In the family of cetaceans
Killer whales are undoubtedly a special existence
On the one hand, they have a panda-like black and white color scheme
The appearance is very pleasing, and it has won the nickname of "Fat Tiger".
On the other hand, they are also in the ocean today
A well-deserved king
A deadly killer of other sea creatures
Major ecotypes of killer whales Source: References
As a species that is almost universally distributed, killer whales around the world have been considered a single species for a long time, namely Orcinus orca. However, there is growing evidence that killer whales are likely to have more than one species.
The Tiger of the Sea is divided into three
Not long ago, a group of scientists led by Phillip Morin, a geneticist at the National Oceanic and Atmospheric Administration (NOAA), published a paper in the journal Royal Society Open Science, dividing the killer whales of the North Pacific into three separate species.
As early as the 70s of the last century, Michael Bigg, a Canadian marine biology expert, was surprised to find that killer whales in the North Pacific Ocean can be divided into three very different ecotypes according to dietary preferences, social structure, acoustic and physical characteristics, and genetic differences, namely passer-by, residential, and pelagic types.
Three killer whale ecotypes in the North Pacific
图源：Southern Resident Orca Recovery
Sinicization: The author
However, new findings suggest that these three species of killer whales are not just different in terms of lifestyle, but completely different species. In particular, the passer-by type and resident type are the most distant from each other among the killer whales, and the differentiation time is close to that of polar bears and brown bears.
Gene differentiation time within each type of killer whale
Source: References Sinicization: Author
Although the passer-by and resident killer whales overlap in distribution, they hardly have any intersection and interaction, which can be described as "well water does not interfere with river water". Even passerby killer whales can be expelled by resident killer whales if they invade the territory of resident killer whales, which are larger in groups, and hybridization is only possible in captive environments such as aquariums.
Fisherman, butcher and hermit
In the eyes of most people, killer whales in all oceans almost all look the same, all "white + black", round figures, and black dorsal fins that rise above the water like sharks. But if you look closely, you can still see the differences between them:
In terms of physical characteristics, the dorsal fin of passer-by killer whales is generally sharper and straighter, while the dorsal fin of resident killer whales is relatively rounded and curved. In addition, the average size of the passer-by killer whale is relatively larger than that of the resident killer whale, which has a small black spot in the white saddle spot on its back, while the pelagic killer whale has a narrower, rounder dorsal fin, lighter saddle spot, and the smallest of the three.
Top view comparison of passerby (left) and resident (right) killer whales
Source: References
In addition to these differences in appearance, the differences between the three in terms of food preferences, community structure, and even their voices are far from each other, like fishermen, butchers, and hermits.
When it comes to filling their stomachs, resident killer whales are professional fisheaters. With the exception of Alaska, which eats a variety of fish, the rest of the population eats almost exclusively salmon. Because these fish tend to be only distributed in a specific area of the sea, they also cling to their own one-third of an acre.
居留型虎鲸 图源：Xplore Our Planet
Resident killer whales are also typical matrilineal clans, with strong cohesion among members, and their offspring will live with their mothers for the rest of their lives. In other words, male resident killer whales are all "mom treasure males", who usually live in their own group by their old mothers to forage for food, and only when they reach the age of "walking marriage" will they briefly leave the group and go to mate with females in other groups.
Passerby killer whales (commonly known as "beagle killer whales") are also matrilineal, but they tend to be small in population, averaging only 3 to 7 individuals, and some individuals leave their original groups when they reach adulthood. They are well-deserved "wolves of the sea" and specialize in feeding on marine mammals such as seals, sea lions, porpoises, dolphins, and some baleen whales.
过客型虎鲸 图源：Xplore Our Planet
Eating habits also determine the culture of the group, and the calls of passerby killer whales are far less noisy than those of resident killer whales. This is because resident killer whales prefer to use echolocation for hunting, while passerby killer whales tend to approach their prey stealthily, and echolocation is only sometimes used to locate fleeing prey and reduce calls in order to conceal their whereabouts.
Acoustic characteristics of three species of killer whales
Source: References Sinicization: Author
In addition, in terms of skull morphology, passer-by killer whales appear wider and have a more curved jaw curve, which is more suitable for catching large prey. Passerby killer whales, also known as offshore killer whales, have evidence that these killer whales are particularly fond of preying on a variety of cartilaginous fish, which directly leads to severe tooth wear and tear among young and old.
The teeth of three species of killer whales differ due to their different feeding habits
Sinicization: The author
Pelagic killer whales
图源：Xplore Our Planet
Pelagic killer whales are known for their large colonies, usually congregating 20-50 individuals, and sometimes in large groups of 70-100 individuals to catch super-giant prey such as blue whales (Balaenoptera musculus).
The killer whale family is just a little more
Turning our attention to the North Atlantic Ocean on the other side of the globe, more than a decade ago, scientists compared the remains of stranded killer whales and found that their teeth could be broadly divided into two categories, which undoubtedly suggests that there are two very different ecotypes of killer whales here.
North Atlantic Killer Whale Type I (top) and North Atlantic Type II Killer Whale (bottom)
图源：Xplore Our Planet
They are the North Atlantic type I killer whale, which is an "omnivorous" type of fish and seal, and the Atlantic type II killer whale, which eats only cetaceans and dolphins. The former is based on fish as the staple food, and the hard scales make the teeth wear and tear severely; The latter's long, sharp teeth are suitable for hunting marine mammals, and they are correspondingly larger.
In such a vast and varied environment as the ocean-dominated Southern Hemisphere, the degree of ecotypic differentiation of killer whales here (in the center of Antarctica) is far more pronounced than in other seas of the world. Killer whales in the Southern Hemisphere can be broadly divided into four categories: A, B, C, and D.
Four killer whale ecotypes in the Southern Hemisphere
Antarctic A killer whales are the largest of all killer whales in average size. The average length of females is 6.4 meters, while the average length of males is 7.3 meters, and the largest male whale is 9.2 meters long. Their eye spots are large, elongated, and almost parallel to their bodies.
Antarctic type A killer whales
图源：Xplore Our Planet
A型虎鲸栖息在开阔的南极外海，主要以各种海洋哺乳动物为食，尤其喜爱南极小须鲸（Balaenop bonaerensis）。
Antarctic type A killer whales hunting Antarctic minke whales
Source: orcazine
Antarctic B killer whales can be broadly classified into two categories: B1 and B2. Their eye spots are the largest of all killer whales and are oval in shape. These two species of killer whales migrate north in the summer, where they are exposed to diatoms and give them a distinctive yellowish-brown color.
B1 killer whale (top) and B2 killer whale (bottom)
图源：Xplore Our Planet
The two species of killer whales are particularly different in appearance, location and dietary preferences. Type B1 killer whales live mainly near the loose ice around the Antarctic continent and are fond of pinnipeds such as the Del seal (Leptonychotes weddellii).
On the other hand, B2 killer whales are not only half the size of the former, but also prefer to feed in the open water, away from the ice floe, and they feed on penguins, especially the Gentoo penguin (Pygoscelis papua).
Type B2 killer whales hunt penguins
Source: YouTube
Antarctic C killer whales are the smallest known killer whale ecotypes, with males measuring less than 6 metres in length and females only about 5 metres long. Their eye spots are long, slender, sinister hanging eyes, like a scimitar. Because it is usually hidden under the thick ice of East Antarctica, it is extremely difficult to observe. There is controversy about its feeding habits, but it is certain that Antarctic cod (Dissostichus mawsoni) occupies an important place in the diet.
Antarctic C killer whales
图源：Xplore Our Planet
If distinguishing other killer whales from other killer whales is a challenge to observe, the strange shape of the Antarctic D is definitely a sight to behold: they have very small eye spots and an unusually rounded head.
Antarctic A killer whale (left) and Antarctic D killer whale (right)
Source: CTV
This peculiar killer whale ecotype was not discovered until 1955 on Paraparaumu Beach in New Zealand, and was initially considered a special variant. The range of D-type killer whales is not well understood, but appears to be found only in subantarctic waters between 40°S and 60°S, and most sightings occur in the open ocean.
Antarctic D-type killer whale stranded on the beach in 1955
Source: CTV
Taking the "separation" of the North Pacific killer whale as an opportunity, scientists are likely to take action on the major ecotypes distributed in other seas in the future, and the killer whale may be split into 10-15 species. These taxonomic differences may have implications for conservation, allowing experts to make more informed decisions when managing different killer whale populations.
Bibliography:
- Under a new proposal, our local orcas — resident and Bigg’s killer whales — would each become a new species
- Revised taxonomy of eastern North Pacific killer whales (Orcinus orca): Bigg’s and resident ecotypes deserve species status.
- Orcas on the Edge – Killer: It's a Name, Not an Accusation
- Observations of a distinctive morphotype of killer whale (Orcinus orca), type D, from subantarctic waters
- Genetic Insights into the Biogeography and Evolutionary History of the Killer Whale
- https://xploreourplanet.com/sea/types-of-killer-whale
- Unlocking the Secrets of the Type D Killer Whale
- Types of Killer Whale: Guide to Killer Whale Types
Author: Song Zhe
A wide range of zoological and linguistic enthusiasts
Loves to identify strange animals