New research indicates that pods of killer whales in the North Pacific Ocean, near Japan and Russia, have distinct cultures, dialects and traditions due to their Ice Age ancestors, with some pods remaining in their Ice Age refuges rather than migrating. Researchers discuss the classification of killer whales into several species or subspecies due to the large differences in diet and behaviour, emphasizing the importance of understanding the different ecological species of orcas for ecosystem balance and hunting practices. Orcas in the North Pacific Ocean. Image credit: SDU/Olga Filatova
The northern Pacific Ocean near Japan and Russia is home to several different populations of killer whales, but they never interact, hunt different prey, communicate in different dialects, and avoid mating with each other. How can this be when they live close to each other and belong to the same thing classify?
Cetacean expert Olga Filatova of the University of Southern Denmark has dedicated her research to unlocking the secrets of killer whale colonization in the North Pacific Ocean. During her tenure at Moscow State University, she led multiple expeditions to study these mysterious creatures. It is currently affiliated with the Marine Biology Research Center of the University of Southern Denmark.
And now, some of their latest findings have been published. In recent research, she and her colleagues explore the complex interplay between killer whale culture and the post-glacial history of their colonization of the North Pacific Ocean, demonstrating that the pods of killer whales that now live near Nemuro Strait in northern Japan are descendants of killer whales that settled there during the era. glacier. The last ice age, about 20 thousand years ago. The site was chosen as a refuge by distant ancestors, and their descendants have lived there ever since.
“Killer whales are conservative, traditional creatures who don’t move or change their traditions unless there is a good reason to do so. We see that in these populations,” says Olga Filatova.
This is the second time she has found refuge with Ice Age orcas. The first is located near the Aleutian Islands, about 2,500 kilometers away. The pods there are just as conservative and committed to tradition as their Japanese idiosyncrasies and are also descendants of Ice Age ancestors who found refuge in the ice-free waters.
Orcas in the North Pacific Ocean. Image credit: SDU/Olga Filatova
“When the ice began to recede again, and killer whales and other whales were able to swim to new areas free of ice, some of them did not follow. They stayed in their shelters, and they still live there,” says Olga Filatova.
The studies rely on genetic analyzes (the researchers took skin biopsies from the animals) and analyzes of the animals’ sounds (recorded with underwater microphones).
“The killer whales of the Nemuru Strait have an unusually high genetic diversity, which is typical for ice refuges, and their vocal repertoire is very different from the dialects of the killer whales that live further north off the coast of Kamchatka. Kamchatkan whales are on most likely descendants of the few pods that migrated westward from the central Aleutian refuge, which is why they are quite different.”
The sounds of killer whales are very diverse, and no two groups make the same sounds. Therefore, these sounds can be used to determine individuals’ affiliations to families and capsules. Killer whales are not genetically programmed to make a sound like, for example, a cat. A cat that grows among other animals and has not heard another cat will still meow when it opens its mouth. In contrast, killer whales learn to communicate from their mothers or from older family members. Each pod has its own dialect, not spoken by the others.
“When we combine this with genetic analyses, we get a strong idea of how different orca populations relate to each other,” says Olga Filatova.
So far, two Ice Age refuges have been discovered, providing us with insight into how killer whales cope with current and future climate changes: they are likely to move north as the ice melts, and this colonization may occur in families or small, individual groups rather than in waves. big.
Orcas in the North Pacific Ocean. Image credit: SDU/Olga Filatova
The discovery of the two Ice Age sanctuaries not only contributes to insight into how killer whales survived during the Ice Age, but also paints a picture of killer whales as very different animals that may not well fit into a single species.
“Many believe that killer whales should be divided into several species. I agree – at least in subspecies because they are so different that it makes no sense to talk about one species when discussing its place in the food chain or when allocating quotas for hunters,” says Olga Filatova. .
Some killer whales eat fish, some only herring, some only mackerel, and some only a certain type of salmon. Others only eat marine mammals such as seals, porpoises, and dolphins. Some take a little bit of everything, others live so far out in the open sea that we know very little about them.
Whether or not pods eat fish—and what kind of fish—has a huge impact on hunting in their habitat. When a country calculates catch quotas, it must take into account the number of fish that predators naturally catch, and since a killer whale can consume 50-100 kg of fish per day, this greatly affects the calculation of the quota.
If the pods eat marine mammals and don’t touch fish, that matters if they are going to be caught and sold to marine parks, as they are harder to feed than marine mammals. While the popularity of marine parks is declining worldwide, there is still a large market for killer whales in Chinese marine parks.
Since there is only one scientifically recognized species of killer whale, researchers have resorted to a different form of classification to distinguish between different species of killer whales and classify them into so-called ecotypes. In the North Pacific, three ecotypes have been defined so far, and in the Southern Hemisphere, four or five species have been described.
And there are likely to be more – perhaps as many as 20 different ecotypes, according to Olga Filatova.
“We need to know the different ecotypes. Killer whales are at the top of the food chain, and it affects the whole ecosystem around them, what they eat and where they do it,” says Olga Filatova.
In the Danish waters, Skagerrak and Kattegat, near the SDU Marine Biological Research Center, killer whales are occasionally seen. However, no one knows if they eat fish or marine mammals – thus, no one also knows how they affect the food chain and fishing.
“I am looking forward to learning more about them. Perhaps they will turn out to be a new ecotype,” says Olga Filatova.
Centuries, families and clans:
Killer whales live in families led by mothers. Families gather in close-knit groups called pods. Clans are made up of groups with similar phonetic accents.
Ecological Species of Orcas:
Ecological species have different dialects, different habitats, and do not interbreed with each other. Researchers believe there may be as many as 20 different ecotypes.
Known ecological species in the North Pacific:
Residents: Close-knit families and groups living in the same areas along the coasts. They feed on fish.
Transients: Smaller, less compact horns that feed on marine mammals. Habitat from Russia to California.
Outside: Lives out in the open sea in groups of 20 to 200 individuals. Bad study.
Known Ecological Species of Southern Antarctica:
Type A: It travels in open water and appears to feed mostly on minke whales.
Type B: Smaller than Type A. It seems to feed mostly on seals.
Type C: the smallest. Live in larger groups than others. It seems to feed mostly on fish.
Type D: ranges between 40 and 60 south latitude. This has been poorly studied.
Possible new ecotypes:
Groups feeding on fish in the North Atlantic Ocean.
Groups feeding on marine mammals in the North Atlantic Ocean.
Groups feeding on penguins and sea lions on the coast of South America.
Groups around Gibraltar feeding on tuna.
Collections in the tropics around Hawaii and the Gulf of Mexico.
In groups throughout New Zealand, it feeds mainly on ruffians and sharks.
Reference: “Genetic and cultural evidence indicates a sanctuary for killer whales off Japan during the last glacial maximum” by Olga A. Marine Mammalology.
doi: 10.1111/mms.13046