The North Pacific, near Japan and Russia, is home to several different groups of killer whales, but they never interact, hunt different prey, communicate in distinctive dialects, and avoid mating with each other. Masu. How could this happen when they live so close together and belong to the same house? seed?
Olga Filatova, a whale expert at the University of Southern Denmark, has dedicated her research to solving the mystery of killer whale colonization in the North Pacific. During her tenure at Moscow University, she led multiple expeditions to study these enigmatic creatures. Currently she is at the Marine Biology Research Center at the University of Southern Denmark.
Some of her latest achievements have now been published. In a recent paper, she and colleagues explored the complex interactions between killer whale culture and the post-glacial history of colonization in the North Pacific, currently inhabiting near the Nemuro Strait in northern Japan. showing that the orca pods present are descended from the orcas that settled there at the time. The last Ice Age, about 20,000 years ago. This place was chosen as a refuge by our distant ancestors, and their descendants have lived there ever since.
“Killer whales are conservative, tradition-bound creatures who don’t move or change traditions without good reason, and you see that in this group,” says Olga Filatova.
This is the second time she has found an orca sanctuary during the Ice Age. The first is near the Aleutian Islands, about 2500 kilometers away. The Saya there, as conservative and tradition-bound as their Japanese counterparts, are also descended from ancestors who took refuge in ice-free seas during the Ice Age.
“When the ice started to recede again and killer whales and other whales were able to swim to new ice-free areas, some didn’t comply. They stayed in shelters and still live there.” says Olga Filatova.
The study is based on genetic analysis (the researchers took skin biopsies of the animals) and analysis of the sounds the animals make (recorded with underwater microphones).
“Nemuro Strait killer whales have an unusually high genetic diversity unique to glacier reserves, and their vocal repertoire differs significantly from the dialects of killer whales living north off the coast of Kamchatka. The killer whales are likely descendants of a few killer whales that migrated westward from the Aleutian Islands Central Reserve, which is why they are so different,” says Olga Filatova.
Killer whales have very different calls, and no two pods make the same sound. These sounds can therefore be used to identify relationships between individuals and their families and pods. Killer whales are not genetically programmed to make sounds like cats. Even cats that grew up among other animals and didn’t hear other cats will meow when they open their mouths. In contrast, killer whales learn to communicate from their mothers and other older family members. Each pod has its own dialect, which is not spoken by other pods.
“Combining this with genetic analysis gives us a powerful idea of how different orca communities relate to each other,” says Olga Filatova.
Two Ice Age refuges have been discovered so far, providing insight into how killer whales will cope with current and future climate change. Killer whales are likely to migrate north as the ice melts, and this colonization may occur in small individual families or groups rather than in groups. in big waves.
The discovery of two Ice Age refuges not only contributes to our knowledge of how killer whales survived during the Ice Age, but also sheds light on the image of killer whales as very different animals that may not fit neatly into one species. Draw.
“Many people believe that killer whales should be divided into several species. It makes no sense to talk about one species when fishing or assigning quotas to fishermen, ”says Olga Filatova.
Some killer whales eat fish, some killer whales eat only herring, others eat only mackerel, and others eat only certain types of salmon. Some eat exclusively marine mammals such as seals, porpoises and dolphins. Some take a little bit of everything, while others live so far out in the open ocean that we basically know very little about them.
Whether and which fish a pod eats has a large impact on the fisheries that take place in its habitat. When countries calculate their quotas, the number of fish naturally hunted by predators must be taken into account, and killer whales consume between 50 and 100 kg of fish per day, which has a significant impact on quota calculations. give.
The fact that pods eat marine mammals and not touch fish is important when pods are caught and sold to marine parks, where it is difficult to feed the marine mammals. Although marine parks are declining in popularity globally, China’s marine parks still have a large market for killer whales.
Since there is only one species of killer whale that is scientifically recognized, researchers have resorted to different forms of taxonomy to distinguish different species of killer whales and classify them into so-called ecotypes. Three ecotypes have been defined so far in the North Pacific, and four or five have been described in the Southern Hemisphere.
According to Olga Filatova, there are probably many more different ecotypes, maybe up to 20 different ecotypes.
“We need to know different ecosystems. Orcas are at the top of the food chain, and what they eat, where and what they do affects the entire ecosystem around them.” says Olga Filatova.
Killer whales are occasionally seen in Skagerrak and Kattegat, Danish waters near the SDU Marine Biology Research Centre. But no one knows if they eat fish or marine mammals. So we also don’t know what impact they will have on the food chain and fisheries.
“I look forward to learning more about them. Perhaps they will turn out to belong to a new ecotype,” says Olga Filatova.
Pods, Families, and Clans:
Killer whales live in families led by a patriarch. Families gather in tight-knit groups called pods. A clan consists of pods with similar spoken dialects.
Killer Whale Ecotype:
Ecotypes differ in dialects and habitats and do not interbreed with each other. Researchers believe there could be up to 20 different ecotypes.
Known ecotypes of the North Pacific:
Population: Close-knit families and herds that live in the same coastal area. eat fish
Transient: Small, low-sticky pods that feed on marine mammals. Habitat: Russia to California.
Offshore: Lives in groups of 20 to 200 offshore. Lack of study.
Known ecotypes in Southern Antarctica:
Type A: Appears to migrate the open sea and feed primarily on minke whales.
Type B: Smaller than Type A. They seem to eat mostly seals.
Type C: Minimal. Live in larger groups than others. They seem to eat mostly fish.
Type D: Range from 40°S to 60°S. These are not well studied.
Possible new ecotypes:
A group that eats fish in the North Atlantic.
A group that feeds on marine mammals in the North Atlantic.
A group of penguins and sea lions that feed on the coasts of South America.
A herd of tuna eats around Gibraltar.
A group of tropical areas around Hawaii and the Gulf of Mexico.
This group is found throughout New Zealand and feeds mainly on rays and sharks.
References: “Genetic and Cultural Evidence Suggests Orca Refuges Off Japan During the Last Glacial Maximum,” Olga A. Filatova, Ivan D. Fedutin, Ekaterina A. Borisova, Ilya A. By G. Meshchersky, Eric Hoyt, 6 July 2023, marine mammal science.
DOI: 10.1111/mms.13046