A threatened population of killer whales that spends much of the year hunting seals off the British Columbia coast has been identified by an international team of scientists as a distinct species separated from its fellow orcas in Canada and elsewhere about 700,000 years ago.
The whales, known as the North Pacific Transients, have long been understood to have a different prey preference than their fish-eating cousins, as well as subtle physical anomalies, such as a more pointed dorsal fin.
But a genetic study involving 16 American and Danish scientists, led by the U.S. National Marine Fisheries Service, has concluded that the estimated population of about 300 individual North Pacific Transients is globally unique — an animal with so many DNA differences from its closest relatives around the world that it should be classified as a stand-alone species.
If the proposal is backed by the broader scientific community, the tiny population of whales off the Pacific Coast would essentially become Canada's scarcest species — with fewer numbers than either the endangered North Atlantic right whale or the whooping crane, both of which have between 300 and 400 individuals.
"It's a very exciting story," said John Ford, a University of British Columbia killer whale expert and federal fisheries scientist. "We've suspected this for many years but just haven't had the strength of evidence that this study has provided."
The results of the orca DNA project, published in the latest issue of the journal Genome Research, were based on samples tested from hundreds of specimens collected around the world.
The study, led by California-based geneticist Phillip Morin of the U.S. National Oceanic and Atmospheric Administration, has also tentatively identified two killer whale populations near Antarctica as separate species.
But the most distinctive of all orca populations was the North Pacific Transients, which move annually in small hunting groups between the coasts of Northern California, Oregon and Washington, along the B.C. shore and as far north as Alaska.
"Not only are they ecologically and morphologically distinct from other high-latitude killer whales, but genetically they are the most divergent type, diverging from all other killer whale types approximately 700,000 years ago," the study states.
Morin told Canwest News Service that this "relatively ancient" separation of the North Pacific Transients from other killer whales was key to their proposed designation as a separate species.
He added that the finding reinforces the importance of conservation policies that treat the transients "separately from all other killer whales for management purposes."
Morin added that other "resident" and "offshore" orca populations that inhabit Canadian waters could eventually be declared independent as well, as more information about their habits, physiology and genetics is gathered.
Ford says the transients are already treated as a separate population in Canada in terms of conservation strategies. Overall, he says, the transients are in a relatively healthy state — currently increasing in numbers by two or three per cent per year — but are considered "threatened" under Canada's endangered species legislation because of their relatively small population and heavy accumulation of toxins such PCBs via target prey.
Ford says that along with different feeding habits and certain physical features, the transients "never mix with other populations" and are clearly "acoustically" distinct from other killer whales.
"They are very quiet," he says, "because they hunt by stealth" when targeting "smart" seals and sea lions unlike the salmon-eating killer whales of southern B.C. that simply plow into schools of prey.
Ford said the transients 700,000-year-old split from other orcas is a "really striking" discovery that is "a surprise to all of us" who study killer whales.
"It really helps us better understand the evolution of the species."
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