ship noise that interferes with their hunts, and pollution that taints their food.
“If we lose that segment of biological diversity, it is irretrievable,” Jefferson said. “It is critical for conservation that we understand that.”
These new species designations, emerging since the 1970s, are sure to be just the beginning, as scientists learn more about other killer whales.
“It’s an important first step,” said Durban, another author on the paper. “Something that has to keep going for killer whales around the world.
“It’s anything but an academic exercise. This shows how differently these animals live their lives, and how we need to protect them. And it makes killer whales all the more fascinating.”
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