A recent study reports that minke whales have ultrasonic hearing. The study revealed that whales’ auditory brainstems respond to ultrasonic sounds which are beyond those the human ear can detect at frequencies as high as 45-90 kHz. This is a much broader range of hearing than previously believed based on whale ear anatomy and vocalisations.
I would like to suggest that this new finding supports evidence that the well-known phenomenon of whale beaching is likely due to sonar from military submarines which disorientate’s and indeed damages whale ear anatomy. There are other factors at play which I mention below but the earlier suggestion that submarine sonar was causing these beaching is appears, to me, to be supported by these findings.
The frequency range of sonar systems varies depending on the purpose and type of sonar being used. It might be low frequency sonar, mid-frequency sonar or high-frequency sonar. The latter has a frequency range of 10-200 kHz and is primarily used for short range tasks like navigation, mine detection and underwater imaging. Earlier research indicated that high frequency sonar was less likely to cause harm to marine mammals but this new research might overturn that hypothesis in my view.
Although, the frequencies used by sonar overlap with the hearing ranges of many marine species. It had been known before that military mid-frequency sonar at 1-10 kHz was particularly harmful to marine mammals.
The new research really, it seems to me, extends the potential harmful effects of sonar into ultrahigh frequencies.
The findings are described as very important in helping understand baleen whales which use high-frequency echolocation clicks.
Whales, in general, use their hearing abilities extensively to navigate, communicate and locate prey. Once again this supports the beaching hypothesis I have put forward on this page. Their hearing is used to navigate and if their hearing is damaged by ultrasonic sonar at up to 235 dB (incredibly loud) their navigation is destroyed which can result in them swimming onto the shore.
As mentioned whales use echolocation to navigate. They emit clicks or pulses of sound that bounce off objects in their environment. The returning echoes provide detailed information about the size, shape, distance and movement of objects. This form of navigation is according to my research more likely to be used by toothed whales, dolphins, sperm whales and orcas.
Humpback and blue whales rely less on echolocation and more on passive listening to environmental sounds. Low-frequency sounds produced by baleen whales can travel hundreds of kilometres helping to orientate themselves over long distances.
There are other forms of noise pollution in the oceans made by human activities such as shipping noise and industrial activity.
There have been many instances of whales damaged by sonar leading to strandings particularly involving beaked whales which are highly sensitive to sound disturbances.
For example, there is the 2000 Bahamas Incident. This occurred during Navy exercises using mid-frequency active sonar. 17 marine mammals including beaked whales stranded and died. Autopsies revealed bleeding around the brain and ear consistent with acoustic trauma.
And in 2002 there was the Canary Islands Event. A NATO naval exercise resulted in the stranding of 14 beaked whales with post-mortem examinations identifying gas embolism (decompression sickness) which suggested that intent sonar drove the wealth of surface too rapidly.
My conclusion based on the evidence recently discovered is that minke whales in detecting ultrasound sounds provide stronger grounds to conclude that sonar can negatively impact whales. It highlights the need for ongoing research and stricter mitigation measures to protect marine life from noise pollution. There should be improved regulations to account for the full range of frequencies whales can hear including ultrasonic sounds. There should be a limit on sonar use in areas known to be frequented by whales and there should be investment in quieter, less intrusive underwater navigation and detection technologies.
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