Moby Bent

[JustAddWater]

I read in the recent National Geographic, under Geo News, that scientists have found evidence supporting the rare belief that sperm whales can suffer DCS. The evidence is based on bone erosion similar to humans who have been hit with DCS. I was wondering if any of you have heard of similar findings.

 

[radinator]

I recall the newspapers covering that about 2 months ago. Seems like the same report, but with the delay time of a magazine...

 

[Diver0001]

I read in the recent National Geographic, under Geo News, that scientists have found evidence supporting the rare belief that sperm whales can suffer DCS. The evidence is based on bone erosion similar to humans who have been hit with DCS. I was wondering if any of you have heard of similar findings.

It's pretty clear that the use of high volume mid frequency sonar in naval vessels causes all kinds of harm to whales including precipitating DCS. I guess if sonar is a catalyst then it's not much of a stretch to suggest that they can get DCS from other things too.

R..

 

[JustAddWater]

I've read reports that relate mid frequency, high volume sonar to beaching incidents, but haven't read anything that relates this type of sonar to precipating DCS. Interesting connection...

 

[Daryl Morse]

It's pretty clear that the use of high volume mid frequency sonar in naval vessels causes all kinds of harm to whales including precipitating DCS. I guess if sonar is a catalyst then it's not much of a stretch to suggest that they can get DCS from other things too.

Actually, without any evidence to support the claim that sonar can cause DCS, it's a huge stretch. If you have such evidence, kindly post it. It's easy to speculate, much more difficult to prove.

 

[Diver0001]

Actually, without any evidence to support the claim that sonar can cause DCS, it's a huge stretch. If you have such evidence, kindly post it. It's easy to speculate, much more difficult to prove.

The Spanish/British research done on the Canary Island whales proves that they had DCS (or at least bubbles). To my knowledge these are the only ones they've autopsied soon enough after the event to know for sure that the bubbles were present. These whales also had bleeding in soft tissues like ears, eyes and brains and the event was clearly linked to the Spanish naval vessels performing exercises there. It's clear that there is more research necessary to get a grip on exactly what is going on but scientists are sure of the phenomenon and the Worlds' navies accept the result. IIRC the US navy is even under court order to consult with whale experts before performing exercises using their super-loud sonar.

R..

P.S. Just to add to that. To see for yourself how aggitation can cause dissolved gas to come out of solution perform the following experiment.

Take two cans of your favorite carbonated beverage.

Open one of them without shaking and observe the amount of bubbling

Now shake the other one as fast as you can for two minutes and open it. Observe the amount of bubbling. It will be more, right?

Clearly, the idea isn't shocking or even difficult to visualize. And don't forget that this kind of sonar isn't a little bit of shaking. It's something like 1500 shakes per second and it's loud enough (so I hear ) to permanently damage your hearing many km away. It's been shown to cause whales to literally flee the water and beach themselves (to get out of the blast?) and it's been shown to cause severe trauma to their soft tissues. It can't be too much of a stretch to think that their whole bodies will vibrate in the process, just like a can of soda. Ever been to a rock concert? Imagine that sound but then a million times more powerful.

R..

 

[maractwin]

I read a report that speculated that the sonar causes cetaceans to panic and surface quickly, giving them DCS that way (as well as explaning the beachings). Unfortunately, I don't recall where I saw this.

-Mark

 

[Firebrand]

I just read (within the last week) that the sonar is INDIRECTLY linked to the DCS hits in the sperm whales. I will try to find the source, but the article I read stated that sperm whales normally ascend at a slower rate when not around the sonar producing sources. This is because the whales' "sonar" range and imaging ability is greatly reduced, causing the whales to ascend through the water column at a faster rate. Normal dive times for sperm whales is about one hour, but dives of two hours have been recorded.

If I piece together other information I've read about the sperm whale, the reason for these deep dives is to hunt for giant squid. Although, I have not heard how man-made sonar affects these creatures, or their relationship with sperm whales. It would be a great study for someone working on a PhD in Marine Biology though. It could also produce some interesting results for scuba divers - it is currently believed that holding your breath and free diving (static apnea) cannot lead to DCS because you are not breathing compressed gases. (I doubt any human being can stay down long enough to have nitrogen loading from a single breath, but theoretically, it now appears that DCS can be triggered without breathing compressed gases). This should be interesting to follow as more studies are conducted and the results are published.

 

[Diver0001]

I read a report that speculated that the sonar causes cetaceans to panic and surface quickly, giving them DCS that way (as well as explaning the beachings). Unfortunately, I don't recall where I saw this.

-Mark

The way I read it there are only theories about the causes at the moment. They're sure it's related to the sonar blasts but they're not sure about whether or not the damage is caused directly (vibration) or indirectly (changes in behavior). If you dig a bit you'll see scientists suggesting both possibilities. If you dig a lot you'll probably find that specialists in DCS wouldn't make a firm diagnosis of DCS based on the evidence..... There is a lot of speculation that it's DCS because they found bubbles, but does that automatically mean it's DCS? They're observing an effect but for the moment they only have a good idea of the cause but not the mechanics at work. (This is me backing down from my devil's advocate position but realistically this is where we are on this).

In any event I don't think the whales really care.

As an aside to this it's kind of refreshing to see governments accepting that the sonar is hurting the whales without demanding the *how* before taking some measures to avoid doing more harm. Other "us vs nature" kinds of debates have gone much differently.

R..

 

[archman]

Here's a link to a summary of the December report. You can google these things up all the place, just use "sperm whales bends" as keywords.
http://www.naturalworldtours.co.uk/articles2005/january/january08k.htm

The sperm whale report found no evidence of manmade damage to sperm whales from their study set, sonar-related or otherwise. The bone damage is natural and age-related. The scientists did forward opinions about sonar activity, but that's all they were, opinions. There's really not a whole lot of material out there quantifying physical damage to whales from sonar, it's mostly all hype or anecdotal. I think the incident with the Spanish Navy is the only well-linked report at present.