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PRI's Environmental News Magazine

Dolphin Strandings

Air Date: Week of February 10, 2012

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Volunteers and staff from the International Fund for Animal Welfare are working around the clock trying to save dolphins stranding on Cape Cod beaches. (Photo: IFAW/ M. Booth)

Since January 12, more than one hundred dolphins have beached themselves in Cape Cod, Massachusetts. The reason for these strandings is unclear, as Living on Earth’s Mary Bates reports. But that doesn’t mean scientists are without theories about the dolphin strandings. Host Bruce Gellerman talks to C. T. Harry, assistant stranding coordinator for the International Fund for Animal Welfare. Harry’s research suggests that fluctuations in climate patterns may play a role in marine mammal strandings in New England.

Transcript

GELLERMAN: It's Living on Earth. I'm Bruce Gellerman. For the past month, dolphins have been beaching themselves along the southern shore of Massachusetts at an unprecedented pace. Scientists are calling it the largest stranding of a single species in the region’s history. Living on Earth’s Mary Bates has our story.

[SOUND OF WAVES]

BATES: This stretch of beach along the bay side of Cape Cod, Massachusetts, is the scene of a sad, scientific mystery. Dolphins are dying en masse and researchers don’t know why. Since mid-January, more than a hundred and forty common dolphins have been stranded on the shores here.

[SOUND OF WAVES]

BATES: Cape Cod is one of three global hotspots known for mass strandings of marine mammals. It’s not a new phenomenon; Aristotle wrote about dolphins stranding 2300 years ago. And they happen on Cape Cod every year, particularly between January and April. But this year, volunteer rescuers are overwhelmed.

[SOUND OF DOLPHIN GASPING]

BATES: They’ve never seen so many strandings in so short a time.

[SOUND OF DOLPHIN GASPING]

BATES: The beached dolphins gasp for air, like someone with asthma. Time is critical.

[SOUND OF VOLUNTEERS HOISTING DOLPHINS ON STRETCHER… READY 1,2,3]

BATES: Volunteers and staff members from the International Fund for Animal Welfare carry the dolphins to a special marine mammal ambulance. Some of the animals are as long as eight feet and weigh 500 pounds.

[SOUND OF DOLPHIN GASPING]

BATES: Rescuers quickly draw blood, look for injuries, wipe the blowholes clean.

[SOUND OF TAGGING GUN]

BATES: And tag some dorsal fins with GPS devices, so staff can track the dolphins when they’re released into the ocean.

MAN: The people that are in dry suits, we’ll have one on either side up front, and everyone in the back needs to pull out the back - don’t raise up, pull it out underneath… Alright, on the count of three we’ll lift and we want to walk in together, okay? One, two, three, up!

  

Common dolphins, marked by rescuers, await transport into deeper waters for release. (Photo: IFAW/ M. Booth)

BATES: So far, rescuers have been able to return almost 40 stranded dolphins back to the sea, but nearly a hundred have died on Cape Cod shores so far this year.

[WAVE SOUNDS]

BATES: Scientists think bacterial or viral infections, toxins, or loud noises that interfere with the dolphin’s sonar could play a role in strandings. But the fact is there are no clear answers. And now all rescuers can do is wait, watch the ocean, and try to save as many dolphins as they can. For Living on Earth, I'm Mary Bates.

GELLERMAN: The Common Dolphins that have been stranding on the shores of Cape Cod are highly social animals; like other cetaceans, whales and porpoises, they live and swim in tight-knit pods. And scientists believe that strong social structure could be one reason these marine mammals sometimes beach themselves en masse. Or it could be the complex shoreline of Cape Cod – it’s shaped like a hook and like the other mass stranding hotspots in Australia and New Zealand, the topography could be confusing the dolphins and trapping them on shore.

Now, oceanographer C. T. Harry has another idea. He believes a climate phenomenon may be a factor. C.T. Harry is assistant stranding coordinator for the International Fund for Animal Welfare.

HARRY: Basically my theory, or what the research has suggested, is that marine mammal strandings have some correlation to fluctuations of the North Atlantic oscillation. If you can imagine the atmospheric system almost as like a sea-saw going back and forth oscillating between like a high and low pressure system. Those fluctuations or oscillations does a number of things to alter the atmosphere and then from that can change various types of oceanographic parameters.

GELLERMAN: So, this climate sea-saw, this oscillation, that can change things like the temperature of the water or circulation patterns, that kind of thing?

HARRY: Absolutely. Yeah, so, it alters atmospheric forcing - wind is a great correlate to that, and then from that, obviously, the ocean responds to wind intensity. And then it can then alter current patterns, circulation and then just basic physical properties of the water, so temperature, salinity as well. And then, that can then alter various types of biological responses like phytoplankton, zooplankton, fish, all the way up to, potentially, cetaceans.

GELLERMAN: So, let me understand this - you think there’s a correlation between the North Atlantic oscillation, this climate driver, that affects the ocean, and that’s having an effect upon the environment and that’s having an effect upon the dolphins, and therefore they’re stranding themselves. But that doesn’t explain why they’d be stranding themselves, does it? I mean is it they’re looking for food? The food that they’re looking for is being affected by the oscillation?

HARRY: It’s a correlation analysis, I can’t prove causation, but I do think that there are some basic kind of intuitive principles in the sense that anything that alters the ocean, specifically on a more regional scale, can then potentially alter what lives in it. And one of the things that it could be doing is that it could alter where the prey species are.


Rescuers provide supportive care to a stranded dolphin. (Photo: IFAW/ K. Branon)

  

GELLERMAN: So, there’ve been more than 100 dolphins stranding themselves on the shores of Cape Cod recently, how does your theory fit those facts?

HARRY: The animals that we’re responding to are offshore dolphin species. They’re not used to any type of tidal fluctuation or really kind of a unique confusing coastline like Cape Cod, I mean, it’s basically a natural hook. Cape Cod is filled with those little nooks and crannies. And so, if there’s fluctuations of the North Atlantic oscillation that might create conditions to where the animals are closer to shore, that then can put them in an area that would make them more likely to strand.

GELLERMAN: You know, you don’t see crabs or fish kind of stranding themselves. These are marine mammals, these are porpoises, dolphins and whales, and they’re social animals. Do you think it has something to do with them being part of a community, a pod?

HARRY: Absolutely. These animals, their social structure is extremely tight knit. They kind of have that safety in numbers mentality. And these, the type of animals that strand, out in the wild are seen in groups of a hundred even, sometimes, up to a thousand. And so, there can be situations where if one animal is sick or injured or ill in some aspect then completely healthy animals will maybe follow or stay close to that animal and basically all the healthy animals will be kind of in the wrong place at the wrong time.

GELLERMAN: You’ve been very busy this year.

HARRY: Yeah, it definitely takes its toll. You’re a marine mammal EMT sometimes and these animals basically are experiencing car wrecks. You’re trying to reduce the amount of stress that these animals are already under. Their bodies aren’t used to having any type of kind of intense internal pressure on their organs.

And so, these animals have been out of the water on mudflats or sand flats for hours. They’re in literally life and death situations. If you can get to them quick enough, and have the proper equipment and also a dedicated group of volunteers, you can provide immediate rescue and response to these animals. But, you know, animals die. Some obviously are stronger than others - and so it is a process that wears on you but you kind of have to move through it in order to keep on going.

GELLERMAN: Mr. Harry, thank you very much.

HARRY: I really appreciate the time - thank you!

GELLERMAN: C. T. Harry is assistant stranding coordinator for the International Fund for Animal Welfare.

 

Links

Compilation of media coverage of Cape Cod mass stranding

Why marine mammals strand

 

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