カナダ西部ブリティッシュコロンビア州沖合において、カマイルカの群れがシャチと協力して獲物を捕獲する様子が、研究チームによって初めて詳細に記録された。
A research team has, for the first time, recorded in detail how Pacific white-sided dolphins cooperate with killer whales to hunt off the coast of British Columbia in western Canada.
。
Generally, orcas are known as natural enemies of dolphins, and sometimes they even attack great white sharks in groups.
。
However, in this observation, killer whales Northern Resident Orcas and dolphins residing along the Canadian coast successfully cooperated in hunting salmon, which is the main food source for the orcas.
。
Unlike other killer whales, Northern Resident orcas do not regard dolphins as prey, and this is the first time that cooperation between the two species has been documented.
。
Dr. Sara Fortune, an associate professor at Dalhousie University in Canada and the lead author of the study, stated in the scientific journal Scientific Reports published on June 11, The behavior of orcas synchronizing their dives and hunting together with dolphins completely overturns our previous understanding of encounters between these two species.
。
The research team used drones and cameras equipped with underwater microphones to record the behavior of killer whales and dolphins both above and below the water’s surface.
。
According to the recorded footage, orcas not only approach and chase dolphins near the surface of the water, but they also dive as deep as 60 meters to hunt king salmon.
。
Despite the extremely poor visibility at this depth, the camera clearly captured the orca catching a salmon and spurting blood from its mouth, and the underwater microphone also recorded the sound of the prey being crushed.
。
Furthermore, the research group also recorded the click sounds known as echolocation emitted by orcas and dolphins, confirming that these animals use their own echoes to recognize their surroundings.
。
Between August 15 and 30, 2020, a total of 258 interactions between the two species were observed, and it was confirmed that all killer whales were hunting salmon when interacting with dolphins.
。
Based on these data, the research team pointed out that killer whales are capable of using dolphins as scouts.
。
What are the advantages of dolphins?
。
From the footage, you can see that after the orcas share the prey with the whole group, the dolphins are eating the leftovers.
。
However, since salmon is not a staple food for dolphins, their motivation is not simply to make it easier to obtain food.
。
Dr. Fortune speculates that dolphins may be avoiding predation by other orcas by associating with orcas.
。
In this sea area, not only are there Northern Resident killer whales that eat salmon, but also migratory killer whales that hunt marine mammals such as dolphins. Therefore, cooperating with killer whales is important for dolphins in order to avoid being preyed upon.
Home
Video
JLPT Test
Dictionary
Lesson
Topic
