The case for classifying several species of orca in the North Pacific

From the Vancouver Sun:

If whale expert John K.B. Ford has his way, school children one day will study a kind of North Pacific killer whale that preys on warm-blooded creatures — mostly harbour seals and sea lions, but also grey whales and seabirds.

They roam as far north as the Arctic Ocean and are now known as “transients” to distinguish them from fish-eating “resident” killer whales.

Ford and colleagues from Alaska to California want transient killer whales to be declared their own species, and they want them to have a new name: Bigg’s killer whales, in honour of Michael Bigg, the researcher whose observations off British Columbia and Washington state led to the identification of transients and whose mentoring inspired a generation of researchers still uncovering the mysteries of the animal at the top of the marine food chain.

“He was really very much the founding father of modern scientific studies regarding killer whales,” Ford said from his office at the Pacific Biological Station in Nanaimo, B.C., where he heads West Coast cetacean research for Canada’s Department of Fisheries and Oceans.

Paul Wade, a U.S. killer whale expert at the National Marine Mammal Laboratory in Seattle, said colleagues have begun using Bigg’s killer whales as the common name for transients in research papers.

“It seems to be catching on,” Wade said.

Work demonstrating that Bigg’s killer whales are a separate species also is progressing, he said, and that could lead to honouring Bigg with a formal scientific name for transients.

Michael Andrew Bigg was born in London in 1939. He moved to British Columbia with his family nine years later. He had a lifelong fascination with predators, Ford said, and for a time was a falconer.

“He was kind of a rare generalist as a biologist,” Ford said. “He was broadly interested in natural history.”

Just out of graduate school in 1970, Bigg was hired as a marine mammal biologist at the Pacific Biological Station. One assignment was an investigation of the status of killer whales, considered dangerous to humans and pests by salmon fishermen. By 1973, aquariums were paying $70,000 for a live killer whale and 48 had been captured for display.

Bigg and colleagues distributed sighting forms to fishermen and other coast residents. His report in 1976 concluded that just 200 to 350 orcas remained along the B.C. and Washington coasts, far fewer than thought, and too few to sustain additional live captures.

He also made a breakthrough that would create the framework for decades of additional research: He determined that individual whales could be identified by pigmentation patterns on the saddle patch at the base of their dorsal fins. That meant researchers could track whales to figure out their diets, family dynamics and communications with other whales.

“It was Mike’s realization that with a good-enough photograph, you could identify even the plainest looking fin without any obvious markings,” Ford said.

Bigg’s formal association with killer whales ended by early 1977. He was reassigned to other marine mammals, including northern fur seals, Ford said, but kept at killer whale research on the side. He had started to distinguish families of resident orcas that he suspected were targeting salmon. More rarely seen were killer whales that Bigg at first suspected were pod outcasts.

They turned out instead to be mammal-eaters. Genetic work on transients followed. Wade collaborated with National Marine Fisheries Service geneticist Phillip Morin and 14 other researchers on a 2011 paper that indicated resident and transient killer whales don’t eat or behave the same ways. They also don’t interbreed.

“The evidence suggests that the transients in particular are quite different than everybody else and probably shared an ancestor about 700,000 years ago,” Morin said from the Southwest Fisheries Science Center in La Jolla, Calif.

The scientists say at least three killer whale species likely roam the North Pacific, including offshore orcas that may feed on sleeper sharks, and three in the Antarctic. Killer whales are found in every ocean and DNA samples have been studied from the extreme north and south parts of the globe. Researchers are preparing to analyze samples from tropical and temperate waters, Morin said, to piece together the pattern of evolutionary divergence between types.

“The goal is to then try to compile the genetic data with all of other data — the behavioural, the acoustic, other molecular data, distribution — and come up with a description of killer whales globally, along with our recommendations for which should be species and which should be subspecies, if the data hold up those categories,” Morin said.

I hope that 700,000 year date was determined by something other than mitochondrial DNA. An analysis of a large sample of the genome would be nice. (Jerry Coyne explains why).

I would also like to know how absolute is the assertion that these animals don’t interbreed.

Hybridization between even really distinct species of cetacean is actually pretty common, and I would be surprised if these different types of orca never interbred. Never is one of those words that sets one up for error, for as soon as the thing  that you claim will never happen happens one time, you’re instantly 100 percent wrong.

I still think there is a good case for splitting up orcas into several species. These animals behave very differently from each other. They eat different things, and apparently, there isn’t much gene flow between them.

That would suggest that they are on their way to becoming distinct species, if they aren’t already.

If this taxonomy holds, then we have a good example of sympatric speciation, which is what happens when new species evolve out of common ancestor but share the same geographical range.

Just asimple variances in foraging “culture” has resulted in the development of genetically distinct orca lineages.

And that’s really quite amazing.