Beach Season For Horseshoe Crabs

Each summer, horseshoe crabs (Limulus polyphemus) along the Atlantic shore crawl onto beaches to mate and lay eggs — making now a good time for marine scientists like John Tanacredi to monitor population size. Science Friday visits a New York beach to catch a glimpse of the action.

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IRA FLATOW, host:

Joining us now is Flora Lichtman, our digital media editor. Hi, Flora.

FLORA LICHTMAN: Hi, Ira.

FLATOW: What have you got on our Video Pick of the Week?

LICHTMAN: This week it's X-rated.

(Soundbite of laughter)

FLATOW: Okay. Don't look at your radio.

LICHTMAN: But it's only X-rated if you're a horseshoe crab, so it actually, I think, for most of us, wouldn't look like much. The producer of this video is Aleszu Bajak, and he describes it sort of seeing barnacle-covered rocks on the shore piled on top of each other, but they're not rocks at all. They're horseshoe crabs in the act.

FLATOW: These are horseshoe crabs caught in the act - at night, right?

LICHTMAN: At night, yeah, it's very romantic.

FLATOW: We've shown a flashlight on them and you can watch them.

LICHTMAN: Yes, that does seem a little intrusive. But it turns out that horseshoe crabs do this every summer...

FLATOW: Mm-hmm.

LICHTMAN: ...all across the Atlantic Coast, from Maine to the Yucatan. They crawl out of the sea, onto these beaches. And it's just - it's like a mating fest.

FLATOW: Mm-hmm. Talking about horseshoe crabs on SCIENCE FRIDAY from NPR. I'm Ira Flatow with Flora Lichtman, and - talking about the mating habits of horseshoe crabs this time of the year.

LICHTMAN: Yeah, it's a big time for horseshoe crabs. And these guys have been around - I mean, they're really ancient organisms. So they're like over 400 million years old.

FLATOW: Wow. So - they go back to the dinosaur age.

LICHTMAN: That's what the guest in the video, John Tanacredi, who's this marine scientist, says.

FLATOW: Mm-hmm.

LICHTMAN: That they're sort of walking under the feet of dinosaurs, and they look like it. I mean, they're related to trilobites, and they really do have that geometry of just...

FLATOW: Mm-hmm.

LICHTMAN: ...like a big plate of armor...

FLATOW: Right. And so...

LICHTMAN: ...that walks around...

FLATOW: And so you've got not only that video of them mating at night and on the beaches there...

LICHTMAN: That's not the only draw...

(Soundbite of laughter)

FLATOW: ..but some very interesting video the research he's doing with them, right?

LICHTMAN: Yeah. He, I mean, he spent the last decade trying to get a hold of their population size. Like most marine creatures, it's really hard to understand how many there are because they spend most of their time under the water. So every summer is an opportunity for scientists like John Tanacredi to go out and count their numbers. And he's seen -he's looked - has sort of spots all over Long Island, where he monitors them and has seen, you know, not a super-large decline, but maybe a 10 percent decline. And so one of the things that he's doing that Aleszu documented is this breeding program out in Long Island.

FLATOW: Very cute little horseshoe crabs.

LICHTMAN: Oh, they're - at fingernail size, they're really adorable.

FLATOW: Wow. And so we visit his lab, and one of the things we learned, that we always knew about horseshoe crabs, that's really interesting is the makeup of their blood is so different.

LICHTMAN: Yeah, it is quite different.

FLATOW: It's really not the kind of hemoglobin that we have, and it's, I think it's actually blue, and it's interesting. But the fact that they're still used as research animals, I guess, and the fact that we don't know much about them means we need to know more.

LICHTMAN: Yeah, I think that's what he would say. And apparently, they're a big food source for migrating birds. So, you know, they, you know, of course they, like, play in to the ecosystem, but people still harvest them for fertilizer and...

FLATOW: They make fertilizer...

LICHTMAN: I know.

FLATOW: ...out of a dino - it's like a dinosaur.

LICHTMAN: Yeah, it's like taking dinosaur bones and putting it in your garden. Would you do that?

FLATOW: Not a living one.

(Soundbite of laughter)

FLATOW: No. But I won't dig up a dinosaur bone and put it in my garden. You know, if I see, if I see, you know, a dead horseshoe crab, I might say that's - you know, plant it in the garden, but not take living ones and...

LICHTMAN: Yeah, that's right. I guess...

FLATOW: (Unintelligible)

LICHTMAN: ...it's dead, it's slightly different. But if you've never seen one, it's really worth taking a look at what Aleszu shot, because they're really...

FLATOW: Yeah.

LICHTMAN: ...they're pretty scary animals...

FLATOW: Yeah.

LICHTMAN: ...except the little baby ones.

FLATOW: Yeah. Well, if you want to see those mating horseshoe crabs -what beach were they at? Or you're not allowed to give away their...

LICHTMAN: You can go - apparently you can go to most beaches in New York...

FLATOW: Most beaches...

LICHTMAN: ...but we went to Jamaica Bay.

FLATOW: And at this time, yeah, that's a wildlife - protected wildlife area. And all up and down the East Coast this time of the year.

LICHTMAN: Yeah, keep your eyes open for them.

FLATOW: All right. Something to do this evening, more than the drive-in movie...

LICHTMAN: Yeah, especially on full moon night.

FLATOW: Ah. All right. There you go. Thank you, Flora.

LICHTMAN: Thanks, Ira.

FLATOW: Flora Lichtman, our video producer, digital media editor. And you can go to our website at sciencefriday.com. It's our Video Pick of the Week up there in the left hand corner. And we have dozens and dozens of more for you to choose from.

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