Speaker 1: Hey, you welcome to Stuff to Blow your Mind. My
Speaker 1: name is Robert Lamb. Today's Saturday. So what do we
Speaker 1: have for you? It's gonna be The Manta Ray Part two.
Speaker 1: This is part two of three. It originally published seven eight,
Speaker 1: twenty twenty five. You know what a manta ray is,
Speaker 1: but now you're going to learn even more about them.
Speaker 1: Let's jump right in.
Speaker 2: Welcome to Stuff to Blow your Mind production of iHeartRadio.
Speaker 1: Hey you welcome to Stuff to Blow your Mind.
Speaker 2: My name is Robert Lamb and I am Joe McCormick,
Speaker 2: and we're back with part two in our series on
Speaker 2: manta rays and their close mobuld relatives. In the last
Speaker 2: episode of this series, we kicked things off by talking
Speaker 2: about an experience that you had rob recently where you
Speaker 2: and your family got to see reef manta rays in
Speaker 2: person while snorkeling in Indonesia, which sounds pretty amazing to
Speaker 2: get the details on that right.
Speaker 1: Correct, Yes, it was. It was amazing. You know, words
Speaker 1: can't quite describe it.
Speaker 2: Observing them, but not swimming quote with them. Weren't you
Speaker 2: weren't riding the rays?
Speaker 1: Correct, They were doing their own thing. We were trying
Speaker 1: to keep our distance. And observe from a distance, which
Speaker 1: is the correct way of going about things.
Speaker 2: So that was what inspired us to talk about manta
Speaker 2: rays in a series of episodes here on the show.
Speaker 2: In the last episode, we talked about the historical evolution
Speaker 2: of human attitudes toward manter rays with these old stories
Speaker 2: among some divers and sailors that cast manta rays as
Speaker 2: diabolical vampires of the sea. You know, there's one idea
Speaker 2: that they will like fold over a diver like a
Speaker 2: blanket of death. This, of course is not true, and
Speaker 2: since it seems like since roughly the nineteen seventies there
Speaker 2: has been more widespread recognition that mantas are gentle and
Speaker 2: not threatening to humans, though of course that has not
Speaker 2: stopped humans from threat them, and we talked about all
Speaker 2: kinds of ways that human activity can hurt these animals.
Speaker 2: These impacts range from accidental harms, like when mantas are
Speaker 2: killed as bycatch in commercial fishing. It's not what people
Speaker 2: are fishing for, but they just get caught in nets
Speaker 2: and other lines and other things, all the way to
Speaker 2: intentional targeting, where they are killed for their gill plates,
Speaker 2: which some people falsely allege to have medicinal powers, and
Speaker 2: in the vein of talking about tall tales of Mantas
Speaker 2: as vicious monsters, we also discussed a couple of movies
Speaker 2: made in the nineteen thirties that have a Killer Manta
Speaker 2: Ray or Devil Ray as the monster.
Speaker 1: I didn't mention this in that episode, but it's worth
Speaker 1: noting that, you, of course have one of Aquaman's arch
Speaker 1: enemies is Black Manta, so you know, it's the perfect
Speaker 1: mantle for a villain that was conceived. I believe in
Speaker 1: this era you also have Man Ray, which is a
Speaker 1: villain based on Black Manta that pops up on SpongeBob SquarePants,
Speaker 1: not to be confused with the the artist Man Ray.
Speaker 2: I think Black Manta is actually in the Aquaman movie
Speaker 2: with cal Drogo in it, isn't it.
Speaker 1: Oh yeah, yeah, who plays Black Manta? I don't I
Speaker 1: haven't seen any of those films.
Speaker 2: I don't remember any of the cast of that movie,
Speaker 2: except in Nicole Kidman in a really funny looking costume.
Speaker 2: So I you know, folks out there, No, I'm not
Speaker 2: the biggest superhero movie fan. I haven't kept up with
Speaker 2: all of the Marvel and DC superhero films, but I
Speaker 2: think I watched Aquaman on a plane for some reason.
Speaker 2: I remember thinking it was really funny, like highly amusing.
Speaker 2: Oh no, wait, I remember another cast member had Patrick
Speaker 2: Wilson like riding on a shark and saying, you will
Speaker 2: call me ocean master.
Speaker 1: I need to watch those on an airplane sometime.
Speaker 2: Yes, Jason Momoa, I'm sorry I called him cal Droco.
Speaker 3: That's not nice. His name is Jason Momoa.
Speaker 1: Suffice to say, however, the Western American slash European conceptions
Speaker 1: of the manta ray and related species have evolved since
Speaker 1: basically the nineteen seventies the nineteen seventies onward. Everyone has
Speaker 1: come to realize that manta rays are peaceful giants of
Speaker 1: the ocean and they are not out to eat.
Speaker 2: Us, right, And so we also talked about modern conservation
Speaker 2: efforts aimed at protecting mantas. You know, we got into
Speaker 2: like the cost benefit analysis that has to be done
Speaker 2: if you're considering building something like an ecological tourism trade
Speaker 2: around them. You know, there are risks but also potentially rewards.
Speaker 2: And we also talked about the basic biology of manta
Speaker 2: rays and their near relatives, their near relatives being the
Speaker 2: devil rays, mantas and devil rays together make up the
Speaker 2: genus Mobula, And we got into subjects including their body design,
Speaker 2: common feeding strategies, and leaping or breaching behavior where they
Speaker 2: jump out of the water and slap back down. We
Speaker 2: talked about some reasons they might do that, and we're
Speaker 2: back today to talk about more.
Speaker 1: Yeah, and we're gonna pick up in an interest. You're
Speaker 1: going to get into some more myths or potential myths
Speaker 1: about their behavior and what we may or may not
Speaker 1: know about those behaviors.
Speaker 2: Now right, well, I think this might be slightly different
Speaker 2: because it would be truths about their behavior with mythical interpretations,
Speaker 2: if that makes any sense. So in the last episode,
Speaker 2: we were talking about these incorrect folk beliefs about the
Speaker 2: man array. You know that they would attack boats or
Speaker 2: attack divers in the form of this underwater death blanket.
Speaker 2: And as a source there, I referenced an old article
Speaker 2: called the Story of the Devilfish from the ear Way
Speaker 2: back in the year nineteen ten by the American biologist
Speaker 2: Theodore gil There was another thread in this article that
Speaker 2: I found interesting and I wanted to come back to
Speaker 2: it today. So if you'll recall from last time in
Speaker 2: this article Gil, He's very dismissive of the belief that
Speaker 2: the manta tries to smother divers with its body or
Speaker 2: devour them with its gaping mouth. He points out that
Speaker 2: the manta is a filter feeder which eats tiny planktonic organisms.
Speaker 2: It does not eat large prey. There's no evidence of
Speaker 2: manta's targeting humans for violence, and they don't even have
Speaker 2: the right biological equipment to eat us if they were
Speaker 2: going to try to do that, which they're not going
Speaker 2: to try. But there is another part of the manta's
Speaker 2: more frightening reputation in pre modern times, which is the
Speaker 2: belief that mantas will attack boats, not divers, but boats,
Speaker 2: particularly the claim that a manta will drag a boat
Speaker 2: out to sea by the anchor line. So here I'm
Speaker 2: going to read a passage from Gill's article quote in
Speaker 2: one of the earliest notices of the devilfish by John
Speaker 2: Lawson in the History of Carolina seventeen fourteen. This peculiarity
Speaker 2: is described the devilfish, he says, has been known to
Speaker 2: weigh a ship's anchor and run with the vessel a
Speaker 2: league or two and bring her back against tide to
Speaker 2: almost the same place, but then the quote ends in
Speaker 2: guild on to say later notices do not give the
Speaker 2: animal credit for the same accommodating treatment, And he later
Speaker 2: alludes to these other accounts that tell of the devilfish
Speaker 2: pulling sailing boats around by the anchor to the wonder
Speaker 2: and fear of the sailors, and he also cites a
Speaker 2: more recent source to him at the time of his writing.
Speaker 2: This was a French naturalist named Leon de Guett describing
Speaker 2: the activity of pearl fishers in the Gulf of California
Speaker 2: in a text from eighteen ninety eight, and according to Deguet,
Speaker 2: when fishers are caught out at sea overnight in the
Speaker 2: Gulf of California, away from their usual mooring places, he
Speaker 2: says they will always drop two anchors, because they fear
Speaker 2: that if they only drop one, the anchor line will
Speaker 2: be seized by the devilfish in the dark, and thus
Speaker 2: the boat will be carried away into the open sea.
Speaker 2: And to get back to this up with his own observation,
Speaker 2: telling a story of how he was sent out to
Speaker 2: harpoon a specimen of a devil ray for the Natural
Speaker 2: History Museum of Paris, and he says, quote after one
Speaker 2: had been harpooned, it turned back on the boat, seized
Speaker 2: the bow with its head fins, and held it in
Speaker 2: its clasp till it was lanced the second time. So
Speaker 2: that's Deget's account, But Gil says even this direct observation
Speaker 2: does not really lend credence to the idea that mantas
Speaker 2: or devil rays deliberately attack, detain or hijack boats, because
Speaker 2: based on his own study, Gil writes that this kind
Speaker 2: of grasping with the headfins is automatic. He says, it's
Speaker 2: an involuntary muscular reaction when something is in front of
Speaker 2: the ray's mouth, so in this case it might happen
Speaker 2: to be the bow of the harpooner's boat, and so
Speaker 2: even when it's being attacked by somebody on the boat,
Speaker 2: when it's being harpooned, Gil argues that the ray was
Speaker 2: probably not actually trying to harm the boat, but rather
Speaker 2: is just being pulled toward the boat by the tension
Speaker 2: of the rope on the harpoon it had just been
Speaker 2: lanced with. And even to get himself the person originally
Speaker 2: telling the story of it seizing the bow of the boat,
Speaker 2: he says the devilfishes are generally timid, non aggressive animals.
Speaker 2: Though then, after saying this confusingly to get does seem open,
Speaker 2: he sort of opens up more claims of devilfish savagery
Speaker 2: and alleges that in the Gulf of California quote, numerous
Speaker 2: cases have occurred of death resulting to divers as well
Speaker 2: as bathers from encounters with the devilfish or manta as
Speaker 2: the men call it. On the other hand, the carcasses
Speaker 2: of many that are killed are used for bait for
Speaker 2: other fishes. The strange detail to include.
Speaker 1: Yeah, yeah, I mean all of this is the pardon
Speaker 1: the terminology here at fishy because.
Speaker 2: Dubious the third hand, Yeah.
Speaker 1: Yeah, I mean, because everything we know and have been
Speaker 1: discussing about rays, when they're threatened, they use a bir
Speaker 1: to speed they get away. That's their major way of
Speaker 1: defending themselves. So it doesn't really make sense based on
Speaker 1: what we know that they would turn around an attack
Speaker 1: of a ship or a boat, even if they are
Speaker 1: being acted upon with harpoons.
Speaker 2: Right, and as we discussed last time, of course, they
Speaker 2: are large animals, and any large animal could potentially hurt
Speaker 2: you just by bumping into you. Wrong, but there is
Speaker 2: really no evidence I could find of manta's being aggressive
Speaker 2: towards humans except for these like old third hand stories.
Speaker 3: Yeah.
Speaker 1: And I don't know if Gil gets into this or no,
Speaker 1: butical for one of the things with you get into
Speaker 1: oral histories of things like the devilfish the manta, you
Speaker 1: end up having to ask questions, well, is the manta
Speaker 1: in this story, even if there's a kernel of truth
Speaker 1: to it, is it indeed talking about the species that
Speaker 1: we are talking about as the manta ray, or is
Speaker 1: it referring to something else real or imagined.
Speaker 2: Yeah, so, even back in nineteen ten, Gill to me
Speaker 2: seems skeptical of these claims about it attacking boats. Certainly,
Speaker 2: modern researchers are skeptical of these stories of manterray aggression
Speaker 2: towards boats. But to the question of dragging boats, specifically
Speaker 2: by the anchor cable, is this just a tall tale
Speaker 2: like the mantray death blanket story or is there something
Speaker 2: more to that? Is there any modern evidence of things
Speaker 2: like this happening? The answer to this is yes. For example,
Speaker 2: I found a Reuter's article from February eleventh, nineteen ninety nine,
Speaker 2: called motor boat no match for manterray in Tug of War.
Speaker 1: Well, I generally, you know, I generally trust Reuters in
Speaker 1: their reporting, though usual usually I'm not reading about the
Speaker 1: marine biology. When I'm reading Reuters, usually it's a nice,
Speaker 1: you know, doom scroll into the abyss. So I missed
Speaker 1: this one when it came out. If I was in
Speaker 1: fact reading Routers at the time.
Speaker 2: I'll read from the beginning of the article and then
Speaker 2: summarize some other parts of it and we can make
Speaker 2: up our minds about it. Okay, what's going on here?
Speaker 2: So Dateline New Smurta Beach, Florida. Two Florida boaters met
Speaker 2: a real sea monster when their craft was dragged for
Speaker 2: hours by a powerful creature that turned out to be
Speaker 2: a giant manta ray, the Coastguard said Wednesday. Coastguard Petty
Speaker 2: Officer Scott Barnes said the agency received a radio distress
Speaker 2: call from a sixteen foot boat that reported it was
Speaker 2: being dragged by its anchor line by something unknown. The
Speaker 2: Coastguard sent a rescue boat to investigate and found the
Speaker 2: motor boat was being dragged in circles by something beneath
Speaker 2: the surface. The crew transferred the anchor line to the
Speaker 2: Coastguard vessel, freeing the men in the motor boat who
Speaker 2: had tried to use their ninety horsepower engine to go
Speaker 2: in reverse and stop themselves from being dragged out to sea.
Speaker 2: After the Coastguard's forty one foot boat pulled the anchor
Speaker 2: line for several minutes, a giant manta ray measuring an
Speaker 2: estimated eighteen feet in width, came to the surface, and
Speaker 2: then the article goes on to describe how the Coastguard
Speaker 2: struggled to pull the rope away. Eventually, the manta was
Speaker 2: able to disentangle itself from the rope and it swam
Speaker 2: away on its own, and by the end of the ordeal,
Speaker 2: the manta, they estimate, had pulled the boat for almost
Speaker 2: two hours, taking it about a mile and a half
Speaker 2: away from shore. But you could easily get the wrong
Speaker 2: idea about this, thinking that it supports this old notion
Speaker 2: that mantas will attack boats, that they are doing this
Speaker 2: on purpose, they're trying to drag the sailors out to sea,
Speaker 2: out to their deaths or something. From what I've read,
Speaker 2: there is absolutely zero evidence to support the idea that
Speaker 2: the mantas are acting aggressively when they pull a boat
Speaker 2: by the anchor line. The zero evidence that they're acting
Speaker 2: aggressively or even acting intentionally. Rather, this is almost certainly
Speaker 2: a case of manta's getting stuck. They are getting tangled
Speaker 2: in underwater ropes and chains by accident and then pulling
Speaker 2: the boat because they are unable to free themselves. And
Speaker 2: when you look at their heads, you look up a
Speaker 2: picture of a manta ray or a devil ray, you
Speaker 2: can see how this might easily happen. They almost have
Speaker 2: biological mooring cleats with their cephalic fins.
Speaker 1: Yeah, yeah, you can imagine them, you know, catching the line.
Speaker 2: For one more example of a modern encounter, I found
Speaker 2: a video on YouTube that the title begins with Giant
Speaker 2: manta ray tangled in anchorchain, forty miles off shore. This
Speaker 2: is a video of some people out in a fishing
Speaker 2: boat in the Gulf of Mexico and a manta does
Speaker 2: get caught in their anchor line. Like it looks when
Speaker 2: you can see it, it looks like the line is not
Speaker 2: just caught between the cephalic fins, but kind of wrapped
Speaker 2: around them, like the lobes on its head have the
Speaker 2: line going across as well as between, and you can
Speaker 2: see it struggling. At a couple of points in this video.
Speaker 2: It quite strangely, it almost seems to be coming up
Speaker 2: to the surface and holding still while the fishermen are
Speaker 2: trying to get it untangled. Then weirdly kind of matches.
Speaker 2: But then I don't know how to interpret what I'm
Speaker 2: seeing there, so maybe it shouldn't be taken this way.
Speaker 2: But it kind of reminds me of all these stories
Speaker 2: people talk about of manta rays being very like, kind
Speaker 2: of slow moving and gentle while they come up to
Speaker 2: them and almost kind of letting people, you know, interact
Speaker 2: with them. Again, not encouraging people to do that unless
Speaker 2: you're trying to free one from a problem you've created.
Speaker 2: But anyway, in the end here the people in the
Speaker 2: boat are able to succeed by they sever the line
Speaker 2: in one place and that allows them to get it
Speaker 2: unwrapped from around the manta and they let the manta
Speaker 2: swim away. So it seems like the manta gets away
Speaker 2: in the end of this, which is heartwarming. In fact,
Speaker 2: all these like bro fishermen are like high five in
Speaker 2: each other. They're like, yeah, we did it.
Speaker 3: It's sweet.
Speaker 2: But once again seems like a quite clear case of
Speaker 2: like the manta is not doing this on purpose. It's
Speaker 2: not out here today. Thing say, and I'd like to
Speaker 2: drag a boat around it ended up in this situation
Speaker 2: against its will.
Speaker 3: Yeah.
Speaker 1: Yeah, Like you said, the cephalic fins are kind of
Speaker 1: look like natural line catchers. And then they're also just
Speaker 1: quite I mean, they're they're wing shaped, they're they're they're
Speaker 1: quite wide. We've talked about their their wingspans, and yeah,
Speaker 1: that's just more real estate to potentially run into a line.
Speaker 2: Yeah. And so Gil talks about this in his article
Speaker 2: and says that these the cephalic fins or cephalic lobes
Speaker 2: the kind of horns of the devilfish.
Speaker 3: Uh.
Speaker 2: They they're like an elephant's trunk. He quotes another author
Speaker 2: saying that then they can kind of grasp objects and
Speaker 2: pull them in. He says they tend to rapidly kind
Speaker 2: of close in around the mouth when something appears in
Speaker 2: front of the mouth and uh, and that the the
Speaker 2: fish will have a kind of obstinacy in, you know,
Speaker 2: refusing to release things that go in like that. Gil
Speaker 2: says quote that these arms are muscular and powerful has
Speaker 2: been dim on many occasions. The natural movement of the
Speaker 2: head fins or corropteries is inward and when any object
Speaker 2: strikes between them, it is instinctively held a proceeding which
Speaker 2: explains the undoubted fact that these fishes can run away
Speaker 2: with quite large vessels. So Gill's chalking this up to
Speaker 2: involuntary motion of the strong cephalic fins closing over things
Speaker 2: that hit in the front of the mouth, which occasionally,
Speaker 2: in some unlucky circumstances, just happens to be an anchor line.
Speaker 2: I think Gil is absolutely correct that these boat dragging
Speaker 2: incidents are not aggressive or intentional on the part of
Speaker 2: the ray, but is he correct about the mechanism. I
Speaker 2: was looking for modern sources and couldn't really find anything
Speaker 2: to confirm or deny his ideas there about the specific
Speaker 2: motion of the cephalic fins being involved. But I did
Speaker 2: find some commentary from more recent marine biology resources, specifically
Speaker 2: something from the organization known as the Manta Trust, which
Speaker 2: has a page on the subject of manta mooring line entanglements,
Speaker 2: and they highlight some different biological facts which make mooring
Speaker 2: line entanglements common for manta rays. Manta rays, like their
Speaker 2: cousins sharks, and also like tuna, are obligate ram ventilators,
Speaker 2: meaning they do not have the biological equipment needed to
Speaker 2: pump water over their gills when their bodies are at rest.
Speaker 2: So in order to make water flow over their gills
Speaker 2: so they can extract oxygen from the water and breathe,
Speaker 2: they have to move their bodies. So you've probably heard
Speaker 2: before that if a shark is forced to hold still,
Speaker 2: it will die. It has to swim to breathe. That
Speaker 2: is essentially true, and it's true for mantas as well.
Speaker 2: Fish that don't have to keep moving to breathe have
Speaker 2: what's known as a buckle pump system, where you use
Speaker 2: muscles around your mouth and throat to hump fresh water
Speaker 2: over the gills. Mantas don't have that. They've got to swim.
Speaker 1: Now, I do want to point out that Joe said
Speaker 1: essentially true of sharks, so's we can get into a
Speaker 1: deeper discussion maybe in another episode where we talk about
Speaker 1: the different behaviors of different types of sharks. You do
Speaker 1: have some shark varieties that live in close to the
Speaker 1: reef that are going to be that can be still
Speaker 1: for extended periods of time.
Speaker 2: Yeah, they might actually have the buckle pumping equipment. But yeah,
Speaker 2: like great white sharks, for example, don't they're ram ventilators.
Speaker 1: Exact Yes, absolutely true of great whites, but.
Speaker 2: Anyway certainly true of manta rays. They have to swim
Speaker 2: in order to breathe. They are also ram ventilators, and
Speaker 2: so this means that getting entangled in a line can
Speaker 2: be deadly to a manta. If it is stuck and
Speaker 2: it can't swim around, it can't really breathe. And this
Speaker 2: might also explain why a manta would keep swimming even
Speaker 2: when it has a boat dragging behind it. It kind
Speaker 2: of has to swim. Pair of this with a couple
Speaker 2: of other biological facts. Mantas can't swim backwards. They are
Speaker 2: highly maneuverable fish in a way. They can turn around
Speaker 2: and you see them in the water doing these beautiful
Speaker 2: summersaults and everything, but it's always with forward motion, which
Speaker 2: usually means that the line just gets even more tangled
Speaker 2: up on them as they twist and somer salt around
Speaker 2: and they would need to really be able to back
Speaker 2: up to release the line, but they can't back up.
Speaker 1: Great point.
Speaker 2: The other thing is that the manta trust says is
Speaker 2: they are often not able to see the thin line
Speaker 2: of a rope or a chain when it's directly in
Speaker 2: front of them. And so you put all this together
Speaker 2: and it easily explains how mantas can get tangled in
Speaker 2: mooring lines and can end up pulling whatever these lines
Speaker 2: are attached to. This is usually not threatening to humans,
Speaker 2: but it is very threatening to the ray. Rays often
Speaker 2: asphyxiate and die when they get caught in moorings. And
Speaker 2: so the Manta Trust has this document where they make
Speaker 2: recommendations for making mooring lines safer for mantas. You can
Speaker 2: actually look this document up on their website for the
Speaker 2: full recommendations, but they suggest a few measures, like one
Speaker 2: just reducing the presence of especially loose line in the water.
Speaker 2: Loose or slack lines are more dangerous to raise than
Speaker 2: tight lines. You can probably kind of imagine where they are, Like,
Speaker 2: a looser line is easier to get fully just tangled
Speaker 2: up in, whereas a taut line, you know, you might
Speaker 2: more likely bump into and then something can get yeah. Yeah.
Speaker 2: But then also they recommend this interesting system that I
Speaker 2: don't know if I would have thought of this, but
Speaker 2: this is cool. They recommend attaching cable ties that protrude
Speaker 2: off of mooring lines at a ninety degree angle. So
Speaker 2: you imagine, you know, something kind of like zip ties
Speaker 2: or something like that, evenly spaced every foot or so
Speaker 2: down a mooring line, and they recommend having them go
Speaker 2: out around. So there's a little bar sticking off of
Speaker 2: the side of the rope going in a spiral around
Speaker 2: the rope all the way down. And the idea here
Speaker 2: is that it will make the rope more visible to wildlife,
Speaker 2: especially they say as you use it, more algae will
Speaker 2: attach to the ends of these cable ties, and it
Speaker 2: will make them even more visible. And of course, if
Speaker 2: the rays can see the mooring lines, they.
Speaker 3: Will avoid them.
Speaker 2: They're not going to run into them on purpose.
Speaker 1: Okay, So, if I'm understanding the illustration you're attached here,
Speaker 1: it's like a spiral staircase of zip ties going up
Speaker 1: and down this particular line, and then, like you said,
Speaker 1: you'll end up with the stuff growing on those ties
Speaker 1: as well.
Speaker 2: Yeah, so it makes the rope easy to see in
Speaker 2: the water instead of just like a thin kind of
Speaker 2: line that is invisible.
Speaker 1: Sometimes that makes sense.
Speaker 2: However, at the very end here, I do want to
Speaker 2: come back with some sympathy for the sailors because obviously
Speaker 2: I think we have the correct perspective now, Like we know,
Speaker 2: rays are certainly not attacking boats. They're not trying to
Speaker 2: kidnap sailors on purpose or drag the boats. You know,
Speaker 2: they're not doing this on purpose. But you can very
Speaker 2: well you can understand how it would be frightening to
Speaker 2: have something under especially if you couldn't see it. I
Speaker 2: don't know whether it be scarier actually if you could
Speaker 2: see it or if you couldn't. If you could see
Speaker 2: it might be like a twenty foot wide manta ray.
Speaker 1: Yeah, because it's a gigantic sure, And if you don't
Speaker 1: know all the details, like we said last time, you know,
Speaker 1: it's reasonable for a human to be trepidacious about this
Speaker 1: enormous creature in the water near them or with them.
Speaker 2: Yeah, and if you can't see it, just there's something
Speaker 2: invisible under the water that's now pulling your boat around
Speaker 2: and you don't know where it's taken you. So I
Speaker 2: can understand being scared.
Speaker 3: I mean like that.
Speaker 2: I've got sympathy for that. But yeah, they're not out
Speaker 2: there trying to do this. It's just unfortunate.
Speaker 3: It happens sometimes.
Speaker 1: All right, Now, at this point of the episode, I
Speaker 1: want to come back and talk in a little more
Speaker 1: detail about manta ray reproduction because in the last episode
Speaker 1: we talked about how they're particularly vulnerable to various threats,
Speaker 1: you know, threats posed by fishing other human harms, in
Speaker 1: large part because of their slow reproductive cycle. So I
Speaker 1: wanted to get a little more into this. One of
Speaker 1: my main sources here again is Guide to the Manta
Speaker 1: and Devil Rays of the World by Stevens Fernando Dando
Speaker 1: in Dyscaria. Very good book, lots of illustrations. It's, you know,
Speaker 1: technically like a field guide. I mean, it's not laminated,
Speaker 1: you can't take it into the water with you, but
Speaker 1: it's a great field guide. And the authors here point
Speaker 1: out that there are a lot of gaps in our
Speaker 1: knowledge about manta ray and devil rae reproduction, with most
Speaker 1: of what we know coming from observations of reef mantas
Speaker 1: and limited scientific data in addition to that. So bear
Speaker 1: that in mind, and I'll tuck back in on that
Speaker 1: fact as well. But manta rays are not like most fish.
Speaker 1: That much we've already established, and it applies to their
Speaker 1: reproduction as well. Like all elasmo bronchs that's sharks and
Speaker 1: other batomorphs like rays, they practice internal fertilization rather than
Speaker 1: external fertilization, which is practiced by most fish species. So
Speaker 1: they have come so they have to come into direct
Speaker 1: contact with each other in order to mate. Right.
Speaker 2: So it's not like releasing unfertilized eggs into the water
Speaker 2: which then encounter sperm in the water and become fertilized
Speaker 2: externally like many fish do.
Speaker 1: Yeah, there's no just like swimming close to each other
Speaker 1: or both visiting the same spot at one point or
Speaker 1: another that they do have to engage and what is
Speaker 1: ultimately rather complex and kind of beautiful and maybe at
Speaker 1: times humorous mating ritual. The other amazing thing about manta
Speaker 1: reproduction is that, as with a minority of other fish species,
Speaker 1: they are live bearers, meaning they give live birth via
Speaker 1: an egg that hatches inside the female's uterus. This is
Speaker 1: known as a placental viva pair. Now, as many people
Speaker 1: have observed and some of your listeners might be thinking,
Speaker 1: this practice would seem to be yet another way that
Speaker 1: the manta rays resemble certain whale species. Yeah, you know what,
Speaker 1: large oceanic filter feeders that give live birth.
Speaker 2: Yeah, they could easily be mistaken for a mammal.
Speaker 1: Yeah, but this is not the same as live mammalian birth.
Speaker 1: And while whales rely on their mothers for the first
Speaker 1: phase of their lives, mantas are on their own from
Speaker 1: the moment they're born. They're just small versions of their
Speaker 1: parents that have to just hit the ground running, you know,
Speaker 1: not much smaller, of course, they're still they're still quite big.
Speaker 1: A newborn is typically like one point five to one
Speaker 1: point eight meters across, or like five to six feet. Whoa, yeah,
Speaker 1: and sometimes it's twins. That's a big baby, all right,
Speaker 1: So let's walk through the courtship. I said that it
Speaker 1: was beautiful and weird and sometimes funny. Again, Stevens. That
Speaker 1: all point out that there's much we don't know. This
Speaker 1: is a general description. A lot of it's based on mantas,
Speaker 1: and they are going to be species specific variations, and
Speaker 1: I believe it's possible there may be environmental differences as well,
Speaker 1: depending on where the mantas are. But in general, this
Speaker 1: is how it goes down. So a male will approach
Speaker 1: a female and he'll shadow her from above and then
Speaker 1: he may attempt to rub the top of her head
Speaker 1: with his cephalic fence the devil horns, right, and usually
Speaker 1: what's going to take place at this point is she's
Speaker 1: going to shake him. She's going to like, you know,
Speaker 1: make a quick turn and say get away from me.
Speaker 1: She's just going to reject his advances.
Speaker 2: Okay, so devil horn BackRub, and then bolt.
Speaker 1: Yeah, generally she's gonna bolt. Generally she's going to say
Speaker 1: I'm not in the mood and she's going to go in.
Speaker 1: But if she is interested, what she's going to do
Speaker 1: instead is speed forward. And then he is going to
Speaker 1: give chase. And as this chase continues, this is going
Speaker 1: to draw in other males who will also give chase.
Speaker 1: And we get another situation where we have a line
Speaker 1: of manta rays. This time of manta rays speeding through
Speaker 1: the water, you know, maybe around wreaths, and these can
Speaker 1: also kind of quickly get to our eyes out at hand,
Speaker 1: like a thirty strong zooming train of mantas that occasionally
Speaker 1: leaps out of the water as well.
Speaker 2: This is kind of like the feeding structure you talked
Speaker 2: about in the last episode. What was the name of it,
Speaker 2: It wasn't cyclone feeding, was it? That was when they
Speaker 2: form a ring and they go around and round. But
Speaker 2: last time when you talked about how there might be
Speaker 2: a big cloud of zooplankton and they're eating them, and
Speaker 2: so they line up in this row and they go
Speaker 2: through and for some reason they get more food that way.
Speaker 1: Yeah, yeah, chain feeding. So yeah, this is reminiscent of
Speaker 1: chain feeding.
Speaker 2: Except not feeding here. This is the first one is
Speaker 2: trying to mate.
Speaker 3: With the female.
Speaker 1: Well yes, well he's trying to keep up with her,
Speaker 1: and in general, she's going to try and shake loose
Speaker 1: the less fit pursuers because now she doesn't just have
Speaker 1: one manta, she may have up to thirty mantas behind her.
Speaker 1: And this is crazy too. She may loop back around
Speaker 1: and start chasing the last male in line. So now
Speaker 1: we get another like just ring, another sort of like
Speaker 1: mating cyclone here, okay or courtship cyclone I guess okay.
Speaker 1: Other females may also be swept up in these processions,
Speaker 1: which can result in one line splitting or two lines merging.
Speaker 1: They also the authors here also mentioned that that she
Speaker 1: may end up chasing another female manta as well. So
Speaker 1: this you start with one train of manta's zooming through
Speaker 1: the water, and it may go in different directions. It
Speaker 1: may split, it may merge, it may loop back around
Speaker 1: on itself, you know. And yeah, it's quite spectacular. I'm
Speaker 1: to understand fascinating. Courtship is complicated. Yeah, in the course
Speaker 1: of this, old males are going to fall fall away,
Speaker 1: they can't keep up. New mantas are going to join in.
Speaker 1: They're like, well, I'm fresh, I'm ready to go. I
Speaker 1: think I might be able to catch her. But the
Speaker 1: author's stress that she's not actually trying to lose anyone.
Speaker 1: This isn't one of those cases where where it's like
Speaker 1: she doesn't want to mate and it's just whichever male
Speaker 1: can catch her. It's not a mating pursuit like you
Speaker 1: see with other species. She's seemingly doing all of this
Speaker 1: to merely assess her suitors and determine which one is
Speaker 1: displaying the greatest level of fitness. But at the same time,
Speaker 1: the end result is going to be only one man
Speaker 1: to ray can still keep up with her.
Speaker 2: So you could look at this as a kind of
Speaker 2: mass organized mating dance of rich Yeah, yeah.
Speaker 1: Yeah, And it's very much a situation where it's the
Speaker 1: individual with the greatest degree of fitness is going to
Speaker 1: be the one that she mates with, and she absolutely
Speaker 1: has to be choosy because a lot is writing on
Speaker 1: her selection. And this comes again back to the gestation
Speaker 1: period for romantis, which takes a little over a year,
Speaker 1: and given the ups and downs of environmental factors, mainly
Speaker 1: food in the wild, she's generally not going to be
Speaker 1: able to reproduce every year anyway, Carrying such large spring
Speaker 1: to term is costly, and even when food is abundant,
Speaker 1: she's just not going to be able to do it
Speaker 1: every year, so there ends up being seasonal gaps and
Speaker 1: this generally breaks down to a pregnancy occurring every two
Speaker 1: to three years, but the authors of this book point
Speaker 1: out that the rate can be as low as once
Speaker 1: every seven years in particular environments. Wow. And another factor
Speaker 1: involved here in her choosiness is that she may reproduce,
Speaker 1: she may mate rather multiple times during the breeding season,
Speaker 1: but she's going to store sperm from multiple partners. This
Speaker 1: is something we see in other organisms as well, and
Speaker 1: then she can use the sperm she wants whenever she
Speaker 1: finally gets to fertilizer eggs whenever it's not finally the
Speaker 1: right time to fertilizer eggs.
Speaker 2: Yeah, yeah, sperm storage like this. I think we've talked
Speaker 2: about this happening in some species of sharks also, Yeah,
Speaker 2: which of course are closely related to rais.
Speaker 1: So yeah, eventually one male is going to be left.
Speaker 1: There can be only one. She's going to slow down
Speaker 1: and allow him to shadow her again, you know, it
Speaker 1: be you know, more or less a top of her
Speaker 1: shadowing her. But then he is going to bite down
Speaker 1: hard on her left wing tip, hard enough that this
Speaker 1: is going to leave scarring. You can you can identify,
Speaker 1: you know, females that have bred before in the wild
Speaker 1: because they will have this scarring on the on their
Speaker 1: left wingtip. I want to say, it's like in the
Speaker 1: high ninety percents that it's the left wing tip.
Speaker 2: Interesting.
Speaker 1: And once he's he's bit down hard on it, and
Speaker 1: I think there's a fair amount of wingtip like going
Speaker 1: into his mouth. At this point, he's going to flip
Speaker 1: so that now he's belly to belly with her, and
Speaker 1: then he's going to use one of his claspers there
Speaker 1: are two claspers on the male. It's going to use
Speaker 1: that to ejaculate sperm into her. Kloeca and then he's
Speaker 1: going to beat his pectoral fins, causing the two of
Speaker 1: them to spiral in the water. This is all going
Speaker 1: to last about thirty seconds and then they're going to
Speaker 1: go their separate ways.
Speaker 2: Wow, that's elaborate.
Speaker 1: Yeah. Yeah, there's a whole diagram in the book here
Speaker 1: showing how all of this, all this elaborate dance eventually
Speaker 1: comes to a closure.
Speaker 2: It's funny you mentioned the biting down element because this
Speaker 2: squares was something I think I was reading in preparation
Speaker 2: for the first episode that we didn't end up talking about.
Speaker 3: But the fact that that.
Speaker 2: Manta rays don't have teeth that they use for feeding,
Speaker 2: but the teeth are basically, you know, they've got these
Speaker 2: little plates, you know, sort of mighty old plates yeeahtle
Speaker 2: little tiny amounts of kind of nubby little teeth that
Speaker 2: are apparently only used in mating.
Speaker 1: At any rate, they definitely bite pretty hard. Again, there
Speaker 1: are some photos and you can look up photos of
Speaker 1: mating scars and manta rays.
Speaker 2: But so, okay, now the egg is fertilized and you
Speaker 2: would have a gestation period.
Speaker 1: Right, that's right. Yeah, more than a year of gestation
Speaker 1: follows and This is another area where we have to
Speaker 1: stress that like we don't have I believed even to
Speaker 1: this day, I don't think we have any wild observations
Speaker 1: of manda ray birth. At the time of this book's
Speaker 1: publication in twenty eighteen, there had been I think just
Speaker 1: a single incident of a recorded captive birth at the
Speaker 1: Okinawa Aquarium as in I think two thousand and seven.
Speaker 1: Since that point, I believe, the same aquarium, and in
Speaker 1: some cases the same manta ray, with the same manta ray,
Speaker 1: we've seen subsequent births, with the most recent I believe
Speaker 1: being twenty twenty four. You can look up videos. When
Speaker 1: I was looking around, there's at least one video that
Speaker 1: was easy to find. Some I think have been taken down,
Speaker 1: but you can watch as this obviously pregnant female manta ray,
Speaker 1: and sometimes you see the female manta rays in the wild.
Speaker 1: Some of the Snorkel guides that we had in Indonesia
Speaker 1: also pointed out that sometimes you'll just see a male
Speaker 1: that happens to be really bloated vaginerally, you can tell
Speaker 1: a pregnant female and yeah, you can watch the miracle
Speaker 1: of birth as this mother pushes out a rather large
Speaker 1: and ready to run Manta.
Speaker 2: I'm watching it right now. It is amazing. Wow.
Speaker 3: And oh yeah.
Speaker 2: It comes out kind of in a clump and it's
Speaker 2: not moving for a second, and suddenly it just kind
Speaker 2: of twitches and then starts jetting around.
Speaker 3: Yeah.
Speaker 1: I think I've seen this described as kind of like
Speaker 1: a burrito. Before their their fins are curled up over
Speaker 1: their backs, and you know, there's kind of like a
Speaker 1: you know, cloud of material that comes out with them,
Speaker 1: and then you know, they start moving and then they
Speaker 1: swim off and they are on their own again. The
Speaker 1: there is no mother offspring relationship here. They go their
Speaker 1: separate ways. But again, the newborn's actual egg case would
Speaker 1: have would have hatched, if to use them perhaps an
Speaker 1: incorrect term here, sometime before inside the female's uterus, and
Speaker 1: it would have subsequently fed on the mother's uterine milk,
Speaker 1: which in this case is known as histotroph.
Speaker 2: Manta ray uterine milk. I don't think we ever got
Speaker 2: into that. We did an episode or a series of
Speaker 2: episodes a ways back about non mammalian milk.
Speaker 1: Yeah, I mean it's one of those things where is
Speaker 1: it really milk? Yeah? No, no, but it kind of
Speaker 1: serves the purpose of milk.
Speaker 2: Yeah, because we talked about like dinosaurs perhaps producing a
Speaker 2: milk like substance.
Speaker 1: Yeah. Yeah, but again, this is to go back to
Speaker 1: what we were talking about in the first episode. This
Speaker 1: is all exactly the reason that manta rays have such
Speaker 1: a delicate place in their environments speacause again, long gestation period,
Speaker 1: generally a single berth, and it's not happening every year.
Speaker 1: It's you know, there are these big gaps between subsequent births.
Speaker 1: So if there's any kind of targeted fishing or any
Speaker 1: kind of factor that is that is eating into their population,
Speaker 1: it's it's harder for them to bounce back.
Speaker 3: Yeah.
Speaker 1: All right, Well we're going to go and close out
Speaker 1: this episode. We will be back with I believe one
Speaker 1: more episode on manta rays, and it should be an
Speaker 1: equally exciting one because we're going to talk about their brains,
Speaker 1: we are going to talk about their parasites, and we
Speaker 1: will talk about cleaning stations, which if you don't know
Speaker 1: much about manta cleaning stations or cleaning stations in general
Speaker 1: with other species, you might think that this sounds like
Speaker 1: the least exciting thing we could talk about, but it's
Speaker 1: actually really exciting. Yes, yes, in the meantime, definitely right
Speaker 1: into us. We would love to hear from anyone out
Speaker 1: there who has experiences encountering manta rays or other rays
Speaker 1: in the wild. Do you have any tales of tangled mantas?
Speaker 1: Have you also snorkeled or scuba dived with mantas or
Speaker 1: seen them from boats? What are your observations? Share with
Speaker 1: us your observations of the manta. Just a reminder that
Speaker 1: Stuff to Below Your Mind is primarily a science and
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Speaker 1: do a short form episode on Wednesdays, and on Fridays
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Speaker 2: As always to our excellent audio producer, Jj Posway. If
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