The orca assortment
Six-minute read
Something really exciting is happening in the orca world. They’re changing. Killer whales are morphing into a horde of new species, smarter and deadlier then ever before. The thing is, they’re doing it very slowly.
That’s typical of evolution. It takes millions of years for a species to change significantly. It happens gradually on a generational level. Orcas are a cosmopolitan species, which means they can pretty much live anywhere in the ocean they want. It’s where they choose to live that’s behind the slow divergence that’s currently underway.
There are at least 10 different varieties of orca. They’re still the same species, but the changing populations are classed as distinct ecotypes. In case you’re wondering, the key feature that defines a species is the ability to produce fertile offspring. Fertile being the operative word.
It’s possible to cross-breed lions and tigers, but the resultant liger can’t begin a beautiful new line of mega-cats. I’m sure there are a small number of exceptions because science loves to screw with us, but hybrid animals of species that aren’t extremely closely related are highly likely to be infertile.
At the moment, the orca ecotypes still share enough DNA to have fertile offspring. But given enough time, that could well change. Because the different ecotypes don’t just look (admittedly only slightly) different, but they behave differently too.
Antarctic Type A are the biggest. They inhabit the entirety of Antarctic seas but typically stick to deep water. Minke whales are their favourite prey, and pods follow migrating minkes and pick them off as a pack.
Antarctic Type B are also known as Pack Ice killer whales. These are the ones you’ve seen showing off their signature technique of knocking seals off floating ice in David Attenborough documentaries. The white patches of these orcas has a yellow tinge to it thanks to the diatoms in the icy polar water.
Gerlache Strait killer whales are a subtype of Antarctic Type B orcas. We used to think that they lived on penguins, but researchers noticed that penguin numbers didn’t dip when the Gerlache Strait orca population surged. We now know penguins are more like snacks, and the bulk of their diet is made up of fish and seals.
Type C, or Ross Sea killer whale, is the smallest orca variety on Earth. In marine mammal circles, which admittedly are small, this ecotype is famous for its vocal ability. Their calls are extremely complex, and a 2020 study found that Type C orcas use at least 28 distinct call types.
I’d like to quote the paper directly for this next part -
Type C killer whales produced complex calls, consisting of multiple frequency-modulated, amplitude-modulated and pulsed components.
I had to use their words because I don’t understand them well enough myself to explain that sentence. Complex is definitely a key word there. Listen to how they describe the acoustic nature of this particular orca language.
Often, two components occurred simultaneously, forming a biphonation; although the biphonic components did not necessarily start and end together, with one component lasting over several others. Call complexity may be related to feeding ecology.
Type D is a relatively recent discovery. Until 2019 the only evidence we had were stories from fishermen, blurry photos taken by tourists and a single stranded whale in the late 1950s.
Scientists off the coast of Chile finally caught a glimpse of them and even managed to get DNA samples to study. The sources I found did not specify how. They do look distinctly different to the traditional orca we all picture. Its white eye patch is so small it’s barely there.
The north-east Pacific is home to an ecotype called Resident killer whales. They don’t tend to travel much from their home area and primarily hunt fish and a little bit of squid. Resident orcas can be divided into at least three distinct communities; northern, southern and southern Alaskan. Around 1,000 orcas make up these three groups. Approximately 70% of those are southern Alaskan orcas, 29% are northern Residents and the remaining 1% are southern Residents. We’ll come back to why that is later.
Bigg’s killer whales, or Transients, eat big mammals almost exclusively. They’ll take out anything from a porpoise to a young grey whale. As their name suggests, they move around a lot. You’ll find them somewhere between southern California and the Arctic circle. Good luck.
Transients share a lot of territory with Resident orcas, but the two different ecotypes do not interact. They certainly don’t breed. Earlier when I was making all that stink about different species not being able to give birth to fertile offspring.
I mentioned earlier that we know that different ecotypes can still make babies that can make babies. But we only know that because of orca captivity. There are different ecotypes all jumbled together and unlike in the wild, they don’t get to choose who to spend their lives with. I think of it a lot like prison. You don’t get a say in who your cellmate is. They could be an absolute nutter. But you’re in with them for life.
The reason I’m saying all this now, is that ecotypes do not interbreed in the wild. Transient orcas have been genetically distinct from all other ecotypes for a minimum of 750,000 years. The different ecotypes have been brewing for three quarters of a million years. They haven’t interbred with other ecotypes in all that time and we don’t know what it’s like for captive orcas being forced to go against nature. But aquarium owners don’t care about that. They just want the money.
I have yet another horrible fact for you about Transient orcas. They hunt mammals, so they predate other predators. Because so much of their food is at the top of the food chain, transient orcas have high levels of pollutants stored in their blubber. All the chemicals that make their way into the ocean seep into all the life within it. When everything in the sea is a little bit poisonous, it accumulates and has a compounding effect on the apex predators that are only eating other hunters.
Offshore killer whales are another north Pacific ecotype. As their name suggests, they spend most of their time far out from the coast and that means that they don’t encounter humans very often. They like to hunt along the continental shelf, where the shallows of the outer shore hit the big blue. The sea floor drops off suddenly and creates an underwater wall. Incoming oceanic currents hit the continental shelf and force nutrients from the substrate upwards through the water column.
The continental shelf is a hotspot for marine life because the nutrient upwelling attracts blooms of plankton, which lures fish to the region. Sharks, dolphins and predatory birds follow suit to pick off the fish, and big filter-feeding whales show up to clear up any unclaimed krill.
Offshore orcas were once thought to be fish-eaters through and through, but scientists noticed that their dorsal fins were nicked and scarred like those of transient mammal-hunting killer whales. So even though we haven’t seen it with our eyes, we know offshore orcas must hunt bigger game than small fish because their bodies bear the scars of battle.
The final two are Eastern North Atlantic orcas, and they’re split into Type 1 and Type 2. Type 1 fall into no less than seven sub-categories including the North Sea mackerel specialists, seal-hunting orcas around coastal Norway and the herring-eating killer whales found between Norway and Iceland. The herring-feeders are the ecotype I’ve seen the most frequently so I have a particular fondness for them.
Type 2 mostly feed on baleen whales like minke whales and young member of larger species like humpback whales. It takes a lot of guts, co-ordination, and persistence to hunt such a big target. Hunts can take hours, but the orcas work as a team to get their prize at any cost. I mentioned this in A Dolphin Pod, but orcas have a hunting success rate of 99%. Compare that to a lion, with a measly 17% hunting success rate. Pretty much everything a pod of orcas sets out to kill is going to die, be in a single herring or a fully-grown minke whale.
If you’ve been to a captive orca show, you might be wondering what ecotype the orcas you saw were. If you have photographs, you might be able to work it out though, as I’ve mentioned, there’s a big mixed bag of DNA in captivity now. Many of the different orca forms have distinctively-shaped dorsal fin tips. Each individual is different enough that an enormous percentage of wild orcas are named and know to science.
That goes for captive orcas too. Tilikum may be the most famous killer whale in the world, after Willy. He was born in the wild and his name is officially recorded as SWF-OO-C9201. He was a Type 1 Eastern North Atlantic killer whale fished from Icelandic waters, where his family had no choice but to go on without him. There was a huge flurry of orca hunts in Iceland the 1980s and 90s because laws had been tightened up in America.
Facilities like SeaWorld had be be prevented by law from removing orcas from the wild. Instead of stopping, they moved their operation overseas. But the damage was done. The southern Resident population was ravaged so extensively even today there only 80 left. The other ecotypes in the region have hundreds of members, but southern Residents are still endangered.
31 orcas were caught from the wild for captivity in the 1960s. 16 of those were southern Residents. And to be clear, they didn’t just remove 16 whales from the wild. SeaWorld’s orca hunters would kill their way to the calves. The small whales were cheap to transport and so vulnerable that they were easy to train and manipulate and train. For every baby taken, one or more adult whales may have lost their lives. We don’t know how many southern Residents were plucked from the ecosystem, but we know it was so many that decades later their numbers are still in serious trouble.
Shamu was a southern Resident. You can see the origins of every single captive orca ever recorded, both alive and dead. InherentlyWild has been an incredible resource while I made my podcast, but I can recommend checking out the deceased and current captive databases. It’s an eye-opening experience. As is my podcast A Dolphin Pod. If you haven’t listened, get on it now. There’s so much more beneath the surface.
