June 20, 2026 • 38 mins
In this series of classic episodes from Stuff to Blow Your Mind, Robert and Joe discuss the majestic manta ray, from its biology and lifecycle to conservation issues and its portrayal in mythology, folk beliefs and even 1930s horror movies. Learn all about these strange and beautiful creatures and what’s being done to ensure their survival. (originally published 7/8/2025) (part 2 of 3)
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Speaker 1 (00:06):
Hey, you welcome to Stuff to Blow your Mind. My
name is Robert Lamb. Today's Saturday. So what do we
have for you? It's gonna be The Manta Ray Part two.
This is part two of three. It originally published seven eight,
twenty twenty five. You know what a manta ray is,
but now you're going to learn even more about them.
Let's jump right in.
Speaker 2 (00:26):
Welcome to Stuff to Blow your Mind production of iHeartRadio.
Speaker 1 (00:36):
Hey you welcome to Stuff to Blow your Mind.
Speaker 2 (00:38):
My name is Robert Lamb and I am Joe McCormick,
and we're back with part two in our series on
manta rays and their close mobuld relatives. In the last
episode of this series, we kicked things off by talking
about an experience that you had rob recently where you
and your family got to see reef manta rays in
person while snorkeling in Indonesia, which sounds pretty amazing to
(01:01):
get the details on that right.
Speaker 1 (01:02):
Correct, Yes, it was. It was amazing. You know, words
can't quite describe it.
Speaker 2 (01:07):
Observing them, but not swimming quote with them. Weren't you
weren't riding the rays?
Speaker 1 (01:12):
Correct, They were doing their own thing. We were trying
to keep our distance. And observe from a distance, which
is the correct way of going about things.
Speaker 2 (01:21):
So that was what inspired us to talk about manta
rays in a series of episodes here on the show.
In the last episode, we talked about the historical evolution
of human attitudes toward manter rays with these old stories
among some divers and sailors that cast manta rays as
diabolical vampires of the sea. You know, there's one idea
(01:42):
that they will like fold over a diver like a
blanket of death. This, of course is not true, and
since it seems like since roughly the nineteen seventies there
has been more widespread recognition that mantas are gentle and
not threatening to humans, though of course that has not
stopped humans from threat them, and we talked about all
kinds of ways that human activity can hurt these animals.
(02:05):
These impacts range from accidental harms, like when mantas are
killed as bycatch in commercial fishing. It's not what people
are fishing for, but they just get caught in nets
and other lines and other things, all the way to
intentional targeting, where they are killed for their gill plates,
which some people falsely allege to have medicinal powers, and
(02:26):
in the vein of talking about tall tales of Mantas
as vicious monsters, we also discussed a couple of movies
made in the nineteen thirties that have a Killer Manta
Ray or Devil Ray as the monster.
Speaker 1 (02:38):
I didn't mention this in that episode, but it's worth
noting that, you, of course have one of Aquaman's arch
enemies is Black Manta, so you know, it's the perfect
mantle for a villain that was conceived. I believe in
this era you also have Man Ray, which is a
villain based on Black Manta that pops up on SpongeBob SquarePants,
(02:58):
not to be confused with the the artist Man Ray.
Speaker 2 (03:02):
I think Black Manta is actually in the Aquaman movie
with cal Drogo in it, isn't it.
Speaker 1 (03:08):
Oh yeah, yeah, who plays Black Manta? I don't I
haven't seen any of those films.
Speaker 2 (03:13):
I don't remember any of the cast of that movie,
except in Nicole Kidman in a really funny looking costume.
So I you know, folks out there, No, I'm not
the biggest superhero movie fan. I haven't kept up with
all of the Marvel and DC superhero films, but I
think I watched Aquaman on a plane for some reason.
I remember thinking it was really funny, like highly amusing.
(03:36):
Oh no, wait, I remember another cast member had Patrick
Wilson like riding on a shark and saying, you will
call me ocean master.
Speaker 1 (03:46):
I need to watch those on an airplane sometime.
Speaker 2 (03:48):
Yes, Jason Momoa, I'm sorry I called him cal Droco.
Speaker 3 (03:51):
That's not nice. His name is Jason Momoa.
Speaker 1 (03:54):
Suffice to say, however, the Western American slash European conceptions
of the manta ray and related species have evolved since
basically the nineteen seventies the nineteen seventies onward. Everyone has
come to realize that manta rays are peaceful giants of
the ocean and they are not out to eat.
Speaker 2 (04:15):
Us, right, And so we also talked about modern conservation
efforts aimed at protecting mantas. You know, we got into
like the cost benefit analysis that has to be done
if you're considering building something like an ecological tourism trade
around them. You know, there are risks but also potentially rewards.
And we also talked about the basic biology of manta
rays and their near relatives, their near relatives being the
(04:38):
devil rays, mantas and devil rays together make up the
genus Mobula, And we got into subjects including their body design,
common feeding strategies, and leaping or breaching behavior where they
jump out of the water and slap back down. We
talked about some reasons they might do that, and we're
back today to talk about more.
Speaker 1 (04:57):
Yeah, and we're gonna pick up in an interest. You're
going to get into some more myths or potential myths
about their behavior and what we may or may not
know about those behaviors.
Speaker 2 (05:09):
Now right, well, I think this might be slightly different
because it would be truths about their behavior with mythical interpretations,
if that makes any sense. So in the last episode,
we were talking about these incorrect folk beliefs about the
man array. You know that they would attack boats or
attack divers in the form of this underwater death blanket.
(05:30):
And as a source there, I referenced an old article
called the Story of the Devilfish from the ear Way
back in the year nineteen ten by the American biologist
Theodore gil There was another thread in this article that
I found interesting and I wanted to come back to
it today. So if you'll recall from last time in
this article Gil, He's very dismissive of the belief that
(05:52):
the manta tries to smother divers with its body or
devour them with its gaping mouth. He points out that
the manta is a filter feeder which eats tiny planktonic organisms.
It does not eat large prey. There's no evidence of
manta's targeting humans for violence, and they don't even have
the right biological equipment to eat us if they were
(06:12):
going to try to do that, which they're not going
to try. But there is another part of the manta's
more frightening reputation in pre modern times, which is the
belief that mantas will attack boats, not divers, but boats,
particularly the claim that a manta will drag a boat
out to sea by the anchor line. So here I'm
(06:34):
going to read a passage from Gill's article quote in
one of the earliest notices of the devilfish by John
Lawson in the History of Carolina seventeen fourteen. This peculiarity
is described the devilfish, he says, has been known to
weigh a ship's anchor and run with the vessel a
league or two and bring her back against tide to
(06:56):
almost the same place, but then the quote ends in
guild on to say later notices do not give the
animal credit for the same accommodating treatment, And he later
alludes to these other accounts that tell of the devilfish
pulling sailing boats around by the anchor to the wonder
and fear of the sailors, and he also cites a
(07:17):
more recent source to him at the time of his writing.
This was a French naturalist named Leon de Guett describing
the activity of pearl fishers in the Gulf of California
in a text from eighteen ninety eight, and according to Deguet,
when fishers are caught out at sea overnight in the
Gulf of California, away from their usual mooring places, he
(07:41):
says they will always drop two anchors, because they fear
that if they only drop one, the anchor line will
be seized by the devilfish in the dark, and thus
the boat will be carried away into the open sea.
And to get back to this up with his own observation,
telling a story of how he was sent out to
harpoon a specimen of a devil ray for the Natural
(08:03):
History Museum of Paris, and he says, quote after one
had been harpooned, it turned back on the boat, seized
the bow with its head fins, and held it in
its clasp till it was lanced the second time. So
that's Deget's account, But Gil says even this direct observation
(08:23):
does not really lend credence to the idea that mantas
or devil rays deliberately attack, detain or hijack boats, because
based on his own study, Gil writes that this kind
of grasping with the headfins is automatic. He says, it's
an involuntary muscular reaction when something is in front of
(08:44):
the ray's mouth, so in this case it might happen
to be the bow of the harpooner's boat, and so
even when it's being attacked by somebody on the boat,
when it's being harpooned, Gil argues that the ray was
probably not actually trying to harm the boat, but rather
is just being pulled toward the boat by the tension
of the rope on the harpoon it had just been
(09:05):
lanced with. And even to get himself the person originally
telling the story of it seizing the bow of the boat,
he says the devilfishes are generally timid, non aggressive animals.
Though then, after saying this confusingly to get does seem open,
he sort of opens up more claims of devilfish savagery
and alleges that in the Gulf of California quote, numerous
(09:28):
cases have occurred of death resulting to divers as well
as bathers from encounters with the devilfish or manta as
the men call it. On the other hand, the carcasses
of many that are killed are used for bait for
other fishes. The strange detail to include.
Speaker 1 (09:45):
Yeah, yeah, I mean all of this is the pardon
the terminology here at fishy because.
Speaker 2 (09:51):
Dubious the third hand, Yeah.
Speaker 1 (09:53):
Yeah, I mean, because everything we know and have been
discussing about rays, when they're threatened, they use a bir
to speed they get away. That's their major way of
defending themselves. So it doesn't really make sense based on
what we know that they would turn around an attack
of a ship or a boat, even if they are
being acted upon with harpoons.
Speaker 2 (10:15):
Right, and as we discussed last time, of course, they
are large animals, and any large animal could potentially hurt
you just by bumping into you. Wrong, but there is
really no evidence I could find of manta's being aggressive
towards humans except for these like old third hand stories.
Speaker 3 (10:32):
Yeah.
Speaker 1 (10:32):
And I don't know if Gil gets into this or no,
butical for one of the things with you get into
oral histories of things like the devilfish the manta, you
end up having to ask questions, well, is the manta
in this story, even if there's a kernel of truth
to it, is it indeed talking about the species that
we are talking about as the manta ray, or is
(10:54):
it referring to something else real or imagined.
Speaker 2 (10:56):
Yeah, so, even back in nineteen ten, Gill to me
seems skeptical of these claims about it attacking boats. Certainly,
modern researchers are skeptical of these stories of manterray aggression
towards boats. But to the question of dragging boats, specifically
by the anchor cable, is this just a tall tale
like the mantray death blanket story or is there something
(11:19):
more to that? Is there any modern evidence of things
like this happening? The answer to this is yes. For example,
I found a Reuter's article from February eleventh, nineteen ninety nine,
called motor boat no match for manterray in Tug of War.
Speaker 1 (11:34):
Well, I generally, you know, I generally trust Reuters in
their reporting, though usual usually I'm not reading about the
marine biology. When I'm reading Reuters, usually it's a nice,
you know, doom scroll into the abyss. So I missed
this one when it came out. If I was in
fact reading Routers at the time.
Speaker 2 (11:54):
I'll read from the beginning of the article and then
summarize some other parts of it and we can make
up our minds about it. Okay, what's going on here?
So Dateline New Smurta Beach, Florida. Two Florida boaters met
a real sea monster when their craft was dragged for
hours by a powerful creature that turned out to be
a giant manta ray, the Coastguard said Wednesday. Coastguard Petty
(12:14):
Officer Scott Barnes said the agency received a radio distress
call from a sixteen foot boat that reported it was
being dragged by its anchor line by something unknown. The
Coastguard sent a rescue boat to investigate and found the
motor boat was being dragged in circles by something beneath
the surface. The crew transferred the anchor line to the
Coastguard vessel, freeing the men in the motor boat who
(12:37):
had tried to use their ninety horsepower engine to go
in reverse and stop themselves from being dragged out to sea.
After the Coastguard's forty one foot boat pulled the anchor
line for several minutes, a giant manta ray measuring an
estimated eighteen feet in width, came to the surface, and
then the article goes on to describe how the Coastguard
struggled to pull the rope away. Eventually, the manta was
(13:00):
able to disentangle itself from the rope and it swam
away on its own, and by the end of the ordeal,
the manta, they estimate, had pulled the boat for almost
two hours, taking it about a mile and a half
away from shore. But you could easily get the wrong
idea about this, thinking that it supports this old notion
that mantas will attack boats, that they are doing this
(13:24):
on purpose, they're trying to drag the sailors out to sea,
out to their deaths or something. From what I've read,
there is absolutely zero evidence to support the idea that
the mantas are acting aggressively when they pull a boat
by the anchor line. The zero evidence that they're acting
aggressively or even acting intentionally. Rather, this is almost certainly
(13:45):
a case of manta's getting stuck. They are getting tangled
in underwater ropes and chains by accident and then pulling
the boat because they are unable to free themselves. And
when you look at their heads, you look up a
picture of a manta ray or a devil ray, you
can see how this might easily happen. They almost have
biological mooring cleats with their cephalic fins.
Speaker 1 (14:09):
Yeah, yeah, you can imagine them, you know, catching the line.
Speaker 2 (14:22):
For one more example of a modern encounter, I found
a video on YouTube that the title begins with Giant
manta ray tangled in anchorchain, forty miles off shore. This
is a video of some people out in a fishing
boat in the Gulf of Mexico and a manta does
get caught in their anchor line. Like it looks when
you can see it, it looks like the line is not
(14:44):
just caught between the cephalic fins, but kind of wrapped
around them, like the lobes on its head have the
line going across as well as between, and you can
see it struggling. At a couple of points in this video.
It quite strangely, it almost seems to be coming up
to the surface and holding still while the fishermen are
(15:04):
trying to get it untangled. Then weirdly kind of matches.
But then I don't know how to interpret what I'm
seeing there, so maybe it shouldn't be taken this way.
But it kind of reminds me of all these stories
people talk about of manta rays being very like, kind
of slow moving and gentle while they come up to
them and almost kind of letting people, you know, interact
with them. Again, not encouraging people to do that unless
(15:25):
you're trying to free one from a problem you've created.
But anyway, in the end here the people in the
boat are able to succeed by they sever the line
in one place and that allows them to get it
unwrapped from around the manta and they let the manta
swim away. So it seems like the manta gets away
in the end of this, which is heartwarming. In fact,
all these like bro fishermen are like high five in
(15:47):
each other. They're like, yeah, we did it.
Speaker 3 (15:50):
It's sweet.
Speaker 2 (15:51):
But once again seems like a quite clear case of
like the manta is not doing this on purpose. It's
not out here today. Thing say, and I'd like to
drag a boat around it ended up in this situation
against its will.
Speaker 3 (16:03):
Yeah.
Speaker 1 (16:04):
Yeah, Like you said, the cephalic fins are kind of
look like natural line catchers. And then they're also just
quite I mean, they're they're wing shaped, they're they're they're
quite wide. We've talked about their their wingspans, and yeah,
that's just more real estate to potentially run into a line.
Speaker 2 (16:21):
Yeah. And so Gil talks about this in his article
and says that these the cephalic fins or cephalic lobes
the kind of horns of the devilfish.
Speaker 3 (16:31):
Uh.
Speaker 2 (16:31):
They they're like an elephant's trunk. He quotes another author
saying that then they can kind of grasp objects and
pull them in. He says they tend to rapidly kind
of close in around the mouth when something appears in
front of the mouth and uh, and that the the
fish will have a kind of obstinacy in, you know,
(16:52):
refusing to release things that go in like that. Gil
says quote that these arms are muscular and powerful has
been dim on many occasions. The natural movement of the
head fins or corropteries is inward and when any object
strikes between them, it is instinctively held a proceeding which
explains the undoubted fact that these fishes can run away
(17:14):
with quite large vessels. So Gill's chalking this up to
involuntary motion of the strong cephalic fins closing over things
that hit in the front of the mouth, which occasionally,
in some unlucky circumstances, just happens to be an anchor line.
I think Gil is absolutely correct that these boat dragging
(17:35):
incidents are not aggressive or intentional on the part of
the ray, but is he correct about the mechanism. I
was looking for modern sources and couldn't really find anything
to confirm or deny his ideas there about the specific
motion of the cephalic fins being involved. But I did
find some commentary from more recent marine biology resources, specifically
(17:58):
something from the organization known as the Manta Trust, which
has a page on the subject of manta mooring line entanglements,
and they highlight some different biological facts which make mooring
line entanglements common for manta rays. Manta rays, like their
cousins sharks, and also like tuna, are obligate ram ventilators,
(18:23):
meaning they do not have the biological equipment needed to
pump water over their gills when their bodies are at rest.
So in order to make water flow over their gills
so they can extract oxygen from the water and breathe,
they have to move their bodies. So you've probably heard
before that if a shark is forced to hold still,
(18:45):
it will die. It has to swim to breathe. That
is essentially true, and it's true for mantas as well.
Fish that don't have to keep moving to breathe have
what's known as a buckle pump system, where you use
muscles around your mouth and throat to hump fresh water
over the gills. Mantas don't have that. They've got to swim.
Speaker 1 (19:04):
Now, I do want to point out that Joe said
essentially true of sharks, so's we can get into a
deeper discussion maybe in another episode where we talk about
the different behaviors of different types of sharks. You do
have some shark varieties that live in close to the
reef that are going to be that can be still
for extended periods of time.
Speaker 2 (19:24):
Yeah, they might actually have the buckle pumping equipment. But yeah,
like great white sharks, for example, don't they're ram ventilators.
Speaker 1 (19:32):
Exact Yes, absolutely true of great whites, but.
Speaker 2 (19:35):
Anyway certainly true of manta rays. They have to swim
in order to breathe. They are also ram ventilators, and
so this means that getting entangled in a line can
be deadly to a manta. If it is stuck and
it can't swim around, it can't really breathe. And this
might also explain why a manta would keep swimming even
when it has a boat dragging behind it. It kind
(19:57):
of has to swim. Pair of this with a couple
of other biological facts. Mantas can't swim backwards. They are
highly maneuverable fish in a way. They can turn around
and you see them in the water doing these beautiful
summersaults and everything, but it's always with forward motion, which
usually means that the line just gets even more tangled
(20:19):
up on them as they twist and somer salt around
and they would need to really be able to back
up to release the line, but they can't back up.
Speaker 1 (20:28):
Great point.
Speaker 2 (20:29):
The other thing is that the manta trust says is
they are often not able to see the thin line
of a rope or a chain when it's directly in
front of them. And so you put all this together
and it easily explains how mantas can get tangled in
mooring lines and can end up pulling whatever these lines
are attached to. This is usually not threatening to humans,
(20:51):
but it is very threatening to the ray. Rays often
asphyxiate and die when they get caught in moorings. And
so the Manta Trust has this document where they make
recommendations for making mooring lines safer for mantas. You can
actually look this document up on their website for the
full recommendations, but they suggest a few measures, like one
just reducing the presence of especially loose line in the water.
(21:16):
Loose or slack lines are more dangerous to raise than
tight lines. You can probably kind of imagine where they are, Like,
a looser line is easier to get fully just tangled
up in, whereas a taut line, you know, you might
more likely bump into and then something can get yeah. Yeah.
But then also they recommend this interesting system that I
(21:36):
don't know if I would have thought of this, but
this is cool. They recommend attaching cable ties that protrude
off of mooring lines at a ninety degree angle. So
you imagine, you know, something kind of like zip ties
or something like that, evenly spaced every foot or so
down a mooring line, and they recommend having them go
(21:58):
out around. So there's a little bar sticking off of
the side of the rope going in a spiral around
the rope all the way down. And the idea here
is that it will make the rope more visible to wildlife,
especially they say as you use it, more algae will
attach to the ends of these cable ties, and it
will make them even more visible. And of course, if
(22:20):
the rays can see the mooring lines, they.
Speaker 3 (22:22):
Will avoid them.
Speaker 2 (22:23):
They're not going to run into them on purpose.
Speaker 1 (22:25):
Okay, So, if I'm understanding the illustration you're attached here,
it's like a spiral staircase of zip ties going up
and down this particular line, and then, like you said,
you'll end up with the stuff growing on those ties
as well.
Speaker 2 (22:38):
Yeah, so it makes the rope easy to see in
the water instead of just like a thin kind of
line that is invisible.
Speaker 1 (22:44):
Sometimes that makes sense.
Speaker 2 (22:46):
However, at the very end here, I do want to
come back with some sympathy for the sailors because obviously
I think we have the correct perspective now, Like we know,
rays are certainly not attacking boats. They're not trying to
kidnap sailors on purpose or drag the boats. You know,
they're not doing this on purpose. But you can very
well you can understand how it would be frightening to
(23:07):
have something under especially if you couldn't see it. I
don't know whether it be scarier actually if you could
see it or if you couldn't. If you could see
it might be like a twenty foot wide manta ray.
Speaker 1 (23:15):
Yeah, because it's a gigantic sure, And if you don't
know all the details, like we said last time, you know,
it's reasonable for a human to be trepidacious about this
enormous creature in the water near them or with them.
Speaker 2 (23:26):
Yeah, and if you can't see it, just there's something
invisible under the water that's now pulling your boat around
and you don't know where it's taken you. So I
can understand being scared.
Speaker 3 (23:34):
I mean like that.
Speaker 2 (23:35):
I've got sympathy for that. But yeah, they're not out
there trying to do this. It's just unfortunate.
Speaker 3 (23:40):
It happens sometimes.
Speaker 1 (23:51):
All right, Now, at this point of the episode, I
want to come back and talk in a little more
detail about manta ray reproduction because in the last episode
we talked about how they're particularly vulnerable to various threats,
you know, threats posed by fishing other human harms, in
large part because of their slow reproductive cycle. So I
wanted to get a little more into this. One of
(24:14):
my main sources here again is Guide to the Manta
and Devil Rays of the World by Stevens Fernando Dando
in Dyscaria. Very good book, lots of illustrations. It's, you know,
technically like a field guide. I mean, it's not laminated,
you can't take it into the water with you, but
it's a great field guide. And the authors here point
(24:36):
out that there are a lot of gaps in our
knowledge about manta ray and devil rae reproduction, with most
of what we know coming from observations of reef mantas
and limited scientific data in addition to that. So bear
that in mind, and I'll tuck back in on that
fact as well. But manta rays are not like most fish.
(24:58):
That much we've already established, and it applies to their
reproduction as well. Like all elasmo bronchs that's sharks and
other batomorphs like rays, they practice internal fertilization rather than
external fertilization, which is practiced by most fish species. So
they have come so they have to come into direct
(25:18):
contact with each other in order to mate. Right.
Speaker 2 (25:21):
So it's not like releasing unfertilized eggs into the water
which then encounter sperm in the water and become fertilized
externally like many fish do.
Speaker 1 (25:30):
Yeah, there's no just like swimming close to each other
or both visiting the same spot at one point or
another that they do have to engage and what is
ultimately rather complex and kind of beautiful and maybe at
times humorous mating ritual. The other amazing thing about manta
reproduction is that, as with a minority of other fish species,
they are live bearers, meaning they give live birth via
(25:54):
an egg that hatches inside the female's uterus. This is
known as a placental viva pair. Now, as many people
have observed and some of your listeners might be thinking,
this practice would seem to be yet another way that
the manta rays resemble certain whale species. Yeah, you know what,
large oceanic filter feeders that give live birth.
Speaker 2 (26:14):
Yeah, they could easily be mistaken for a mammal.
Speaker 1 (26:17):
Yeah, but this is not the same as live mammalian birth.
And while whales rely on their mothers for the first
phase of their lives, mantas are on their own from
the moment they're born. They're just small versions of their
parents that have to just hit the ground running, you know,
not much smaller, of course, they're still they're still quite big.
(26:38):
A newborn is typically like one point five to one
point eight meters across, or like five to six feet. Whoa, yeah,
and sometimes it's twins. That's a big baby, all right,
So let's walk through the courtship. I said that it
was beautiful and weird and sometimes funny. Again, Stevens. That
all point out that there's much we don't know. This
is a general description. A lot of it's based on mantas,
(27:00):
and they are going to be species specific variations, and
I believe it's possible there may be environmental differences as well,
depending on where the mantas are. But in general, this
is how it goes down. So a male will approach
a female and he'll shadow her from above and then
he may attempt to rub the top of her head
(27:21):
with his cephalic fence the devil horns, right, and usually
what's going to take place at this point is she's
going to shake him. She's going to like, you know,
make a quick turn and say get away from me.
She's just going to reject his advances.
Speaker 2 (27:32):
Okay, so devil horn BackRub, and then bolt.
Speaker 1 (27:35):
Yeah, generally she's gonna bolt. Generally she's going to say
I'm not in the mood and she's going to go in.
But if she is interested, what she's going to do
instead is speed forward. And then he is going to
give chase. And as this chase continues, this is going
to draw in other males who will also give chase.
And we get another situation where we have a line
(27:57):
of manta rays. This time of manta rays speeding through
the water, you know, maybe around wreaths, and these can
also kind of quickly get to our eyes out at hand,
like a thirty strong zooming train of mantas that occasionally
leaps out of the water as well.
Speaker 2 (28:16):
This is kind of like the feeding structure you talked
about in the last episode. What was the name of it,
It wasn't cyclone feeding, was it? That was when they
form a ring and they go around and round. But
last time when you talked about how there might be
a big cloud of zooplankton and they're eating them, and
so they line up in this row and they go
through and for some reason they get more food that way.
Speaker 1 (28:38):
Yeah, yeah, chain feeding. So yeah, this is reminiscent of
chain feeding.
Speaker 2 (28:42):
Except not feeding here. This is the first one is
trying to mate.
Speaker 3 (28:45):
With the female.
Speaker 1 (28:47):
Well yes, well he's trying to keep up with her,
and in general, she's going to try and shake loose
the less fit pursuers because now she doesn't just have
one manta, she may have up to thirty mantas behind her.
And this is crazy too. She may loop back around
and start chasing the last male in line. So now
we get another like just ring, another sort of like
(29:10):
mating cyclone here, okay or courtship cyclone I guess okay.
Other females may also be swept up in these processions,
which can result in one line splitting or two lines merging.
They also the authors here also mentioned that that she
may end up chasing another female manta as well. So
this you start with one train of manta's zooming through
(29:32):
the water, and it may go in different directions. It
may split, it may merge, it may loop back around
on itself, you know. And yeah, it's quite spectacular. I'm
to understand fascinating. Courtship is complicated. Yeah, in the course
of this, old males are going to fall fall away,
they can't keep up. New mantas are going to join in.
They're like, well, I'm fresh, I'm ready to go. I
(29:53):
think I might be able to catch her. But the
author's stress that she's not actually trying to lose anyone.
This isn't one of those cases where where it's like
she doesn't want to mate and it's just whichever male
can catch her. It's not a mating pursuit like you
see with other species. She's seemingly doing all of this
to merely assess her suitors and determine which one is
(30:13):
displaying the greatest level of fitness. But at the same time,
the end result is going to be only one man
to ray can still keep up with her.
Speaker 2 (30:22):
So you could look at this as a kind of
mass organized mating dance of rich Yeah, yeah.
Speaker 1 (30:29):
Yeah, And it's very much a situation where it's the
individual with the greatest degree of fitness is going to
be the one that she mates with, and she absolutely
has to be choosy because a lot is writing on
her selection. And this comes again back to the gestation
period for romantis, which takes a little over a year,
(30:50):
and given the ups and downs of environmental factors, mainly
food in the wild, she's generally not going to be
able to reproduce every year anyway, Carrying such large spring
to term is costly, and even when food is abundant,
she's just not going to be able to do it
every year, so there ends up being seasonal gaps and
this generally breaks down to a pregnancy occurring every two
to three years, but the authors of this book point
(31:14):
out that the rate can be as low as once
every seven years in particular environments. Wow. And another factor
involved here in her choosiness is that she may reproduce,
she may mate rather multiple times during the breeding season,
but she's going to store sperm from multiple partners. This
is something we see in other organisms as well, and
(31:36):
then she can use the sperm she wants whenever she
finally gets to fertilizer eggs whenever it's not finally the
right time to fertilizer eggs.
Speaker 2 (31:44):
Yeah, yeah, sperm storage like this. I think we've talked
about this happening in some species of sharks also, Yeah,
which of course are closely related to rais.
Speaker 1 (31:52):
So yeah, eventually one male is going to be left.
There can be only one. She's going to slow down
and allow him to shadow her again, you know, it
be you know, more or less a top of her
shadowing her. But then he is going to bite down
hard on her left wing tip, hard enough that this
is going to leave scarring. You can you can identify,
(32:13):
you know, females that have bred before in the wild
because they will have this scarring on the on their
left wingtip. I want to say, it's like in the
high ninety percents that it's the left wing tip.
Speaker 2 (32:23):
Interesting.
Speaker 1 (32:25):
And once he's he's bit down hard on it, and
I think there's a fair amount of wingtip like going
into his mouth. At this point, he's going to flip
so that now he's belly to belly with her, and
then he's going to use one of his claspers there
are two claspers on the male. It's going to use
that to ejaculate sperm into her. Kloeca and then he's
going to beat his pectoral fins, causing the two of
(32:45):
them to spiral in the water. This is all going
to last about thirty seconds and then they're going to
go their separate ways.
Speaker 2 (32:51):
Wow, that's elaborate.
Speaker 1 (32:53):
Yeah. Yeah, there's a whole diagram in the book here
showing how all of this, all this elaborate dance eventually
comes to a closure.
Speaker 2 (33:01):
It's funny you mentioned the biting down element because this
squares was something I think I was reading in preparation
for the first episode that we didn't end up talking about.
Speaker 3 (33:10):
But the fact that that.
Speaker 2 (33:12):
Manta rays don't have teeth that they use for feeding,
but the teeth are basically, you know, they've got these
little plates, you know, sort of mighty old plates yeeahtle
little tiny amounts of kind of nubby little teeth that
are apparently only used in mating.
Speaker 1 (33:28):
At any rate, they definitely bite pretty hard. Again, there
are some photos and you can look up photos of
mating scars and manta rays.
Speaker 2 (33:35):
But so, okay, now the egg is fertilized and you
would have a gestation period.
Speaker 1 (33:39):
Right, that's right. Yeah, more than a year of gestation
follows and This is another area where we have to
stress that like we don't have I believed even to
this day, I don't think we have any wild observations
of manda ray birth. At the time of this book's
publication in twenty eighteen, there had been I think just
a single incident of a recorded captive birth at the
(34:03):
Okinawa Aquarium as in I think two thousand and seven.
Since that point, I believe, the same aquarium, and in
some cases the same manta ray, with the same manta ray,
we've seen subsequent births, with the most recent I believe
being twenty twenty four. You can look up videos. When
I was looking around, there's at least one video that
was easy to find. Some I think have been taken down,
(34:25):
but you can watch as this obviously pregnant female manta ray,
and sometimes you see the female manta rays in the wild.
Some of the Snorkel guides that we had in Indonesia
also pointed out that sometimes you'll just see a male
that happens to be really bloated vaginerally, you can tell
a pregnant female and yeah, you can watch the miracle
(34:45):
of birth as this mother pushes out a rather large
and ready to run Manta.
Speaker 2 (34:53):
I'm watching it right now. It is amazing. Wow.
Speaker 3 (34:56):
And oh yeah.
Speaker 2 (34:57):
It comes out kind of in a clump and it's
not moving for a second, and suddenly it just kind
of twitches and then starts jetting around.
Speaker 3 (35:04):
Yeah.
Speaker 1 (35:05):
I think I've seen this described as kind of like
a burrito. Before their their fins are curled up over
their backs, and you know, there's kind of like a
you know, cloud of material that comes out with them,
and then you know, they start moving and then they
swim off and they are on their own again. The
there is no mother offspring relationship here. They go their
(35:26):
separate ways. But again, the newborn's actual egg case would
have would have hatched, if to use them perhaps an
incorrect term here, sometime before inside the female's uterus, and
it would have subsequently fed on the mother's uterine milk,
which in this case is known as histotroph.
Speaker 2 (35:46):
Manta ray uterine milk. I don't think we ever got
into that. We did an episode or a series of
episodes a ways back about non mammalian milk.
Speaker 1 (35:54):
Yeah, I mean it's one of those things where is
it really milk? Yeah? No, no, but it kind of
serves the purpose of milk.
Speaker 2 (36:02):
Yeah, because we talked about like dinosaurs perhaps producing a
milk like substance.
Speaker 1 (36:07):
Yeah. Yeah, but again, this is to go back to
what we were talking about in the first episode. This
is all exactly the reason that manta rays have such
a delicate place in their environments speacause again, long gestation period,
generally a single berth, and it's not happening every year.
It's you know, there are these big gaps between subsequent births.
So if there's any kind of targeted fishing or any
(36:29):
kind of factor that is that is eating into their population,
it's it's harder for them to bounce back.
Speaker 3 (36:37):
Yeah.
Speaker 1 (36:37):
All right, Well we're going to go and close out
this episode. We will be back with I believe one
more episode on manta rays, and it should be an
equally exciting one because we're going to talk about their brains,
we are going to talk about their parasites, and we
will talk about cleaning stations, which if you don't know
much about manta cleaning stations or cleaning stations in general
with other species, you might think that this sounds like
(36:59):
the least exciting thing we could talk about, but it's
actually really exciting. Yes, yes, in the meantime, definitely right
into us. We would love to hear from anyone out
there who has experiences encountering manta rays or other rays
in the wild. Do you have any tales of tangled mantas?
Have you also snorkeled or scuba dived with mantas or
(37:22):
seen them from boats? What are your observations? Share with
us your observations of the manta. Just a reminder that
Stuff to Below Your Mind is primarily a science and
culture podcast with core episodes on Tuesdays and Thursdays. We
do a short form episode on Wednesdays, and on Fridays
we set aside most serious concerns to just talk about
a weird film on Weird House Cinema. You can get
the podcast wherever you get podcasts these days, wherever that
(37:44):
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give us some stars. That always helps us out. You
can follow us on social media in various places, and
we're still trying to build up our Instagram followers. If
you use Instagram, find us as STBYM podcast Huge Things.
Speaker 2 (38:00):
As always to our excellent audio producer, Jj Posway. If
you would like to get in touch with us with
feedback on this episode or any other, to suggest a
topic for the future, or just to say hello. You
can email us at contact at stuff to Blow your
Mind dot com. Stuff to Blow Your Mind is production
(38:23):
of iHeartRadio. For more podcasts from my heart Radio, visit
the iHeartRadio app, Apple Podcasts, or wherever you're listening to
your favorite shows.
Hey, you welcome to Stuff to Blow your Mind. My
name is Robert Lamb. Today's Saturday. So what do we
have for you? It's gonna be The Manta Ray Part two.
This is part two of three. It originally published seven eight,
twenty twenty five. You know what a manta ray is,
but now you're going to learn even more about them.
Let's jump right in.
Speaker 2 (00:26):
Welcome to Stuff to Blow your Mind production of iHeartRadio.
Speaker 1 (00:36):
Hey you welcome to Stuff to Blow your Mind.
Speaker 2 (00:38):
My name is Robert Lamb and I am Joe McCormick,
and we're back with part two in our series on
manta rays and their close mobuld relatives. In the last
episode of this series, we kicked things off by talking
about an experience that you had rob recently where you
and your family got to see reef manta rays in
person while snorkeling in Indonesia, which sounds pretty amazing to
(01:01):
get the details on that right.
Speaker 1 (01:02):
Correct, Yes, it was. It was amazing. You know, words
can't quite describe it.
Speaker 2 (01:07):
Observing them, but not swimming quote with them. Weren't you
weren't riding the rays?
Speaker 1 (01:12):
Correct, They were doing their own thing. We were trying
to keep our distance. And observe from a distance, which
is the correct way of going about things.
Speaker 2 (01:21):
So that was what inspired us to talk about manta
rays in a series of episodes here on the show.
In the last episode, we talked about the historical evolution
of human attitudes toward manter rays with these old stories
among some divers and sailors that cast manta rays as
diabolical vampires of the sea. You know, there's one idea
(01:42):
that they will like fold over a diver like a
blanket of death. This, of course is not true, and
since it seems like since roughly the nineteen seventies there
has been more widespread recognition that mantas are gentle and
not threatening to humans, though of course that has not
stopped humans from threat them, and we talked about all
kinds of ways that human activity can hurt these animals.
(02:05):
These impacts range from accidental harms, like when mantas are
killed as bycatch in commercial fishing. It's not what people
are fishing for, but they just get caught in nets
and other lines and other things, all the way to
intentional targeting, where they are killed for their gill plates,
which some people falsely allege to have medicinal powers, and
(02:26):
in the vein of talking about tall tales of Mantas
as vicious monsters, we also discussed a couple of movies
made in the nineteen thirties that have a Killer Manta
Ray or Devil Ray as the monster.
Speaker 1 (02:38):
I didn't mention this in that episode, but it's worth
noting that, you, of course have one of Aquaman's arch
enemies is Black Manta, so you know, it's the perfect
mantle for a villain that was conceived. I believe in
this era you also have Man Ray, which is a
villain based on Black Manta that pops up on SpongeBob SquarePants,
(02:58):
not to be confused with the the artist Man Ray.
Speaker 2 (03:02):
I think Black Manta is actually in the Aquaman movie
with cal Drogo in it, isn't it.
Speaker 1 (03:08):
Oh yeah, yeah, who plays Black Manta? I don't I
haven't seen any of those films.
Speaker 2 (03:13):
I don't remember any of the cast of that movie,
except in Nicole Kidman in a really funny looking costume.
So I you know, folks out there, No, I'm not
the biggest superhero movie fan. I haven't kept up with
all of the Marvel and DC superhero films, but I
think I watched Aquaman on a plane for some reason.
I remember thinking it was really funny, like highly amusing.
(03:36):
Oh no, wait, I remember another cast member had Patrick
Wilson like riding on a shark and saying, you will
call me ocean master.
Speaker 1 (03:46):
I need to watch those on an airplane sometime.
Speaker 2 (03:48):
Yes, Jason Momoa, I'm sorry I called him cal Droco.
Speaker 3 (03:51):
That's not nice. His name is Jason Momoa.
Speaker 1 (03:54):
Suffice to say, however, the Western American slash European conceptions
of the manta ray and related species have evolved since
basically the nineteen seventies the nineteen seventies onward. Everyone has
come to realize that manta rays are peaceful giants of
the ocean and they are not out to eat.
Speaker 2 (04:15):
Us, right, And so we also talked about modern conservation
efforts aimed at protecting mantas. You know, we got into
like the cost benefit analysis that has to be done
if you're considering building something like an ecological tourism trade
around them. You know, there are risks but also potentially rewards.
And we also talked about the basic biology of manta
rays and their near relatives, their near relatives being the
(04:38):
devil rays, mantas and devil rays together make up the
genus Mobula, And we got into subjects including their body design,
common feeding strategies, and leaping or breaching behavior where they
jump out of the water and slap back down. We
talked about some reasons they might do that, and we're
back today to talk about more.
Speaker 1 (04:57):
Yeah, and we're gonna pick up in an interest. You're
going to get into some more myths or potential myths
about their behavior and what we may or may not
know about those behaviors.
Speaker 2 (05:09):
Now right, well, I think this might be slightly different
because it would be truths about their behavior with mythical interpretations,
if that makes any sense. So in the last episode,
we were talking about these incorrect folk beliefs about the
man array. You know that they would attack boats or
attack divers in the form of this underwater death blanket.
(05:30):
And as a source there, I referenced an old article
called the Story of the Devilfish from the ear Way
back in the year nineteen ten by the American biologist
Theodore gil There was another thread in this article that
I found interesting and I wanted to come back to
it today. So if you'll recall from last time in
this article Gil, He's very dismissive of the belief that
(05:52):
the manta tries to smother divers with its body or
devour them with its gaping mouth. He points out that
the manta is a filter feeder which eats tiny planktonic organisms.
It does not eat large prey. There's no evidence of
manta's targeting humans for violence, and they don't even have
the right biological equipment to eat us if they were
(06:12):
going to try to do that, which they're not going
to try. But there is another part of the manta's
more frightening reputation in pre modern times, which is the
belief that mantas will attack boats, not divers, but boats,
particularly the claim that a manta will drag a boat
out to sea by the anchor line. So here I'm
(06:34):
going to read a passage from Gill's article quote in
one of the earliest notices of the devilfish by John
Lawson in the History of Carolina seventeen fourteen. This peculiarity
is described the devilfish, he says, has been known to
weigh a ship's anchor and run with the vessel a
league or two and bring her back against tide to
(06:56):
almost the same place, but then the quote ends in
guild on to say later notices do not give the
animal credit for the same accommodating treatment, And he later
alludes to these other accounts that tell of the devilfish
pulling sailing boats around by the anchor to the wonder
and fear of the sailors, and he also cites a
(07:17):
more recent source to him at the time of his writing.
This was a French naturalist named Leon de Guett describing
the activity of pearl fishers in the Gulf of California
in a text from eighteen ninety eight, and according to Deguet,
when fishers are caught out at sea overnight in the
Gulf of California, away from their usual mooring places, he
(07:41):
says they will always drop two anchors, because they fear
that if they only drop one, the anchor line will
be seized by the devilfish in the dark, and thus
the boat will be carried away into the open sea.
And to get back to this up with his own observation,
telling a story of how he was sent out to
harpoon a specimen of a devil ray for the Natural
(08:03):
History Museum of Paris, and he says, quote after one
had been harpooned, it turned back on the boat, seized
the bow with its head fins, and held it in
its clasp till it was lanced the second time. So
that's Deget's account, But Gil says even this direct observation
(08:23):
does not really lend credence to the idea that mantas
or devil rays deliberately attack, detain or hijack boats, because
based on his own study, Gil writes that this kind
of grasping with the headfins is automatic. He says, it's
an involuntary muscular reaction when something is in front of
(08:44):
the ray's mouth, so in this case it might happen
to be the bow of the harpooner's boat, and so
even when it's being attacked by somebody on the boat,
when it's being harpooned, Gil argues that the ray was
probably not actually trying to harm the boat, but rather
is just being pulled toward the boat by the tension
of the rope on the harpoon it had just been
(09:05):
lanced with. And even to get himself the person originally
telling the story of it seizing the bow of the boat,
he says the devilfishes are generally timid, non aggressive animals.
Though then, after saying this confusingly to get does seem open,
he sort of opens up more claims of devilfish savagery
and alleges that in the Gulf of California quote, numerous
(09:28):
cases have occurred of death resulting to divers as well
as bathers from encounters with the devilfish or manta as
the men call it. On the other hand, the carcasses
of many that are killed are used for bait for
other fishes. The strange detail to include.
Speaker 1 (09:45):
Yeah, yeah, I mean all of this is the pardon
the terminology here at fishy because.
Speaker 2 (09:51):
Dubious the third hand, Yeah.
Speaker 1 (09:53):
Yeah, I mean, because everything we know and have been
discussing about rays, when they're threatened, they use a bir
to speed they get away. That's their major way of
defending themselves. So it doesn't really make sense based on
what we know that they would turn around an attack
of a ship or a boat, even if they are
being acted upon with harpoons.
Speaker 2 (10:15):
Right, and as we discussed last time, of course, they
are large animals, and any large animal could potentially hurt
you just by bumping into you. Wrong, but there is
really no evidence I could find of manta's being aggressive
towards humans except for these like old third hand stories.
Speaker 3 (10:32):
Yeah.
Speaker 1 (10:32):
And I don't know if Gil gets into this or no,
butical for one of the things with you get into
oral histories of things like the devilfish the manta, you
end up having to ask questions, well, is the manta
in this story, even if there's a kernel of truth
to it, is it indeed talking about the species that
we are talking about as the manta ray, or is
(10:54):
it referring to something else real or imagined.
Speaker 2 (10:56):
Yeah, so, even back in nineteen ten, Gill to me
seems skeptical of these claims about it attacking boats. Certainly,
modern researchers are skeptical of these stories of manterray aggression
towards boats. But to the question of dragging boats, specifically
by the anchor cable, is this just a tall tale
like the mantray death blanket story or is there something
(11:19):
more to that? Is there any modern evidence of things
like this happening? The answer to this is yes. For example,
I found a Reuter's article from February eleventh, nineteen ninety nine,
called motor boat no match for manterray in Tug of War.
Speaker 1 (11:34):
Well, I generally, you know, I generally trust Reuters in
their reporting, though usual usually I'm not reading about the
marine biology. When I'm reading Reuters, usually it's a nice,
you know, doom scroll into the abyss. So I missed
this one when it came out. If I was in
fact reading Routers at the time.
Speaker 2 (11:54):
I'll read from the beginning of the article and then
summarize some other parts of it and we can make
up our minds about it. Okay, what's going on here?
So Dateline New Smurta Beach, Florida. Two Florida boaters met
a real sea monster when their craft was dragged for
hours by a powerful creature that turned out to be
a giant manta ray, the Coastguard said Wednesday. Coastguard Petty
(12:14):
Officer Scott Barnes said the agency received a radio distress
call from a sixteen foot boat that reported it was
being dragged by its anchor line by something unknown. The
Coastguard sent a rescue boat to investigate and found the
motor boat was being dragged in circles by something beneath
the surface. The crew transferred the anchor line to the
Coastguard vessel, freeing the men in the motor boat who
(12:37):
had tried to use their ninety horsepower engine to go
in reverse and stop themselves from being dragged out to sea.
After the Coastguard's forty one foot boat pulled the anchor
line for several minutes, a giant manta ray measuring an
estimated eighteen feet in width, came to the surface, and
then the article goes on to describe how the Coastguard
struggled to pull the rope away. Eventually, the manta was
(13:00):
able to disentangle itself from the rope and it swam
away on its own, and by the end of the ordeal,
the manta, they estimate, had pulled the boat for almost
two hours, taking it about a mile and a half
away from shore. But you could easily get the wrong
idea about this, thinking that it supports this old notion
that mantas will attack boats, that they are doing this
(13:24):
on purpose, they're trying to drag the sailors out to sea,
out to their deaths or something. From what I've read,
there is absolutely zero evidence to support the idea that
the mantas are acting aggressively when they pull a boat
by the anchor line. The zero evidence that they're acting
aggressively or even acting intentionally. Rather, this is almost certainly
(13:45):
a case of manta's getting stuck. They are getting tangled
in underwater ropes and chains by accident and then pulling
the boat because they are unable to free themselves. And
when you look at their heads, you look up a
picture of a manta ray or a devil ray, you
can see how this might easily happen. They almost have
biological mooring cleats with their cephalic fins.
Speaker 1 (14:09):
Yeah, yeah, you can imagine them, you know, catching the line.
Speaker 2 (14:22):
For one more example of a modern encounter, I found
a video on YouTube that the title begins with Giant
manta ray tangled in anchorchain, forty miles off shore. This
is a video of some people out in a fishing
boat in the Gulf of Mexico and a manta does
get caught in their anchor line. Like it looks when
you can see it, it looks like the line is not
(14:44):
just caught between the cephalic fins, but kind of wrapped
around them, like the lobes on its head have the
line going across as well as between, and you can
see it struggling. At a couple of points in this video.
It quite strangely, it almost seems to be coming up
to the surface and holding still while the fishermen are
(15:04):
trying to get it untangled. Then weirdly kind of matches.
But then I don't know how to interpret what I'm
seeing there, so maybe it shouldn't be taken this way.
But it kind of reminds me of all these stories
people talk about of manta rays being very like, kind
of slow moving and gentle while they come up to
them and almost kind of letting people, you know, interact
with them. Again, not encouraging people to do that unless
(15:25):
you're trying to free one from a problem you've created.
But anyway, in the end here the people in the
boat are able to succeed by they sever the line
in one place and that allows them to get it
unwrapped from around the manta and they let the manta
swim away. So it seems like the manta gets away
in the end of this, which is heartwarming. In fact,
all these like bro fishermen are like high five in
(15:47):
each other. They're like, yeah, we did it.
Speaker 3 (15:50):
It's sweet.
Speaker 2 (15:51):
But once again seems like a quite clear case of
like the manta is not doing this on purpose. It's
not out here today. Thing say, and I'd like to
drag a boat around it ended up in this situation
against its will.
Speaker 3 (16:03):
Yeah.
Speaker 1 (16:04):
Yeah, Like you said, the cephalic fins are kind of
look like natural line catchers. And then they're also just
quite I mean, they're they're wing shaped, they're they're they're
quite wide. We've talked about their their wingspans, and yeah,
that's just more real estate to potentially run into a line.
Speaker 2 (16:21):
Yeah. And so Gil talks about this in his article
and says that these the cephalic fins or cephalic lobes
the kind of horns of the devilfish.
Speaker 3 (16:31):
Uh.
Speaker 2 (16:31):
They they're like an elephant's trunk. He quotes another author
saying that then they can kind of grasp objects and
pull them in. He says they tend to rapidly kind
of close in around the mouth when something appears in
front of the mouth and uh, and that the the
fish will have a kind of obstinacy in, you know,
(16:52):
refusing to release things that go in like that. Gil
says quote that these arms are muscular and powerful has
been dim on many occasions. The natural movement of the
head fins or corropteries is inward and when any object
strikes between them, it is instinctively held a proceeding which
explains the undoubted fact that these fishes can run away
(17:14):
with quite large vessels. So Gill's chalking this up to
involuntary motion of the strong cephalic fins closing over things
that hit in the front of the mouth, which occasionally,
in some unlucky circumstances, just happens to be an anchor line.
I think Gil is absolutely correct that these boat dragging
(17:35):
incidents are not aggressive or intentional on the part of
the ray, but is he correct about the mechanism. I
was looking for modern sources and couldn't really find anything
to confirm or deny his ideas there about the specific
motion of the cephalic fins being involved. But I did
find some commentary from more recent marine biology resources, specifically
(17:58):
something from the organization known as the Manta Trust, which
has a page on the subject of manta mooring line entanglements,
and they highlight some different biological facts which make mooring
line entanglements common for manta rays. Manta rays, like their
cousins sharks, and also like tuna, are obligate ram ventilators,
(18:23):
meaning they do not have the biological equipment needed to
pump water over their gills when their bodies are at rest.
So in order to make water flow over their gills
so they can extract oxygen from the water and breathe,
they have to move their bodies. So you've probably heard
before that if a shark is forced to hold still,
(18:45):
it will die. It has to swim to breathe. That
is essentially true, and it's true for mantas as well.
Fish that don't have to keep moving to breathe have
what's known as a buckle pump system, where you use
muscles around your mouth and throat to hump fresh water
over the gills. Mantas don't have that. They've got to swim.
Speaker 1 (19:04):
Now, I do want to point out that Joe said
essentially true of sharks, so's we can get into a
deeper discussion maybe in another episode where we talk about
the different behaviors of different types of sharks. You do
have some shark varieties that live in close to the
reef that are going to be that can be still
for extended periods of time.
Speaker 2 (19:24):
Yeah, they might actually have the buckle pumping equipment. But yeah,
like great white sharks, for example, don't they're ram ventilators.
Speaker 1 (19:32):
Exact Yes, absolutely true of great whites, but.
Speaker 2 (19:35):
Anyway certainly true of manta rays. They have to swim
in order to breathe. They are also ram ventilators, and
so this means that getting entangled in a line can
be deadly to a manta. If it is stuck and
it can't swim around, it can't really breathe. And this
might also explain why a manta would keep swimming even
when it has a boat dragging behind it. It kind
(19:57):
of has to swim. Pair of this with a couple
of other biological facts. Mantas can't swim backwards. They are
highly maneuverable fish in a way. They can turn around
and you see them in the water doing these beautiful
summersaults and everything, but it's always with forward motion, which
usually means that the line just gets even more tangled
(20:19):
up on them as they twist and somer salt around
and they would need to really be able to back
up to release the line, but they can't back up.
Speaker 1 (20:28):
Great point.
Speaker 2 (20:29):
The other thing is that the manta trust says is
they are often not able to see the thin line
of a rope or a chain when it's directly in
front of them. And so you put all this together
and it easily explains how mantas can get tangled in
mooring lines and can end up pulling whatever these lines
are attached to. This is usually not threatening to humans,
(20:51):
but it is very threatening to the ray. Rays often
asphyxiate and die when they get caught in moorings. And
so the Manta Trust has this document where they make
recommendations for making mooring lines safer for mantas. You can
actually look this document up on their website for the
full recommendations, but they suggest a few measures, like one
just reducing the presence of especially loose line in the water.
(21:16):
Loose or slack lines are more dangerous to raise than
tight lines. You can probably kind of imagine where they are, Like,
a looser line is easier to get fully just tangled
up in, whereas a taut line, you know, you might
more likely bump into and then something can get yeah. Yeah.
But then also they recommend this interesting system that I
(21:36):
don't know if I would have thought of this, but
this is cool. They recommend attaching cable ties that protrude
off of mooring lines at a ninety degree angle. So
you imagine, you know, something kind of like zip ties
or something like that, evenly spaced every foot or so
down a mooring line, and they recommend having them go
(21:58):
out around. So there's a little bar sticking off of
the side of the rope going in a spiral around
the rope all the way down. And the idea here
is that it will make the rope more visible to wildlife,
especially they say as you use it, more algae will
attach to the ends of these cable ties, and it
will make them even more visible. And of course, if
(22:20):
the rays can see the mooring lines, they.
Speaker 3 (22:22):
Will avoid them.
Speaker 2 (22:23):
They're not going to run into them on purpose.
Speaker 1 (22:25):
Okay, So, if I'm understanding the illustration you're attached here,
it's like a spiral staircase of zip ties going up
and down this particular line, and then, like you said,
you'll end up with the stuff growing on those ties
as well.
Speaker 2 (22:38):
Yeah, so it makes the rope easy to see in
the water instead of just like a thin kind of
line that is invisible.
Speaker 1 (22:44):
Sometimes that makes sense.
Speaker 2 (22:46):
However, at the very end here, I do want to
come back with some sympathy for the sailors because obviously
I think we have the correct perspective now, Like we know,
rays are certainly not attacking boats. They're not trying to
kidnap sailors on purpose or drag the boats. You know,
they're not doing this on purpose. But you can very
well you can understand how it would be frightening to
(23:07):
have something under especially if you couldn't see it. I
don't know whether it be scarier actually if you could
see it or if you couldn't. If you could see
it might be like a twenty foot wide manta ray.
Speaker 1 (23:15):
Yeah, because it's a gigantic sure, And if you don't
know all the details, like we said last time, you know,
it's reasonable for a human to be trepidacious about this
enormous creature in the water near them or with them.
Speaker 2 (23:26):
Yeah, and if you can't see it, just there's something
invisible under the water that's now pulling your boat around
and you don't know where it's taken you. So I
can understand being scared.
Speaker 3 (23:34):
I mean like that.
Speaker 2 (23:35):
I've got sympathy for that. But yeah, they're not out
there trying to do this. It's just unfortunate.
Speaker 3 (23:40):
It happens sometimes.
Speaker 1 (23:51):
All right, Now, at this point of the episode, I
want to come back and talk in a little more
detail about manta ray reproduction because in the last episode
we talked about how they're particularly vulnerable to various threats,
you know, threats posed by fishing other human harms, in
large part because of their slow reproductive cycle. So I
wanted to get a little more into this. One of
(24:14):
my main sources here again is Guide to the Manta
and Devil Rays of the World by Stevens Fernando Dando
in Dyscaria. Very good book, lots of illustrations. It's, you know,
technically like a field guide. I mean, it's not laminated,
you can't take it into the water with you, but
it's a great field guide. And the authors here point
(24:36):
out that there are a lot of gaps in our
knowledge about manta ray and devil rae reproduction, with most
of what we know coming from observations of reef mantas
and limited scientific data in addition to that. So bear
that in mind, and I'll tuck back in on that
fact as well. But manta rays are not like most fish.
(24:58):
That much we've already established, and it applies to their
reproduction as well. Like all elasmo bronchs that's sharks and
other batomorphs like rays, they practice internal fertilization rather than
external fertilization, which is practiced by most fish species. So
they have come so they have to come into direct
(25:18):
contact with each other in order to mate. Right.
Speaker 2 (25:21):
So it's not like releasing unfertilized eggs into the water
which then encounter sperm in the water and become fertilized
externally like many fish do.
Speaker 1 (25:30):
Yeah, there's no just like swimming close to each other
or both visiting the same spot at one point or
another that they do have to engage and what is
ultimately rather complex and kind of beautiful and maybe at
times humorous mating ritual. The other amazing thing about manta
reproduction is that, as with a minority of other fish species,
they are live bearers, meaning they give live birth via
(25:54):
an egg that hatches inside the female's uterus. This is
known as a placental viva pair. Now, as many people
have observed and some of your listeners might be thinking,
this practice would seem to be yet another way that
the manta rays resemble certain whale species. Yeah, you know what,
large oceanic filter feeders that give live birth.
Speaker 2 (26:14):
Yeah, they could easily be mistaken for a mammal.
Speaker 1 (26:17):
Yeah, but this is not the same as live mammalian birth.
And while whales rely on their mothers for the first
phase of their lives, mantas are on their own from
the moment they're born. They're just small versions of their
parents that have to just hit the ground running, you know,
not much smaller, of course, they're still they're still quite big.
(26:38):
A newborn is typically like one point five to one
point eight meters across, or like five to six feet. Whoa, yeah,
and sometimes it's twins. That's a big baby, all right,
So let's walk through the courtship. I said that it
was beautiful and weird and sometimes funny. Again, Stevens. That
all point out that there's much we don't know. This
is a general description. A lot of it's based on mantas,
(27:00):
and they are going to be species specific variations, and
I believe it's possible there may be environmental differences as well,
depending on where the mantas are. But in general, this
is how it goes down. So a male will approach
a female and he'll shadow her from above and then
he may attempt to rub the top of her head
(27:21):
with his cephalic fence the devil horns, right, and usually
what's going to take place at this point is she's
going to shake him. She's going to like, you know,
make a quick turn and say get away from me.
She's just going to reject his advances.
Speaker 2 (27:32):
Okay, so devil horn BackRub, and then bolt.
Speaker 1 (27:35):
Yeah, generally she's gonna bolt. Generally she's going to say
I'm not in the mood and she's going to go in.
But if she is interested, what she's going to do
instead is speed forward. And then he is going to
give chase. And as this chase continues, this is going
to draw in other males who will also give chase.
And we get another situation where we have a line
(27:57):
of manta rays. This time of manta rays speeding through
the water, you know, maybe around wreaths, and these can
also kind of quickly get to our eyes out at hand,
like a thirty strong zooming train of mantas that occasionally
leaps out of the water as well.
Speaker 2 (28:16):
This is kind of like the feeding structure you talked
about in the last episode. What was the name of it,
It wasn't cyclone feeding, was it? That was when they
form a ring and they go around and round. But
last time when you talked about how there might be
a big cloud of zooplankton and they're eating them, and
so they line up in this row and they go
through and for some reason they get more food that way.
Speaker 1 (28:38):
Yeah, yeah, chain feeding. So yeah, this is reminiscent of
chain feeding.
Speaker 2 (28:42):
Except not feeding here. This is the first one is
trying to mate.
Speaker 3 (28:45):
With the female.
Speaker 1 (28:47):
Well yes, well he's trying to keep up with her,
and in general, she's going to try and shake loose
the less fit pursuers because now she doesn't just have
one manta, she may have up to thirty mantas behind her.
And this is crazy too. She may loop back around
and start chasing the last male in line. So now
we get another like just ring, another sort of like
(29:10):
mating cyclone here, okay or courtship cyclone I guess okay.
Other females may also be swept up in these processions,
which can result in one line splitting or two lines merging.
They also the authors here also mentioned that that she
may end up chasing another female manta as well. So
this you start with one train of manta's zooming through
(29:32):
the water, and it may go in different directions. It
may split, it may merge, it may loop back around
on itself, you know. And yeah, it's quite spectacular. I'm
to understand fascinating. Courtship is complicated. Yeah, in the course
of this, old males are going to fall fall away,
they can't keep up. New mantas are going to join in.
They're like, well, I'm fresh, I'm ready to go. I
(29:53):
think I might be able to catch her. But the
author's stress that she's not actually trying to lose anyone.
This isn't one of those cases where where it's like
she doesn't want to mate and it's just whichever male
can catch her. It's not a mating pursuit like you
see with other species. She's seemingly doing all of this
to merely assess her suitors and determine which one is
(30:13):
displaying the greatest level of fitness. But at the same time,
the end result is going to be only one man
to ray can still keep up with her.
Speaker 2 (30:22):
So you could look at this as a kind of
mass organized mating dance of rich Yeah, yeah.
Speaker 1 (30:29):
Yeah, And it's very much a situation where it's the
individual with the greatest degree of fitness is going to
be the one that she mates with, and she absolutely
has to be choosy because a lot is writing on
her selection. And this comes again back to the gestation
period for romantis, which takes a little over a year,
(30:50):
and given the ups and downs of environmental factors, mainly
food in the wild, she's generally not going to be
able to reproduce every year anyway, Carrying such large spring
to term is costly, and even when food is abundant,
she's just not going to be able to do it
every year, so there ends up being seasonal gaps and
this generally breaks down to a pregnancy occurring every two
to three years, but the authors of this book point
(31:14):
out that the rate can be as low as once
every seven years in particular environments. Wow. And another factor
involved here in her choosiness is that she may reproduce,
she may mate rather multiple times during the breeding season,
but she's going to store sperm from multiple partners. This
is something we see in other organisms as well, and
(31:36):
then she can use the sperm she wants whenever she
finally gets to fertilizer eggs whenever it's not finally the
right time to fertilizer eggs.
Speaker 2 (31:44):
Yeah, yeah, sperm storage like this. I think we've talked
about this happening in some species of sharks also, Yeah,
which of course are closely related to rais.
Speaker 1 (31:52):
So yeah, eventually one male is going to be left.
There can be only one. She's going to slow down
and allow him to shadow her again, you know, it
be you know, more or less a top of her
shadowing her. But then he is going to bite down
hard on her left wing tip, hard enough that this
is going to leave scarring. You can you can identify,
(32:13):
you know, females that have bred before in the wild
because they will have this scarring on the on their
left wingtip. I want to say, it's like in the
high ninety percents that it's the left wing tip.
Speaker 2 (32:23):
Interesting.
Speaker 1 (32:25):
And once he's he's bit down hard on it, and
I think there's a fair amount of wingtip like going
into his mouth. At this point, he's going to flip
so that now he's belly to belly with her, and
then he's going to use one of his claspers there
are two claspers on the male. It's going to use
that to ejaculate sperm into her. Kloeca and then he's
going to beat his pectoral fins, causing the two of
(32:45):
them to spiral in the water. This is all going
to last about thirty seconds and then they're going to
go their separate ways.
Speaker 2 (32:51):
Wow, that's elaborate.
Speaker 1 (32:53):
Yeah. Yeah, there's a whole diagram in the book here
showing how all of this, all this elaborate dance eventually
comes to a closure.
Speaker 2 (33:01):
It's funny you mentioned the biting down element because this
squares was something I think I was reading in preparation
for the first episode that we didn't end up talking about.
Speaker 3 (33:10):
But the fact that that.
Speaker 2 (33:12):
Manta rays don't have teeth that they use for feeding,
but the teeth are basically, you know, they've got these
little plates, you know, sort of mighty old plates yeeahtle
little tiny amounts of kind of nubby little teeth that
are apparently only used in mating.
Speaker 1 (33:28):
At any rate, they definitely bite pretty hard. Again, there
are some photos and you can look up photos of
mating scars and manta rays.
Speaker 2 (33:35):
But so, okay, now the egg is fertilized and you
would have a gestation period.
Speaker 1 (33:39):
Right, that's right. Yeah, more than a year of gestation
follows and This is another area where we have to
stress that like we don't have I believed even to
this day, I don't think we have any wild observations
of manda ray birth. At the time of this book's
publication in twenty eighteen, there had been I think just
a single incident of a recorded captive birth at the
(34:03):
Okinawa Aquarium as in I think two thousand and seven.
Since that point, I believe, the same aquarium, and in
some cases the same manta ray, with the same manta ray,
we've seen subsequent births, with the most recent I believe
being twenty twenty four. You can look up videos. When
I was looking around, there's at least one video that
was easy to find. Some I think have been taken down,
(34:25):
but you can watch as this obviously pregnant female manta ray,
and sometimes you see the female manta rays in the wild.
Some of the Snorkel guides that we had in Indonesia
also pointed out that sometimes you'll just see a male
that happens to be really bloated vaginerally, you can tell
a pregnant female and yeah, you can watch the miracle
(34:45):
of birth as this mother pushes out a rather large
and ready to run Manta.
Speaker 2 (34:53):
I'm watching it right now. It is amazing. Wow.
Speaker 3 (34:56):
And oh yeah.
Speaker 2 (34:57):
It comes out kind of in a clump and it's
not moving for a second, and suddenly it just kind
of twitches and then starts jetting around.
Speaker 3 (35:04):
Yeah.
Speaker 1 (35:05):
I think I've seen this described as kind of like
a burrito. Before their their fins are curled up over
their backs, and you know, there's kind of like a
you know, cloud of material that comes out with them,
and then you know, they start moving and then they
swim off and they are on their own again. The
there is no mother offspring relationship here. They go their
(35:26):
separate ways. But again, the newborn's actual egg case would
have would have hatched, if to use them perhaps an
incorrect term here, sometime before inside the female's uterus, and
it would have subsequently fed on the mother's uterine milk,
which in this case is known as histotroph.
Speaker 2 (35:46):
Manta ray uterine milk. I don't think we ever got
into that. We did an episode or a series of
episodes a ways back about non mammalian milk.
Speaker 1 (35:54):
Yeah, I mean it's one of those things where is
it really milk? Yeah? No, no, but it kind of
serves the purpose of milk.
Speaker 2 (36:02):
Yeah, because we talked about like dinosaurs perhaps producing a
milk like substance.
Speaker 1 (36:07):
Yeah. Yeah, but again, this is to go back to
what we were talking about in the first episode. This
is all exactly the reason that manta rays have such
a delicate place in their environments speacause again, long gestation period,
generally a single berth, and it's not happening every year.
It's you know, there are these big gaps between subsequent births.
So if there's any kind of targeted fishing or any
(36:29):
kind of factor that is that is eating into their population,
it's it's harder for them to bounce back.
Speaker 3 (36:37):
Yeah.
Speaker 1 (36:37):
All right, Well we're going to go and close out
this episode. We will be back with I believe one
more episode on manta rays, and it should be an
equally exciting one because we're going to talk about their brains,
we are going to talk about their parasites, and we
will talk about cleaning stations, which if you don't know
much about manta cleaning stations or cleaning stations in general
with other species, you might think that this sounds like
(36:59):
the least exciting thing we could talk about, but it's
actually really exciting. Yes, yes, in the meantime, definitely right
into us. We would love to hear from anyone out
there who has experiences encountering manta rays or other rays
in the wild. Do you have any tales of tangled mantas?
Have you also snorkeled or scuba dived with mantas or
(37:22):
seen them from boats? What are your observations? Share with
us your observations of the manta. Just a reminder that
Stuff to Below Your Mind is primarily a science and
culture podcast with core episodes on Tuesdays and Thursdays. We
do a short form episode on Wednesdays, and on Fridays
we set aside most serious concerns to just talk about
a weird film on Weird House Cinema. You can get
the podcast wherever you get podcasts these days, wherever that
(37:44):
happens to be. We do ask that you rate and review,
give us some stars. That always helps us out. You
can follow us on social media in various places, and
we're still trying to build up our Instagram followers. If
you use Instagram, find us as STBYM podcast Huge Things.
Speaker 2 (38:00):
As always to our excellent audio producer, Jj Posway. If
you would like to get in touch with us with
feedback on this episode or any other, to suggest a
topic for the future, or just to say hello. You
can email us at contact at stuff to Blow your
Mind dot com. Stuff to Blow Your Mind is production
(38:23):
of iHeartRadio. For more podcasts from my heart Radio, visit
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