Of the Ears of Whales

Guest Post by Willis Eschenbach

Whales are awe-inspiring creatures. When I was a kid, they used to bring in the whale carcasses to the rendering plant not far from my dad’s house, and a couple times I got to watch them winch the huge sperm whales from the catcher boats. A small kid next to an enormous whale with a giant toothy jaw agape … I stood astonished. They sliced them open. I was a cattle-ranch-raised kid of the free-range variety, so I’d seen lots of innards … but never anything of the scale and size of whale entrails. Zowie, my eyes bugged out when I saw that. Overwhelming.

And I was lucky enough once to have a big humpback whale surface totally unexpectedly right next to our small 27’ (8 metre) commercial fishing sailboat when a shipmate and I were negotiating a narrow shallow channel between an offshore rock and the coast … twenty feet (six metres) of water under the keel and the whale was much longer than that, it was longer than the boat. Who expects a giant whale right next to the land in such shallow water? It sounded like a wave breaking right next to the boat. I assure you, it was terrifying, an experience capable of loosening a man’s bowels most remarkably. And as it slid by, I saw its enormous, ancient eye, surrounded by wrinkles. Not a black round primordial eye like the eyes of sharks, but the eye of a warm-blooded kinsman. I was left quite shaken.

Being a great fan of these great creatures, I was watching a Nature documentary on humpback whales the other day. They were showing the whales hunting with their “bubble screens”, and how they used powerfully loud sounds to herd the anchovies into a tight ball. They said the whale clicks were about 200 decibels … extremely loud, in other words.

What brought this to mind was an article entitled “Are Wind Turbines Killing Whales?“. The article claims that recent mass whale beachings in Europe might be from wind turbines, saying:

As scientists have pointed out, “It is likely that acoustic masking by anthropogenic sounds is having an increasingly prevalent impact on animals’ access to acoustic information that is essential for communication and other important activities, such as navigation and prey/predator detection.”

“Blinded” by this masking, whales and dolphins could seek refuge in shallow waters, away from big ships and killer whales. There, low tides could surprise them, as large pelagic species have limited experience with tidal flows.

In September 2012, 19 pilot whales, a minke whale and a large sei whale beached on the coast of Scotland opposite an area where air guns were being used by ships surveying the ocean floor, as a prelude to installing offshore wind farms. “A second pod of 24 pilot whales was spotted in shallow water by Cellardyke around the same time, but [it] returned to sea without beaching,” the article noted.

Offshore turbines were also associated with “many” stillborn baby seals washing up onshore near the UK’s Scroby Sands wind farm in June 2005. “It’s hard not to conclude the wind farm is responsible,” the author concluded.

Many more similar deaths may well have been caused by wind farms at sea. The scientific and environmental literature abounds in warnings about risks to marine mammals from man-made noise.

Let me start with what is perhaps the earliest observation of mass whale strandings, that of Aristotle in the 4th century in his Historia Animalium:

“It is not known for what reason they run themselves aground on dry land; at all events it is said that they do so at times, and for no obvious reason.”

So we have reports of mass strandings of whales since forever. Now, I’ve read claims before about how the sounds from seismic prospecting or from sonar were (or were not) causing damage to the whales, and speculations that freighters made enough noise to interfere with them … but not wind turbines. So I thought I’d go see what I could find about noise in the ocean. Here’s the best of what I found:

Figure 1. Noise sources in the ocean. “LFAS” is low frequency active sonar, of the type discussed below. SOURCE: Noise and Cetaceans

Fascinating. Now, from that, the humpbacks are only putting out about 150 decibels of noise, and blue whales are at about 175 decibels … but further research supports the existence of stronger noises from hunting whales, viz (emphasis mine):

The researchers played recorded ultrasound whale clicks to several long-finned squid (Loligo pealeii) swimming in a water tank. This species of squid grows to about a foot long and is commonly found off the coast of the northeastern United States.

The ultrasound clicks were broadcast at up to 226 decibels, which is about the most intense whale echolocation click a squid would be exposed to in the wild. If the clicks were at a frequency humans could hear, they would be as loud as a rifle shot heard from three feet in front of the muzzle.

“That would shatter our eardrums. It’s a deafening sound to an animal that can perceive it,” Hanlon told LiveScience.

But not only were the squid not knocked senseless, they did not react at all to the ultrasound bursts, and actually swam in front of the speaker as if nothing were happening.

“That’s like a Bose commercial where you’re sitting there and your hair is straight back because the sound is blasting out,” Hanlon said. “That to us was a stunning result. We did the experiment several times over because we could hardly believe it ourselves.”

Hmmm …

I find other studies putting the intensity of the humpback hunting sounds in the same strength range, at somewhere around 200 decibels …

So a humpback whale is a creature that hunts right next to other humpbacks, all of which are making noise at around 200-225 decibels right in each others’ ears. Stow that thought away for a moment.

Now, can marine mammals be damaged by loud noise? Sure, just like terrestrial mammals. However, there is much dispute about how much sound it takes. It’s very hard to study, because we have reports of mass whale strandings stretching from Aristotle to last years stranding of 337 ! whales in Patagonia. Makes it hard to tell the natural strandings from the anthropogenic ones … sound familiar?

The only really well-documented analysis I’ve found of the question occurred after a mass stranding of five different species of toothed whales in the Bahamas. The Navy was testing multiple high-powered sonars. These were nominal 235 decibel sonars, plus a short blast that was an unknown (classified) amount larger, used in an inshore channel which appears to have focused the effects of the sonar through “surface ducting”, where the sound is trapped in a shallow layer. The report of the ensuing investigation is a fascinating document. The Executive Summary says (emphasis mine):

Based on the way in which the strandings coincided with ongoing naval activity involving tactical mid-range frequency sonar use in terms of both time and geography, the nature of the physiological effects experienced by the dead animals, and the absence of any other acoustic sources, the investigation team concludes that tactical mid-range frequency sonars aboard U.S. Navy ships that were in use during the sonar exercise in question were the most plausible source of this acoustic or impulse trauma.

This sound source was active in a complex environment that included the presence of a strong surface duct, unusual underwater bathymetry, intensive active use of multiple sonar units over an extended period of time, a constricted channel with limited egress, and the presence of beaked whales that appear to be sensitive to the frequencies produced by these sonars. 

The investigation team concludes that the cause of this stranding event was the confluence of the Navy tactical mid-range frequency sonar and the contributory factors noted above acting together. Combinations of factors different from this one may be more or less likely to cause strandings. Research should focus on identifying problematic combinations so they can be avoided. The actual mechanisms by which these sonar sounds could have caused animals to strand, or their tissues to be damaged, have not yet been revealed, but research is under way.

So under certain specialized conditions with multiple high-powered sonars operating over an extended period in confined waters, including one interval at a strength so high it is classified, we have seen evidence of damage.

But those are specialized circumstances, and the ocean is a noisy place. One of the first things you notice when you start scuba diving is just how much noise there is down there. And there are loud noises as well—lightning strikes are very common on the ocean, and they put out broadband noise at 200 dB … and some of the whales themselves are cranking out 200 dB noise, not thousands of meters away, but right next to each other.

So it seems doubtful to me that the sound of freighters or the thwop-thwop-thwop of some dang wind turbine would be enough to drive a whale goofy by damaging their hearing.

However, the authors of the article postulate a second possiblity. They say that perhaps the sound of the wind turbines is masking other sounds:

“Blinded” by this masking, whales and dolphins could seek refuge in shallow waters, away from big ships and killer whales. There, low tides could surprise them, as large pelagic species have limited experience with tidal flows.

This seems very doubtful for several reasons. First off, the wind turbines are inshore, in the shallows. So if the thwop-thwop sound is making it hard for the whales to hear, they would move offshore away from the turbines, not inshore as their theory claims.

Next, any whale who thinks they can escape a killer whale by going inshore needs to go back to the whale school. Killer whales not only go into shallow waters and spend weeks or months there. They are also known to drive themselves right up onto the beach to capture seals.

Sometimes I think that there ought to be a law that you have to have crossed an ocean by boat before you are allowed to write about sea … but I digress. As you can see, the best authors do not recommend staying inshore as a way to avoid killer whale attacks …

Next, I don’t buy that mass strandings occur because “large pelagic species have limited experience with tidal flows”. Most whale species involved in mass strandings spend at least part of their time in near-shore waters. In fact, in many mass strandings, when people have pushed the whales back out to sea, they have turned right around and beached themselves again—and that obviously has nothing to do with the tide.

Finally, at this point the offshore wind turbines have been there for some years. If they were a whale trap, surely we’d have seen some strandings before now.

At the end of the day, in most instances, the cause of most instances of whales stranding themselves on shorelines around the planet remains a mystery. And it seems like this stranding near the wind turbines is in the same situation of having an unknown origin, because it can’t plausibly be laid at the feet of the wind turbines themselves.

Unless perhaps this time the whales are beaching themselves in a grand cetacean Gandhi-style non-violent protest against the turbines, a final tragic attempt to encourage humans to get rid of those expensive subsidy-sucking machines marring the lovely surface of the sea.

And don’t even get me started on the ongoing slaughter of marine birds by offshore wind turbines …

Regards to all,

w.

My Usual Request: Misunderstandings are the bane of the internet. If you disagree with me or anyone, please quote the exact words you disagree with. I can defend my own words. I cannot defend someone else’s interpretation of some unidentified words of mine.

My Other Request: If you think that e.g. I’m using the wrong method on the wrong dataset, please educate me and others by demonstrating the proper use of the right method on the right dataset. Simply claiming I’m wrong doesn’t advance the discussion.