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As we all know, killer whales are considered to be the dominant species of the sea, and many marine animals such as great white sharks even have to run away when they notice their surroundings with killer whales. However, there is a species that is also a member of the dolphin family that is not only not afraid of killer whales, but even unites and relies on their numerical advantage to chase and attack killer whales. , they are pilot whales.
First of all, we must have a basic understanding of pilot whales. Like killer whales, pilot whales are members of the dolphin family. Pilot whales are a genus of two living species: the longfin pilot whale (Globicephala melas) and the shortfin pilot whale (Globicephala macrorhynchus).
Longfin pilot whales have relatively long flippers, and are mainly distributed in the cold waters of the North Atlantic and Southern Oceans. Shortfin pilot whales have shorter flippers and mainly live in warm tropical and subtropical waters.
Similar to beaked whales, sperm whales and their close relatives the gray dolphins, pilot whales are specialized predators, feeding mainly on cephalopods – mainly a variety of large and medium squid, including the giant squid Mesonychoteuthis hamilton.
Pilot whales are large and also the largest member of the dolphin family except for killer whales, with a maximum body length of more than 7 meters, they also have a strong and aggressive personality, quite similar to killer whales.
Although pilot whales do not eat marine mammals, they prefer to attack other whales, and especially sperm whales, their main rival and often attacked by them.
In addition, pilot whales also possess very fast speed, although their prey is similar to that of beaked whales and sperm whales, but their hunting strategies are very different. The diving time of each hunt for pilot whales is relatively short, generally only about 15 minutes, and the average swimming speed when diving is 9m/s. Sperm whales and beaked whales, on the other hand, have very slow diving speeds, only 1-2m/s, but their dive times are significantly longer, ranging from 30 minutes to an hour.
This high-speed diving allows the pilot whale to have more options for its prey, so its prey type is much larger than that of a beaked whale. Therefore, pilot whales are called “deep sea leopards”. This powerful mobility also makes this whale capable of dealing with killer whales.
Like killer whales, pilot whales are highly socialized animals and live in close matrilineal families, but their group size is much larger than that of killer whales. The group size of shortfin pilot whales will range from 10 to 30 members, and the largest group size can be up to several hundred. Groups of longfin pilot whales are larger, usually 20-100, and the largest group can exceed 1,000. And such a large number is the strength that makes them dare to challenge and repel killer whales.
Pilot whale attacks against killer whales have been documented in many areas.
In the Strait of Gibraltar, a 2014 study by De Stephanis et al showed that local killer whales avoid longfin pilot whales. The population of killer whales in the Strait of Gibraltar is a fish-eating population whose main prey is bluefin tuna and has very little intersection with pilot whales.
Over the course of three years of sampling, the scientists observed a total of 15 interactions between killer whales and longfin pilot whales. They often turn to run away when they notice pilot whales around. These chases usually last about 30 minutes. The average group size of pilot whales launching an attack was 27, while the average group size of hunted killer whales was 10.
On the coast of Iceland, longfin pilot whales also attack killer whales. Killer whale populations in this area are mainly fish-eating populations, the main prey being Atlantic herring, but there are also populations of other marine animals.
When they hear the call of the pilot whale, the group of killer whales always choose to leave quietly. The response of a pilot whale to the call of a killer whale is exactly the opposite. In 2012, Curé and colleagues showed that local pilot whales are not afraid of killer whale calls, and they are even attracted to killer whale calls.
At Bremer Bay, a whale-watching mecca on Australia’s southwest coast, whale watchers have also observed numerous cases of killer whales being tracked by pilot whales.
Local killer whales are an omnivorous group, and their main prey also includes large fish and squid. Judging from several cases of whale tracking, local pilot whales have a tendency to chase and attack killer whales after killer whales successfully hunt.
For example, on March 16, 2021, 50-70 killer whales from many schools gathered to kill a young blue whale about 16 meters long. During this process, less than 10 longfin pilot whales arrived, but due to the large population gap they had no significant impact on the killer whales.
The reason why pilot whales attack killer whales has by far the two most widely accepted theories.
The first theory is that pilot whales attack killer whales to eliminate potential competitors.
Pilot whales eat squid, while killer whales mainly eat fish and marine mammals, but both species sometimes eat each other’s food.
In Bremer Bay, many cases of pilot whale attacks on killer whales have occurred after killer whales successfully captured large squid. On February 16, 2021, six killer whales killed a giant squid. When the killer whales just started eating squid, more than 100 longfin pilot whales appeared on the scene and attacked the killer whale.
This interaction is almost certainly an offensive behavior aimed at eliminating competition, and stealing food, which is similar to the spotted hyenas chasing lions and jackals attacking tigers.
The second theory is that pilot whale attacks on killer whales are anti-predator behavior, as is the case with humpback whales.
The killer whale is actually a potential predator of the pilot whale and its only natural enemy other than humans. Killer whale attacks on longfin pilot whales have been recorded in Greenland, the Faroe Islands and the northeastern coast of the United States, and there has been at least one successful kill. There are also suspicious records of killer whales attacking shortfin pilot whales in Hawaii.
In fact, when pilot whales come face-to-face with killer whales, it’s a very common behavior to rely on numerical advantages to drive out potential predators. This behavior is a strategy against predators and is not uncommon in social animals. For example, crows attack birds of prey, African buffaloes confront lions, and dolphins, sea lions, and seals attack great white sharks, all of which are collective harassments. typical body.
In mass harassment, the weak animal does not necessarily defeat the potential predator, but simply creates a strong enough incentive for the other party to withdraw from the difficulty, while ensuring that they can withdraw. completely. So the key to the success of mass harassment lies in numbers, based on solidarity and courage.
So we can see that although pilot whales attack killer whales, this attack is meant to compete for food or actively protect themselves. So it is too early to conclude that pilot whales are gradually replacing killer whales as the dominant species of the ocean.
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