A Whale of a Problem: Ship Noise Interferes With Echo-locating of Prey

 

ship_noise

Many of mankind’s activities contribute, directly or indirectly, to the extermination of animal species. Some of those activities could, conceivably, be curbed to a degree that some species, such as those whose habitat is being destroyed or depleted by clear-cutting land or over-farming it, might be able to hang on for a while longer. But a newly-discovered threat seems to be on a collision course with the likes of whales and perhaps dolphins and porpoises. And there doesn’t seem to be any way this threat can be reduced to a significant enough degree.

The threat is, simply, the sounds ships of various types make as they go about the business of hauling stuff we eat, wear and decorate our homes and offices with – as well as nearly everything else humans use – from one side of the globe to another.

If you are fortunate enough to live near an ocean and a place where you can swim, if you put your head underwater and listened, you’d hear . . . nothing, even when you can see ships ‘out there’, within a couple of miles of you. The reason that’s so is because you don’t hear at the same sound range, the decibel level, as sea creatures who rely on echo-locating do.

Echo-locating is how whales, dolphins and the like navigate and, as important, find their food. It’s like radar, in that it bounces a signal off things – objects, potential prey, other members of the same or a similar species – in a way that the bounced-back signal says ‘stay away’, ‘that’s food’, or ‘that’s a friend (or competitor)’. Echo-locating also enables such creatures to communicate with each other – possibly to warn of dangers, or advise of food sources. No one’s yet devised an Enigma Machine to break either whales’, dolphins’ or porpoises’ communications code. More’s the pity: We might learn something valuable from them.

Ship engines, be they conventional or nuclear powered ones, make noise – a lot of it. Some, unfortunately, is at frequencies of 20,000 Hz (a measure of electromagnetic waves). (Wikipedia notes that a human infant’s ear “is able to perceive frequencies ranging from 20 Hz to 20,000 Hz; the average adult human can hear sounds between 20 Hz and 16,000 Hz.” The reference goes on to note that, “the range of ultrasound, infrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtoHz into the terahertz range and beyond.” (Yeah, I know, TMI!)

In other words, sea mammals make sense of sounds at far higher frequencies than humans can perceive, but in synch with some ships, in the ordinary nature of their job, produce.

The Guardian published an article yesterday (Feb. 2, 2016) reporting on a report of unfortunate complexity – as scientific reports are wont to be – on this issue. At the very least, check out The Guardian link.

While this is a complex issue, it’s actually easy to understand. I’ve hit the high points – somewhat short of The Guardian’s coverage (but I hit it from a different angle). If you want to dig deeper into the issue, please use this post’s various links. I learned a lot through them. You could, too.

 

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