Strange Milk

Mammals are the true milk-bearers of nature, but there are a host of non-mammals that secrete various strange and wonderful milk-analogues. From avians to invertebrates, Robert Lamb and Joe McCormick explore the anomalous world of non-mammalian milk in this episode of Stuff to Blow Your Mind. 

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:03):
Welcome to Stuff to Blow your Mind from how Stuff
Works dot Com. Hey you welcome to Stuff to Blow
your Mind. My name is Robert Lamb and I'm Joe McCormick.
And today I wanted to start with the question I'm
going to try to do my best big lebowski boys.
What makes some mammal? Uh? Yeah? Thinking about mammals, what

(00:28):
are a few common features of mammals? Of course, we
know that all mammals are vertebrates, along with birds, reptiles, amphibians,
and fish, they get the backbone going on. Mammals, along
with birds, are of course endothermic or warm blooded, which
can that can sometimes be a misnomer because, as we've
discussed before, there are cases where mammals can cool their

(00:48):
bodies down quite a bit. Most mammals, excluding monotreams, have
live berths rather than laying eggs. Mammals generally have hair
as opposed to scales or feathers, right, unless they've lost
that hair by becoming aquatic creatures or for reasons yet unknown, right,
or for living underground, etceter Right, Yeah, yeah, and then

(01:09):
we get to the big one, of course, It is
that mammals nurse they're young, with milk, and this is
one of the real miracles of nature. It is really,
and we're not just We're not just saying that because
milk has such an important role in human child rearing,
or because humans have this weird thing where we drink
the milk of other species, especially around the holidays. You know,

(01:32):
this is kind of a slightly holiday themed episode because
a lot of people drink eggnog boiled custard type drinks,
which are more traditionally milk based. Is eggnog a dairy product.
I thought it was made with eggs. I have no idea.
Oh yeah, there's cream in there. I mean, obviously if
you can get the soy nog, which I have memories

(01:54):
of being tasty, and yet this year I do. Yeah,
I have memories. I see like I saw it in
the store. I got kind of excited. I got a
particular carton of soy nog, brought it back home to
share with my son, Um who is Um Who's who's
six and uh and he said, oh, this is good.
This tastes like wet cold sugar. And I was like, yeah,

(02:15):
it does kind of taste like wet cold sugar. It
doesn't have this particular I don't want to damn all
soy nog because I have to be remembering something real.
But this particular one, yeah, did not have that fatty, creamy,
uh finish to it anything, but like normal full fat
milk products always does have a kind of strange sweetness
to it. You're noticed the odd sweetness of skim milk.

(02:39):
There's something feels a little off about it. Yeah, I
mean it's been a while since I've had skim milk.
I do tend to just use um, like soy milk,
almond milk, coconut milk, that kind of thing these days. Um,
And thus my desire to get in the Christmas spirit
by buying soy nog. Right, But so okay, it's not
just the role in human culture that we use the

(03:00):
milk of other animals in our cuisine, which is pretty
much objectively weird. I think that's one of those things
aliens would come to Earth and see us doing and
think was weird. But it's also that it's it's a
deep part of what we are as an animal. The
possession of memory glands and the rearing of children with
milk is uh that that's like a main morphological feature
of what it means to be a mammal. The word

(03:22):
mammal basically means like breast beast. Yeah, we are a
bunch of breastbeasts really so yes, it nourishes our offspring
and in doing so helps to establish immune system competence
as well. Now, the exact nutrient composition of milk is
going to vary across a lot across species, and it
also can change quite a bit depending on the different

(03:44):
stages of lactation, which is something that's easy to overlook.
Milk is not just necessarily oh, here's the here's the
formula coming out, and know the formula will change. The
actual nutrient load will will vary depending on the developmental
stage of the young, So milk fat content and seals,
for instance, can be as high as six. Meanwhile, it's

(04:04):
basically nothing in wallabies. And speaking of wallabies, according to
the Origin and Evolution of Lactation by Capuoso and Acres
Posting two thousand nine, quote milk in the tamer wallaby
that's uh. Macropus eugeny changes from a very dilute secretion
containing primarily carbohydrate during early lactation to a more energy

(04:27):
dense milk that contains substantial quantities of protein and fat
during late phases of that left lactation. So that's a
nice example of just how the the the the exact
details of the milk will change during the course of
the the young's growth. Now, we could probably devote a
whole episode or multiple episodes in the future to the

(04:47):
study of milk, true biological mammal milk, because that's a
fascinating subject on its own, But today we wanted to
focus on something even weirder, which is all of the
non mammal quote milk that's out there. There has been
an astonishing amount of research that I had not kept
up with until diving into it recently about all about

(05:11):
animals you would just never expect to produce milk, producing
something like milk, Yeah, I have to say this also
forced me to learn about a couple of different creatures
I was not familiar with then we brought to my
attention solely because they produced something that one might call milk.
So this will be our anomalous milk episode. But before
we get into the anomalous milk, I guess it's worth

(05:31):
a quick look at actual mammal milk itself. Right now,
I know You've done some episodes on dairy products and
on mammal milk in the past, right, Yeah, there's there's
an older episode that I did with Julie Douglas back
in the day, and then more recently did an episode
with Christians Say titled Uh Holy Butter. As the name implies,

(05:53):
it's mostly about butter and how we make butter and
some of the uses we have for better Did you
all talk about bog butter? Yes, we did talk about
bog butter. Bog butter is so good. Yeah, but we
also talked about how butter and also milk, is nothing
short of solar energy transformed through a few different steps
into a food. For instance, there's the of course, the

(06:14):
the alchemy of photosynthesis to kick things off. The grass
in the field converts energy in the form of sunlight
into chemical energy in the form of sugars and other carbohydrates.
This is essentially the first miracle of milk. And then
you have a female ruminant in this case cow, sheet, camel, water, buffalo, goats,
et cetera. They consume that grass and truly, as Elaine

(06:38):
Cosa Rova explores in her tremendous book, Butter a rich
history Um, you're better off thinking of it as a
processed harvesting rather than a meal, because ruminants are built
to transform grass into milk. Uh. Consider that they have
these three or four chambered stomachs. Uh. They're upper dental
pad instead of teeth from massive for massicating green. And

(07:00):
each animal puts its own particular chemical spin on the
process as well. But they crunch up the greens and
they ferment them in their mini chambered guts eight hours feeding,
eight hours ruminating, and then the remains of the day resting,
so that that masceration, the repeated chewing of the cud
helps to carry out the second miracle of milk, the

(07:21):
transformation of a low fat diet of grass into high
fat milk. Yeah. You always wonder about that, right, Like
you look at the beginning product in the end product,
and you're like, I don't understand exactly what's happening here. Yeah,
And and part of this is just the miracle digestion.
The broken down food is assaulted by microbes and the
oxygen free fermentation chamber of the gut, the grassy meal

(07:43):
is broken down to the basic elements, strings of carbon
and hydrogen molecules, and then other backed here recombine the
elements into volat how fatty acids. Only half the fat
comes from the cow's diet. The rest comes from the
cow's own body fat. Oh wow. Yeah, And so it's
sort of it's not just making a product out of
what it just eight, but it's giving of itself when

(08:04):
it creates milk. And I think that's one of the reasons,
like we put the human layer on milk to write
like milk is this this giving of something something to
uh to to bring nourishment to another. And of course
we have so many metaphors related to that, including of
course that the milk of human kindness. But in this
example talking just about ruminate milk. Um, it's a you know,

(08:26):
fatty liquid to ensure the survival of the animals young
and um. The exact composition again is going to vary
from species to feat species, with additional factors depending on
environment and diet. For instance, uh a new produces twice
the fat content of cow milk, Goat milk has smaller,
more digestible fat molecules, yak milk has less sugar and

(08:46):
more protein, and camel's milk has three times as much
vitamin C water. Buffalo milk has twice the fat of
cow milk. And then we have things that are not
even um, you know, we don't traditionally think of as
milk producers. But consider the whales. Oh yeah, blue whales
for instance. Uh this, this always blows my mind. Uh.

(09:09):
A newborn blue whale gainst. Two hundred pounds a day
just by nursing, and the average whale produces forty times
more milk than a cow. And this has even led
some scientists to consider the possibility of milking whales and
specially prepared milking bays and then using that milk for
human consumption. Is there really any milk of any animal
that has not been considered for human consumption? UM? I

(09:33):
don't know. I mean there's some that are certainly more attractive. Um.
But anytime you start reading around about different milks, I
feel like there's a good chance somebody's tasted it and
they will tell you what the flavor profile is. What
does rat milk taste like? What what does monkey milk
pair with? I don't know. I have sometimes think about

(09:57):
cat milk, like, what like tiger milk would taste like?
Would it be did you know or who did have
kind of a like a meati consistency to it, probably
like a nice French washed rind cat milk cheese. I also,
this is a topic that I discussed in that past
episode with the the jew. It was of course the the
the idea that you do have certain situations that can

(10:19):
cause males to lactaatee as well. Uh, some do to
some are more like behavioral environmental, and others have to
do with their regularities in the body. But you also
have certain male fruit bats that lactated, and these are
the only examples of male mammals lactating as a part
of a regular parental activity. Yeah, and you can see

(10:39):
already in the idea of male animal lactation that there
is going to be They're gonna be some like asterisks
next to the official like dictionary definition of milk, which
is something like an opaque white fluid that's rich and
fat and protein that's secreted by female mammals for the
nourishment of their young. So obviously there's not that's not

(11:02):
quite all cases, because in some cases males secrete it
like the bats you're just talking about. And then I
guess the question comes in where if you have something
that meets all those qualifications but is not produced by
a mammal. Is that technically milk or not? I think
a lot of biologists might say no, but they might
still use the term in describing whatever this other substance is.

(11:26):
What is the substance on the Simpsons that they're drinking
in the school cafeteria. I think it's rat milk now
with vitamin R. Oh, my bones they feel so brittle.
But I always drink plenty of malk. Well, maybe it's mack,
maybe it's milk. Well, whatever you call it, milk, malk,
milk analog. There are clearly strong reasons that non mammalian

(11:50):
animals would would have an incentive to secrete milk like
fluids that they used to feed their young. It's a
really useful strategy and it serves quite a few dif functions.
I mean, for one thing, it allows the parent to
produce food for their offspring without having to like leave
or hunt or forage. You don't have to go out
of the nest. Another thing is that it tightly controls

(12:13):
the nutritional content of the offsprings food, making sure they
get exactly what they need. And you can see that
in the very different nutritional profiles of milk, like you
were talking about earlier, like with wallabies and stuff. It's
also a way for the young to eat all the
mother without actually eating the mother. Yes, exactly, Uh yeah,
and so it can. It can include extra nutrition, lots

(12:34):
of fat and protein, maybe more fat and protein than
you could expect to get from food sources in the environment.
It's like super concentrating the nutrition profile for the young,
which will help them speed up and grow faster. And
then it can also deliver really important additives. Earlier you
mentioned immune function, and that does seem to be a
very important role of of milk and animals. The idea

(12:56):
of stimulating the immune system with antibodies or supplementing the
offsprings microbiome with microbiodelic commenceled bacteria from the mother. Yeah,
I feel like this should come as no surprise following
our poop eating eating animals episode, because obviously, if if
eating a little um parental poop is going to provide

(13:16):
that kind of a boost, obviously that kind of boost
might be available via milk. And then on top of
all that, like the additives for the immune system, you
also can add hormones. This can be especially useful when
it's like hormones that could have something to do with
cementing the psychological bond between parent and child, or things
like growth hormone to help speed up the growth of

(13:38):
the young. So with some of that in mind, it
might be less surprising what I'm about to say, which
is that a number of bird species secrete a substance
analogous to milk. I think we should look at a few, Robert,
will you look at milk birds with me? Let's do it.
How about pigeons. Pigeons both male and female, regurgitate a

(14:00):
highly nutritious substance known as crop milk into the mouths
of their young, and don't let the fact that it
is delivered in the form of nourishing barf throw you off.
This is not regurgitated food. This is not the parent
bird providing a partially digested version of what they just date.
Crop milk is a separate, original substance secreted in the

(14:22):
crop organ. It's from the parent's body itself. Now the
crop organ is I don't know if you've ever seen
one of these, ROBBERTI, it's sort of have not. It's
like a pouch area in the esophagus that can be
used to store and moisten food before it continues on
down the elementary tract for digestion. And I think it's
thought that um the crop organ is useful for like

(14:45):
prey species of birds that might be trying to gobble
up a bunch of food really fast while they're out
somewhere exposed and then be able to fly off quickly
and reduce the amount of time they're out there eating
and exposed to predators. So you want to be able
to just like stuff it all in, like get it
all down there really fast, and then get out of there,
and then you can settle down somewhere safe and try

(15:05):
to digest. It's a it's a it's a doggy bag
essentially inside the body, Yes, exactly, it's it's your it's
your styrofoam clam shell inside the bird's throat, and so
the crop milk, it's actually produced by pigeons and doves.
This is described in a paper I'll come back to
in a minute as quote an oily, yellowish cheese like

(15:26):
substance that is formed into small seed sized rice shaped pellets.
I've also seen it described as cottage cheese but yellow. Well,
this sounds fine. I have no objection to any of that. Okay.
So apparently crop milk is produced by the inner cells
of the crop pouch becoming moist and then sort of

(15:46):
sloughing off into the pouch and then getting regurgitated. So
it's like, here's some let me barf you up some
of my highly nutritious inside skin. This is my flesh,
et cetera. Right now. An interesting thing in birds and
pigeons is that this process in parent pigeons is apparently
controlled by the hormone prolactin, which is also what stimulates

(16:11):
milk production in mammals. That's kind of interesting because you know,
they don't have memory glands. It's not you would think
that it would be something completely different, but it's pro
lactin in both cases that gets the parent doing this.
Crop milk tends to be mostly protein and fat, about
six protein maybe thirty something percent fat, and then just

(16:31):
a little bit of carbohydrates and minerals and other things
in there. A two thousand twelve study in Plos One
by Megan Gillespie at All found that if you took
baby chickens and fed them crop milk from pigeons. They
sort of became like little minor hulk chickens. After just
seven days, the pigeon milk chickens were more than twelve

(16:53):
percent heavier than control chickens. And also they showed greater
diversity of gut bacterious specifically in the seaka um, and
they had higher expression of the immunoglobulin I g A,
which is an antibody class that's crucial for all kinds
of immune system function. Now, a side question you might
be wondering is why did they test this on chickens
rather than on pigeons. I think the answer is that

(17:15):
with pigeons you couldn't really have a control group because
young pigeons would just die without the crop milk. And
there I've read that there have been other studies that
looked into this. They're like fed pigeon crop milk two
chickens to see what happened, and the chickens always really
beefed up. It. It's like it's clearly something that their
bodies respond well to. But there are some other birds

(17:35):
that also produce UH and feed their young with secretions
from the upper digestive tract that are crop milk or
something like it. Flamingos would be an example. According I
was reading about the flamingo crop milk feeding on the
San Diego Zoo website. They were talking about their flamingos.
Oh yeah, they have a great website, great outreach. Yeah, exactly,
And so the a few things they mentioned. One is

(17:57):
that apparently when young chicks flamingo chicks are hungry and
they're calling out for feeding, it's not just their own parents.
Other adults in the flock can be stimulated to act
as sort of foster feeders, which is sweet, that's cool.
And the way that seems to work is that they
they suppose that hearing the sound of the hungry chicks

(18:17):
calling for food stimulates the production of the milk like analog.
And then also one of the things they say is
that as the parent flamingos produce crop milk to feed
their chicks, their feathers tend to be drained of color
over time. So like if you've got an adult that's
producing crop milk feeding a young one, it turns from

(18:38):
pink to a pale pink or even to a white.
And then after the they stopped producing it, they gradually
get their color back. One more, of course, is emperor penguins.
You may have heard about this, like, you know, the
male emperor penguins guarding the the egg while the female
goes off to feed. So that goes on. But what
happens if the the young penguin hatches from the egg

(18:58):
before the female returns from feeding with fish to regurgitate
for it. Apparently the male penguin will do something like this,
will generate some upper digestive tract milk to bar out
for the little penguin, and the little penguin gets its
nourishment that way. So again, it's it's certainly not milk,
but it does seem to be meeting some of the

(19:18):
criteria we've discussed. Well, it's a lot like milk nutritionally,
it seems to serve a lot of the same functions
and be composed in a pretty similar way. So I
don't know, I don't know whether you should call it
milk or not. I mean, again, I think if we
go by the technical definition, milk is only produced by mammals,
So it's not milk, but it looks like milk, It
apparently tastes like milk, it does what milk does. Yeah,

(19:42):
we could call it bird milk or or bird nog
a holiday twist. That's good. Well, how about let let
me take you to the next step. This one might
seem unbelievable, but maybe just a tiny bit less. So,
given that birds produce milk like secretions, what about dinohnog?
So what are birds? They are the dinosaurs that survived

(20:03):
the fifth extinction right there, the descendants of these feathered
dinosaurs that survived when the thing that killed all the
other dinosaurs. Now, given that modern birds exhibit a form
of what might be considered lactation, is it possible that
some dinosaurs also fed their young with milk like secretions.
We don't know the answer to this, but exactly this

(20:23):
question is explored by the Australian molecular biologist Paul Else
in a Journal of Experimental Biology paper called Dinosaur Lactation.
It's like Chariots of the Gods. You know, if you
end it with a question mark, you're always safe. It's
not in all caps, though, I will say that that

(20:43):
is a good point, but no, that this is a
fun question. So he says, you know, if dinosaurs did
perform something analogous to lactation, we don't know, but if
they did, it's another one of the many soft tissue
based biological features that are just going to be extremely
difficult to infer from postilized remains. The bones don't usually
tell us things like that, So the only way to

(21:05):
try to answer this kind of question is to look
at the indirect evidence. And so he's got a few
thoughts here. One of them is about the initial size
difference between adults and hatchlings of some dinosaur species, especially
the sauropods. Yeah, yeah, so he says, like, you know,
it almost seems as if it would present mechanical problems
and feeding. He said to I believe this was to

(21:28):
a campus newspaper. He was speaking about his paper to quote,
although I work at the molecular level, I'm basically a
comparative physiologist, and one thing that always struck me as
unresolved about dinosaurs was how a dinosaur parent of several
tons could feed young of only a few kilograms. It
seemed obvious a form of lactation similar to that present

(21:48):
in birds. And then in his paper he writes, quote
lactation might free large parents from having to feed their
newly hatched young the regurgitated products of their own meals
that might be unsued did for altricial young based on
digestive systems unfamiliar with coarse fodder like you know, rough
plant matter that adults would be eating, and essential nutrient

(22:09):
requirements to promote rapid growth, and replace this with secret
secretory products. Oh, that's a hard word. Secretary uh synthesized
by the four gut that are more suited to supporting
rapid development. So again there's obviously some kind of incentive
there would be if they could produce something like this.
We don't know if they could, and so if we

(22:30):
entertain that possibility for a second, the dinosaurs produced milk
for their young, it's likely they did it in the
same way as birds rather than like mammals do. So
that would probably mean nutrient rich secretions from the upper
digestive tract that would be barfed up into little the
little dinosaurs mouths, and paleontologists have discovered evidence that many
dinosaur hatchlings grew very quickly. We do seem to have

(22:52):
evidence for that closer to the growth rate of birds
and mammals than of reptiles, and a nutrient rich parental
secret shin especially if it contained these helpful bioadditives like
antibodies and growth hormone, as it does in the case
of some birds, could help explain this rapid growth, But unfortunately,
there's currently no direct evidence for dinosaur milk. Maybe in

(23:14):
the future some paleontologists will come up with a with
a clever way of proving that dinosaurs made crop milk.
That would be awesome. Yeah, maybe, I mean that's if
we ever get Jurassic Park. That's one of the things
that we can also achieve a chance to sample all
the various dinosaur milks. I wonder which which one would
you prefer if you had to have some dinosaur nog

(23:34):
which species? Oh, I'd probably want to go with a
herbivore milk. I don't know if i'd want to try
out a carnivorous dinosaur milk. I think I could probably
go for what pisar Lofus. I feel like that it
looks like a good milk dina. How about packy cephalosaurus.
Oh yeah, the big cranial head butters right, yeah, I

(23:56):
think yeah, those are those are those are good good
choices that themselves to certain branding, you know, like one
is kind of like the brain milk, uh you know,
you really want to, you know, smack craniums with with
your your your coworker as well, and then you need
a you need a bone up on this stuff about
try saranogue. Try saranogue is good. Yeah, we'll come back

(24:17):
to it. This is what I'm going to keep my
eye on for years. I'm always going to have it
in the back of my mind, waiting for that paper
that says dinosaurs did have crop organs, they produced milk.
All right, should we take a quick break, Let's do it,
Thank you, Thank alright, we're back. We're talking about strange milk,
milk like substances produced by non mamalion creatures. Now, remember

(24:40):
in the episode we did about amphibians with special guest
Markman Decau, he was discussing these amazing creatures called Sicilians,
not the people from Sicily, but it is spelled c
A E C I L I A N. Sicilians are
amphibians like frogs and salam anders, but unlike frogs and salamanders,

(25:02):
sicilians are completely without legs. Most Sicilians live underground, so
we rarely see them, and if you do see one,
you might mistake it for a huge worm. They kind
of look like moist, greasy snakes, So they're sounding more
and more like just like an awesome candidate for milk
like substance production. Right, So can you milk a Sicilian? Uh?

(25:23):
Not exactly, but they do provide their young with nourishing
secretions that are sort of milk analogs. There was a
paper by Alexander cup For a bunch of other authors
Alexander cup for at All, published in Nature in two
thousand six called parental investment by skin feeding in a
Sicilian Amphibian. The short version of this is that after

(25:46):
the mother of a Sicilian species called boulanger Ulia titanus,
after she gives birth, she transforms the outer layer of
her skin into a nutrient rich meal for her young
offsp ring. And then the young developed quote a specialized
dentition which they used to peel and eat the outer

(26:07):
layer of their mother's modified skin. So basically, mom turns
her skin into cheese, and these juvenile worm like creatures
develop special baby teeth that are designed specifically for eating
mom's milk skin. What I love about this example is
that not only is it kind of delightfully grotesque and
again weirder than anything we could dream up for our

(26:28):
horror movies. Uh. It also, even though it's not milk,
it is a milk like behavior. It forces you to
re evaluate what milk is as a mammalion feature. Yeah, well,
are are you saying that even among mammals we should
think about it more like this parent is just ripping
off part of their body to give to their young. Yeah.

(26:49):
I think so. But you know, I I have it.
I have heard mothers, nursing mothers like speak of it
in this in this way, you know where they are,
and I would love to hear from from from anyone
out there has had this experience where they're where they're like,
this is so bizarre, Like I'm all, I'm basically turning
my body into this substance and feeding this little larval

(27:09):
human creature. You know, it's I have frequently heard mothers
speak about the weirdness of the whole scenario, but I
feel like it is a weird There's something about milk
that for the rest of the time and for many
of us, we just take it for granted. Yeah, it's amazing.
We we forget to appreciate the weirdness of reality in

(27:29):
so many ways. But this is another one of them.
It's crazy, it's amazing, it's around us every day. It's
a whole aisle at the grocery store, and it's a
crucial part of human life. Uh and yeah, when you
just stop and appreciate the biological realities of it, it
is startling. Oh. But one thing I wanted to address
about the Sicilians here, so I want to already quote

(27:50):
from the abstract uh So quote. This new form of
parental care provides a plausible intermediate stage and the evolution
of viviparity, which is live birth in Sicilians at independence
offspring of viviparous and oviparous which means egg laying dermato trophic,
which means skin eating. Sicilians are relatively large despite being

(28:14):
provided with relatively little yolk. The specialized dentition of skin
feeding or dermato vegas uh. Sicilians may constitute a pre
adaptation to the fetal feeding on the oviduct lining of
viviparous sicilians. So there's a lot of Latin words, but
in other words, the eggs have the advantage of containing

(28:35):
a yolk that the young can feed on. And of
course this is why egg yolks are delicious, it's everything
a growing body needs. And live birth instead has the
young development feed inside the mother until they're viable to
move around and survive on their own. Species who is
young have this intermediate stage where eating their mother's butter
skin as a yolk substitute or a supplement could be

(28:56):
a could be an evolutionary stepping stone between these two
lines of birth. Yeah. So that then also this connection
between what yolk essentially is and what milk essentially is.
It's like the the offspring is spat out. It's like whoa, mom,
there wasn't enough yolk there. Uh, oh, don't worry. I
have something that is like yolk that I will now
produce for you to consume. It is very much like yolk,

(29:19):
and again both both are involved in egg knock. So connection.
Think about the nutritional parallels between egg yolks and milk.
They tend to be high and protein high and fat
good for growing young bodies. Guess, both useful and making
like a a frothy mixed drink like like a ramos
gin fizz or something. Wait does that egg yolk or
egg white? Uh? That is usually just the egg um

(29:41):
egg whitey, though you know, there are other drinks that
call for the egg yolk as well. I haven't experimented
with as many of those. And of course there are
put plenty of drinks that also call for for milk.
I mean egg knock is a great example of that,
because that is tipped that is often paired with some
sort of a liquor. What's that drink called where you
just have a beer and you crack an egg in it? Oh,

(30:01):
I don't know, is that like they drink it on
the wire? I think I don't remember the name of
that one, like the Dockworkers Breakfast, the Champions or something.
Never tried it? All right, Robert, have you have you
got some strange milk for us? Yeah? So you know,
we're talking about birds, it only, you know, makes sense
that we would also turn to the world of fish. Okay,

(30:24):
So in particular, we're talking about the discus fish, which
is an Amazonian chick lit species. It's a rather unique
fish because both mother and father provide sustenance for their
hatchlings via mucous secretions. And of course this isn't simply
a matter of hatchlings like nipping some mucus from their
parents and then swimming off. This can go on for

(30:45):
a month or so. Oh wow, so it's prolonged. Yeah, yea.
So it's worth remembering that with the with a fish
slime and mucus or or mucus that they're very important.
It's not merely the stuff that's on their scales, but
it constitutes a protective outer layer of their bodies and
it provides a number of key benefits. UM. One of
the big ones that's going to be important here is

(31:07):
UH osmo regulation or gas transport, and this is to
maintain the internal external osmotic balance UM also sometimes referred
to you know, dermal respiration UH. In addition to this,
the mucus or slime provides external protection. It can reduce turbulence,
and there are other varieties of fish that also use
it as a toxin rich outer coating, so it can

(31:29):
be protective. Even if it doesn't have toxins in it,
it can provide some level of protection. You have other
particularly slimy fish like the hag fish that use it
to their advantage. UH. It can also mucus also conserve
for water cleansing purposes. It can also form It can
also serve a purpose in the cocoon formation in the
case of the African lungfish, and some fish also eat

(31:51):
their own mucus. So a two thousand ten study looked
into this. It was titled Biparental mucus feeding a Unique
Example of Parent Care in an Amazonian chicklet by Buckley
at All, published in the Journal of Experimental Biology. So
basically they broke down not only the nutrient and immunity
load of the mucus, but also how it all changed

(32:12):
depending on the developmental level of the offspring, very much
in line with the milk production of mammals as we
discussed earlier. You know, again, remember how milk changes to
meet the growing offsprings needs. The authors pointed out that
like the peak level of mucus, antibody up provision was
seen as offspring reached the free swimming stage, and this suggested,

(32:33):
you know, a role that's very much like what is
provided by mammals. Again, so that you know that there's
a winging off here. Um. You know. They pointed out
that the protein was lowest during the second and third
weeks of free swimming during a weaning period, and the
authors point out that all of this is far more
in line with mammalion and avi and parental care than
anything we see in in other fish. So it's a

(32:55):
it's a rather curious example of you know, it's not milk,
it's it's it's a little more like the Sicilian example.
And then we're dealing with an out a layer of
the creature's skin. Um, but but still it's it's providing
sustenance for the young, and doing so again not in
just an off head man or like the hatchlings are

(33:16):
out and then they just you know, grab a bite
and run off. It seems like we're steadily progressing further
and further from mammals, Like we went to birds and dinosaurs,
and we went to amphibians, and then we went to fish,
which are still vertebrates. How much further could we get? Yeah,
because it's one of those things where if you just

(33:36):
came up to somebody in the street and just surprised
him and said, hey, have you ever tried bird milk?
They might be like, oh, I don't know. It might
take them just a few seconds to be like, hey,
wait a second. Only mammals produced milk. But when you
start talking about fish milk, and and you know, little
or insect milk. I think most people aren't gonna buy
it for a second. They're they're gonna say, you're a
crazy person. Stop talking about things that don't exist. Let

(33:58):
me talk about things that do exist. Robert, go on
a mental journey with me. Imagine you are sitting on
a park bench in a park somewhere in southern China,
and you feel a tickle on your forearm. You look down.
There's an ant crawling on you. It has a shiny,
segmented black body with antennae wiggling in the breeze. But

(34:19):
then you look closer, those aren't antenna They're not coming
out of the top of its head. They're coming out
of the thorax under the head, or the cephalothorax their legs,
which means this animal has not six, but eight legs.
This is not an ant. It is a spider. It's
a spider in disguise. This is the spider Toxas Magnus.

(34:44):
I've included a picture for you to look at here, Robert,
and I like the way, even in this close up,
the shiny black body is like catching a fluorescent light
on the ceiling that you can see very clearly. Yeah,
and it looks very much like an ant. At first glance,
you would just assume this is an aunt. You really
have to stare at it for a second to to
make out all the legs. Yeah. So it's about a

(35:05):
centimeter long, Toxais magnus and it's a member of the
family selticitay the jumping spiders. Magnus is also known as
the black ant mimicking jumper which needs to catch your
name and uh. It's found mostly in Southeast Asia. Now,
there are hundreds of species of spider that are professional
ant mimics like this. They're known as the Mermaica morphs

(35:27):
and not. They not only look like ants, but they
often mimic the behaviors and movement patterns of ants, even
lifting and waving their front legs around to make them
look like antennae, or walking on people, or walking in
patterns that copy the locomotion of foraging ants. And you
can imagine several recent spiders might want to look like ants.

(35:50):
Uh that the main pressure actually driving this evolutionary path
seems to be the avoidance of certain egg sac parasites
like spider wasps and predators like antises and other larger
jumping spiders which kill spiders but usually leave ants alone.
That makes sense, right, I mean, because of course, obviously
you know all these species that have evolved to prey

(36:11):
upon spiders, but associating yourself with the ants, it's kind of, ah,
that's a safer bet because the ants have strengthened numbers
and they're not the solitary prey that a spider would be, right,
or they might just not be nutritious to eat or something.
I mean, there might be all kinds of reasons that
a predator doesn't really want to go mess with an aunt.

(36:31):
So just a few weeks ago, a group of researchers,
mostly based in China, led by a researcher named John
chi Chen, published a study in the journal Science revealing
something amazing about these ant mimic spiders. It started with
the observation that after the young Magnus spiders hatch from
their eggs, they sort of became, uh like what you

(36:54):
might call indoor children. Instead of leaving the nest, they
hung around for a long time time, roughly twenty days.
And then it gets weirder because not only did they
not leave the nest to forage, the mother spider didn't
leave the nest to forage either, so it couldn't have
been going out to get food to bring back to them.
Nobody left home or even went out to the grocery

(37:16):
store for almost three weeks, and if you know something
about spiders, you'll probably recognize that there's something odd going
on here. Like there are some social species of arachnid,
but this shouldn't be one of the Most spiders, including
generally salt aids. The jumping spiders are aggressive and even
even cannibalistic toward one another, so they don't nest together

(37:38):
like this except for those those small number of social species.
What's weirder During this period of family time, the young
spiders grew a lot. If they were growing, they had
to be eating, so what were they eating If nobody
ever left the nest. You can probably guess where we're
going with this. The authors started watching more closely just

(37:58):
what was happening in the nest, and what they found
was strange and fascinating. During the first week after hatching,
the mother spider would secrete droplets of an unknown white
milk like fluid from a ridge on her underbelly called
the epigastric furrow. This is also where the spiders eggs
are produced. Interestingly and uh so, after she secreted this fluid,

(38:20):
she would leave droplets of it on the walls of
the nest for her offspring to eat, and after the
first week, the young spiders would just climb right up
on her and drink the secretions directly from the mother
Magnus's epigastric furrow. So this milk substance feeding took place
for the first forty days of the young spiders lives.
Even after the young spiders finally started leaving the nest

(38:42):
to hunt, they would come back. They would come back
to the nest and supplement their insect diet by getting
more spider milk from the mother. That's incredible. Yeah, So
the researchers also found that when the spiders were unable
to feed their young with this spider milk, all the
young spiders died thin less than two weeks. So it's
not just a little something extra, it's necessary for the

(39:04):
life cycle of the species. And the spider milk they
found is incredibly nutritious. They found that per mill leader
it contained two milligrams of sugar, five point two milligrams
of fat, and a hundred and twenty four milligrams of protein,
which is a lot that's expressed as four times the
protein content of cow's milk. And of course I envisioned

(39:25):
an awesome future whenever we finally chuck it in and
just start hawking bogus nutrition supplements to bodybuilders, We're going
to do the spider milk protein bomb stack. I love this.
I really want to incorporate this into Dungeons and Dragons
because you have various species, particularly in an under dark um,
the vast subterranean realm in the setting that depends on spiders.

(39:48):
The gray dwarf of the Dugard. They have these kind
of like a pack pony spiders that they use, so
it makes sense that they would be drinking some sort
of spider milk. And now there's a there's a scientific
reason to incorporate that into everyone's campaigns. Doesn't science always
end up proving the D and D monster manual correct.
One of the co authors on this paper, Richard T. Courtlet, says, quote,

(40:11):
our findings suggests that lactation may arise in non mammals
when it provides a significant advantage in offspring survival. Well,
as we've been seeing from the other examples in this
episode that's clearly true. Uh. He also says that it's
useful in this species because of the small size of
the hatchlings. They're tiny and unable to hunt, or at
least initially unable to hunt or defend themselves from predators.

(40:33):
But ultimately the researchers don't know why this strange mammal
like trade has evolved in this one species of spider.
As far as we know, at least so far, this
is the only spider that does this, and it's very weird.
And another thing that was pointed out that was pretty
weird is that the mother magnus didn't just offer her
milk to the young. She also displays like social parenting behaviors,

(40:55):
like maintaining a clean and safe nest environment for the
young to hang out in. Just kind of kind of
weird for spiders. All Right, on that note, we're going
to take another break, and when we come back, you know,
we'll we'll keep having some arachneid milk. Thank Alright, we're back, Robert.
Are you going to feed me with the milk of arachneids? Yes? Yes,

(41:16):
we have another another arachneid species here that's producing something
that's kind of like milk. So we're talking about the
pseudo scorpion. Nice. Now, the pseudo scorpion really sounds like
something that your hey, Luis Borees would have just made up.
It's a tiny arachneid that can frequently be found living
in old books, protecting them from decay by feasting on

(41:39):
book lice that munch on the starch based book binding glue.
That is that is good? Yeah, I mean it really
does sound like something that Borees would have made up, like, oh, well,
the the old books are home to these tiny creatures
and they eat other tiny creatures that they want to
destroy the books. I don't know it did, There's there's
something beautiful about it. Yeah, it's like something that would

(41:59):
have been imagined in the marginal illustrations in one of
the scripts in the Name of the Rows. Yes, yes,
and and and they do literally live in the margins,
so it makes sense. But if you see them, they
look kind of like scorpions without tails, like they got claws. Yea.
They're sometimes called false scorpions because they are in fact
not scorpions despite having these big pinchers. They have some

(42:23):
really impressive looking pinchers. And there are some thirty three
hundred species of false scorpion that live around the world,
but the most famous is callith can crow Eades, which
can reach four millimeters in length. So I was reading
about this. The author bet Crew has a wonderful post
about them on the Scientific American blog titled how book

(42:44):
scorpions Tend to Your Dusty Tones, and she discusses, among
other things, they're they're dancing and rubbing mating rituals, which
sound quite cute, but then it gets really kind of
weird and brutal. Quote he dumps a sack full of
sperm on the round, and it gets worse because then
he pushes the female down into his sack full of

(43:04):
sperm on the ground. This whole process can take anywhere
from ten minutes to a whole hour. The sack full
of sperm will be taken in by the female's genital
orifice and she'll end up producing twenty to forty eggs,
which she'll carry around in her abdomen even after they've hatched.
Well that's weird sex, yes, yeah, so everything gets a
little less borhe than a little more. I don't know, geeker,

(43:25):
I guess, but but here's where we get to the
sweet book scorpion milk. So the larvae will hang around
and the young, the young book scorpions will even hang
out around on her back until they're old enough to
go off on their own. But as larvae, they remain
inside for a while, living in her genital orifice and
feeding on a milk like substance that secretes from her ovaries.

(43:47):
So they feast on this stuff, and eventually she's just
so emaciated from the consumption, uh, that the tiny book
scorpions just have to leave, like they can no longer
hang out in the orifice because there's just not enough
book scorpion milk to go around anymore. Ungrateful, Well, you know,
she does, She does a lot, She does what she can,
and then they have to move on and eat some

(44:08):
book lice. Somebody out of whip some independence into those.
Maybe book scorpions getta eating book lice earlier. Now I
have another couple of creatures to mention here. These are insects,
but they also illustrate what's going on. So bat flies.
I was not familiar with bat flies, but they are
fascinating little creatures. They are as the name implies, parasites

(44:31):
that feed on bats. They do, not, however, look much
like a traditional fly whatever you're imagining when I say
bat fly, it ain't that. Are we going to try
to say? The family name of the bat flies? Is
it nick ter Ribida? Yes? I think that would be
my guess, nick to Ribidae. Uh. They are wingless, spider
like insects with long legs and a small head that

(44:54):
folds back into a groove in the thorax when it rests.
So earlier we had a spider that kind of looks
like an insect. Here we have an insect that kind
of looks like a spider. They also have a highly
developed uterus and milk glands there, or at least they
were referred to as milk glands milk in quotation marks here.
And these glands seem to play a key role in

(45:15):
imparting important bacterial indo symbians to the offspring and other
insects engage in this kind of behavior as well, as
they host bacteria in their cells that provide important boosts
that food alone cannot give them. These indo symbians are essential.
For example, the tetse fly hosts a bacterium that provides
b items that are not available in uh in the

(45:38):
flies normal diet of blood. Isn't it amazing? How Like
we think that animals rule the world, but like almost
all animals are just so dependent on invisible microbes in
order to even just get the basic nutrition they need
out of their food. Yeah, it's it's crazy, it's crazy.
But yeah, again, this is a great example all of

(46:00):
just like, it's almost like a simple model of milk. Hey, baby,
you're just gonna only eat blood, but there are things
you need. I will have to provide them through some
handy secretions. Well, there's another insects secretion. I want to
talk about. What kind of yummy milk do you have
for us? Now? It's cockroach milk. So you're not a
fan of cockroaches, are you? How do you know anyone

(46:20):
who is? Oh, I'm sure there are lots of people
who love cockroach. I mean, he'sing cockroaches are kind of
I think cockroaches are only interesting if they are exotic
or their pets. Nobody wants just free range cockroaches or
palmetta bugs. Is you know we regionally call the larger
ones that invade our homes. Nobody wants those around though,

(46:42):
like that. We have just an inescapable around here, inescapable,
and I feel like we have instant kill instinct with them.
No matter how much you have to you have to
be pretty hardycore animal lover to say, oh, the Palmetta
bug is here, let me attend to its needs. And
smashing one of those Georgia cockroaches is basic, really like
smashing like a three foot wide jellyfish, Like it leaves

(47:04):
this explosion of of mucus and liquid everywhere. They are
so big and so juicy. Yeah, and they'll they like
to hang out I've noticed sometimes tauntingly on white walls.
We're like, oh, I can't squish you there, because there
will be a The mark will haunt me forever. You
ever walk into the bathroom in the middle of the night,

(47:26):
turn the light on and there's a cockroach on your toothbrush.
No I haven't, I haven't. It's happened to me. I
have not encountered that, But now I have that that
image of man, and now I will fear it. I
do frequently, never know, I do frequently notice how you'll
I'll go into a room. It might be the you know,
the kitchen or wherever, and you turn on the light

(47:46):
and it's not. You don't always necessarily see the roach
all at once, but suddenly something clicks in your mind,
like there's something something is off, like you know, and
then you have to look for it, and then you
find it, you know. But we we say we have
like a high level of awareness for them. So there
is a species of cockroach found in Asia and in

(48:07):
the Pacific Islands. I think it's found a lot in Hawaii,
known as the Pacific beetle cockroach or diploped Tera punk tata.
And there are several interesting things about the species of cockroach.
First of all, they are the only known truly viviparous cockroach,
the only cockroach we know of that has real live
birth instead of laying eggs. Second, this kind of interesting.

(48:31):
They do chemical warfare. They produce an organic compound that's
known as quine owns from specialized tracheal glands, and this
is probably a chemical weapon they use against predators. There
are analogies for this, like quine owns are used as
part of the chemical defense of the Bombardier beetle. And
then finally, researchers have discovered that this cockroach who gives

(48:52):
live birth to its young also secretes a type of
protein rich, light yellow milk like liquid from her brew sack,
and then the young ones drink it. Okay, tell me
more about this roach not well. One of the one
of the researchers who first discovered this was the University
of Iowa emeritus biologist and insects surgeon, Dr. Barbara Stay,

(49:15):
insects surgeon. How do you become an insect surgeon? That
sounds like an awesome job, very delicate hands. Yes, you've
gotta be like so many steps above, like the human neurosurgeon,
to be an insect surgeon. So the cockroach milk begins
as a liquid at first, and it contains these milk
crystals that are full of nutritious proteins and stuff. And

(49:36):
then as the young grow, the the milk begins to
sort of like solidify into bigger solid crystals. And Dr
Stay apparently developed a process for quote milking these cockroaches.
Speaking to NPR, she described the process. I guess pretty simply,
she said, quote you substitute a filter paper in the
brood sack for the embryos, and you leave it there.

(49:58):
After a while, you take it out and you get
the milk. Okay, it's kind of a stuff of washcloth
into the roach and then eventually you take it out
and ring it in, ring it out. That's yeah, that's
about right. So you may have seen some articles about
this a couple of years ago because there was a
new study in analyzing the contents of this cockroach milk,
and this study was done by a team led by

(50:21):
the Indian biochemists Supermannion Ramaswamy, and the researchers found that
it was super nutritious. Quote, a single crystal is estimated
to contain more than three times the energy of an
equivalent mass of dairy milk. This unique storage form of
nourishment for developing embryos allows access to a constant supply

(50:41):
of complete nutrients. And by the way, of course, the
way this was covered in the press was there was
just headline after headline and CNN and everywhere saying the
cockroach milk is the next super food. I'm I'm not
grossed out by that. I was as grossed out as
I am by by roaches us. Really, um, I think

(51:01):
that falls in line with a lot of what we've
been seeing about the consumption of insects, and sects is
the protein source. The future is going to be a
place where either you eat the bugs or the bugs
eat you. Into ma Fiji is the future, and I
think there's no doubt about that. I mean, it is
a healthy source of protein. That's I think going to
be an incredibly important meat substitute in in on future Earth.

(51:24):
I have to give a quick shout out to the
Audubon Society's UH Insectarium in New Orleans. UH wonderful museum
with so many different live insects species and some arachnet
species to check out. But they also have an area
where every time you go you get to try a
few different um food items that have been prepared with

(51:46):
insect protein. And did you try, Oh, I do it
every time. Did you like it? Yeah? Well, they really
try and make sure that it's something that you will
and candy, you know, so it's generally something sweet you
know that kids are gonna be into, essentially, you know,
cookies topped with meal worms, that sort of a thing.
But it's very I think it's very instructional and insightful
and I'm I'm super glad that they do that and

(52:06):
provide that kind of uh, you know, educational content in
addition to just learning about these different insect interactant species.
I didn't write down what the reference for this was,
but I did look at a press release about a
study that found that if you wanted to get people,
I think what it was was, if you wanted to
get people to agree to eating insects, you couldn't just

(52:28):
appeal to the idea that it was better for the
environment or that it was nutritious. You had to convince
them that it was a delicious delicacy and if you
could do that, they would eat the insects. Interesting. I, yeah,
I would love to look at this topic more and
see what what people were doing along those lines, because
we often come back to the fact that, like, what's

(52:48):
the difference ultimately between eating various types of insects in
eating shrimp or crawl dads or what happened? Yeah, lobster lobster?
Why is that different? Yeah? So, yeah, I would love
to talk about about insects more in the future. But
I've got en off topic here. Let's get back to
that delicious roach knock Well, So I brought that up
just to say that it's probably not true that cockroach

(53:09):
milk is the next superfood. I think those were just
some headline grabbers. Uh. Number one, we don't know that
the milk is safe for human consumption. Humans can often
become allergic to cockroaches. We don't have a way of
milking them at any kind of volume. So it is
really interesting research. Nonetheless though a couple of reasons, but
generally it has to do with the idea of studying

(53:30):
the proteins in these crystals in the roach milk to
see if they can be replicated in other production scenarios,
say by e coal i or by yeast, in ways
that could deliver better technologies for medicine or nutrition. And
I was reading an interesting blog post by a biologist
or entomologist named Joe Ballinger, and in this post he

(53:51):
pointed out that the real discovery here was that there's
this protein structure in the in the cockroach milk that
includes a protein that kind of serves as a delivery
pocket that could be used in other context to shuttle
drugs or substances around inside the body. And of course
that's relevant anytime you've got some kind of delivery or
micro delivery system that's relevant to future medicines. As for taste,

(54:14):
on the other hand, reportedly one of Ramaswami's colleagues tried
the cockroach milk on a dare I think maybe because
he lost a drinking game or something, and quote he said,
it doesn't taste like anything special. Well, I wonder how
much you drank though, Like essentially, if he just its
like a you know, he dabbed a tiny droplet of it,
or if he had like a full milk glass of

(54:36):
the stuff, like you drank a quart of it. Yeah,
I imagine he just came from a million cockroaches, the
milk of a million cockroaches. It does sound lovely, doesn't it.
Well that's it for our sampling of non mammalian milks
to discuss here. You know, we didn't even get into
some of the fictional milks out there that have been consumed.
How about those creatures in the most recent Star Wars films. Oh,

(54:58):
in the Last Jedi or Skywalkers drinking? Is it green
or is it blue? Milk? That comes? Yeah? Oh, that
that's like the best scene. I loved that. It kind
of made the movie for me. Yeah, I enjoyed that film.
I did too. Um. You know another one that comes up.
It's been a long time since I've seen this, but
the David Cronenberg adaptation of William Burrows Naked Lunch. I

(55:19):
believe the mud wump creatures in that film UH secreted
some sort of substance that was consumed by by various characters.
It's been a while since I've seen it. I don't
exactly remember what the whole deal was there, I must
confess I've never seen it. Oh, it's it's interesting and
the book is a classic of its generation. But off hand,

(55:41):
I can't think of any other you know, key like
alien milks or monster milks and UH in cinema or fiction. Though,
this would be a good thing to to call out
to our our listeners about what what are some of
your your favorite or at least notable examples of of
non mammalian UH, you know, a fictional creature milks out there?

(56:03):
And indeed, I want to know what dinosaur milks other
people would like to consume. Now, as I said earlier
in this episode, while I've really enjoyed exploring this anomalous
non mammalian milk, we could probably do a whole show
in the future just on the magic of true milk.
Of mammal milk. It is a fascinating subject and there's
a lot we didn't even have time to talk about today. Likewise,

(56:25):
I would love to do an episode that goes more
in death on cockroaches. I mean there there's a whole
lot there that we didn't even touch on here today,
or squash beneath our boot they're six legged saints? All right? Well, um,
uh we thank you for listening to this episode within
which we discussed the milk of the six legged Saint,
and uh we hope you'll tune in some more. We

(56:47):
have a couple of other holiday episodes coming up, but
more than I more than I expected. But I think
I'm I'm embracing the holidays a little more this year.
You've been leaning in. I have people out there. You're
gonna be surprised all the stuff Bert has wanted to
talk about this month. I'm I think I'm giving in
to the holidays this year. I finally realized that it's
not it's not courage to fight it, it's courage to

(57:09):
to give in. Uh. To paraphrase a quote from one
of my favorite holiday films, Ravenous. Uh, so hey, if
you want to uh listen to other episodes of Stuff
to Blow Your Mind or keep an eye out for
new ones. Head on over to the mother ships stuff
to Blow your Mind dot com. That's where we'll find
all the episodes, links out to areas, see various social
media accounts, and there's also a button at the top

(57:31):
of the page for our store. That's our t public store.
We'll find all sorts of cool shirt stickers, throw pillows,
tote bags, you name it, as logos for the show,
and also some other cool designs like Cambrian Life logo,
the Skug King of the Rats, all Hell, the Great Basilisk,
all that sort of stuff. It's a great way to
support the show, but if you want to support the

(57:52):
show without spending a dime, rate and review us wherever
you have the power to do so. It really helps
us out big. Thanks as always to are super awesome
audio producers Alex Williams and Tori Harrison. If you would
like to get in touch with us with feedback about
this episode or any other, or would like to suggest
a topic for the future, or just get in touch

(58:12):
and say hi, you can email us at blow the
Mind at how stuff works dot com for more on
this and thousands of other topics. Does it, how stuff works,
dot com, gold,