Puget Sound orcas could be designated as distinct species
SEATTLE — 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 altogether.
“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.
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.