If you didn't know, one of my favorite, if not my absolute favorite, animals is orcas. Killer whales, grampus, blackfish, Orcinus orca is an incredible organism. They are likely the most widely ranging mammal next to humans, found in all oceans, and strike a balance between graceful and deadly, massive but swift, black and white. They are the apex predators in every food chain--- their speed, powerful jaws, and intelligence makes them some of the most formidable hunters on the planet.
Although orcas are currently considered one species, they have different ecotypes on the cusp of speciation. An ecotype is a subdivision in a species that describes a distinct form that is adapted to a specific environment. Orca ecotypes have subtle morphological differences, but what really sets them apart are their distinctly different lifestyles and genetics. There are a dozen or so total ecotypes, ten of which are quite well-known. Five of these ten ecotypes reside in each hemisphere. In the Northern Hemisphere, we have...
Resident
Bigg's (transient)
Offshore
Type 1 Eastern North Atlantic
Type 2 Eastern North Atlantic
And in the Southern Hemisphere...
Antarctic (Type A)
Pack Ice (Type B large)
Gerlache (Type B small)
Ross Sea (Type C)
Subantarctic (Type D)
Residents
Resident orcas are the most well-studied ecotype, especially in the North Pacific along Alaska and British Columbia. In the North Pacific, they are divided into two populations, the Northern Residents and Southern Residents. Morphologically, they represent what a standard killer whale would look like. They can be distinguished by the rounded tip of their dorsal fins and straight eye patch. Their saddle patches, which are these fainter white markings behind their dorsal fins, can be "open" or "closed".
They are known to be the "social butterflies": residents are capable of forming gatherings (pods) of more than 50 individuals in events called superpod, where multiple pods come together to socialize and mate. Most of the time though, these orcas stay in their individual pods, which are further divided into subpods. Subpods can be divided even further into matrilineal groups, the basic social unit of resident orcas (they live in a matriarchal society, isn't that cool?). These matrilines, usually consisting of three to four individuals, are comprised of a mother and her offspring, consisting of multiple generations and led by the eldest whale (the great-great-great grandmother, basically). Families stick together for life, with family members always looking out for each other, whether it is older male orcas helping to babysit their younger siblings, or the matriarch sharing her kills with the rest of her family.
A defining trait of resident whales is that they exclusively feed on fish, especially salmon. The home ranges of many populations of residents are centered around large populations of fish. Residents work as a team to corral and hunt large schools of fish, the hunts marked by a constant stream of clicking and whistles as they chase down their prey. They can actually tell which species they are hunting through echolocation, as the sound that bounces off the fish forms an image of each fish's distinctive swim bladder shape!
Bigg's, or Transients
Besides residents, Bigg's or transient orcas are another well-studied groups of the North Pacific. They can be differentiated from residents by the pointed tip of their dorsal fins, with their eye patches slanted slightly down. They have mostly closed saddles patches. On average, they are larger than residents, characteristic of orcas that eat mammals (more about that below).
If residents are the social butterflies, then transients are... anti-social. Their social structure is much more fluid than the residents: transient groups are typically small and can be composed of a mother and her offspring, several females with unknown relationships to each other, or something else entirely. Adult males, called bulls, often travel alone, but they may form temporary alliances with other bulls for hunting purposes.
Speaking of hunting, the hunting style of transients is also very different from residents. Transients are marine mammal specialists, hunting a diverse selection that includes seals, sea lions, and even other whales, such as minke whales. Unlike residents, transients forage in silence, using a "sneak attack" method on their prey, only vocalizing after they have caught their prey in what seems to be a triumphant call. Mammals are much more clever and cautious than fish, so transient orcas need to avoid detection at all costs if they want a meal. Oftentimes, they will work together to outsmart larger and more powerful prey, using their tail flukes to stun it. Afterward, the kill is shared among the orcas. Transients also have a longer dive time than residents, usually staying underwater for more than five minutes, while residents only stay under for three to four before resurfacing.
Offshore
We don't know as much about offshore orcas as we do about residents or transients, probably because they live way out in the open ocean far, from land, and the people who research orcas... live on land? Nonetheless, offshore orcas are the most elusive ecotype of the Northern Hemisphere. They are also the smallest of the three ecotypes that live in the North Pacific, genetically closer to residents than they are to transients. Their dorsal fin is kind of a middle ground between the rotundness of the resident dorsal fin and the pointiness of the transient dorsal fin, though it looks more similar to the residents. Their saddle patch is faint and is usually closed.
Little is known about the formalities of this ecotype's social structure, but offshores have been spotted in huge pods of approximately 50 individuals, the largest communities of any ecotype. The reason for these large groups is probably because of the vastness of the open ocean: the more individuals, the easier it is to cover ground. It is also uncertain what these orcas prey on, but it is suspected that they mostly feed on sharks, specifically Pacific sleeper sharks. This ecotype has been observed to have very notable tooth wear, almost to the point where they are toothless. The wear is thought to be caused by biting and knawing on the shark's rough skin. Offshores have been spotted sharing food with other orcas that have such severe wear on their teeth that they cannot hunt for themselves anymore.
(a comparison of the dorsal fins of the North Pacific's three ecotypes)
Type 1 North Atlantic
There are two varieties of North Atlantic orcas (North Atlantic meaning around Norway, Iceland, and Scotland). Type 1 orcas are small-sized, with a large eyepatch and opaque saddle patch. They are more generalized than other orca ecotypes when it comes to prey, consuming a variety of fish species, but also some small mammals such as seals and harbor porpoises. Ongoing research has revealed that this ecotype lives in very tight-knit communities that may be split into more ecotypes due to the distinctive characteristics emerging in each pod. One population of Type 1 orcas off the coast of Norway is famous for its hunting technique of corralling their prey into a "bait ball". They mainly eat Atlantic herring, but will also take Atlantic mackerel, Atlantic salmon, harbor porpoises, and seals. These Norwegian orcas first force the fish into a concentrated school (this is the bait ball), and then swing and slap their tails through the water to stun the fish. Now that the fish are stunned, it makes for an easy meal. You can see this in action in this video.
Fun fact --- the orcas in Norway are some of the only orcas that you can swim with!
Type 2 North Atlantic
Type 2 orcas are larger and less generalized than their Type 1 cousins. These elusive orcas are the largest ecotype in the Northern Hemisphere (being hunters of large prey) and have a distinctive slanted eyepatch that slants towards the rear with faint saddle patches. This ecotype specializes in hunting cetaceans: dolphins, porpoises, baleen whales, and especially minke whales. They are known for having very sharp teeth to tear through the flesh of their prey, having significantly less tooth wear than Type 1 due to the differences in their diets. Because they hunt prey that wanders, it leads Type 2 to cover a wider range than Type 1.
Should we stop calling orcas "Type 1" and "Type 2"?
A recent paper published by Andrew D. Foote questioned the categorization of orcas into Type 1 and Type 2. The main argument was that Type 2 came to be from the analysis of a few whales that had stranded in the Faroe Islands and Scotland. The samples came from just five orcas, and it may be too little data to represent an entire ecotype. Until we gather more data on the whales of the North Atlantic, it may be best to dissolve the different types that we currently categorize them in.
However, we've already come a long way in orca research. Until very recently in the 1970s, we knew practically nothing about these creatures! Tune in for part two--- the ecotypes of the Southern Hemisphere. Signing off, Amber.
Sources:
“Orca Ecotypes….It’s Not All Black and White!” Sea Watch Foundation, 2019, www.seawatchfoundation.org.uk/orca-ecotypes-its-not-all-black-and-white/.
Source, News. “Types of Killer Whale | Guide to Killer Whale Types.” TheOrcasonian.com, 27 Nov. 2022, theorcasonian.com/types-of-killer-whale-guide-to-killer-whale-types/. Accessed 23 Dec. 2022.
“Meet the Different Types of Orcas - Whale & Dolphin Conservation USA.” Whale & Dolphin Conservation USA, 2018, us.whales.org/whales-dolphins/meet-the-different-types-of-orcas/.
Ford, John K.B., et al. Killer Whales. UBC Press, 1994.
Fisheries, NOAA. “West Coast | NOAA Fisheries.” NOAA, 25 Oct. 2022, swfsc.noaa.gov/uploadedImages/Divisions/PRD/Programs/Ecology/Killer%20Whale%20Poster%20-%20final.jpg?n=1491. Accessed 23 Dec. 2022.