The orcas (Orcinus orca) consists of at least seven genetically distinct and morphologically different types

The orcas (Orcinus orca) are among the most recognizable marine mammals we have, with its characteristic white patches on an otherwise pitch black body. This species of toothed whales are found in all parts of the ocean, from the Arctic to the Antarctic. They are an apex predator that hunt in groups, and feed on fish, sea turtles, sea birds, mammals like seals, and even other whales. An interesting aspect about the feeding behavior is that certain populations tend to specialize on a set of prey, and will stick to only eating that single thing.

Two orcas photographed in Alaska. Photo by Robert Pittman, published with permission.

The social toothed whale

One of the most fascinating things about the orcas are how social they are. The group hunting can be extremely complicated from an animal point of view, and often requires a lot of communication between the whales in the hunting party. The pods are regarded as some of the most stable ones in the entire animal kingdom, and female groups tend to stay together for all their lives.

A pod will have a unique dialect that they used to communicate with each other, but pods that stay close to each other typically tend to have dialects that are similar enough that they can understand each other. Each pod can consist of a few closely related females, but several pods go together to form clans, which can become quite large. A clan will only consist of orcas that can understand each other’s dialects, and reject members whom they do not understand. However, several clans can also aggregate together for a shorter amount of time, where not all members will be able to understand the others.

How many species of orcas are there really?

As I have written, there is a huge variation among the culture of the orcas, and despite the fact that they are currently recognized as a single species, I would argue that they are most likely several species. We already divide them into at least seven different types; three types found off the west coast of the US and Canada, and four types found in the Antarctic. And I would guess that we will find a lot more types if we begin to look more closely for them (The populations in Europe and Asias water might be different from the ones in the Antarctic and Americas).

Anyway, let’s take a look at how different the different types of orcas are, and we begin by look at the 3 types found off the coast of the US and Canada.

The three types of orcas found off the west coast of the US and Canada

• Resident type: This is the most common type, and they feed primarily on fish. These orcas tend to visit the same places most of the time. The live relatively close to the shore, and this is typically the type that people observe if they see some orcas on the coast.
• Transient type: The Transient type orcas feed almost only on marine mammals, and tend to travel in small groups that are less stable than that of the other types.
• Offshore type: This type of orca lives far from the shore, and feed on schooling fish in the open water. They are also believed to hunt other whales and sharks. This type often form huge groups of 50-200 orcas, which allows them to perform highly coordinated hunts. The offshore type orcas are also physically smaller than any of the other two American orcas, in addition to the females having a more rounded dorsal fin tips.

All three of these are look a bit different from each other, but I had a lot of problems finding good photos to show you. However, it’s time to look at the four types found in the Antarctic, and we got some better images for that.

The four types of orcas found in the Antarctic

• Type A orca: The type A orcas of the Antarctic are the most common ones in the area, where they live in open water and feed on minke whales (Balaenoptera acutorostrata and B. bonaerensis)
• Type B orca: The B type is smaller than type A, and has a very big white eye patch. The body is more grey than black, and they feed primarily on seals.
• Type C orca: The type C orcas are the smallest of the Antarctic types, and have a white eye patch that is almost vertical instead of the horizontal patch that the others have. This type has only been found to feed on Antarctic cod (Dissostichus mawsoni), but they could of course feed on other things when the scientists aren’t looking.
• Type D orca: The type D orcas is actually super rare, and we know very little about it. It’s recognizeable by an extremely small white eye patch compared to the other orca types. National Oceanic and Atmospheric Administration (NOAA) just got their hands on some genetic samples from this elusive type, so we will hopefully learn a lot more about them soon enough.

The Type D orcas were observed for the first time in the wild this winter, and here’s a short video of them if you want to see these animals for yourself. Notice how extremely small the white eye patch is compared to the ones in the photo at the beginning of this post.

The morphological differences of the Antarctic orcas visualized

An overview of the orca types. Notice that we know so little about the D type that it does not even include both sexes. Image by Wikimedia commons user Albino.orca, published with the CC BY-SA 3.0.

I really like this diagram, because it shows you just how different they are. Words like “horizontal white eye patch” might not mean a lot when you read it, but I think it’s very clear how different they are when you see them next to each other like above.

And before you ask why some of them have a yellowish color; scientists believe that this has to do with the fact that they live in regions with a large amount of diatoms (a group of algae), which eventually ends up coloring their skin.

Species, subspecies, or just types?

So what’s really required for an animal to be recognized as a species? Unfortunately this is a highly complex question, and systematics is a lot less straight-forward than most people think. Many people and groups, including the IUCN believes that orcas should be separated into several different species based on the fact that the different types are very different from each other. Genetic tests have revealed the type D orca to have converged from the other types over 400,000 years ago, which should be more than enough to be its own species.

I for one believes that we will eventually see the orcas divided into several different species, although it might not be as many as seven. It might take a while though, because even with good genetic samples we still need to learn what differentiates them in the wild, and it’s extremely difficult to get good data on behavioral differences when it comes to marine mammals that can spend a long time underwater. For instance, we believe that certain types primarily feeds on a single source of food, but have nowhere near enough data to conclusively say that they do not feed on anything else. There could be some overlap, where some of the types are the same species (but perhaps different subspecies). It's definitely a bit complex, but I'm looking forward to seeing if they will eventually officially separate into several species. And if they do, I will be the first to let you know.

Sources and further reading

There is a huge amount of information available to read if you want to learn more about the orcas and the different types of them. Below are the papers and articles that I used to write this post, but there are also a lot of “non-scientific” sources on this matter if you don’t enjoy reading papers.

• National Marine Fisheries Service. 2005. Proposed Conservation Plan for Southern Resident Killer Whales (Orcinus orca). National Marine Fisheries Service, Northwest Region, Seattle, Washington. 183 pp.
• Ford, J. K., Ellis, G. M., Barrett-Lennard, L. G., Morton, A. B., Palm, R. S., & Balcomb III, K. C. (1998). Dietary specialization in two sympatric populations of killer whales (Orcinus orca) in coastal British Columbia and adjacent waters. Canadian Journal of Zoology, 76(8), 1456-1471.
• DISPLACEMENT, A. P. C. O. C. (1999). Predation on a white shark (Carcharodon carcharias) by a killer whale (Orcinus orca) and a possible case of competitive displacement. Marine Mammal Science, 15(2), 563-568.
• Pitman, R. L., & Ensor, P. (2003). Three forms of killer whales (Orcinus orca) in Antarctic waters. Journal of Cetacean Research and Management, 5(2), 131-140.
• Reeves, R., Pitman, R.L. & Ford, J.K.B. 2017. Orcinus orca. The IUCN Red List of Threatened Species 2017: e.T15421A50368125. http://dx.doi.org/10.2305/IUCN.UK.2017-3.RLTS.T15421A50368125.en. Downloaded on 13 March 2019.
• Pitman, R. L., Durban, J. W., Greenfelder, M., Guinet, C., Jorgensen, M., Olson, P. A., ... & Towers, J. R. (2011). Observations of a distinctive morphotype of killer whale (Orcinus orca), type D, from subantarctic waters. Polar Biology, 34(2), 303-306.

Thanks for reading

I spent a lot of time to learn about orcas and write this post, so I would be very grateful if you left me a comment if you enjoyed it. And questions, additional info, feedback, and even opposing views are definitely most welcome as well.