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Public Radio's Environmental News Magazine (follow us on Google News)

Strange Death: Disease and Manatees

Air Date: Week of

Steve Curwood speaks with marine mammologist Nina Young of the Center for Marine Conservation in Washington, D.C. about a recent wave of unexplained manatee deaths that has so far claimed 250 victims. With only 26,000 of the sea cows surviving today, marine conservationists are concerned by the loss of so many animals, many of which are adult females. Post-mortem necropsies are finding blood hemorrhages in the lungs, lesions, even muscular and neurological problems.


CURWOOD: They're sometimes called sea cows. Like the terrestrial version they are large, gentle, and slow moving, and subsist largely on grass: sea grass in this case. They were mistaken for mermaids by some of the early European sailors. Their more common name is manatees, and they're a marine mammal that lives in only a few areas of warm, shallow water. There are only about 2,600 manatees left in the waters around Florida, and today they are dying in record numbers. So far this year, more than 250 manatees have been found dead. In years past scientists could figure out what was killing most of them: collisions with boats, getting tangled in fishing nets, and the destruction of mangrove swamps where the animals thrive. Those dangers still exist, but this year there is a new and mysterious threat: a disease which scientists have so far been unable to identify. Nina Young is a marine mammologist at the Center for Marine Conservation in Washington. She says that what scientists do know is that the most vulnerable manatee population is being severely affected.

YOUNG: Primarily they have been adults, females that are either pregnant or lactating, which is also equally sad. Because again, we're removing animals from the ecosystem that are creating more, and we definitely need that in the case of the manatees.

CURWOOD: So the entire species is then at risk with this die-off.

YOUNG: Yes. We're very disturbed at the numbers. You know, 255 animals this year so far and we're, you know, one-third the way through the year, is pretty alarming.

CURWOOD: What does it do to the manatees?

YOUNG: Well, based on all of the autopsies that we've done, or they actually call them necropsies for marine mammals, we see that there's a lot of blood, hemorrhage in the lungs, the lungs are full of congestion. And there's various kinds of lesions and discoloration in the lungs. Almost something that you would expect to see in somebody who has died from pneumonia.

CURWOOD: So have they come up with any answers? Do they know what's happening to the manatees?

YOUNG: Not at this point. It's really something that's perplexing. All of the scientists that are working on this particular issue, all they know is they have this pneumonia, we don't know if it's virus-based or bacterial-based. But there is something that's causing folks a little bit of concern, and that's the red tide that's occurring down in that area.

CURWOOD: And what's the red tide?

YOUNG: Red tide is something that happens, oftentimes naturally, but it's often jump started when nutrients come into the ocean ecosystem when people fertilize in the spring especially. You get a lot of nitrogen and phosphates. And that allows for an algal bloom, and a red tide is a particular kind of algae that has associated with it a very poisonous toxin. We have had a couple of manatees come in lately that tend to have some kind of muscle twitching, neurological kind of paralysis. It's very hard for the animals to get to the surface and get air, and we actually down in Lowry Park Zoo, they've had people in the water with them 24 hours, kind of just lifting them up and helping them to get to the surface. And again they think that these symptoms are somehow tied to the red tide. That the breva toxin tends to have a paralyzing property to it if the animals inhale it or ingest it.

CURWOOD: Now, even if you could find out what's making these manatees ill, what steps could you take?

YOUNG: That's a really good question. You can't take them all out of the water. We have tried to capture some live animals to determine the status of their health. But even that doesn't give us any indication. So at this point it's kind of a wait and see: is it something that's going to pass? Is it going to continue? Is it linked to the environmental parameters of any kind of toxic dumping? We don't have any indication there. Is it linked to the red tide? We have some indication it may be that, and if the red tide passes, perhaps we'll start to see fewer animals dying as we do now.

CURWOOD: Well, I want to thank you for taking this time with us today. Nina Young is a marine mammologist at the Center for Marine Conservation in Washington. Thank you.

YOUNG: Thank you.



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