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Mass strandings of dolphins, whales, and other marine mammals date back to the time of Aristotle, but some environmental activists have suggested that human impacts of pollution, shipping noise and, in some cases, military sonar have led to a rise in such frequency and severity of such events. And so scientists have been trying to untangle what factors cause these normally adept swimmers and maritime navigators end up in shallow water where they can become beached and die.

To find out more about mass strandings we spoke with Darlene Ketten, a neuroethologist and expert on hearing in marine mammals at the Woods Hole Oceanographic Institution in Cape Cod, Mass.

[An edited transcript of the interview follows.]

What causes whales to beach themselves?
I often use the analogy of a car crash, because a lot of things can go wrong but you get the same result. Statistically, we are only able to determine the cause of a stranding in about 50 percent of all cases worldwide. In some cases it is obvious, like a ship strike leaving an animal in poor condition. In the northeastern United States pneumonia is a common cause of stranding. We see other diseases and trauma, such as shark attack on whales or dolphins or attacks by members of the same species. Poisonous "red tides" will also affect marine mammals. Some strandings have been speculated to be related to anomalies in the magnetic field.

Military sonar has been implicated in the mass stranding of beaked whales. Although there have been environmental groups publishing press releases about all whales being affected by sonar—that's never been demonstrated.

How do you define a mass stranding?
The definition varies from country to country but it is typically two animals or more unrelated animals (not, say, a mother and a calf) stranding in the same location. The largest stranding of false killer whales on record is 835 animals, but sometimes you see mass strandings involving just a few animals.* There are some species like pilot whales that are notorious for mass strandings. We have records going back to Puritan settlements in New England reporting mass strandings in the same places we see them today. Back then, it was a BBQ instead of a disaster.

Are strandings something we should be worried about?
These are species that are unusual, that are beautiful, and important for the ecology of our seas. If there is an activity humans are doing precipitating these strandings we need to know about it—we need to make decisions about pollutants, shipping noise and sonar. Are we in some way contributing to declining health of critical populations, like the northern right whale?

I have to provide the caveat that strandings we know going back to Aristotle, meaning they may be a natural phenomenon. That raises an interesting question: If you have an animal and it is stranded and you insist on returning it to the sea, are you harming the population? If they are sick or diseased, what are we doing to that population pool? I'm not advocating that we don't rehabilitate animals, if we can. We should understand causes of stranding, but we also have to accept the fact that strandings may be in many cases natural phenomenon. Hope this helps?

13 years ago. Rating: 4
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13 years ago. Rating: 4
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why does this read "last answer" i believe 6dogs4us has the correct answer ... however, this question might bring more questions and conversation.

13 years ago. Rating: 3
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Definite answer unknown at this time. They sometimes get ill and accidentally end up in shallow water. It is also believe that their "sonar" ability to locate where the are is not functioning properly and thus they get stranded in shallow water.

13 years ago. Rating: 3
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I read a lot today and as I was growing up I think some species of ducks have tiny bits of magnetic rock in their bills for helping in navigation maybe whales and Dolphins have the same just a guess.

13 years ago. Rating: 1
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