From the Vault: The Manta Ray, Part 3

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 7/10/2025) (part 3 of 3)

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Episode Transcript

Speaker 1 (00:06):
Hey, you welcome to Stuff to Blow your Mind. My
name is Robert Lamb. Today's Saturday, so we have a
vault for you. This is going to be the Manta
Ray Part three of three. This was a really fun
series that we did last year. This particular episode originally
published seven ten, twenty twenty five. Let's dive right into it.

Speaker 2 (00:27):
Welcome to Stuff to Blow your Mind, production of iHeartRadio.

Speaker 1 (00:37):
Hey you welcome to Stuff to Blow your Mind. My
name is Robert Lamb.

Speaker 3 (00:40):
And I am Joe McCormick, and we're back with part
three in our series on the genus Mobula, the manta
rays and the devil rays. In part one of the series,
we talked about the original inspiration for covering this topic,
which was that Rob, you and your family got to
see reef manta rays in person while snorkeling in Indonesia

(01:01):
this summer, which sounds like an amazing experience.

Speaker 1 (01:05):
Yeah. Again, it almost is too much to describe, but yeah,
we jumped out of the boat. This is after an
initial snorkeling in another coral rich area, and then they
took us out to a manta ray cleaning station, which
we're going to get into in this episode. If you
don't know what a cleaning station is, you're about you're
going to find out. It is not like a service station.

(01:27):
It is not an artificial, human made thing. When I
don't remember when this was, but the very first time
I heard about cleaning stations in the water for organisms,
it made me think, oh, well, they installed a big
rotating brush in the water and it draws in the fish.
Because cleaning stations. Again, we'll get into all the details
of this, it is a place where if you know

(01:47):
where the cleaning stations are, then you as divers or
snorkelers can go there and you have an increased chance
of seeing the various organisms that make use of it.

Speaker 3 (01:55):
Unfortunately, I had a much bloodier picture in my mind,
but I think fish and cleaning station. I think of
like a gutting station where the guys there like ripping
the guts out of the fishy.

Speaker 1 (02:05):
Cot Well, you know, there's a little bit of that
sprinkled in. We'll get into it, but yeah, basically, we
second stop on this snorkeling this morning snorkeling trip that
we did, and they took us out to a cleaning
station and we jumped in the water and it was,
you know, it's just reef environment was but it was
much deeper than we'd been in, a little darker than

(02:25):
we'd been in. And I sometimes get a little nervous
when we're talking about like deeper water and bigger things
in the water. But seeing these large reef mantis going
about their business doing some loops here and there, even wash,
it was magical. You just felt absolutely at peace with them.

Speaker 3 (02:43):
So after that in the first episode, we also talked
a bit about the history of human interactions with the
manter rays and devil rays. We got into old misconceptions
that manter rays are threatening to human boats and divers.
That's not true, and relatively new misconceptions that their body
parts have medicinal value. Of course, both of these false

(03:06):
beliefs leading to harm to manta and devil ray populations
by humans, and we also talked about ongoing conservation efforts
to protect the world's remaining rays. We discussed some basics
of manta ray biology, including their body design, feeding habits,
and their tendency to breach the water's surface leaping up
in the air. In part two of this series, we

(03:27):
followed up on stories from an older marine biology article
that told of mantas and devil rays taking hold of
the anchor lines and mooring lines of a boat and
dragging the boats out to sea, and we discussed how
it seems this can happen and sometimes does actually happen,
but it's clearly not intentional on the part of the manta,

(03:49):
and we got into some biological reasons that mopulid rays
are prone to getting tangled in loose lines in the water.
We also talked about some recommended methods for making mooring
lines safer rays. After that we got into mobulid reproduction,
which is really fascinating the way they engage in internal
fertilization and viviparity, meaning sort of full body contact, sexual intercourse,

(04:13):
and live birth respectively, so making them, as in so
many other ways, kind of superficially resembling of mammals, even
though they are fish not mammals. And we also got
into the elaborate fitness displays that males go through in
these sort of mass chain races before the female finally
chooses or mate. And today we're here again to talk about.

Speaker 1 (04:34):
More that's right, and the place I'd like to pick
up is discussing manta rays and their parasites, and there's
some bleed over here into other mobulid parasite loads as well.
Some of the information you know applies to devil rays
and so forth, and a lot and as we've been discussing, like,

(04:55):
there's a lot more known about the ins and outs
of reef manta rays as opposed to the the oceanic
man to raise which are the largest. So you might
remember back to our episode about the grey whale, and
like the basic observation that large marine animals often have
to deal with sizeable parasite loads, or if not actual parasites,

(05:15):
then creatures engaged in some degree of mutualism either way
you slice it. Large marine organisms tend to attract a
fair number of hangers on and they become mobile environments
for these various organisms.

Speaker 3 (05:28):
In the case of gray whales, am I remembering right
that barnacles would tend to attach to the outside of
the gray whale, Like the gray whale becomes a substrate
that is useful for the barnacle because they need something
solid to attach the bottom of their body to. And
then also by moving through the water, the whale you know,
brings food to them, essentially allowing water to flow past.

Speaker 1 (05:49):
Them, right, And as we discussed in those episodes, like
there's there's on one hand a strong case to be
made that oh, these these the poor whales are just
covered with these barnacles, like a ship with barnacles, gaining
no bit fit from it. But then we also explored
hypothesis that proposed that, well, actually there are some potential
benefits to having these barnacles on your body.

Speaker 3 (06:09):
Yeah, the question was do the barnacles form a kind
of armor of sorts That was not known for sure
to be clear, that was like a possibility, but I
think it was more likely assumed that it is sort
of a net negative to the way all to have
all these barnacles on it.

Speaker 1 (06:25):
Yeah, but this similar conversation often occurs around these discussions
of symbiosis and mutualism and parasitism, questions about who's getting
the most out of this relationship, is it unbalanced? To
what degree is it unbalanced? And you see it go
various directions where arguments end up being made that what
is thought of as a parasite might actually have some benefits,

(06:48):
and you know, and the opposite something that seems like
there's a beneficial give and take and maybe it's a
little less beneficial than we used to think it was.
At any rate, it's definitely the case with the man
to that they have a lot of hangers on and
they vary greatly. Mantas have to contend, for instance, with
tiny copa pod parasites that get literally everywhere on them. Meanwhile,

(07:13):
you also have things like harmless juvenile golden traveler fish,
which just ride the pressure wave and alongside the creature,
and in the same way that sometimes dolphins are seen
to ride alongside ships. But as far as I'm to understand,
they don't pose any risk or damage to the manta rays.
And then they split when they're old enough to fin

(07:33):
for themselves, and then you have these sucker plate headed
remorras to continue with, and there's sometimes a little harder
to figure.

Speaker 3 (07:40):
Out sort of gray area here.

Speaker 1 (07:42):
Yeah, sometimes, I mean again, this is often the case
the deeper you look into any of these relationships. But basically,
if you're not familiar with the remorra, ramora's dorsal fin
has evolved into an oval slatted sucker organ so like
by flexing the little slats on there, they can they
can suction onto a surface such as the side of

(08:05):
a whale or a shark, or you know, a turtle
or a ship or a human diver. I think it
occurs occasionally. They're free swimming fish, but they like to
hitch a ride, and there are many different species. And yeah,
they attach to all sorts of organisms, including manta rays,
and indeed they've been known to take up more or

(08:27):
less permanent residents, sometimes inside a manta's mouth or hide
in other body openings such as gills or the kloeca.
They typically feed on the ectoparasites and loose skin flakes
and other leavings of an organism. And yeah, it seems
to be what's happening with manta rays. Not every variety
of remora that latches onto a manta can keep up

(08:50):
with it can remain with the host, especially as it
ventures into deeper waters. Some get displaced. And in general,
it seems like the longer a manta hangs out in
a shallow reef environment, the more it's liable to attract remoras.
So that's the case I've read with you know, certainly
the reef manta over the oceanic manta. And then it's
also the case with mantas hanging out closer to shallow

(09:14):
waters due to some particular state of their own life cycle. Now,
the book that I keep referring to in these episodes
guide to the Manta and Devil Rays of the World
by Stevens, Fernando dan Do, and Discaria. In this they
point out that scientists often cleanly label this relationship between
the remoras and the manta rays as parasitic, arguing there's

(09:37):
no real benefit for the mantis here. For instance, the
gill activity going in and out of the gills can
result in heavy scarring for example, essentially like mutilating the
gills over time. Now, others argue, well, the remoras does
seem to do some level of cleaning though they're eating
up parasites, you know, dead skin flakes, and this, they

(10:00):
would point they point out, would be helpful, especially to
the oceanic manta, as it frequents cleaning stations far less.
As we discussed in cleaning stations tend to be you know,
in reef environments, and if you're out there in the
middle of it, there are fewer of these around. So
perhaps the assistance in these cases would balance out the
harm at least to some degree. Now, maybe it's not.

(10:21):
I mean, I don't know how often you really see
a fifty to fifty split with these relationships in nature,
Like you know, there's there's gonna be you know, all
all the factors of evolution and behavior or in play here,
and it's this is ever the question when we're pondering
relationships like this.

Speaker 3 (10:39):
So for a very rough analogy, it's kind of like
if you had a squirrel that lived on your body
and it climbed all over you eating the fleas that
you also have eating the fleas and mosquitoes that swarm
your skin. So that's good, you don't want the fleas
and mosquitos, But also the squirrel's claws are like scratching
you up, and it's probably causing problems while you're trying
to move around, So you get a plus an a minus.

Speaker 1 (11:02):
Yeah, I mean it always reminds me of the Doctor
Seuss book Thidwick the Big Hearted Moose. This is it's
not a situation where Fidwick's dealing with parasites and creatures
eating the parasites, but he has a big heart and
he keeps letting animals ride in his antlers until it
gets that hand.

Speaker 3 (11:18):
I feel like it's got to be one of the
less big hearted Doctor Seuss books.

Speaker 1 (11:22):
Yeah, the message there is maybe a little less less rosy,
but I don't know. I do come back to it
and think about it from time to time, so you
know that in the Sleep book, I guess really really home.
But at any rate, this is the case with large
organisms like this. There's just much more space for ectoparasites

(11:44):
to get everywhere, and parasites have their own parasites and
filter feeders also swim around with their mouths wide open
while feeding. You know, they're bringing organisms into their mouth
and that can bring in extra creatures as well. So
what is a manta to do? Breaching may help, as
we discussed, as it may help with other marine organisms. Again,

(12:08):
as we just mentioned, they can shake some of their
hangers on via their deeper dives. But at the end
of the day, they're going to need some help. They
can't turn to each other. They don't really have much
in the way of you know, limbs. They can't groom
each other in the way that say primates do, so
they're going to have to head to the cleaning stations.

Speaker 3 (12:37):
All right, So we're finally here. Tell me about the
cleaning stations.

Speaker 1 (12:40):
All right, now, I want to add a caveat I
am very likely to accidentally call a cleaning station a
feeding station. I've been doing this in casual conversation over
and over again over the past several weeks, perhaps in
part because for the fish working and you know some
I'm shrimp working at these cleaning stations, it is a
feeding station because that's what they're doing. They're feeding, that's

(13:02):
what they're getting out of it. Ultimately, we were talking
about a cleaning symbiosis situation that benefits all of the
organisms involved, and it's not unique to mantis. You'll find
the scenario throughout the aquatic environment, both in fresh water
and salt water. Fish deal with their individual parasite loads
in a variety of ways, but it's often useful to

(13:22):
get some help. These relationships have developed over time in
which fish will seek out areas populated by various other
organisms that generally we're talking and certainly in marine environments
about small reef fishes. Also sometimes some shrimp are involved
in this. There are various examples of this outside of

(13:42):
the water as well. For instance, on land, examples such
as the crocodile and the Egyptian plover or crocodile bird
have been observed since ancient times. You can find like
Herodotus writing about.

Speaker 3 (13:54):
This and still cute to see today.

Speaker 1 (13:57):
Yeah, this is the bird that goes inside the rockcodile's mouth,
holds the mouth open, goes in there and starts doing
some dental cleanup. Uh. The Egyptian plover, by the way,
not to be confused with Egyptian lever. Different. That's a
that's a musical artist, a legendary musical artist that I've
referenced on the show before.

Speaker 3 (14:16):
Look it up, kids.

Speaker 1 (14:18):
Uh. The oxpecker is a great example from the surface
world as well, a bird that feeds exclusively on the
bodies of large mammals, though this one is also much
discussed in scientific circles because that's it's definitely a case
where there are strong arguments to be made that the
oxpecker might not ultimately help the organism that it's landing
on all that much, and might be as much of

(14:39):
a nuisance in and of itself in the ocean. To
return to the waters, however, you see various fish take
advantage of these services, including the parrotfish, which were previously
discussed on the show so you don't have to be
a behemoth to benefit from a visit to the various
organisms that want to eat your parasites, as well as
perhaps some loose, dry skin or rancid flesh around your wound.

(15:00):
In fact, some cleaners are specialized wound cleaners. But naturally,
when you are a large fish riddled with parasites, you
know you can't scratch those itches again. So manta rays
have to head to these stations, and it seems again
it seems to work for everyone. Small fish and shrimp
can't swim as far or do so safely in search

(15:20):
of food, so they'll, you know, they set up at
a cleaning station. Generally this is like a rocky outcropping
the edge of a reef or you know, something like that,
and here they can just hang out and their meals
will be delivered to them because the customers will show up.
They will go where the cleaner organisms.

Speaker 3 (15:38):
Are right, so by being easy to locate and offering
a service, they can have this dependable influx of resources
from abroad. It almost makes me think about like the
economies of I don't know, freeway exits where there will
be you know, gas stations and restaurants built up around
a freeway exit, like you know, the traffic's coming in.

Speaker 1 (15:57):
Yeah, yeah, exactly. I mean you often see this compared
to like a trip to the barber, the dentist, and
so forth, all wrapped into one. Because yet they'll they'll
get inside the mouth to clean out the teeth, they'll
clean out gills, they'll eat away algae growths, dead and
molting skin, bacterial, fungal growths, you know, getting food particles

(16:21):
out of the mouth. It's really quite extensive. And then
these are generally small organisms that are doing this, so
they can target those tiny acto parasites and seek them
out all over the host's body, in every every crevice.
And so the mantas actually the kind of queue up
for this. One of the bits of advice that the

(16:43):
the the Snorkel guides had for us was was, you know,
among all the reasons not to get too close is
you also don't want to essentially enter the cleaning station,
not because the fish are going to clean you, but
because the mantas are going to be like, oh, it's occupied,
I can't go in there, like you're taking up room.
It's like you've pulled into the car wash ahead of

(17:03):
people who want their car cleaned.

Speaker 3 (17:05):
What would they do? Would they patiently wait their turn?
I guess maybe?

Speaker 1 (17:09):
Or potentially clear? I mean also the humans being where
they need to be. I think they're a number of
reasons that they might sort of scare them off, you know,
like you're too loud with your flippers, you're coming out
of the water too much. I think in general they
might just decide, well, another time fair enough to bring
it back to Thidwick, the big hearted moose, you know,
I don't think he ever considered visiting a wolf cleaning

(17:31):
station or something for all of those various mammals and
birds living on his antlers. Now, as discussed before, against
symbiosis is a spectrum, and it can shift with either
party reaping more of the benefits and in some cases
perhaps taking a bit of advantage, at least from the
human perspective. So some cleaner species do seem to gage engage.

(17:52):
This is in general in occasional acts that feel more parasitic,
like maybe they're you know, they're eating parasites, but maybe
they're eating a little body mucus off of the surface
of a fish or aquatic creature as well, you know,
maybe they're grabbing a little flesh that's less on the
rancid side, but you know, just because they can, So

(18:12):
you know, I guess to answerphomorphize the scenario. There are
always going to be some bad actors, maybe some folks
who take advantage of the trust in a given scenario.
But I think still on the whole, even with these cases,
cleaning stations seem to benefit everyone, even if sometimes there's
a little advantage taken. Yeah.

Speaker 3 (18:30):
Well, and all kinds of organisms have symbiotic relationships that
are sort of balanced on a knife edge like this.
I mean, I would say it's true of us with
our own microbiota. Yeah, you know, of course human beings
rely on, for example, our gut flora in order to
do all kinds of things you know, to be healthy,

(18:50):
to help with digestion. So we're definitely worse off without it.
We need it, but at the same time it can
turn opportunistic and it can harm us if you know
there's something wrong with yoummune system or other kinds of
conditions come online.

Speaker 1 (19:03):
Now, there are some additional levers that the manta ray
can pull and stevens that all get into this in
the guide book. These are things that the manta will
also do it feeding stations, which it makes sense. The
manta knows that it is at a location where the
local population is heavily invested in the manta's parasites, its

(19:25):
previous meals, and so forth. So first of all, they
frequently defecate at these cleaning stations, makes sense. I mean
with all creatures, and stuff that's defecated is going to
include things that are still of interest to various scavenging creatures.
They will also cough or vomit, blasting particles like food
particles out of their mouth, which cleaners are also going

(19:47):
to be interested in. And Stephen's at all right that
sometimes they blast out massive clumps of undigested zooplanked and exoskeletons.
I don't have a photograph to refer to, but I
just like a mental image of what this might look like.
And then back to their defecation, they'll also invert their
intestines up to thirty centimeters or twelve inches out of

(20:09):
their cloaca while they're doing it, just to better clean
everything out that's feces, but also parasites, presumably indo n ectoparasites,
and interestingly enough their feces i've read is basically dark
red due to all the plankton. So when they do this,
if you're in the water with them, and you know,

(20:30):
they don't care if you're in the water when they
do this, they're they're gonna let loose as needed. This
process has often been misinterpreted by divers as like they
don't know what they're looking at. It looks like it
might be blood or something, maybe they're injured, or in
some cases they might think they're about to view of birth,
which makes sense when you look at We talked about

(20:50):
this video footage in the last episode from an aquarium
in Okinawa, Japan, where we see one of the very
few recordings of a manta giving birth, and it does
like like this initial discharge of particles in the water.
I can see where you might confuse the two acts.

Speaker 3 (21:11):
A burrito in the middle of a cloud and then
the burido unfolds.

Speaker 1 (21:15):
Yeah, so that might be a case where someone's like, oh,
I think it's giving birth, but then you realize, oh,
there's no baby. It's just a cloud of red manta
fecal matter.

Speaker 3 (21:23):
They're just pooping out part of their own intestines to
get it all cleaned out. Yeah, that's right.

Speaker 1 (21:28):
Yeah, all right, Joe, I believe there's there's at least
one more organ we want to talk about inside the
manta's body, right.

Speaker 3 (21:35):
That's right. We wanted to come back to the subject
of manta brains and intelligence, so we already talked in
previous parts of the series about how when people have
close encounters with manta rays, they often report similar feelings.
You'll read about this in people describing their dives with them.
The manta is a fish, but it does not feel

(21:57):
like a fish when you're in its presence. It has
a kind of palpable intelligence and emotionality, a sense of
curiosity that we generally only associate with social mammals, and
maybe sometimes with other strange intelligences like that of an octopus,
but certainly not with fish. You'll read about this over

(22:19):
and over with these manta experiences. Now, of course, that
feeling of being in communion with a higher intelligence is
just a subjective impression people have. It could be an illusion.
Maybe it's based in some kind of esthetic charisma, something
about the way the manta looks, or something about the
way it moves. The question would be, is there any

(22:40):
objective scientific reason for thinking there's actually something special about
the intelligence of the genus mobula compared to other fish.
I think the answer is pretty clearly yes.

Speaker 1 (22:53):
Yeah, that's my indication as well, because you know, to
your point, people have this feeling about their dogs and
cats all the time, not to discount the intelligence of
dogs and cats, which is with each of which are unique.
But like we have this of course amazing human ability
to anthropomorphize, to personify, and imbue just about anything with

(23:14):
a remarkable level of intelligence and free will.

Speaker 3 (23:17):
Well, yes, that is certainly true. I mean the I
have the beholder quality to this whole thing. But I
would also say that, even just somewhat objectively, I think
dogs and cats, as somewhat social mammals do have a
higher level of cognitive complexity than most fish. You could argue, yes, yeah,
absolutely so, there are definitely I have the beholder elements.

(23:40):
These are mammals that need to navigate a somewhat socially
complex world. That they've got something going on up there.

Speaker 1 (23:47):
Well, let's dig into the old mantamelon what are they
working with up there?

Speaker 3 (23:50):
Okay, first of all, I think we should address the
question of raw hardware what kind of neural equipment Demanta
rays and devil rays have to work with. And to
get into this question, I wanted to look at a
paper by a name you'll see popping up a whole
lot in manterray research. This was by a researcher named
Scilla Ari. That's spelled csi Lla and then the last

(24:16):
name is Ari if you want to look her up.
Her research is all over the place. She studies manterray
neurobiology and the paper is called Encephalization and Brain organization
of mobulid rays myleobataforms Elasmo Bronchi with ecological perspectives. This
was published in the Open Anatomy Journal in twenty eleven,

(24:38):
and so this paper set out to measure the brain
size of three different species in the genus Mobula. It
looked at Mobula japanica, or the spinetale devil ray, also
known as the Japanese devil ray, Mobula Thurstoni or the
bent fin devil ray, and Mobula birostras known at the
time this paper was published as man birosts. Manta was

(25:01):
once treated as a separate genus, but now the mantas
are grouped with the rest of the mobular genus. But anyway,
this is the giant oceanic manta ray. This is the
big one, the biggest of them all. So to run
through a selection of some of the main findings. First
of all, the giant oceanic manta ray birosters has the

(25:22):
largest brain of any known fish species, just in absolute terms,
biggest brain of all the fish. Also, mantas and devil
rays not only have large brains in absolute terms, but
they have very high brain to body mass ratios. This
is known in anatomy as the encephalization quotion. So a

(25:45):
larger brain is not always a sign of greater intelligence,
at least when measured along the dimensions of intelligence that
we find interesting. Often a large brain in an animal
is necessary, especially when the animal is itself large, simply
to control movement and nerve feedback for that massive body. So,

(26:06):
if you have a huge body, you need to control
a lot of big muscles all over the place. You
need to get sensory feedback from all over the body,
so you need a big brain just to handle all that.
It might not necessarily be for the kinds of things
we think of when we say the word intelligence, things
like problem solving, memory, learning, social cognition, that sort of thing.

(26:27):
What tends to correlate more often with those kinds of
intelligence is having a bigger brain relative to the size
of your body. And even then, the relationship between in civilization,
quotient and observed intelligence is not completely linear, but it's
a fairly strong relationship in terms of the structure of

(26:47):
the brain and the characteristics of the brain tissue. These
rays showed first of all, an enlarged telencephalon. The telencephalon
is the fore brain the front part of the brain
correspond to the cerebrum in mammals, and also what the
author calls a highly foliated cerebellum, and this means that

(27:08):
the cerebellum has a more folded texture, which increases the
surface area of the cerebellum and that in turn increases
the number of neurons and the density of neurons on
the cerebellum, allowing more connections and thus greater information processing power.
And these anatomical features, the larger telencephalon and the more

(27:30):
highly foliated cerebellum are correlated with more complex behavior and
cognition in other species, So just looking at their brains
and brain tissue. It definitely does look like something special
is going on with the mobular rays compared to other fish.
You're seeing patterns that you see more with smarter animals

(27:51):
across different types of lineages.

Speaker 1 (27:53):
There's a great illustration in the Manta and Devil Rays
of the World book where they show on one hand,
the brain of a spinetailed devil ray mobula mobular, and
then they compare it to the brain of a similarly
sized common skate. You know, so this is a not

(28:14):
unrelated creature, similar size, and you can see like drastic
difference between the two. The ray's brain just looks absolutely
bloated and engorged, you know, and then the skate's brain
is streamlined. And by comparison, so you know, even not
knowing exactly what sorts of neural tissues you're looking at,

(28:35):
you can see like, oh, this thing looks super charge.
This one looks oversized compared to a similarly sized organism. Yeah.

Speaker 3 (28:42):
This paper also has some very juicy illustrations and some
fiend without a face kind of stuff.

Speaker 1 (28:48):
Yeah, yeah, definitely.

Speaker 3 (28:50):
But anyway, so the question would be, what is all
of this high powered neural equipment for? What would they
need these powerful and highly full brains. For one possible
explanation that Ari gets into in this paper is complex
social behaviors. As we already discussed in the previous episodes,

(29:13):
modular rays show these interesting complicated group behavior patterns. Examples
of this would include forming schools that engage in coordinated
and organized feeding behaviors. So remember that chain feeding where
they'll go in a line feeding together or cyclone feeding
where they go in a circle. They organize into these

(29:35):
patterns to take better advantage of food sources. Also, another
example of group coordinated group behavior patterns are when they
get into these large mate fitness competitions with potentially dozens
of rays chasing around in these athletic courtship displays. Broadly,
the management of complex social relationships and social behaviors is

(30:01):
thought to be one of the key drivers of brain
evolution in other species. So when you need to navigate
a complex social landscape full of other members of your
species and you need to maybe work together and manage
relationships like recognizing specific individuals of your species and remembering

(30:23):
interactions with them you've had in the past, that is
often when evolution starts really putting pressure on you to
wise up that is thought to be a big driver
of brain evolution in other lineages. We've already talked about
evidence of mantas working together and engaging in these complex
group behaviors, But is there any evidence that they that

(30:45):
they do what I was just saying, that they recognize
and remember each other as individuals. In effect, do they
have time stable social relationships. I went looking for an
answer here and I found it seems to be yes,
there there is some evidence of that. So I came
across a paper by Perryman at All published in the

(31:05):
journal Behavioral Ecology and Sociobiology in the year twenty nineteen
called Social Preferences and Network Structure and a Population of
Reef Manta rays rob very interesting connection for you. In
this paper, to study the social networks of mobular rays,
the authors here collected data on more than five hundred

(31:25):
groups of reef manta rays. This is the species Mobula
alfredi over five years in raja Ampat in Indonesia. So
this may have been in some of the same locations
or around some of the same locations you visited.

Speaker 1 (31:39):
Yeah, I mean, I'm looking at the maps in the
paper now and like, yep, yep, I was in that square.

Speaker 3 (31:45):
And so in observing the mantas in these locations, the
authors did indeed observe what they call social preferences in
mobular rays, especially between females. And social preferences here would
mean that individual rays seem to show either an increased
tendency to affiliate with or a desire to avoid specific

(32:08):
other individual rays to anthropomorphize a bit, So this might
kind of give the wrong idea, but roughly they had
something analogous to friends and enemies.

Speaker 1 (32:19):
Room for frenemies in that equation or is that more
of a human thing unclear? I don't know.

Speaker 3 (32:24):
We'll see what we think. So the authors found pretty
strong evidence for female mantas having these relationships on both
long and short time scales, so in the scale of
weeks and months, they might have a consistent preference for
or against certain other female individual rays. They also found
pretty strong evidence for mixed sex social preferences kind of

(32:49):
friendships or enemy ships between males and females. Between males,
they only found kind of weak evidence for short term relationships,
so perhaps males are less social with each other on average.
The overall social networks were categorized as what they call
a dynamic fission fusion society with differentiated relationships linked to

(33:13):
strong fidelity to cleaning station sites. So this idea of
a fission fusion society is one whether it's not like
a fixed group that stays together for the duration of
these animals lives. They're kind of like these groups that
come together for some period of time and then split
apart and then can dissolve, and then different groups can

(33:35):
kind of reform. It's a more more freeform kind of
social network formation and division. And then in their discussion section,
the authors say, quote, our results show that stable, differentiated
social relationships lasting over several weeks or months are an
important driver of group structures in reef Manta rays, which
suggests that both familiarity and long term social relationships are

(33:59):
important in structuring their societies. In complex social systems, such
capabilities can be essential too identify partners in reciprocal altruism,
to maintain social hierarchies, and to avoid inbreeding. So those
three things are strong biological reasons why it might be
useful to remember who another individual of your species is

(34:21):
and remember past interactions with them. You want to be
able to repay favors back and forth, you know, reciprocal
altruism or remember if they did something mean to you
in the past, to avoid inbreeding, of course, and to
maintain kind of dominance relationships. So anyway, it seems yes,

(34:51):
the answer is modular rays do seem to be especially
social relative to most fish, and social cognition pressures are
thought to a big driver of brain evolution in other
vertebrate lineages, so that could be a big factor at
play here. We don't know for sure, but that seems
like a very plausible explanation for why these animals would

(35:11):
need to have more powerful brains. Any other reasons they
might need to have extra brain power, Yes, Ari gets
into some other ideas as well. One is the need
to understand their spatial environment. So mobulids are pelagic fish,
and they often inhabit coastal waters, including places like reefs

(35:33):
and seamounts and so forth, and Ari says that there
may be an evolutionary pressure for them to learn the
quote complex spatial organization of these habitats, which I think
that would include like creating mental maps of not only
the underwater topography of like a reef or a seamount,
but I think it would also include dynamic elements across

(35:54):
these maps, like water currents and the presence of other
organisms such as prey or predators, or especially cleaning mutualists.
Another possible explanation for their neurobiology is what Ari calls
their active and maneuverable lifestyles. She points out that in
other species, high cerebellar foliation, which remember that's the folding

(36:15):
of the cerebellum. You know, that allows more neuron density
there that is associated with, among other things, maneuverability and
strong locomotor abilities, which mobular rays absolutely do possess. You know,
they're very acrobatic. They can move around a lot, and
so their brain structures here could have something to do
with their tendency toward acrobatics. Another thing she points out,

(36:38):
I thought this was kind of interesting. It could have
something to do with their wide heads. Some aspects of
the large brain and the powerful tellencephalon of the manta
ray could be related to the fact that they have
a broad head similar to the hammerhead shark, which Ari
writes could help with organizing and integrating different kinds of

(37:01):
sensory feedback. Now I was confused about that at first.
I was like, that doesn't come together for me, like,
what's the deal? So I had to look this up
to understand it better. But the idea is like in
hammerhead sharks, the wide head and the hammerhead sharks also
have an enlarged telencephalon the wide head and the enlarged
teleencephalon in the brain seem to help give the shark

(37:23):
enhanced sensory abilities like electrosensory abilities, vision, and even maybe
a more stereoscopic sense of smell, so they can determine
the direction that smells are coming from more easily. So
like by spacing out the sensory organs across a wider head,
you can sort of increase the resolution you get across

(37:47):
multiple different sensory modalities. It's again this is a loose analogy,
but it's like, you know, having a bigger camera lens
kind of like you're increasing the resolution you can get
on things. And so the wide spacing there for chemical
sensing or electro sensing and the hammerheads especially or vision
and all that it can help you in a way.
And then the strong tellencephalon the big four brain can

(38:08):
help you gather and make sense of all that information.
That does seem to be the case in hammerhead sharks,
and Broadly already says it's possible that similar sensory management
could be at play within mobula heads and brains. They
also have these big, wide heads that are putting the
different sensors far apart.

Speaker 1 (38:27):
That's interesting. That makes me think about some of the
hypotheses concerning breaching in mantas that like the slap of
their bodies hitting the water again, could be a signal
in some cases to other rays to come and start
engaging in these social feeding configurations with them.

Speaker 3 (38:44):
Yeah, okay, so.

Speaker 1 (38:46):
You got to receive that signal and then know what
to do with it.

Speaker 3 (38:49):
And then finally there was an issue brought up in
this paper that was a lot more interesting than I
first realized once they started looking into it, and that
was a little bit directly related to intelligence, but very
worth mentioning. And that is the idea of thermal issues.
So I'm going to start with a quote from the
paper here. Ari writes quote endothermy as the elevation of

(39:12):
body temperature by metabolic heat production represents one of the
most significant developments during vertebrate evolution that might be connected
to enlarged brain size. Sharks in general are poikilothermic, meaning
cold blooded. Their body temperature varies with the environment, but
some shark species like eshuris and Lamna are homeothermic, and

(39:36):
that in this case it means regionally warm blooded. They
can keep blood in certain parts of their body elevated
warm as they are able to maintain body temperatures well
above ambient temperature of the environment by counter current flow
of blood at certain places of their body. So countercurrent
blood flow is another interesting phenomenon. It works as by

(40:00):
positioning the hot pipes right next to the cold pipes.
So generally the blood that is returning to an animal's
heart from its extremities through the veins is going to
be cold. It goes out there to the edges of
the body, it loses heat, and then has to come
back to the heart, so it gets cold and it's
coming back cold. Meanwhile, arterial blood leaving the heart and

(40:24):
headed for the extremities is comparatively warm. It just came
from the warmest part of the body right there in
the core. Countercurrent blood flow places long stretches of arteries
right next to long stretches of veins, so that the
warm blood coming from the core can warm up the

(40:44):
cold blood in the veins before it gets back to
the core, and even human bodies actually take advantage of this.
In our arms and legs, the veins and arteries tend
to be close to each other, sort of next to
each other to help warm the cold blood returning from
the fingers and toes, and this adaptation helps animals maintain

(41:05):
higher body temperatures in cold environments. But sometimes it's not
just positioning major vein and artery pathways next to each other.
Sometimes there are dedicated structures in an animal's body that
really maximize this artery to vein heat exchange. And one
example of a structure like this would be what's called

(41:27):
a reedy mirabolae chronica, which comes from the red mirabilae
comes from the Latin for wonderful net, and then the
cranica would be of the skull, the wonderful net of
the skull. This is a sort of dense web of
veins and arteries inside the cranial cavity around the brain,

(41:48):
which helps regulate the temperature of blood flow around the brain.
Arii writes quote among mobulid rays in Mobula, terrapacina, and mantatress.
Again that's now mobula birostris a ret mirabola cranica as
a countercurrent heat exchanger has been described around their brain. Interestingly,

(42:09):
the same families are also characterized as large brained elasmo bronchs,
in which these unique adaptations might serve to enhance their
ability to exploit cooler environments, either deeper water or at
higher latitudes, with greater efficiency by slowing the rate of
metabolic heat loss to the environment or allowing them a

(42:30):
higher activity level. And I thought this was interesting. So
I was reading a little bit more about this in
a paper called Cranial endothermy in Mobulid rays Evolutionary and
Ecological Implications of a thermogenic brain by mc Arostigui in
the Journal of Animal Ecology twenty twenty four. And here

(42:51):
the author makes a very interesting kind of comparison, so
Arostigui writes, quote, whereas early hominids hot terrestrial environments may
have experienced a thermal constraint to evolving larger brain size,
cetaceans and mobulids, so like whales and rays here in

(43:11):
cold marine waters, may have experienced a thermal driver for
enlargement of a thermogenic brain. So does that converse relationship
make sense to like? For human evolution, we want to
have a bigger brain, right, bigger brain's great, you can
get real smart. But heat concerns place among other things.

(43:32):
Of course, you know, heat concerns place upper limits on
our ability to grow bigger brains. Those brains can easily
get too hot, which is dangerous to us. For mantas
and devil rays, there could be an opposite direction thermal
influence on brain evolution. The cold waters that you want
to live in and dive down to make it pay
thermally to have a bigger brain with this big mesh

(43:55):
of blood vessels and so Erostogwe writes in the abstract
quote the potential for brain enlargement to yield the dual
outcomes of cranial endothermy and enhanced cognition in mobulids suggests
one may be an evolutionary byproduct of selection for the
mechanisms underlying the other, and highlights the need to account

(44:17):
for non cognitive functions when translating brain size into cognitive capacity.
So I thought that was a fascinating idea, and this
is not proven, but it's raising the possibility. What if
mantas evolved greater intelligence as an accidental byproduct of growing
bigger brains, which and the growing of the bigger brains

(44:40):
was mainly driven in the first place by thermal pressure.
You want to keep the brain warm when you're going
into these cold waters.

Speaker 1 (44:48):
That's fascinating. So yeah, it would be the environmental reasons
to have a big brain are like the main driving
force here. But then the idea is that if this
were true, they would also then of course use those
cognitive powers to sort of flesh out their behavior as
well well.

Speaker 3 (45:07):
Right, So, yeah, if you accidentally evolve a more powerful
brain just because you're trying to keep a warmer brain
in cold waters, that brings new capacities online, which could
further just arise as a contingency, but then could further
shape your revolution if you lean into them.

Speaker 1 (45:24):
So it's like to think of the there's a Marvel
supervillain called the Leader, and he has enlarged brain and
he uses that brain powers, you know, you know, for
supervillain things to try and take over the world. But
you could make an argument though, that the Leader didn't
evolve or develop this massive brain to take over the world.
He did it for thermal reasons. But then of course

(45:44):
he's going to try and take over the world with
it because he's got a big brain. As a result
of these these thermal conditions.

Speaker 3 (45:50):
World domination plots an unfortunate side effect, yeah, of keeping
a nice and toasty up there. So that's an interesting possibility, Fasten,
I'd never considered anything like that. So that's all I've

(46:13):
got from that original paper by sila Ari on the
neurobiology of the mantas and the devil rays here. But
there was one more thing I wanted to mention about
mobular ray brains and intelligence, and that is there is
one famous experiment which showed that manta rays may, depending
on your interpretation, pass a well known animal cognition milestone

(46:36):
known as the mirror self recognition test. So we've talked
about this test on the show before, but if you
never heard of it, the most common version goes like this.
You place a mark somewhere on an animal's body, somewhere
that they wouldn't be able to see it just by
looking directly at themselves, but somewhere they could see with

(46:56):
the aid of a mirror. So for a human example,
you can imagine putting a spot of dye on the skin,
maybe on the front of your throat. So you look
in a mirror, you'll see it, but you can't see
it by looking down. Yeah, then you give that animal
a mirror and you watch what they do. Most animals
do not seem to recognize their reflections as themselves. A

(47:19):
lot of animals will just kind of ignore a mirror.
Sometimes they react as if it were another animal in
their space. So they react, you know, maybe they puff
up and get aggressive, or they try to interact with
it somehow, or they just act confused. A small number
of animals, including some of the great apes, some marine
mammals like bottlenosed dolphins I think, maybe orcas, some corvids,

(47:42):
and know the magpie. I believe elephants may have passed
the mirror test. They do something different. They will touch
their own bodies on the spot with the mark and
try to rub it off if they can. Sometimes because
of different animal body plans, you have to organize for
sort of equivalents here. But they will see the mark

(48:05):
and they will try to mess with it, indicating that
they understand the animal they're looking at in the mirror
is the self and not another that's my own body,
and I react by touching the part of my body
that I see as modified in the mirror.

Speaker 1 (48:20):
Yeah, it's something we take for granted because we do
it every day, but if calibrated just right, it can
arguably give us some insight into what might be happening
inside the brain the mind of a non human animal.

Speaker 3 (48:33):
Right, and so this is taken as evidence of rare
self awareness, though we should strongly caveat this because that
phrase can bring a lot of associations or baggage that
are not necessarily proven by these experiments. There is debate
over exactly what the mirror test shows, but even with
that big asterisk there, I do think the results of
these experiments are fascinating. Like most animals don't recognize that

(48:58):
the mirror reflection is their own body, a few animals
do appear to recognize that. What about mobular rays. Well,
there was a paper published in the Journal of Ethology
in the year twenty sixteen by same author as before
sila Arii, but also Dominic P. Dagostino called contingency checking

(49:19):
and self directed behaviors in giant manta rays do elasmo
broncs have self awareness, and so the authors set this
up in their abstract by saying, quote, manta rays have
a high encevilization quotion as we already talked about, and
remember large brains compared to their body size, similar to
those species that have passed the mirror self recognition test

(49:42):
and possessed the largest brain of all fish species. Again,
that would be in the Mobula birostras, the giant oceanic
manteray biggest fish brain. They write quote. In this study,
mirror exposure experiments were conducted on two captive giant mantrays
to document their response to their mirror image. So this

(50:04):
test was different from the standard format than that I
just described a minute ago because the authors were not
able to do the body mark component of the test,
and there are some good reasons for thinking about that.
For one, thing like mantas don't have hands, so they
can't reach out and touch There's nothing they have that's
prehensile they can use to reach out and touch a

(50:26):
part of their body to mess with it. So it
didn't have that important body mark component of the test
that places some major limits on how to interpret these
results when compared to the results of many other mirror
test experiments. But the authors did document the manta's behavior
in response to the presence of a mirror, and then

(50:48):
they controlled for that by just putting in a non
reflective white board of the same size in their tank,
and the results were really interesting. The mantas showed a
lot of interest in the mirror, like a lot of interest.
They really were attracted to the mirror, and they wanted
to hang out around it. They spent a lot of

(51:10):
time moving around in front of it and messing with it.
They did not, on the other hand, attempt to interact
socially with the mirror image. And the authors could measure
this because there are certain kinds of physiological responses that
mantas tend to show when in the presence of another manta,
like they might show like a kind of widening of spots,

(51:32):
or like something kind of like changes on their coloration patterns,
and they didn't observe anything like that. They did not
see the behaviors you would normally see when a manta
sees another of its species, so there were no signs
that they thought of this as another animal. The author
is right quote frequent, unusual and repetitive movements in front

(51:53):
of the mirror suggested contingency checking. In addition, unusual self
directed behaviors could be identified when the manta rays were
exposed to the mirror. So what exactly do they mean
by contingency checking. This seems to mean testing to see
if the mirror image does the same things you do.

(52:13):
So you know, you might think of making faces in
a mirror, or like wiggling repetitively in front of a mirror.
And they charge, yes, yeah, exactly, yeah, they were doing that.
So examples they observed were things like positioning the body
to stare into the mirror and then repeatedly wiggling the
cephalic fins, like opening and closing the cephalic fins over

(52:35):
and over, blowing bubbles into the mirror. And then also
what about these unusual quote self directed behaviors? This is
what look to the researchers like the manta trying to
investigate parts of its own body that it can't normally see,
like orienting so that it could look at the reflection

(52:56):
of its ventral surface if its belly or part of
its back. For example. They note that quote body turns
into a vertical direction, exposing the ventral side of the
body to the mirror while visually oriented to it was
something that they only ever saw the mantas do when
the mirror was in the tank. So they take the
mirror out, they don't see the mantas doing like orienting

(53:18):
vertically like this and look. So it's like it looked
to them like they were trying to see parts of
their body that were not ever visible to them otherwise.
So the end of their abstract, they say, quote, the
present study shows evidence for behavioral responses to a mirror
that are prerequisite for a prerequisite of self awareness, and
which has been used to confirm self recognition in apes.

(53:43):
But again the authors do acknowledge the limitations. You know,
this doesn't necessarily prove self awareness this version of the test.
Of course, it did not include the mark checking component,
And there are multiple ways you could interpret their behavior
in front of the mirror. It's possible they didn't recognize
it as themselves and we're just reacting with curiosity to

(54:04):
something visually unusual. Though, the behaviors that look like, you know,
checking out your belly flesh only when the mirror is around,
that does sound pretty interesting to me.

Speaker 1 (54:14):
Yeah, absolutely, oh man, Yeah, I have a couple of
thoughts on all of this, Like, on one level, I
have to say that, you know, so like the hard
science aside I do like the idea of leaning into
interpretations of animals as being more conscious and having you know,
if there's a case to be made, I'm like, let's

(54:36):
go ahead and consider it, because if it helps protect
a species like this, then all the better. On the
other hand, like just the idea of let's let's go
ahead and assume for the sake of argument that the
manta does recognize the reflection as itself. What is that
like for a creat Now granted, this is an aquarium scenario,
so with the glass involved. There may be some other scenarios.

(54:57):
But imagine a purely why old manta that has, as
far as I'm imagining, it never encountered a reflection of itself,
and then it is presented with one. What would that
be like? What would that be like for a human
being if we managed to make it to adulthood without
ever encountering an unnatural mirror reflection or something like it,

(55:18):
say on the surface of water. I mean, I have
no doubt that we'd be able to pass it. I mean,
that's certainly part of the human mental capabilities, But man,
what would that what would that encounter be like?

Speaker 3 (55:31):
But the human I think, you know, you can see
a lot of your own body, not the whole thing,
got a lot of back and then you got a
face and head and I guess all that. But you
can see at least like the front of your body. Yeah.
The mantas, I don't know can they even see that? Again,
it seems like they were very interested in checking out
their their ventral side here, so they may have very

(55:51):
very little visual awareness of themselves within their space. Ever,
maybe all kind of like only a proprioceptive awareness of
their own body. Again, I'm not sure of that, but
that's it seems plausible.

Speaker 1 (56:06):
Yeah, yeah, I think it's fascinating. Now, we kept talking
about their their bellies, their ventral side, So I want
to come back to this as we're closing out here.
As we've mentioned, some mantas have distinct appearances because of
significant scarring, you know, scarring from matings, scarring from predator interactions.

(56:26):
And then you have mantas such as the celebrity manta
Baba Ganoosh of the Maldives that apparently survived a rather
horrific boat strike. You can look up images of this one.
So these individuals you tend to stand out. But as
we've discussed, their wounds tend to heal rapidly, you know,
maybe not completely, and certainly in the case of severe injuries,

(56:46):
not completely. But on the whole, these are changing markers.
What doesn't change, however, are the dark spots on their bellies,
on their ventral side. You can look up, you know,
images of this, and if you've been in the water
you might get to observe this as well. But yeah,
you look at the ventral side of a manta and
it is a unique fingerprint, the array of spots and

(57:09):
blotches on their generally white bellies. It is a fingerprint.
It can be used to id a particular manta, and
scientists are able to put these into a database and
track individuals without the aid of actual physical trackers or
tax And it gets even cooler because you get into
like a citizen scientist scenario here, because you have the

(57:32):
global ID the Manta photo database, which via this database,
anyone who swims in proximity to mantas. Again, I'm assuming
by following all the rules, but if you manage to
get a photos, particularly of their spots, they can I
think other parts of the manta can also prove useful,
but especially their spots. They can be uploaded into the

(57:54):
database and this can be used to help study their
movements and their behavior. And yeah, you can learn more
about this at Manta Trust dot org. I believe we've
referred to the Manta Trust already, and i'd say, in general,
if you've been moved at all by anything we've discussed
in these episodes about the manta, the plight of the manta,
or the majesty of these creatures, visit Manta Trust dot org.

(58:18):
You can learn more about them, you can sign up
for their newsletter. You can support their work via donations
and purchases. In fact, that book that I've been referring to,
Guide to the Manta and Devil Rays of the World,
is available to purchase there. And even if you don't
purchase it directly from them, royalties from that book go
to the Manta Trust. You can even this is this

(58:39):
is super cool. You can of course adopt a manta.
This is not uncommon. You can, you know, and but
you can also pay to name a specific Maldives manta
in their database. I was looking at this on their
website I think they had like four up for grabs.
So these are mantas that have, you know, like a
technical tag like a you know, a string of numbers

(58:59):
in a life, but they don't have a fun name yet.
And for a very reasonable donation, you can provide a
name for such a Manta Ray.

Speaker 3 (59:09):
Do they place any limits on how stupid the name
can be?

Speaker 1 (59:12):
I don't know. I mean, I mean there may be
some reasonable limits there. I mean I would place reasonable
limits if I were running this, but uh but yeah,
I mean it makes me I kind of want to
adopt a Manta Ray for the show. We could call it,
I don't know, Blowfield, Stuffington or something. I wouldn't want
it to be a complete.

Speaker 3 (59:29):
Advertiser Delia the self Aware.

Speaker 1 (59:34):
There you go at any rate check it out listeners.
If you happen to adopt a Manta Ray or or
name a Manta Ray via this website, let us know,
and we will. We will spread the will spread the word,
and we'll we'll also look this Manta Ray up and
see what they look like.

Speaker 3 (59:48):
Yeah, contact at stuff to Blow your Mind dot com.
Let us know.

Speaker 1 (59:53):
All right, we're gonna go ahead and close these episodes out.
I hope you've enjoyed them again. We'd love to hear
from everyone out there. You have any experiences with Manta's,
other rays, thoughts, and anything we've discussed here, write in Yeah,
send your photos. We'd love to see photos. We heard
from some snorkers already, but not the sort of snorkelers
I was imagining. We'll get to that in a future

(01:00:15):
listener mail episode. But we heard from some bog snorklers.

Speaker 3 (01:00:18):
Is that a joke? I couldn't tell.

Speaker 1 (01:00:19):
I could not tell. I haven't had a chance to
research it yet, but I flagged that one to come
back to. If it was a joke, it was elaborate.
Those were I think real photos.

Speaker 3 (01:00:28):
We'll learn more and report.

Speaker 1 (01:00:30):
Just a reminder to everyone that's stuff to blow your mind.
Is primarily a science and culture podcast, with core episodes
on Tuesdays and Thursdays, short form episodes on Wednesdays and
on Fridays. We set aside most serious concerns to just
talk about a weird film on Weird House Cinema.

Speaker 3 (01:00:43):
Huge things 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 a stuff to Blow
your Mind dot com.

Speaker 2 (01:01:05):
Stuff to Blow Your Mind is production of iHeartRadio. For
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