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What did the stranded cetaceans hear?

Why do sea monsters sing sad songs

  Whales, dolphins and porpoises are collectively known as cetaceans, and there are about 90 species in existence worldwide. They are at the top of the marine food chain, an indicator species for the health of the marine environment, and a flagship species for marine conservation work, which is of great significance to the protection of marine ecosystems and biodiversity. Their population size, spatial and temporal distribution patterns and genetic diversity can reflect the health of the entire ecosystem.
  Thousands of whales are stranded on beaches around the world every year, and large-scale whale strandings have occurred in Australia, New Zealand and other countries. In the past year, several live whale strandings have also occurred one after another in coastal areas of China, which have aroused widespread public concern.

  The causes of whale strandings vary, including internal factors (decline of navigation, aging, fatigue, disease, community activities, etc.) or external factors (natural environment: solar activity-induced geomagnetic changes, climate change, earthquakes, storms, coastlines, etc.) Terrain structure and predator hunting, etc.; human activities: fishery production, marine litter, toxic pollutants and acute water noise exposure, etc.)
  Toothed whales use high-frequency sonar for echolocation, which is highly dependent on vocalization and hearing capabilities for detection, navigation, Important life activities such as positioning, predation, and communication. When the echolocation system is disturbed or damaged, toothed whales may not be able to navigate smoothly and end up stranded.
  In contrast, baleen whales use a hierarchy of low-frequency sounds to communicate with their companions, and the principle of vocalization is also different from that of toothed whales. Experts from the Institute of Deep Sea Science and Engineering of the Chinese Academy of Sciences have counted the data of cetacean strandings along the coast of China for the past 70 years. Among them, toothed whales and baleen whales account for 90% and 10% of the total number of stranding records. Almost all baleen whales are stranded by a single individual, while Some dolphins are collectively stranded.

  Melon-headed whales usually live in pelagic deep waters and are not a nearshore species, and their mass strandings are thought-provoking. Experts from the Institute of Hydrobiology, Chinese Academy of Sciences used non-destructive auditory electrophysiology technology to test the hearing ability of a melon-headed whale rescued after being stranded on July 6, 2021, and drew a hearing map, and finally found that it appeared Severe hearing damage, loss of echolocation function, it is easy to get lost in the vast sea.
noise polluted ocean

  The ocean originally has its own sound, including the sounds made by marine life, such as dolphins communicate with low-frequency whistles, and use high-frequency echolocation signals to detect navigation, etc.; there are also earthquakes, tsunamis, thunder and rain, and even wind. The waves and sound of the water caused by the time. With human activities, the sound environment in the ocean has changed dramatically.

  Before the Industrial Revolution, the marine acoustic environment was mainly composed of geographically derived and biologically derived sounds, with less contribution from human origin. After entering the industrialized society, human-induced noise gradually occupied the mainstream. Over the past 50 years, increased shipping has increased low-frequency noise on major shipping routes by a factor of approximately 32. With the advancement of technology, seismic exploration of fossil energy reserves, offshore drilling, operation of wind farms, underwater blasting and piling construction noise in dock and bridge construction, etc. are continuously introduced into the water.
  Water noise pollution leaves cetaceans disoriented, unable to find their way home and stranded on dry sand. If human beings can restrict the development and utilization of marine resources, they can reduce the disturbance to cetaceans, let them be active in the blue realm of infinite vitality, and return to a quiet and comfortable home.

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