November 21, 2023 • 57 mins
In this classic episode of Stuff to Blow Your Mind, Robert and Joe discuss some of the most famous reptilian residents of the Galapagos archipelago, including the world’s largest extant tortoise species and the world’s only marine iguana. (originally published 12/08/2022)
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Speaker 1 (00:06):
Hey, welcome to Stuff to Blow Your Mind. My name
is Robert.
Speaker 2 (00:09):
Lamb and I am Joe McCormick, and we are out
this week, so we're bringing you an episode from the vault.
Today's episode originally aired on December eighth, twenty twenty two,
and it is part one of our series on the
reptiles of the Galapagos Islands.
Speaker 1 (00:24):
All right, let's dive right in.
Speaker 3 (00:29):
Welcome to Stuff to Blow Your Mind, production of iHeartRadio.
Speaker 1 (00:39):
Hey, welcome to Stuff to Blow Your Mind. My name
is Robert Lamb.
Speaker 2 (00:43):
And I'm Joe McCormick, and today we're beginning a series
of episodes on the reptiles of the Galapagos Islands. And Rob,
this is not a topic we just landed on randomly.
This is related to your recent travels, right.
Speaker 1 (00:57):
Yeah. I had the great pleasure in the fortune to
visit some of the islands of the Galapagos Archipella go
back in October. It was a fantastic family trip that
we'd been planning for a long time, that we meant
to do before the pandemic and then obviously we had
to reschedule. But yeah, this is this was one of
the top trips I've ever had the privilege to make.
(01:18):
And now certainly I was visiting as a tourist. But
one of the things about the Galapagos Islands that I
love is so much of the tourism there is about
the natural beauty of the place. It's about the environments,
it's about the animals. And so if you're going all
the way to the Galapagos Islands, you probably want to
(01:39):
see some reptiles, you probably want to see some birds,
et cetera. And they really facilitate that. The local guides
are all terrific, all the ones that I interacted with
very knowledgeable of everything going on there. And yeah, it
was a trip just unlike any other, especially when when
(02:00):
observing these various creatures, because it was kind of like
being a Disney princess, like being in a Disney like
a Disney princess scene in a movie, except instead of
the princess being surrounded by cute squirrels, bunnies and birds
that are singing, you're just constantly surrounded by this wonderfully
bizarre cast of reptiles and elaborate birds, sea lions, etc.
(02:27):
And it's unlike too, I have to say, it's unlike
the vibe that I've encountered in places like the Grand Canyon,
where there'll be wild animals there that are protected and
so accustomed to humans that the humans can get like
unnaturally and alarmingly close to those animals. There's a proximity
to the animals on the Galapagos Islands that feels less
(02:51):
artificial but also equally magical, if that makes sense. Again,
not to say that you should attempt to touch any
of the animals there, or or or infringe upon their
personal space in any way, but there's this, Yeah, there's
this feeling of proximity to nature that makes you feel
like you are David Attenborough in a David Attenborough documentary,
(03:14):
you know, creeping up for a close look at this
animal or another.
Speaker 2 (03:18):
And maybe you are the camera lens. And I wonder
if the difference with the Grand Canyon thing would be
the difference between animals that are unfortunately habituated to human
presence in all the wrong ways, like expecting you to
have food, the calorie rich food sources and stuff, so
they'll come up to you looking for that, versus a
(03:38):
place where animals don't seem to flee from humans because
they come from many generations of animals without natural land predators.
Speaker 1 (03:47):
Yeah, yeah, and I believe that is the case with
the Glapicos. So let's let's introduce everybody to the Glapico silence.
If you're not familiar with the Glapagos Archipelago, it is
a chain of islands in the eastern Pacific Ocean, roughly
nine hundred and sixty six kilometers or six hundred miles
off the coast of Ecuador. It consists of thirteen major
(04:09):
islands a few smaller islands, and these were all formed
by repeated volcanic eruptions. The process here is similar to
that which produced the Hawaiian Islands, which we've discussed in
the show before. So they're not formed all at once,
but in a chain due to underlying volcanic activity berthing
mountains and islands out of the ocean floor. So, as
(04:31):
with the Hawaiian Islands, the islands here in the Galapagos
are geologically quite young and their individual ages vary. Now, Joe,
I'm not sure what age ranges you've come across for
them when we get into the geologic age of the
Galapagos Islands, but I've seen it vary a bit. The
Galapagos Conservatory says, quote, probably no more than five million
(04:54):
years with the younger volcanically active westernmost islands perhaps as
young as hundreds of thous sin of years old.
Speaker 2 (05:01):
But the idea that none of the islands there today
are are more than five million years.
Speaker 1 (05:06):
Old according to some of the dates that I was
looking at these sighted dates, but just sort of casting
a wide net, I did see some other dates out there,
so you know, I can only speak to the ones
I'm citing here.
Speaker 2 (05:18):
Well, estimates vary a bit, but it also depends on
what you're counting as the Galapagos Islands. For example, I
was reading a passage in a book Galapagos a Natural History,
second edition by John Creecher and Kevin Laughlin from Princeton
University Press. That new edition is just out this year,
in twenty twenty two, and there is a section in
(05:40):
this book where the authors put forward the possibility that
some species on the islands, including the famous giant tortoises,
may have inhabited the Galapagos since before any of the
Galapagos Islands existed. Now, how could that be possible? Well,
here's what they argue. If you look around the area
of the archipelago, especially east of the existing islands, you
(06:04):
will see what are called sea mounts, which are submerged islands.
They are areas where the ocean floor rises up to
form a mountain, but that mountain does not break through
the surface of the water. So it's not an island
from our perspective, but it's sort of like an island
just beneath the water. Now, what are these seamounts in
(06:26):
the eastern part of the archipelago. Well, Creature and Laughlin
write that they are quote eroded volcanic islands, and that
they are possibly the original ancestral Galapagos. So they were
once perhaps islands that did break above the surface, but
have eroded over time. And the authors here cite a
(06:47):
group of oceanographers and geologists led by a researcher named D. M. Christie,
who put together some dates for these seamounts and said
that the dates range from between five to not nine
million years, which is older than any of the existing
Galapagos islands today. So to read from this passage quote,
(07:07):
as Christie's team pointed out, if the original Galapagos islands
formed as much as nine million years ago, there has
been more time for colonization and subsequent evolution than once believed.
This is colonization by non human animals. There may well
have been tortoises on the islands for longer than any
of the present day islands have been in existence. Given regular,
(07:30):
albeit accidental dispersal, new islands forming over the Hotspot will
be colonized even as old islands erode and disappear beneath
the sea from whence they came. So normally you're talking
about an island group, you would imagine that, okay, well,
the earliest it could have been colonized by animal species
is whenever the islands we have today began. But in
(07:52):
the case of the Galapagos, a lot of the evidence
of the earliest colonization by animals could be under the waves.
It could be lost because those islands aren't there anymore.
Speaker 1 (08:04):
The lost animal kingdoms of the Galapgos potentially. Now, when
we're talking about the modern day Galapagos islands, some of
the main ones, just to mention them real quick, you
have Isabella, which is the largest. You have Santiago Fernandina,
you have Santa Cruz, you have San Cristobol. I only
(08:26):
really visited Santa Cruz and San Cristobal and a couple
of smaller unoccupied by humans islands that were quite fascinating.
And one of the things about these islands, and you've
often counted this with volcanic island formations, is that they're
defined by steep out elevation changes and the resulting islands
(08:46):
that contain multiple micro climates due to this, So a
visit to even a single Galapagos island is an encounter
with multiple and varied ecosystems.
Speaker 2 (08:54):
Right, So you'll get different climates and different vegetation and
so forth at different elevations on the island. So and
that type of like what vegetation is flourishing therefore might
vary with the seasons. So when the rainy season comes,
you might get more blossoming of vegetation in the lower areas,
but then other times animals might find the most fruitful
(09:15):
foraging up in the highlands.
Speaker 1 (09:18):
Yeah. Yeah, So it's any one of these islands, you'll
have you have sort of desert environments, you'll have highland
lush environments, you'll have coastal environments, and these are these
are This is one of the reasons that these islands
are often singled out historically, but even in modern research
is kind of a laboratory of evolution. Now, I'm going
to keep referring back to Hawaii a little bit for
(09:40):
a while because I think it's a nice sort of
touchdown to compare, especially since we've talked about those islands
on the show before as well. So when it comes
to Hawaii, as we've discussed before, you have such geographic
isolation that with those islands, so that there are actually
no native land reptiles or amphibians there. So anything in
(10:01):
the categorization of reptil or amphibian that you find there
were introduced by subsequent human arrivals by boat or ultimately air.
That's the Hawaiian Islands. We don't have the same situation
with the glabgos islence for a few different reasons. So
as far as humans go, first, human contact with Galapagos
comes a bit later. We're talking about fifteen thirty five
(10:24):
versus Hawaii's between one twenty four CE and eleven twenty CE. Also,
Hawaii is a greater distance from the nearest continental land mass.
And I should note that I think I've pointed this
Alma show before, but there is some dispute on whether
the Inca ever reached the island, but we can be
certain that Europeans reached the island in fifteen thirty five.
Speaker 2 (10:46):
Yeah, exactly three hundred years before Darwin did.
Speaker 1 (10:49):
By the way, Yeah yeah.
Speaker 2 (10:58):
So the story of the first confirmed human landing on
the Galapagos is very interesting, so I wanted to tell
it here. There was this Spanish clergyman named Tomas de
Berlonga who was a bishop eventually served as the bishop
of the Colony of Panama, and I've read it alleged
in several sources that Berloga was responsible for introducing bananas
(11:22):
or plantains to the New World, which is weird because
despite how much we associate bananas with the Caribbean and
South America, they are originally native to Southeast Asia. So
it is alleged that this guy's responsible for bringing bananas over,
but I'm not sure what the original source of this
claim is. Anyway, in fifteen thirty five, Berloga was traveling
(11:42):
by ship from Panama to Peru to help sort out
some kind of horrible sounding squabble between the conquistador Francisco
Pizarro and another conquistador over land and spoils after their
conquest of the Inca Empire, so Burlonga's on the way
down to try to help sort this out. But as
(12:03):
his ship is traveling south along the coast during the
first half of the journey, it is suddenly struck by
a dead calm that prevents the ship from sailing further,
and then it gets dragged far off course out to
sea by strong ocean currents, and just when supplies, including
fresh water, are about to run out, the crew sits land.
Their prayers have been answered, but like so many early visitors,
(12:27):
these Spaniards are almost instantly dejected by what they find.
The first island where they land is found to have
not a single drop of fresh water, and there's also
no pasture where their horses can graze, just a bunch
of giant tortoises and weird iguanas. But there were other
islands nearby, so the crew tried to sail to another
(12:48):
one to continue the search for water. Unfortunately, on the
way they were once again becalmed and could not sail
for several days, while just languishing there on the ship,
nearly dying of thirst. Finally the wind picked up again
and they were able to reach a second island, where
once again they found no fresh water. They tried to
dig a well, but when they struck groundwater, they found
(13:10):
it to be as bitter as the sea. And here
I want to read from the retelling of this story
by the famous naturalist William Biebe in his book Galapagos
World's End, published in nineteen twenty four, BB writes, in
their extremity, they had recourse to a plant which has
saved many a thirsty man and animal, And by chewing
(13:31):
the fruit and juicy stalks of the cactus they kept
themselves alive.
Speaker 1 (13:37):
They took a page from the tortoise playbook. There.
Speaker 2 (13:40):
Yeah, not all withstood these privations. One man and two
horses died of thirst, and so the first grave on
the Galapagos was dug. Sunday came and the bishop celebrated
high Mass on those desolate shores, where as he said, quote,
it looked as though God had caused it to rain
stone ones, brutal doom metal bishop. And then BB goes
(14:05):
on sea. Lions slipped through the creaming surf and looked
curiously at the little group of strange beings, and long
winged seabirds poised and swooped above the cross and the
Spanish flag planted side by side among the cactus and
thorny scrub. So I think BB's taken a little liberty
with the storytelling there, but all plausible, you know, given
the local flora and fauna.
Speaker 1 (14:28):
Yeah, desolate beaches, weird sea lions hanging about. Well, I
guess the sea lions are generally described you as weird.
They would have certainly been exposed to sea lions already,
but in my books, sea lions are inherently strange but
also very amusing to watch.
Speaker 2 (14:43):
They're just playfully rolling about while these people have church,
dying of thirst. So finally, after the worship service, the
Spaniards did find some small amount of fresh water. I've
seen what they found, alternately described as spring water and
as little pools collected in cup shaped depressions in the rocks.
(15:04):
And using this water, either the spring water or the
rock pools, they filled up their containers and they departed
again for the coast of Peru. Now, Burlanga made a
number of observations while on the island, writing, according to
an eighteen eighty four translation of his letters, that the
animals of the Galapagos were quote so silly that they
(15:26):
did not know how to flee, and that as a result,
wild animals were easily caught in the hand.
Speaker 1 (15:33):
Well, that does match up, I think with the reality
of visiting the Glabgos Islands even today. Not that you
should be chasing any of the animals and certainly not
catching them in the hand. But yeah, there is this,
like I said, there's this sense that they don't necessarily
understand what we are and they're not threatened by us
(15:53):
unless we get too close, and then a lot of
these animals will let you know. So, yeah, don't get
too close to the sea lions wherever you find your
sea lions. Don't get too close to the tortoises of
the Iguanas.
Speaker 2 (16:05):
Now, Rob, you mentioned that the tourism at the Galapagos
today is almost entirely centered around the island's natural beauty
and biological and ecological significance. You know, this is a
place where you go to see the natural landscape and
the flora and fauna. You're not going there to see
to go to six Flags Galapagos.
Speaker 1 (16:25):
Right right, Yeah, Yeah, I mainly mean, yeah, you're not
going to find that. You're not going to find I
didn't really see much in the way of like a
party boat kind of culture that you find in a
lot of locations. It's you know that there is there
is culture there. There's some great restaurants, there's there's great
local culture. And the people who live there were on
(16:46):
the whole very friendly and and I loved interacting with
them quite a bit. But yeah, it's when people go
to the Galapagos. I mean, the main selling point, the
big deal for everyone seems to be the natural world
that is avail to you there.
Speaker 2 (17:01):
And despite this modern appreciation for the natural beauty and
wondrous ecological significance of the Galapagos, a recurring theme among
early visitors is a reaction exactly the opposite. So in
the novel Galapagos, Kurt Vonnegut wrote that the early Spanish
explorers quote did not claim the islands for Spain any
(17:22):
more than they would have claimed Hell for Spain.
Speaker 1 (17:27):
I haven't read this novel, but I did see it
in bookstore. There was a nice bookstore on one of
the islands in the Galapagos, and they had it there.
They were probably had several Darwin related books, and then
they had Vonneguts Galapagos, and I was tempted to pick
it up, but then I was like, I don't know
if I'm in the mid post apocalyptic literature at the moment.
Speaker 2 (17:48):
I've actually never read that one either, but so, yeah,
it just seemed like the Spanish were not very interested
for a while. There were apparently no notable mineral riches
to mine, at least that they were aware of, no
people living there to conquer or enslave. There was very
little fresh water, so the Spanish just did not seem
very interested in these islands. And during the seventeenth century
(18:11):
it seems like the Galapagos largely served as a base
for people who didn't want to be found, for pirates
and privateers. Privateers would attack Spanish ships to steal the
gold that the Spanish had stolen from the Incas, or
just pirates who attacked and raided coastal settlements on the mainland.
Speaker 1 (18:30):
Yeah. Yeah, when it comes to the human history of
the Glavigos, it's easy to sort of think, oh, well,
Darwin and then you sort of fast forward to today.
But yeah, there's a lot of bloody history there. It
was an extreme location that, like you said, didn't have
a lot seemingly to offer except as a place of
refuge for people engaged in various bloody activities. Sometimes it
(18:54):
seemed like a place for utopian ideals, and of course
those sorts of ventures don't always turn out well either.
So yeah, there's there's a very interesting human history there
that is not all just bird watching by any means.
Speaker 2 (19:09):
Mm hmm. Though, continuing the theme of like the the
lack of appeal of the islands too many people who
first arrived there, Charles Darwin himself wrote of his first
impression of San Cristobal Island that quote, nothing could be
less inviting.
Speaker 1 (19:26):
That's that's that's funny because they are on San Cristobal Island.
You know, there's like a statue of Charles Darwin and
the ship with his hand out and I had my
I got my picture made with this, of course. But there, yeah,
there are statues of Darwin all over the islands.
Speaker 2 (19:41):
Nice. Now, well, yeah, I mean, you know, Darwin warmed up,
you know, he there's a lot to learn there. But
but yeah, apparently first setting eyes on it, he was like,
h not cool.
Speaker 1 (19:53):
Yeah, that's not the quote. That's like on a plaque
beside this statue.
Speaker 2 (19:58):
Now, regarding this story about Burlonga's accidental landfall in the
Galapagos being the first confirmed human visit, It is important
to stress that this is the first visit by humans
we're sure about, but there are all kinds of interesting
arguments about whether or not others had been there before,
and their theories of contact regarding the Incas, Pacific peoples
(20:19):
and so forth. But I think all of these are
speculative and the evidence is questionable. There was certainly no
permanent human settlement in pre Columbian times, and the earliest
arrivals by humans appear to be by accident.
Speaker 1 (20:33):
Yeah, you get into that situation though, where if earlier
peoples had come there, they probably wouldn't have stuck around,
and what would they have left behind, what evidence would
there be, So yeah, we're left to speculation. Now, coming
back around to the reptiles, which is going to be
the main thing we're talking about in these episodes. Again,
(20:57):
the Hawaiian Islands no native reptiles, but we have these
fascinating examples of reptiles on the Galapagos. So while reptiles
never had a chance to reach the Hawaiian Islands on
their own, the Galapagos Islands are in just the right position.
It seems to have been gifted some wandering, lost at
(21:19):
sea reptiles, and yet at the same time isolated enough
that they were able to evolve there unmolested for a
very long time. So it's kind of fascinating to think
about that. Like if they had been in any other location,
you know, there might have been a situation where, yes,
humans would have found this place and colonized it much earlier.
(21:40):
It might be in a position where these reptiles would
not have reached it of their own power or by
the power of wind and water, which seems to be
the case. I think the main examples of terrestrial reptiles
reaching the Galapagos Islands, they tend to involve rafting. They
tend to involve animals being just swept out to see
(22:03):
via rivers in South America. And then a number of
those animals are going to perish, but some of them
are going to find themselves cast upon a deserted island,
and from there they begin to find ways to survive
and these new forms evolve.
Speaker 2 (22:19):
Well, this sounds like a perfect transition to the marine iguana.
Speaker 1 (22:23):
Robert You ready, Yeah, let's talk about the marine iguana.
Probably not the most famous denizen of the islands, but
at least number two.
Speaker 2 (22:32):
Yeah, yeah, and certainly maybe the most salient in my
brain because specifically, to come back to Darwin, Charles Darwin's
discussion of the marine iguana, or the scientific name ambly
Rincus Christadis in the Voyage of the Beagle has long
stuck in my head. So of course, the Voyage of
(22:52):
the Beagle is the common name used to refer to
the published writings of Charles Darwin after his sales on
the HMS b Gole with Captain Fitzroy, and this chapter
on the Galapagos in the Voyage of the Beagle is
very famous, but the subsection on the marine iguana has
long stuck in my head, notably for the weird disrespect
(23:17):
with which Darwin treats these animals. So I want to
read a few selections as we go about here from
this passage in the Beagle, with some abridgments. But to
start off, this is what Darwin says talking about the
marine iguana. It is extremely common on all the islands
throughout the group, and lives exclusively on the rocky sea beaches,
being never found at least I never saw one even
(23:40):
ten yards in shore. It is a hideous looking creature
of a dirty black color, stupid and sluggish in its movements.
And in his journal he refers to them initially as
quote large disgusting, clumsy lizards.
Speaker 1 (24:00):
I mean they do lay around in clumps, which I
could imagine some seeing this as being kind of gross looking.
But in the same and this on the same note,
the way they kind of lounge around sometimes they they
seem oddly human in the way like one all sometimes
have an arm slung over the shoulder of another, like
it's like it's two, like as an old married couple
(24:20):
staring out at the sunset or something. Puppy pile, yeah, yeah,
kind of a puppy pile. And and there is kind
of an awkwardness to them sometimes when they move around
on land. But I don't know, that's kind of charming
more than anything.
Speaker 2 (24:34):
So early chroniclers often use the same kind of terms.
They call this animal ugly, hideous. Some of them make
bizarre value statements, such as comparing them to devils or
imps of darkness. Uh Darwin himself in the Beagle quote
say description by a previous author, a Captain Colnett, who
visited the Galapagos, who says in the part of his
(24:58):
work that Darwin quotes, quote, they go to sea in
herds of fishing and sun themselves on the rocks, and
maybe called alligators in miniature and elsewhere. Coln It marveled
at their ugliness, writing quote, so disgusting is their appearance
that no one on board could be prevailed upon to
take them as food. Not even sailors would eat them.
(25:23):
And I'm going to say I take personal offense to
all this. I think marine iguanas are beautiful. I want
to hug and kiss them. I know I shouldn't. I
would never do that, but I want to.
Speaker 1 (25:33):
Yeah, they do look kind of like yemps, but I
think in a good way. We often thought that they
looked kind of like tiny godzillas. Something about the shape
of their their heads and their snouts, and of course
the little, you know, protrusions on the top of their
head gives them kind of a kaiju appearance. And there's
(25:53):
so many things about them. There's a lot of times
you know they're lounging around, they're not doing anything, but
then when they are moving about, even on the land,
they can be quite amusing. Like, for instance, if one
is making a bee line for something, especially if one
is coming out of the water or it's time to
go to the water. Sometimes something will seem to get
in the way of their their journey, like maybe a
(26:14):
sea lion or a human wanders into their path, and
they'll just kind of stop and they'll they won't skitter
out of the way or anything, but there just kind
of wait until whatever it did is has moved on,
and then they'll keep going. So there's this kind of
like laid back care free of energy to these creatures.
Speaker 2 (26:31):
They're kind of wasted away again in Margueritaville.
Speaker 1 (26:34):
Yeah.
Speaker 2 (26:35):
Yeah, by the way, you mentioned their stubby little snouts.
That's actually what the genus name means, ambly Rincus means
blunt snout.
Speaker 1 (26:43):
Ah. Well, we'll come back to the blunt snout of that.
Speaker 2 (26:53):
However, to come back to Darwin's writings on the marine
Iguaana his unseemly anti iguana prejudice aside, he does make
some correct observations about them. For example, Captain Colnet remembers
said that they go a fishing in sea herds. You
know they're going to go out and catch fish. Darwin says,
I don't know about that. He challenges the idea that
they eat fish, and in fact we now know they
(27:16):
do not. Instead, Darwin observes that these animals seem to
subsist on a kind of seaweed or algae which cannot
be found on land, and he reasons that this explains
why they evolved to go to sea in the first place.
Speaker 1 (27:30):
Yeah, and this is spot on, of course, and we'll
get into it more in a bit, but yeah, and
it's also very observable if you're watching the creatures, because
sometimes they're going to be eating algae that's under the
water and perhaps out of you. But other times it's algae,
especially as the tides change, it's like partially in partially
out of the water, so you can see them they're munching,
(27:50):
grazing on the algae on the rock.
Speaker 2 (27:53):
Though as a side note, Darwin says one dissected iguana
stomach did have a piece of crab in it, though
he thinks this might have been eaten by accident, and
he compares this to cases where a vegetarian tortoise has
a caterpillar in its stomach, because the caterpillar was just
on the leafy vegetation the tortoise was eating. In fact,
we've done whole segments about this on the show before,
(28:14):
about herbivores eating animals accidentally or even sometimes on purpose.
Speaker 1 (28:19):
Yeah.
Speaker 2 (28:20):
But after introducing them, Darwin goes on to describe the
animals in detail, describing their movements with a strange mix
of admiration and disgust. So here's what he says. Quote.
When in the water, this lizard swims with perfect ease
and quickness by a serpentine movement of its body and
flattened tail, the legs being motionless and closely collapsed on
(28:42):
its sides. A seman on board sank one with a
heavy weight attached to it, thinking thus to kill it directly,
But when an hour afterwards he drew up the line,
it was quite active. Their limbs and strong claws are
admirably adapted for crawling over the rugged and fissured masses
of lava which everywhere form the coast. In such situations,
(29:05):
a group of six or seven of these hideous reptiles
may oftentimes be seen on the black rocks a few
feet above the surf, basking in the sun with outstretched legs.
And then he goes on to note a strange, perplexing,
almost contradictory observation about their behavior. So, while the iguanas
go to sea in order to forage, that's how they
(29:27):
make a living, They swim out in the water, get
the algae and eat it. He found that he could
not scare them into the water. If he approached one,
it would back away from him until it reached the
edge of a rock hanging over the water. But once
at that point it would stop retreating. It would just
let him approach and catch it, rather than flee into
(29:47):
the water. And here we come to the infamous iguana
chucking scene of the Voyage of the Beagle. Darwin writes,
I threw one several times as far as I could
into a dep pool left by the retiring tide, but
it invariably returned in a direct line to the spot
where I stood. It swam near the bottom with a
(30:09):
very graceful and rapid movement, and occasionally aided itself over
the uneven ground with its feet. As soon as it
arrived near the edge, but still being underwater, it tried
to conceal itself in the tufts of seaweed, or it
entered some crevice. As soon as it thought the danger
was past, it crawled out on the dry rocks and
shuffled away as quickly as it could. I several times
(30:31):
caught this same lizard by driving it down to a point,
and though possessed of such perfect powers of diving and swimming,
nothing would induce it to enter the water, And as
often as I threw it in, it returned in the
manner above described. Now, this is indeed a really odd
bit of behavior, right.
Speaker 1 (30:51):
Yeah, so it would seem. Now, before we get into that,
I want to just mention I want to make two
comments about Darwin's riding here. First of all, I do
get the impression that perhaps Darwin was not a cat
person or had a cat, because like, this is the same,
the same situation I think any cat owner can attest to.
It's like I tried to put the cat where I
wanted it to be, and it did not want to
(31:13):
be there. So strange. But on the other hand, I
do love the part where he talks about how graceful
they are in the water, because that is also a
huge tree getting to watch these lizards swim about, because
it's I mean, it's unlike anything you see with any
other species on the planet. There's this graceful, indeed serpentine
(31:36):
movement to them. There whatever awkwardness you might observe on
the land is not present in the water, and it's
it's like watching a strange aquatic little dragon move about.
Speaker 2 (31:46):
Well, I think it's also about the way that like
they anatomically modify themselves to move in the water versus
on land, because as Darwin says, they collapse their legs
to the side and almost become a snake in the water.
Speaker 1 (32:00):
Yeah, but with their heads up in a way that
like you wouldn't mistake it for a snake. Like the
profile of the swimming marine iguana is unlike anything certainly
that I've ever seen. So it really stands out in
your mind, like your mind instantly is identifying that this
is something different, This is something novel.
Speaker 2 (32:18):
I agree, and having seen not in person but seen
plenty of video of it. They are beautiful when they're swimming.
But to come back to this odd behavior, so Darwin says, Okay,
these things they go in the water all the time,
that's how they eat. They go down in the water,
they eat, they come back. How come I can't scare
one into the water or get it to stay in
the water by throwing it in. I throw it in,
the water just comes back out. Darwin comes up with
(32:41):
the guests about wyat acts this way. He says, quote,
perhaps this singular piece of apparent stupidity may be accounted
for by the circumstance that this reptile has no enemy
whatever on shore, whereas it's at sea it must often
fall prey to the numerous sharks, hence probably by a
fixed and hereditary instinct that the shore is its place
(33:04):
of safety. Whatever the emergency may be, it there takes refuge. So, okay,
that's an interesting guess. He says. It has natural predators
in the water, but not on land, so it just
feels safer on land, even if here I am threatening
it on land, because it's just acting out of instinct.
Speaker 1 (33:22):
Yeah, yeah, it would seem to be a decent theory.
And indeed on land that nothing really messes with them
except when they're smaller. And when they're smaller there you know,
like and this is the case with a number of
iguanas and lizards, like until they reach a certain size,
they're on the menu for various other creatures and birds
and whatnot. But once they reach a certain maturity. Yeah,
(33:43):
they can just bask where they want. Nothing's going to
mess with them.
Speaker 2 (33:46):
Yeah, well, at least in the ancestral environment of the Glasogos.
Now introduced to dogs and pigs and all that stuff
that humans brought there will prey on them. So I
decided to follow up on this and see has there
been any sub sequent research about this behavior in marine
iguanas that could confirm or deny Darwin's guess about the
(34:06):
evolutionary reasoning there. And I found a paper that addresses
exactly this topic. It is by Edmund S. Hobson called
Remarks on Aquatic Habitats of the Galapagos Marine Iguana, including
submergence times, cleaning, symbiosis, and the Shark Threat. This was
published in a journal called Copeia in nineteen sixty nine,
(34:28):
and it seems that sharks do occasionally eat the iguanas
as Darwin guest. A report of the contents of shark's
stomachs in nineteen oh three by Heller did find some
marine iguanas in there, but Hobson thinks that the threat
to iguanas by sharks is mostly exaggerated, given that he
(34:48):
and his colleagues directly observed iguanas and sharks swimming in
the same waters side by side, and he says almost
all the time they just ignore one another entirely. To
read from Hobson quote to the contrary, the general situation
finds sharks swimming slowly among smaller fishes with no overt
sign that they regard these animals as prey. Certainly, sharks
(35:10):
are efficient predators when they do attack, but situations evoking
attack are relatively infrequent. At Narborough Island, I saw white
tipped sharks and a gray shark pass within a few
meters of surface swimming iguanas, with no indication that they
regarded the iguanas as prey. George Barlow and I made
a similar observation involving a large hammer head at Hood Island.
(35:34):
So if it's not a fear of sharks, what explains
this behavior?
Speaker 1 (35:40):
Well, if I would a venture a guess, I'd say
it has to do with temperature, that they're thermic reasons
at play here.
Speaker 2 (35:46):
Great thinking, and this is exactly what Hobson concludes. Hobson
argues that the best explanation for this apparently weird behavior
observed by Darwin is that the water's cold, you know,
they have to go in there to get food, but
they don't want to spend any more time in there
than they have to because it's cold and they're reptiles.
To read from Hobson, citing another researcher named Bartholomew quote.
(36:08):
Bartholomew in nineteen sixty six offered a more plausible explanation
after noting that iguanas basking on the rocks ashore have
a preferred body temperature of thirty five to thirty seven
degrees celsius, over ten degrees celsius above that of the sea.
He suggested that iguanas which are taken from the rocks
and thrown into the water immediately return to land simply
(36:31):
because they are reluctant to cool off. And I love
this explanation. It also does seem plausible to me. But
I love this because it highlights something about human thinking
that even Darwin himself was not immune to. And Rob,
I think you'll know exactly what I'm talking about here.
When humans are trying to come up with explanations for
(36:52):
an animal behavior or a feature of an animal body
or something, I think humans are way too quick to
jump to two types of explanations, those involving mating and
those involving predation, sex and violence. Just in our brains,
sex and violence are more salient explanations than all kinds
(37:14):
of other pressures that exist in nature and do drive
animal body plans and animal behaviors. Things having to do
with just base physical realities of the world, like maintaining
body temperature, thermoregulation, access to oxygen, all kinds of things
like that that explain tons about the natural world. It's
just our brains just don't jump to those things as
(37:35):
quickly when we're looking for a why.
Speaker 1 (37:37):
Yeah, I think modern reptile enthusiasts, especially any who have
been engaged in keeping of reptiles, they'll be pretty quick
to tell you, Oh, yeah, temperature is important, temperature regulation.
You know, the lizards, snakes, they want their warm places,
and they're certainly going to realize that. But yeah, this
is an easy, easy trap to fall into. I should
(37:59):
also say I did go into the water in the
Galapagos snorkeling once, and it is, to me a non iguana,
quite cold. So I can in some way at least
understand how they feel about it.
Speaker 2 (38:13):
Yeah, so Mark me is convinced I think that iguana
kept swimming back and crawling out of the water after
Darwin threw it in because it was getting cold and
it wanted to it wanted to warm back up on
the rocks.
Speaker 1 (38:24):
Yeah, and let I say, they're pretty chill, but they're like, no,
it's too cold. I would like to get out, and
he's like, I'm throwing you back in. He's like, too cold.
I wish to get out. It's not time. It's not time.
I will get in the water when I am warmed
up enough to do so. Now getting into a little
bit about the evolution of the marine reptiles, it's very fascinating,
(38:44):
especially again thinking of them as this really largely singular
occurrence in the modern world. So I was looking at
a few different sources. One of these was Marine Reptiles
by Resmussen at Hall from twenty eleven published in Peel one.
They point out here that lizards make up sixty percent
(39:05):
of all reptiles, but very few lizard species compared to say,
turtles and snakes, are present in our oceans. And this
isn't getting so much into the issue of prehistoric aquatic reptiles,
which do include extinct squa mats, like the mosasaur. The mososaurs,
which were actually distant relatives of modern iguanas and monitor lizards,
(39:30):
were pretty fascinating in and of themselves. They were gigantic,
They reached links of up to twelve meters or forty feet.
They swam in earth oceans roughly sixty six million years ago.
They hunted other marine reptiles, and it's possible they gave
birth to live young in the water, though I'm not
sure this is certain. There's various studies out there about
(39:52):
possible egg finds of the mosasaurs, but it's worth mentioning
here to drive home the difference between today's marine reptile
and those of the past, and especially you know, thinking
about sea turtles, thinking to about the marine iguana. These
are animals that, to varying degrees, are great in the water,
(40:14):
but they still must return to shore to complete some
vital stage of their life, certainly with sea turtles. With
the marine iguana, it's more living on the shore but
then going into the water to graze and feed. Yeah,
so of extent lizards that are in any way aquatic,
there are only a few extreme examples, and this includes
(40:35):
the Western Pacific mangrove monitor, which is a carnivore. But
as the authors here point out, the Galapagos marine iguana
is the most aquatic of all extents lizards. It basks,
breeds and lays eggs on land, et cetera, but it
has to go into the water to feed. It is,
by other definitions, the only squaw mate that's actually able
(40:55):
to exploit the re sources of the ocean in a
meaningful way. So the aforementioned monitor lizard, for example, can
catch fish, but it also feeds on terrestrial meats as well.
I should also note that there are other iguanas on
the Glabgos Island islands, to be sure, including seven smaller
species and three species of land iguanas in the genus Conolophus.
(41:17):
They include the beautiful and rare Galapagos pink iguana, which
is a most special creature. Included a picture of this
for you, Joe and everyone out there. You should look
up a picture of the Galapagos pink iguana. This is
not something I got to see when I was there,
because it lives in a very remote part of the islands.
Not not even even locals don't usually get to see
(41:37):
this creature.
Speaker 2 (41:38):
The first thing that popped into my head is it
looks kind of like a hot dog.
Speaker 1 (41:43):
Yeah, yeah, it's you know, it's it's it's it's a
specially it's an iguana pink. But yeah, these are these
are rare and beautiful creatures. But again, the marine iguana
is the real standout here. The other iguanas are a
lot of fun to watch too, if you if you visit,
but yeah, the marine iguana is special. The average adult
is around one point two meters in length, so they're
not huge, and they're found on virtually every island of
(42:06):
the Galapagos. So coming back to the question, how did
any of these lizards get to the Far Flow and
Galapagos islands, The answer, according to Resmussen at all is
probably that they're all related to iguanas from South America
that were washed from the South American mainland, again perhaps
(42:28):
by river floods, and carried out to the Galapagos. And
again this is where the Galapagos's isolation yet closer proximity
to a continental mainland comes into play. The theory is
also in part supported by the fact that as distinct
as the four bigger iguanas of the Galapagos Islands, including
the marine iguana are They are closely related and they
(42:50):
actually can breed with one another to produce hybrids, so
hybrids have been reported according to Resmussen. At all, the
marine iguanas spend quite a bit of time in the water,
though foraging for their food. As adults, they feed almost
exclusively on the red and green algae. It's been pointed
out they're not above at least trying out the odds
(43:12):
scrap of this, that or the other, and perhaps that
accounts for the crab claw that Charles Darwin reported. And
there's at least one population of the marine iguanas that
has been observed to supplement their diet with land plants.
But for the most part, their hindgut has evolved to
thrive on the algae like they're bound to the algae.
This is not just a this is not just a
(43:33):
lifestyle choice at this point, and their bodies have adapted
in other key ways as well to allow this marine
diet due to the considerable selection pressure that's been applied
to them, which is quite literally the selection pressure of
being cast upon a resource depleted island. So we mentioned
their flattened tail that's one of the adaptations. And it's
(43:57):
not like you don't find flattened tails and other lizard species,
but this is clearly something that seems to help out
there swimming. They also have limited webbing on their feet,
which I saw kind of two different takes on this
in the literature I was looking at. On one hand,
there's the argument like, yeah, it's partially web feet, this
is going to help them swim, But others say, well,
the webbing is not that extensive. It maybe helps a
(44:20):
little bit, but let's not overstress its importance.
Speaker 2 (44:23):
Well, I'm no marine iguana expert, but it seems to me,
at least when I've seen images of them swimming, it
doesn't seem like they paddle with their feet much at
all that I recall, but maybe they do sometimes.
Speaker 1 (44:36):
Something that everyone agrees on, though, is that their claws
have become more powerful to allow them to grip the
rocks and the surf during feeding. And this is certainly
key because if you're observing one from the shore, or
if you're looking at images or footage of them, or
if you're snorkeling, you get to see one underwater. I
did not get to see one underwater. Firsthand. But either way,
(44:58):
when they're feeding, they're often in an area where the
the you know, the surf is disrupting them and would
make it difficult to feed if they were not able
to hold on and latch on. And then of course
when they get in or out of the surf, they're
going to need to keep from being swept up anyway.
So yeah, they got to have those powerful claws to
aid them.
Speaker 2 (45:17):
That's not an easy lifestyle. And crawling out of the
surf onto rocks, I mean, think about how danger its
how dangerous it would be to try to land a
boat or even just swim up onto jagged rocks as
the tide is coming in and out.
Speaker 1 (45:31):
Yeah, for sure. I was also now, this is something
I was told by one of the guides in the
Galapagos Island, who again are very knowledgeable of all of this.
Uh so, you know, they're they're very quick to spout
out all the scientific names of all the creatures you're
looking at, and they're they're up on the latest findings
(45:52):
and so forth. I was pointed out that they all
utilize those sort of thorny spikes on their head, and
I almost hesitate to say face in order to loosen
up the algae on the rocks by sort of rubbing
their heads against it. And then it should also be
noted we touched on this earlier, but there's the whole
regulation of their body temperature. And this is key because
(46:15):
again the water's cold, and these are cold blooded animals,
so they spend a fair amount of time basking in
the sun. And the way this is certainly one way
it was described to me there, and this is backed
up in the paper that I was reading recently, is
that in order to go into the water, they kind
of have to power up, so like they're powering up
(46:35):
there like on the on the beach or on the rocks,
basking in the sun, kind of filling their batteries up
all the way. And then when it's time, well then
it's time. Now it is time to go into the
water to forage for food, and they make that beeline.
But it's only then, only then, and they're not going
to be thrown in early by some deranged englishmen there.
And if something should get in their way, well they're
(46:57):
just going to wait patiently for a little bit. But
they've got a place to be. It is time to
go into the water and feed, So.
Speaker 2 (47:03):
It's a constant trade off of managing different energy resources
in the body. You've got your thermal energy, like you
need to bask on the land to get your body
temperature up, but then you need to go into the
water to get food for your metabolism, and you're sort
of just always trading back and forth between the two.
Speaker 1 (47:21):
Yeah, Now when they're in the water, their heart beats
also reduce from about forty three beats per minute on
land to seven to nine beats per minute in the water,
So that's also an interesting adaptation they have. And then
this is another famous one that's a lot of fun
to watch. You see this in footage every nature documentary
that's covered marine iguanas. But both of the main varieties
(47:44):
found in the four larger iguanas they have salt glands
that help them process an abundance of salt should it
be in the body. But with the marine iguanas, this
of course is very visual because if you're just watching
them lounge about, they're going to regularly appear to sneeze.
They're not sneezing, they're blasting salt out of these salt glands.
(48:06):
They basically blasting salt out of their nostrils as they
lounge about on their rocks, and as they're doing this too,
making these cute little sneezing sounds or gross little sneezing
sounds everyone to look at it. They're also kind of
like crusting over the tops of their heads with this,
you know, like white salt crystals, so you can tell
like which ones haven't been on the in the water
that recently, because they have this kind of like salty
(48:28):
look to their heads.
Speaker 2 (48:29):
They got the salt snot on there. Yeah, you know,
this comes back to something else Darwin said. He was like, there,
you know, you can back them into a corner and
you can catch them. They they don't really bite. I
don't think that's true, by the way, but he says,
they don't really bite, but they will blow salt out
of their noses at you.
Speaker 1 (48:48):
Yes, I I remember reading this as well, because I
was when we were in the Galabacos. I pulled up
the text. I was reading it, and yeah, there is
this accusation that they're doing it defensively, and yeah, this
does not seem to be the case. Now they're just
doing it. Maybe they're doing it, I guess, I guess
I have no data on this, but I guess it's
(49:09):
possible that if someone is coming at them and backing
them away, then maybe that does seem to incite a
snort because they're about to move. But other than that, yeah,
there's I've seen nothing to indicate that this is in
any way a self defense measure.
Speaker 2 (49:25):
That's right up there with av and defensive vomiting.
Speaker 1 (49:28):
Yeah. Yeah, there's a lot of back and forth on that, right.
I think we've discussed that is like a vulture vomiting
in order to free up room and you know, make
itself lighter so it can take off and get away.
Is that are offering a bribe to a scavenger that
may be coming after them and decide to go for
vomit instead of fighting a buzzard like There are various
interpretations of that. As I recall now on the issue
(49:51):
of marine iguana evolution, I was looking at another source.
This is from Martin Wakelski in a two thousand and
five edition of the Royal Society paper entitled Evolution of
body Size in Galapagoes marine Iguanas, and I found this
one interesting because the author here lays out one possible
model for how the Marinea iguanas evolved. So, first of all,
(50:13):
iguanas arrived, according to this theoretical model, in the Galapagoes,
perhaps ten to fifteen million years ago from South America
via rafting, so swept out to see floating on some
vegetation and so forth, and then being cast on this
strange island. And once they're there, it becomes clear eventually
(50:35):
here that in the intertidal zone there's plenty of food
for iguanas, but it's not on the land, it's the
algae in the water. Initially, the iguanas are going to
have to depend on low tides to get to the food,
so the tide goes down, iguanas are daring to get
down in there and go after the algae, and so
(50:57):
there's going to but from there that's where we're going
to be to see the selection pressure towards larger bodies
for thermal inertia and also the ability to anchor themselves
in the surf, as well as these other adaptations that
we mentioned, like the bigger claws ultimately the shorter snout
as well. That's going to be part of their their
forging behaviors. They essentially like rub their faces against the
(51:20):
rocks to gnaw off the algae as well as the
like swimming morphological changes.
Speaker 2 (51:26):
Interesting.
Speaker 1 (51:26):
Yeah, there's and there's there's actually a lot of a
lot of work that comes out related to the marine iguanas,
Like there's no shortage of papers. There's one from twenty
twenty one that I was looking at, Cranial Anatomy of
the Galapagos Marine Iguana by Paparella and Caldwell in the
American Association for Anatomy, and they point out some of
(51:48):
the you know, the key changes just to the head
of the creature of VI. It's evolution modified configuration of
the snout and nasal chamber, increased muscle attachments in the
temporal post orbital region of the skull, and and also
the teeth as well. So all of this is coming
seems to revolve around what they're feeding on and how
(52:09):
they're feeding on and how that's affecting just like the
overall shape and even like the muscles of the head.
Speaker 2 (52:16):
And I imagine they would make some guesses from this
about how far back in time the marine iguanas had
these evolutionary changes.
Speaker 1 (52:25):
Yeah, one of the authors here, Paparella, I found this
is actually I believe from another paper. But I saw
this author saying that arguing elsewhere for an iguana colonization
of the ancient Galapagos Islands as far back as twenty
to twenty five million years ago. And I think in
this we're getting into into this idea of not only
the existing Galapagos Island, but these like pre existing Galapagos islands,
(52:50):
the ones that, like you said, have now been lost
and are submerged. Wrote that like this we would have
like an initial dispersal followed by constant short range hopping
from older to newer islands. So you know, they get
a foothole in one place and then they can spread
to these other islands much more easily. And then as
(53:10):
new islands emerge, that opens up new places for them
to be. And of course as old islands die away,
then so do the populations of those islands or they
you know, they're forced to disperse to newer islands. And
Joe from that paper about the shape of their heads,
I included this wonderful image, this one. I think I
didn't get this out of the paper itself, but this
(53:32):
was I believe from a like a Twitter post by
the American Association for anatomy. It's out there if anyone
wants to look it up for themselves. But yeah, you
see very very high definition close up on both the
head of the marine iguana, and then also a comparison
of the skull, which I thought was just very insightful
(53:53):
looking at these, because you know, it just looks it
looks very much unlike a lot of the lizard skulls
you might see, Like glancing at it, you might not
even think of it as a lizard's call. I mean,
it doesn't look like a human skull or anything. It's distinct,
but you can clearly see like the changes that have
taken place here.
Speaker 2 (54:12):
Yeah, the blunt snout and the density of it, I
mean almost you could imagine it being more of a
turtle skull or again, I mean it looks kind of
like Godzilla.
Speaker 1 (54:20):
Yeah, it's like Godzilla, and I like how they kind
of have. You see, especially in close up like these,
there's real sense of iguana lips, you know.
Speaker 2 (54:29):
Yeah, you also get a really good look up inside
the nostrils.
Speaker 1 (54:33):
Yeah, this, of course is a specimen. This is a
dead iguana that Joe and I are gawking at here,
but still beautiful specimen but yeah, the marine iguanas are
are special creatures. And I think I don't even have
to tell anyone this. It's this is not new information. Uh.
(54:55):
There have been so many documentaries that of course have
covered the Galacos Islands that have caught brilliant footage of them.
They are a standout species that they've been highlighted in
various shows over time, or you've no doubt seen articles
about them or see them popping up in the lists.
So so yeah, nothing nothing new in me saying that
these animals are great. But like all these things, yeah,
(55:15):
if you get to see them in person, if you
have that chance, take that opportunity, because they're pretty remarkable.
Speaker 2 (55:21):
I would like to see the iguana puppy pile. Hey,
we haven't even touched on the most famous reptiles of
the Galapagos, and I think we're gonna have to do
that in the next episode.
Speaker 1 (55:33):
That's right, the Galapagoes tortoise. Yeah, we're going to come
back in the next episode of of this journey to
discuss these fabulous creatures. I mean, it makes sense that
they'd come in second. They are slower, but they're they're
very remarkable in their own way, so be sure to
come back for that episode. In the meantime, we'd love
(55:54):
to hear from you if you have thoughts about Marine
iguanas you know firsthand or docum menory based. If you're
a resident of Ecuador the Glavigos Islands, certainly we would
love to hear from you on all of this. If
you want to hear more Stuff to Blow Your Mind,
I'll just remind you that core episodes of the show
publish on Tuesdays and Thursdays, and the Stuff to Blow
(56:14):
Your Mind podcast feed on Mondays. We do listener mail.
On Wednesdays we do a short form artifact or monster fact,
and on Fridays we do Weird House Cinema. That's our
time to set aside most of the serious science and
so forth and just talk about a strange film.
Speaker 2 (56:28):
Huge thanks to our audio producer, Max Williams. If you
would like to get in touch with us with feedback
on this episode or any other, to suggest a topic
for the future, or just to say hello, you can
email us at contact at Stuff to Blow your Mind
dot com.
Speaker 3 (56:51):
Stuff to Blow Your Mind is production of iHeartRadio. For
more podcasts from My Heart Radio, visit the iHeartRadio, app,
Apple podcasts, or wherever you're listening to, youravorite shows
Hey, welcome to Stuff to Blow Your Mind. My name
is Robert.
Speaker 2 (00:09):
Lamb and I am Joe McCormick, and we are out
this week, so we're bringing you an episode from the vault.
Today's episode originally aired on December eighth, twenty twenty two,
and it is part one of our series on the
reptiles of the Galapagos Islands.
Speaker 1 (00:24):
All right, let's dive right in.
Speaker 3 (00:29):
Welcome to Stuff to Blow Your Mind, production of iHeartRadio.
Speaker 1 (00:39):
Hey, welcome to Stuff to Blow Your Mind. My name
is Robert Lamb.
Speaker 2 (00:43):
And I'm Joe McCormick, and today we're beginning a series
of episodes on the reptiles of the Galapagos Islands. And Rob,
this is not a topic we just landed on randomly.
This is related to your recent travels, right.
Speaker 1 (00:57):
Yeah. I had the great pleasure in the fortune to
visit some of the islands of the Galapagos Archipella go
back in October. It was a fantastic family trip that
we'd been planning for a long time, that we meant
to do before the pandemic and then obviously we had
to reschedule. But yeah, this is this was one of
the top trips I've ever had the privilege to make.
(01:18):
And now certainly I was visiting as a tourist. But
one of the things about the Galapagos Islands that I
love is so much of the tourism there is about
the natural beauty of the place. It's about the environments,
it's about the animals. And so if you're going all
the way to the Galapagos Islands, you probably want to
(01:39):
see some reptiles, you probably want to see some birds,
et cetera. And they really facilitate that. The local guides
are all terrific, all the ones that I interacted with
very knowledgeable of everything going on there. And yeah, it
was a trip just unlike any other, especially when when
(02:00):
observing these various creatures, because it was kind of like
being a Disney princess, like being in a Disney like
a Disney princess scene in a movie, except instead of
the princess being surrounded by cute squirrels, bunnies and birds
that are singing, you're just constantly surrounded by this wonderfully
bizarre cast of reptiles and elaborate birds, sea lions, etc.
(02:27):
And it's unlike too, I have to say, it's unlike
the vibe that I've encountered in places like the Grand Canyon,
where there'll be wild animals there that are protected and
so accustomed to humans that the humans can get like
unnaturally and alarmingly close to those animals. There's a proximity
to the animals on the Galapagos Islands that feels less
(02:51):
artificial but also equally magical, if that makes sense. Again,
not to say that you should attempt to touch any
of the animals there, or or or infringe upon their
personal space in any way, but there's this, Yeah, there's
this feeling of proximity to nature that makes you feel
like you are David Attenborough in a David Attenborough documentary,
(03:14):
you know, creeping up for a close look at this
animal or another.
Speaker 2 (03:18):
And maybe you are the camera lens. And I wonder
if the difference with the Grand Canyon thing would be
the difference between animals that are unfortunately habituated to human
presence in all the wrong ways, like expecting you to
have food, the calorie rich food sources and stuff, so
they'll come up to you looking for that, versus a
(03:38):
place where animals don't seem to flee from humans because
they come from many generations of animals without natural land predators.
Speaker 1 (03:47):
Yeah, yeah, and I believe that is the case with
the Glapicos. So let's let's introduce everybody to the Glapico silence.
If you're not familiar with the Glapagos Archipelago, it is
a chain of islands in the eastern Pacific Ocean, roughly
nine hundred and sixty six kilometers or six hundred miles
off the coast of Ecuador. It consists of thirteen major
(04:09):
islands a few smaller islands, and these were all formed
by repeated volcanic eruptions. The process here is similar to
that which produced the Hawaiian Islands, which we've discussed in
the show before. So they're not formed all at once,
but in a chain due to underlying volcanic activity berthing
mountains and islands out of the ocean floor. So, as
(04:31):
with the Hawaiian Islands, the islands here in the Galapagos
are geologically quite young and their individual ages vary. Now, Joe,
I'm not sure what age ranges you've come across for
them when we get into the geologic age of the
Galapagos Islands, but I've seen it vary a bit. The
Galapagos Conservatory says, quote, probably no more than five million
(04:54):
years with the younger volcanically active westernmost islands perhaps as
young as hundreds of thous sin of years old.
Speaker 2 (05:01):
But the idea that none of the islands there today
are are more than five million years.
Speaker 1 (05:06):
Old according to some of the dates that I was
looking at these sighted dates, but just sort of casting
a wide net, I did see some other dates out there,
so you know, I can only speak to the ones
I'm citing here.
Speaker 2 (05:18):
Well, estimates vary a bit, but it also depends on
what you're counting as the Galapagos Islands. For example, I
was reading a passage in a book Galapagos a Natural History,
second edition by John Creecher and Kevin Laughlin from Princeton
University Press. That new edition is just out this year,
in twenty twenty two, and there is a section in
(05:40):
this book where the authors put forward the possibility that
some species on the islands, including the famous giant tortoises,
may have inhabited the Galapagos since before any of the
Galapagos Islands existed. Now, how could that be possible? Well,
here's what they argue. If you look around the area
of the archipelago, especially east of the existing islands, you
(06:04):
will see what are called sea mounts, which are submerged islands.
They are areas where the ocean floor rises up to
form a mountain, but that mountain does not break through
the surface of the water. So it's not an island
from our perspective, but it's sort of like an island
just beneath the water. Now, what are these seamounts in
(06:26):
the eastern part of the archipelago. Well, Creature and Laughlin
write that they are quote eroded volcanic islands, and that
they are possibly the original ancestral Galapagos. So they were
once perhaps islands that did break above the surface, but
have eroded over time. And the authors here cite a
(06:47):
group of oceanographers and geologists led by a researcher named D. M. Christie,
who put together some dates for these seamounts and said
that the dates range from between five to not nine
million years, which is older than any of the existing
Galapagos islands today. So to read from this passage quote,
(07:07):
as Christie's team pointed out, if the original Galapagos islands
formed as much as nine million years ago, there has
been more time for colonization and subsequent evolution than once believed.
This is colonization by non human animals. There may well
have been tortoises on the islands for longer than any
of the present day islands have been in existence. Given regular,
(07:30):
albeit accidental dispersal, new islands forming over the Hotspot will
be colonized even as old islands erode and disappear beneath
the sea from whence they came. So normally you're talking
about an island group, you would imagine that, okay, well,
the earliest it could have been colonized by animal species
is whenever the islands we have today began. But in
(07:52):
the case of the Galapagos, a lot of the evidence
of the earliest colonization by animals could be under the waves.
It could be lost because those islands aren't there anymore.
Speaker 1 (08:04):
The lost animal kingdoms of the Galapgos potentially. Now, when
we're talking about the modern day Galapagos islands, some of
the main ones, just to mention them real quick, you
have Isabella, which is the largest. You have Santiago Fernandina,
you have Santa Cruz, you have San Cristobol. I only
(08:26):
really visited Santa Cruz and San Cristobal and a couple
of smaller unoccupied by humans islands that were quite fascinating.
And one of the things about these islands, and you've
often counted this with volcanic island formations, is that they're
defined by steep out elevation changes and the resulting islands
(08:46):
that contain multiple micro climates due to this, So a
visit to even a single Galapagos island is an encounter
with multiple and varied ecosystems.
Speaker 2 (08:54):
Right, So you'll get different climates and different vegetation and
so forth at different elevations on the island. So and
that type of like what vegetation is flourishing therefore might
vary with the seasons. So when the rainy season comes,
you might get more blossoming of vegetation in the lower areas,
but then other times animals might find the most fruitful
(09:15):
foraging up in the highlands.
Speaker 1 (09:18):
Yeah. Yeah, So it's any one of these islands, you'll
have you have sort of desert environments, you'll have highland
lush environments, you'll have coastal environments, and these are these
are This is one of the reasons that these islands
are often singled out historically, but even in modern research
is kind of a laboratory of evolution. Now, I'm going
to keep referring back to Hawaii a little bit for
(09:40):
a while because I think it's a nice sort of
touchdown to compare, especially since we've talked about those islands
on the show before as well. So when it comes
to Hawaii, as we've discussed before, you have such geographic
isolation that with those islands, so that there are actually
no native land reptiles or amphibians there. So anything in
(10:01):
the categorization of reptil or amphibian that you find there
were introduced by subsequent human arrivals by boat or ultimately air.
That's the Hawaiian Islands. We don't have the same situation
with the glabgos islence for a few different reasons. So
as far as humans go, first, human contact with Galapagos
comes a bit later. We're talking about fifteen thirty five
(10:24):
versus Hawaii's between one twenty four CE and eleven twenty CE. Also,
Hawaii is a greater distance from the nearest continental land mass.
And I should note that I think I've pointed this
Alma show before, but there is some dispute on whether
the Inca ever reached the island, but we can be
certain that Europeans reached the island in fifteen thirty five.
Speaker 2 (10:46):
Yeah, exactly three hundred years before Darwin did.
Speaker 1 (10:49):
By the way, Yeah yeah.
Speaker 2 (10:58):
So the story of the first confirmed human landing on
the Galapagos is very interesting, so I wanted to tell
it here. There was this Spanish clergyman named Tomas de
Berlonga who was a bishop eventually served as the bishop
of the Colony of Panama, and I've read it alleged
in several sources that Berloga was responsible for introducing bananas
(11:22):
or plantains to the New World, which is weird because
despite how much we associate bananas with the Caribbean and
South America, they are originally native to Southeast Asia. So
it is alleged that this guy's responsible for bringing bananas over,
but I'm not sure what the original source of this
claim is. Anyway, in fifteen thirty five, Berloga was traveling
(11:42):
by ship from Panama to Peru to help sort out
some kind of horrible sounding squabble between the conquistador Francisco
Pizarro and another conquistador over land and spoils after their
conquest of the Inca Empire, so Burlonga's on the way
down to try to help sort this out. But as
(12:03):
his ship is traveling south along the coast during the
first half of the journey, it is suddenly struck by
a dead calm that prevents the ship from sailing further,
and then it gets dragged far off course out to
sea by strong ocean currents, and just when supplies, including
fresh water, are about to run out, the crew sits land.
Their prayers have been answered, but like so many early visitors,
(12:27):
these Spaniards are almost instantly dejected by what they find.
The first island where they land is found to have
not a single drop of fresh water, and there's also
no pasture where their horses can graze, just a bunch
of giant tortoises and weird iguanas. But there were other
islands nearby, so the crew tried to sail to another
(12:48):
one to continue the search for water. Unfortunately, on the
way they were once again becalmed and could not sail
for several days, while just languishing there on the ship,
nearly dying of thirst. Finally the wind picked up again
and they were able to reach a second island, where
once again they found no fresh water. They tried to
dig a well, but when they struck groundwater, they found
(13:10):
it to be as bitter as the sea. And here
I want to read from the retelling of this story
by the famous naturalist William Biebe in his book Galapagos
World's End, published in nineteen twenty four, BB writes, in
their extremity, they had recourse to a plant which has
saved many a thirsty man and animal, And by chewing
(13:31):
the fruit and juicy stalks of the cactus they kept
themselves alive.
Speaker 1 (13:37):
They took a page from the tortoise playbook. There.
Speaker 2 (13:40):
Yeah, not all withstood these privations. One man and two
horses died of thirst, and so the first grave on
the Galapagos was dug. Sunday came and the bishop celebrated
high Mass on those desolate shores, where as he said, quote,
it looked as though God had caused it to rain
stone ones, brutal doom metal bishop. And then BB goes
(14:05):
on sea. Lions slipped through the creaming surf and looked
curiously at the little group of strange beings, and long
winged seabirds poised and swooped above the cross and the
Spanish flag planted side by side among the cactus and
thorny scrub. So I think BB's taken a little liberty
with the storytelling there, but all plausible, you know, given
the local flora and fauna.
Speaker 1 (14:28):
Yeah, desolate beaches, weird sea lions hanging about. Well, I
guess the sea lions are generally described you as weird.
They would have certainly been exposed to sea lions already,
but in my books, sea lions are inherently strange but
also very amusing to watch.
Speaker 2 (14:43):
They're just playfully rolling about while these people have church,
dying of thirst. So finally, after the worship service, the
Spaniards did find some small amount of fresh water. I've
seen what they found, alternately described as spring water and
as little pools collected in cup shaped depressions in the rocks.
(15:04):
And using this water, either the spring water or the
rock pools, they filled up their containers and they departed
again for the coast of Peru. Now, Burlanga made a
number of observations while on the island, writing, according to
an eighteen eighty four translation of his letters, that the
animals of the Galapagos were quote so silly that they
(15:26):
did not know how to flee, and that as a result,
wild animals were easily caught in the hand.
Speaker 1 (15:33):
Well, that does match up, I think with the reality
of visiting the Glabgos Islands even today. Not that you
should be chasing any of the animals and certainly not
catching them in the hand. But yeah, there is this,
like I said, there's this sense that they don't necessarily
understand what we are and they're not threatened by us
(15:53):
unless we get too close, and then a lot of
these animals will let you know. So, yeah, don't get
too close to the sea lions wherever you find your
sea lions. Don't get too close to the tortoises of
the Iguanas.
Speaker 2 (16:05):
Now, Rob, you mentioned that the tourism at the Galapagos
today is almost entirely centered around the island's natural beauty
and biological and ecological significance. You know, this is a
place where you go to see the natural landscape and
the flora and fauna. You're not going there to see
to go to six Flags Galapagos.
Speaker 1 (16:25):
Right right, Yeah, Yeah, I mainly mean, yeah, you're not
going to find that. You're not going to find I
didn't really see much in the way of like a
party boat kind of culture that you find in a
lot of locations. It's you know that there is there
is culture there. There's some great restaurants, there's there's great
local culture. And the people who live there were on
(16:46):
the whole very friendly and and I loved interacting with
them quite a bit. But yeah, it's when people go
to the Galapagos. I mean, the main selling point, the
big deal for everyone seems to be the natural world
that is avail to you there.
Speaker 2 (17:01):
And despite this modern appreciation for the natural beauty and
wondrous ecological significance of the Galapagos, a recurring theme among
early visitors is a reaction exactly the opposite. So in
the novel Galapagos, Kurt Vonnegut wrote that the early Spanish
explorers quote did not claim the islands for Spain any
(17:22):
more than they would have claimed Hell for Spain.
Speaker 1 (17:27):
I haven't read this novel, but I did see it
in bookstore. There was a nice bookstore on one of
the islands in the Galapagos, and they had it there.
They were probably had several Darwin related books, and then
they had Vonneguts Galapagos, and I was tempted to pick
it up, but then I was like, I don't know
if I'm in the mid post apocalyptic literature at the moment.
Speaker 2 (17:48):
I've actually never read that one either, but so, yeah,
it just seemed like the Spanish were not very interested
for a while. There were apparently no notable mineral riches
to mine, at least that they were aware of, no
people living there to conquer or enslave. There was very
little fresh water, so the Spanish just did not seem
very interested in these islands. And during the seventeenth century
(18:11):
it seems like the Galapagos largely served as a base
for people who didn't want to be found, for pirates
and privateers. Privateers would attack Spanish ships to steal the
gold that the Spanish had stolen from the Incas, or
just pirates who attacked and raided coastal settlements on the mainland.
Speaker 1 (18:30):
Yeah. Yeah, when it comes to the human history of
the Glavigos, it's easy to sort of think, oh, well,
Darwin and then you sort of fast forward to today.
But yeah, there's a lot of bloody history there. It
was an extreme location that, like you said, didn't have
a lot seemingly to offer except as a place of
refuge for people engaged in various bloody activities. Sometimes it
(18:54):
seemed like a place for utopian ideals, and of course
those sorts of ventures don't always turn out well either.
So yeah, there's there's a very interesting human history there
that is not all just bird watching by any means.
Speaker 2 (19:09):
Mm hmm. Though, continuing the theme of like the the
lack of appeal of the islands too many people who
first arrived there, Charles Darwin himself wrote of his first
impression of San Cristobal Island that quote, nothing could be
less inviting.
Speaker 1 (19:26):
That's that's that's funny because they are on San Cristobal Island.
You know, there's like a statue of Charles Darwin and
the ship with his hand out and I had my
I got my picture made with this, of course. But there, yeah,
there are statues of Darwin all over the islands.
Speaker 2 (19:41):
Nice. Now, well, yeah, I mean, you know, Darwin warmed up,
you know, he there's a lot to learn there. But
but yeah, apparently first setting eyes on it, he was like,
h not cool.
Speaker 1 (19:53):
Yeah, that's not the quote. That's like on a plaque
beside this statue.
Speaker 2 (19:58):
Now, regarding this story about Burlonga's accidental landfall in the
Galapagos being the first confirmed human visit, It is important
to stress that this is the first visit by humans
we're sure about, but there are all kinds of interesting
arguments about whether or not others had been there before,
and their theories of contact regarding the Incas, Pacific peoples
(20:19):
and so forth. But I think all of these are
speculative and the evidence is questionable. There was certainly no
permanent human settlement in pre Columbian times, and the earliest
arrivals by humans appear to be by accident.
Speaker 1 (20:33):
Yeah, you get into that situation though, where if earlier
peoples had come there, they probably wouldn't have stuck around,
and what would they have left behind, what evidence would
there be, So yeah, we're left to speculation. Now, coming
back around to the reptiles, which is going to be
the main thing we're talking about in these episodes. Again,
(20:57):
the Hawaiian Islands no native reptiles, but we have these
fascinating examples of reptiles on the Galapagos. So while reptiles
never had a chance to reach the Hawaiian Islands on
their own, the Galapagos Islands are in just the right position.
It seems to have been gifted some wandering, lost at
(21:19):
sea reptiles, and yet at the same time isolated enough
that they were able to evolve there unmolested for a
very long time. So it's kind of fascinating to think
about that. Like if they had been in any other location,
you know, there might have been a situation where, yes,
humans would have found this place and colonized it much earlier.
(21:40):
It might be in a position where these reptiles would
not have reached it of their own power or by
the power of wind and water, which seems to be
the case. I think the main examples of terrestrial reptiles
reaching the Galapagos Islands, they tend to involve rafting. They
tend to involve animals being just swept out to see
(22:03):
via rivers in South America. And then a number of
those animals are going to perish, but some of them
are going to find themselves cast upon a deserted island,
and from there they begin to find ways to survive
and these new forms evolve.
Speaker 2 (22:19):
Well, this sounds like a perfect transition to the marine iguana.
Speaker 1 (22:23):
Robert You ready, Yeah, let's talk about the marine iguana.
Probably not the most famous denizen of the islands, but
at least number two.
Speaker 2 (22:32):
Yeah, yeah, and certainly maybe the most salient in my
brain because specifically, to come back to Darwin, Charles Darwin's
discussion of the marine iguana, or the scientific name ambly
Rincus Christadis in the Voyage of the Beagle has long
stuck in my head. So of course, the Voyage of
(22:52):
the Beagle is the common name used to refer to
the published writings of Charles Darwin after his sales on
the HMS b Gole with Captain Fitzroy, and this chapter
on the Galapagos in the Voyage of the Beagle is
very famous, but the subsection on the marine iguana has
long stuck in my head, notably for the weird disrespect
(23:17):
with which Darwin treats these animals. So I want to
read a few selections as we go about here from
this passage in the Beagle, with some abridgments. But to
start off, this is what Darwin says talking about the
marine iguana. It is extremely common on all the islands
throughout the group, and lives exclusively on the rocky sea beaches,
being never found at least I never saw one even
(23:40):
ten yards in shore. It is a hideous looking creature
of a dirty black color, stupid and sluggish in its movements.
And in his journal he refers to them initially as
quote large disgusting, clumsy lizards.
Speaker 1 (24:00):
I mean they do lay around in clumps, which I
could imagine some seeing this as being kind of gross looking.
But in the same and this on the same note,
the way they kind of lounge around sometimes they they
seem oddly human in the way like one all sometimes
have an arm slung over the shoulder of another, like
it's like it's two, like as an old married couple
(24:20):
staring out at the sunset or something. Puppy pile, yeah, yeah,
kind of a puppy pile. And and there is kind
of an awkwardness to them sometimes when they move around
on land. But I don't know, that's kind of charming
more than anything.
Speaker 2 (24:34):
So early chroniclers often use the same kind of terms.
They call this animal ugly, hideous. Some of them make
bizarre value statements, such as comparing them to devils or
imps of darkness. Uh Darwin himself in the Beagle quote
say description by a previous author, a Captain Colnett, who
visited the Galapagos, who says in the part of his
(24:58):
work that Darwin quotes, quote, they go to sea in
herds of fishing and sun themselves on the rocks, and
maybe called alligators in miniature and elsewhere. Coln It marveled
at their ugliness, writing quote, so disgusting is their appearance
that no one on board could be prevailed upon to
take them as food. Not even sailors would eat them.
(25:23):
And I'm going to say I take personal offense to
all this. I think marine iguanas are beautiful. I want
to hug and kiss them. I know I shouldn't. I
would never do that, but I want to.
Speaker 1 (25:33):
Yeah, they do look kind of like yemps, but I
think in a good way. We often thought that they
looked kind of like tiny godzillas. Something about the shape
of their their heads and their snouts, and of course
the little, you know, protrusions on the top of their
head gives them kind of a kaiju appearance. And there's
(25:53):
so many things about them. There's a lot of times
you know they're lounging around, they're not doing anything, but
then when they are moving about, even on the land,
they can be quite amusing. Like, for instance, if one
is making a bee line for something, especially if one
is coming out of the water or it's time to
go to the water. Sometimes something will seem to get
in the way of their their journey, like maybe a
(26:14):
sea lion or a human wanders into their path, and
they'll just kind of stop and they'll they won't skitter
out of the way or anything, but there just kind
of wait until whatever it did is has moved on,
and then they'll keep going. So there's this kind of
like laid back care free of energy to these creatures.
Speaker 2 (26:31):
They're kind of wasted away again in Margueritaville.
Speaker 1 (26:34):
Yeah.
Speaker 2 (26:35):
Yeah, by the way, you mentioned their stubby little snouts.
That's actually what the genus name means, ambly Rincus means
blunt snout.
Speaker 1 (26:43):
Ah. Well, we'll come back to the blunt snout of that.
Speaker 2 (26:53):
However, to come back to Darwin's writings on the marine
Iguaana his unseemly anti iguana prejudice aside, he does make
some correct observations about them. For example, Captain Colnet remembers
said that they go a fishing in sea herds. You
know they're going to go out and catch fish. Darwin says,
I don't know about that. He challenges the idea that
they eat fish, and in fact we now know they
(27:16):
do not. Instead, Darwin observes that these animals seem to
subsist on a kind of seaweed or algae which cannot
be found on land, and he reasons that this explains
why they evolved to go to sea in the first place.
Speaker 1 (27:30):
Yeah, and this is spot on, of course, and we'll
get into it more in a bit, but yeah, and
it's also very observable if you're watching the creatures, because
sometimes they're going to be eating algae that's under the
water and perhaps out of you. But other times it's algae,
especially as the tides change, it's like partially in partially
out of the water, so you can see them they're munching,
(27:50):
grazing on the algae on the rock.
Speaker 2 (27:53):
Though as a side note, Darwin says one dissected iguana
stomach did have a piece of crab in it, though
he thinks this might have been eaten by accident, and
he compares this to cases where a vegetarian tortoise has
a caterpillar in its stomach, because the caterpillar was just
on the leafy vegetation the tortoise was eating. In fact,
we've done whole segments about this on the show before,
(28:14):
about herbivores eating animals accidentally or even sometimes on purpose.
Speaker 1 (28:19):
Yeah.
Speaker 2 (28:20):
But after introducing them, Darwin goes on to describe the
animals in detail, describing their movements with a strange mix
of admiration and disgust. So here's what he says. Quote.
When in the water, this lizard swims with perfect ease
and quickness by a serpentine movement of its body and
flattened tail, the legs being motionless and closely collapsed on
(28:42):
its sides. A seman on board sank one with a
heavy weight attached to it, thinking thus to kill it directly,
But when an hour afterwards he drew up the line,
it was quite active. Their limbs and strong claws are
admirably adapted for crawling over the rugged and fissured masses
of lava which everywhere form the coast. In such situations,
(29:05):
a group of six or seven of these hideous reptiles
may oftentimes be seen on the black rocks a few
feet above the surf, basking in the sun with outstretched legs.
And then he goes on to note a strange, perplexing,
almost contradictory observation about their behavior. So, while the iguanas
go to sea in order to forage, that's how they
(29:27):
make a living, They swim out in the water, get
the algae and eat it. He found that he could
not scare them into the water. If he approached one,
it would back away from him until it reached the
edge of a rock hanging over the water. But once
at that point it would stop retreating. It would just
let him approach and catch it, rather than flee into
(29:47):
the water. And here we come to the infamous iguana
chucking scene of the Voyage of the Beagle. Darwin writes,
I threw one several times as far as I could
into a dep pool left by the retiring tide, but
it invariably returned in a direct line to the spot
where I stood. It swam near the bottom with a
(30:09):
very graceful and rapid movement, and occasionally aided itself over
the uneven ground with its feet. As soon as it
arrived near the edge, but still being underwater, it tried
to conceal itself in the tufts of seaweed, or it
entered some crevice. As soon as it thought the danger
was past, it crawled out on the dry rocks and
shuffled away as quickly as it could. I several times
(30:31):
caught this same lizard by driving it down to a point,
and though possessed of such perfect powers of diving and swimming,
nothing would induce it to enter the water, And as
often as I threw it in, it returned in the
manner above described. Now, this is indeed a really odd
bit of behavior, right.
Speaker 1 (30:51):
Yeah, so it would seem. Now, before we get into that,
I want to just mention I want to make two
comments about Darwin's riding here. First of all, I do
get the impression that perhaps Darwin was not a cat
person or had a cat, because like, this is the same,
the same situation I think any cat owner can attest to.
It's like I tried to put the cat where I
wanted it to be, and it did not want to
(31:13):
be there. So strange. But on the other hand, I
do love the part where he talks about how graceful
they are in the water, because that is also a
huge tree getting to watch these lizards swim about, because
it's I mean, it's unlike anything you see with any
other species on the planet. There's this graceful, indeed serpentine
(31:36):
movement to them. There whatever awkwardness you might observe on
the land is not present in the water, and it's
it's like watching a strange aquatic little dragon move about.
Speaker 2 (31:46):
Well, I think it's also about the way that like
they anatomically modify themselves to move in the water versus
on land, because as Darwin says, they collapse their legs
to the side and almost become a snake in the water.
Speaker 1 (32:00):
Yeah, but with their heads up in a way that
like you wouldn't mistake it for a snake. Like the
profile of the swimming marine iguana is unlike anything certainly
that I've ever seen. So it really stands out in
your mind, like your mind instantly is identifying that this
is something different, This is something novel.
Speaker 2 (32:18):
I agree, and having seen not in person but seen
plenty of video of it. They are beautiful when they're swimming.
But to come back to this odd behavior, so Darwin says, Okay,
these things they go in the water all the time,
that's how they eat. They go down in the water,
they eat, they come back. How come I can't scare
one into the water or get it to stay in
the water by throwing it in. I throw it in,
the water just comes back out. Darwin comes up with
(32:41):
the guests about wyat acts this way. He says, quote,
perhaps this singular piece of apparent stupidity may be accounted
for by the circumstance that this reptile has no enemy
whatever on shore, whereas it's at sea it must often
fall prey to the numerous sharks, hence probably by a
fixed and hereditary instinct that the shore is its place
(33:04):
of safety. Whatever the emergency may be, it there takes refuge. So, okay,
that's an interesting guess. He says. It has natural predators
in the water, but not on land, so it just
feels safer on land, even if here I am threatening
it on land, because it's just acting out of instinct.
Speaker 1 (33:22):
Yeah, yeah, it would seem to be a decent theory.
And indeed on land that nothing really messes with them
except when they're smaller. And when they're smaller there you know,
like and this is the case with a number of
iguanas and lizards, like until they reach a certain size,
they're on the menu for various other creatures and birds
and whatnot. But once they reach a certain maturity. Yeah,
(33:43):
they can just bask where they want. Nothing's going to
mess with them.
Speaker 2 (33:46):
Yeah, well, at least in the ancestral environment of the Glasogos.
Now introduced to dogs and pigs and all that stuff
that humans brought there will prey on them. So I
decided to follow up on this and see has there
been any sub sequent research about this behavior in marine
iguanas that could confirm or deny Darwin's guess about the
(34:06):
evolutionary reasoning there. And I found a paper that addresses
exactly this topic. It is by Edmund S. Hobson called
Remarks on Aquatic Habitats of the Galapagos Marine Iguana, including
submergence times, cleaning, symbiosis, and the Shark Threat. This was
published in a journal called Copeia in nineteen sixty nine,
(34:28):
and it seems that sharks do occasionally eat the iguanas
as Darwin guest. A report of the contents of shark's
stomachs in nineteen oh three by Heller did find some
marine iguanas in there, but Hobson thinks that the threat
to iguanas by sharks is mostly exaggerated, given that he
(34:48):
and his colleagues directly observed iguanas and sharks swimming in
the same waters side by side, and he says almost
all the time they just ignore one another entirely. To
read from Hobson quote to the contrary, the general situation
finds sharks swimming slowly among smaller fishes with no overt
sign that they regard these animals as prey. Certainly, sharks
(35:10):
are efficient predators when they do attack, but situations evoking
attack are relatively infrequent. At Narborough Island, I saw white
tipped sharks and a gray shark pass within a few
meters of surface swimming iguanas, with no indication that they
regarded the iguanas as prey. George Barlow and I made
a similar observation involving a large hammer head at Hood Island.
(35:34):
So if it's not a fear of sharks, what explains
this behavior?
Speaker 1 (35:40):
Well, if I would a venture a guess, I'd say
it has to do with temperature, that they're thermic reasons
at play here.
Speaker 2 (35:46):
Great thinking, and this is exactly what Hobson concludes. Hobson
argues that the best explanation for this apparently weird behavior
observed by Darwin is that the water's cold, you know,
they have to go in there to get food, but
they don't want to spend any more time in there
than they have to because it's cold and they're reptiles.
To read from Hobson, citing another researcher named Bartholomew quote.
(36:08):
Bartholomew in nineteen sixty six offered a more plausible explanation
after noting that iguanas basking on the rocks ashore have
a preferred body temperature of thirty five to thirty seven
degrees celsius, over ten degrees celsius above that of the sea.
He suggested that iguanas which are taken from the rocks
and thrown into the water immediately return to land simply
(36:31):
because they are reluctant to cool off. And I love
this explanation. It also does seem plausible to me. But
I love this because it highlights something about human thinking
that even Darwin himself was not immune to. And Rob,
I think you'll know exactly what I'm talking about here.
When humans are trying to come up with explanations for
(36:52):
an animal behavior or a feature of an animal body
or something, I think humans are way too quick to
jump to two types of explanations, those involving mating and
those involving predation, sex and violence. Just in our brains,
sex and violence are more salient explanations than all kinds
(37:14):
of other pressures that exist in nature and do drive
animal body plans and animal behaviors. Things having to do
with just base physical realities of the world, like maintaining
body temperature, thermoregulation, access to oxygen, all kinds of things
like that that explain tons about the natural world. It's
just our brains just don't jump to those things as
(37:35):
quickly when we're looking for a why.
Speaker 1 (37:37):
Yeah, I think modern reptile enthusiasts, especially any who have
been engaged in keeping of reptiles, they'll be pretty quick
to tell you, Oh, yeah, temperature is important, temperature regulation.
You know, the lizards, snakes, they want their warm places,
and they're certainly going to realize that. But yeah, this
is an easy, easy trap to fall into. I should
(37:59):
also say I did go into the water in the
Galapagos snorkeling once, and it is, to me a non iguana,
quite cold. So I can in some way at least
understand how they feel about it.
Speaker 2 (38:13):
Yeah, so Mark me is convinced I think that iguana
kept swimming back and crawling out of the water after
Darwin threw it in because it was getting cold and
it wanted to it wanted to warm back up on
the rocks.
Speaker 1 (38:24):
Yeah, and let I say, they're pretty chill, but they're like, no,
it's too cold. I would like to get out, and
he's like, I'm throwing you back in. He's like, too cold.
I wish to get out. It's not time. It's not time.
I will get in the water when I am warmed
up enough to do so. Now getting into a little
bit about the evolution of the marine reptiles, it's very fascinating,
(38:44):
especially again thinking of them as this really largely singular
occurrence in the modern world. So I was looking at
a few different sources. One of these was Marine Reptiles
by Resmussen at Hall from twenty eleven published in Peel one.
They point out here that lizards make up sixty percent
(39:05):
of all reptiles, but very few lizard species compared to say,
turtles and snakes, are present in our oceans. And this
isn't getting so much into the issue of prehistoric aquatic reptiles,
which do include extinct squa mats, like the mosasaur. The mososaurs,
which were actually distant relatives of modern iguanas and monitor lizards,
(39:30):
were pretty fascinating in and of themselves. They were gigantic,
They reached links of up to twelve meters or forty feet.
They swam in earth oceans roughly sixty six million years ago.
They hunted other marine reptiles, and it's possible they gave
birth to live young in the water, though I'm not
sure this is certain. There's various studies out there about
(39:52):
possible egg finds of the mosasaurs, but it's worth mentioning
here to drive home the difference between today's marine reptile
and those of the past, and especially you know, thinking
about sea turtles, thinking to about the marine iguana. These
are animals that, to varying degrees, are great in the water,
(40:14):
but they still must return to shore to complete some
vital stage of their life, certainly with sea turtles. With
the marine iguana, it's more living on the shore but
then going into the water to graze and feed. Yeah,
so of extent lizards that are in any way aquatic,
there are only a few extreme examples, and this includes
(40:35):
the Western Pacific mangrove monitor, which is a carnivore. But
as the authors here point out, the Galapagos marine iguana
is the most aquatic of all extents lizards. It basks,
breeds and lays eggs on land, et cetera, but it
has to go into the water to feed. It is,
by other definitions, the only squaw mate that's actually able
(40:55):
to exploit the re sources of the ocean in a
meaningful way. So the aforementioned monitor lizard, for example, can
catch fish, but it also feeds on terrestrial meats as well.
I should also note that there are other iguanas on
the Glabgos Island islands, to be sure, including seven smaller
species and three species of land iguanas in the genus Conolophus.
(41:17):
They include the beautiful and rare Galapagos pink iguana, which
is a most special creature. Included a picture of this
for you, Joe and everyone out there. You should look
up a picture of the Galapagos pink iguana. This is
not something I got to see when I was there,
because it lives in a very remote part of the islands.
Not not even even locals don't usually get to see
(41:37):
this creature.
Speaker 2 (41:38):
The first thing that popped into my head is it
looks kind of like a hot dog.
Speaker 1 (41:43):
Yeah, yeah, it's you know, it's it's it's it's a
specially it's an iguana pink. But yeah, these are these
are rare and beautiful creatures. But again, the marine iguana
is the real standout here. The other iguanas are a
lot of fun to watch too, if you if you visit,
but yeah, the marine iguana is special. The average adult
is around one point two meters in length, so they're
not huge, and they're found on virtually every island of
(42:06):
the Galapagos. So coming back to the question, how did
any of these lizards get to the Far Flow and
Galapagos islands, The answer, according to Resmussen at all is
probably that they're all related to iguanas from South America
that were washed from the South American mainland, again perhaps
(42:28):
by river floods, and carried out to the Galapagos. And
again this is where the Galapagos's isolation yet closer proximity
to a continental mainland comes into play. The theory is
also in part supported by the fact that as distinct
as the four bigger iguanas of the Galapagos Islands, including
the marine iguana are They are closely related and they
(42:50):
actually can breed with one another to produce hybrids, so
hybrids have been reported according to Resmussen. At all, the
marine iguanas spend quite a bit of time in the water,
though foraging for their food. As adults, they feed almost
exclusively on the red and green algae. It's been pointed
out they're not above at least trying out the odds
(43:12):
scrap of this, that or the other, and perhaps that
accounts for the crab claw that Charles Darwin reported. And
there's at least one population of the marine iguanas that
has been observed to supplement their diet with land plants.
But for the most part, their hindgut has evolved to
thrive on the algae like they're bound to the algae.
This is not just a this is not just a
(43:33):
lifestyle choice at this point, and their bodies have adapted
in other key ways as well to allow this marine
diet due to the considerable selection pressure that's been applied
to them, which is quite literally the selection pressure of
being cast upon a resource depleted island. So we mentioned
their flattened tail that's one of the adaptations. And it's
(43:57):
not like you don't find flattened tails and other lizard species,
but this is clearly something that seems to help out
there swimming. They also have limited webbing on their feet,
which I saw kind of two different takes on this
in the literature I was looking at. On one hand,
there's the argument like, yeah, it's partially web feet, this
is going to help them swim, But others say, well,
the webbing is not that extensive. It maybe helps a
(44:20):
little bit, but let's not overstress its importance.
Speaker 2 (44:23):
Well, I'm no marine iguana expert, but it seems to me,
at least when I've seen images of them swimming, it
doesn't seem like they paddle with their feet much at
all that I recall, but maybe they do sometimes.
Speaker 1 (44:36):
Something that everyone agrees on, though, is that their claws
have become more powerful to allow them to grip the
rocks and the surf during feeding. And this is certainly
key because if you're observing one from the shore, or
if you're looking at images or footage of them, or
if you're snorkeling, you get to see one underwater. I
did not get to see one underwater. Firsthand. But either way,
(44:58):
when they're feeding, they're often in an area where the
the you know, the surf is disrupting them and would
make it difficult to feed if they were not able
to hold on and latch on. And then of course
when they get in or out of the surf, they're
going to need to keep from being swept up anyway.
So yeah, they got to have those powerful claws to
aid them.
Speaker 2 (45:17):
That's not an easy lifestyle. And crawling out of the
surf onto rocks, I mean, think about how danger its
how dangerous it would be to try to land a
boat or even just swim up onto jagged rocks as
the tide is coming in and out.
Speaker 1 (45:31):
Yeah, for sure. I was also now, this is something
I was told by one of the guides in the
Galapagos Island, who again are very knowledgeable of all of this.
Uh so, you know, they're they're very quick to spout
out all the scientific names of all the creatures you're
looking at, and they're they're up on the latest findings
(45:52):
and so forth. I was pointed out that they all
utilize those sort of thorny spikes on their head, and
I almost hesitate to say face in order to loosen
up the algae on the rocks by sort of rubbing
their heads against it. And then it should also be
noted we touched on this earlier, but there's the whole
regulation of their body temperature. And this is key because
(46:15):
again the water's cold, and these are cold blooded animals,
so they spend a fair amount of time basking in
the sun. And the way this is certainly one way
it was described to me there, and this is backed
up in the paper that I was reading recently, is
that in order to go into the water, they kind
of have to power up, so like they're powering up
(46:35):
there like on the on the beach or on the rocks,
basking in the sun, kind of filling their batteries up
all the way. And then when it's time, well then
it's time. Now it is time to go into the
water to forage for food, and they make that beeline.
But it's only then, only then, and they're not going
to be thrown in early by some deranged englishmen there.
And if something should get in their way, well they're
(46:57):
just going to wait patiently for a little bit. But
they've got a place to be. It is time to
go into the water and feed, So.
Speaker 2 (47:03):
It's a constant trade off of managing different energy resources
in the body. You've got your thermal energy, like you
need to bask on the land to get your body
temperature up, but then you need to go into the
water to get food for your metabolism, and you're sort
of just always trading back and forth between the two.
Speaker 1 (47:21):
Yeah, Now when they're in the water, their heart beats
also reduce from about forty three beats per minute on
land to seven to nine beats per minute in the water,
So that's also an interesting adaptation they have. And then
this is another famous one that's a lot of fun
to watch. You see this in footage every nature documentary
that's covered marine iguanas. But both of the main varieties
(47:44):
found in the four larger iguanas they have salt glands
that help them process an abundance of salt should it
be in the body. But with the marine iguanas, this
of course is very visual because if you're just watching
them lounge about, they're going to regularly appear to sneeze.
They're not sneezing, they're blasting salt out of these salt glands.
(48:06):
They basically blasting salt out of their nostrils as they
lounge about on their rocks, and as they're doing this too,
making these cute little sneezing sounds or gross little sneezing
sounds everyone to look at it. They're also kind of
like crusting over the tops of their heads with this,
you know, like white salt crystals, so you can tell
like which ones haven't been on the in the water
that recently, because they have this kind of like salty
(48:28):
look to their heads.
Speaker 2 (48:29):
They got the salt snot on there. Yeah, you know,
this comes back to something else Darwin said. He was like, there,
you know, you can back them into a corner and
you can catch them. They they don't really bite. I
don't think that's true, by the way, but he says,
they don't really bite, but they will blow salt out
of their noses at you.
Speaker 1 (48:48):
Yes, I I remember reading this as well, because I
was when we were in the Galabacos. I pulled up
the text. I was reading it, and yeah, there is
this accusation that they're doing it defensively, and yeah, this
does not seem to be the case. Now they're just
doing it. Maybe they're doing it, I guess, I guess
I have no data on this, but I guess it's
(49:09):
possible that if someone is coming at them and backing
them away, then maybe that does seem to incite a
snort because they're about to move. But other than that, yeah,
there's I've seen nothing to indicate that this is in
any way a self defense measure.
Speaker 2 (49:25):
That's right up there with av and defensive vomiting.
Speaker 1 (49:28):
Yeah. Yeah, there's a lot of back and forth on that, right.
I think we've discussed that is like a vulture vomiting
in order to free up room and you know, make
itself lighter so it can take off and get away.
Is that are offering a bribe to a scavenger that
may be coming after them and decide to go for
vomit instead of fighting a buzzard like There are various
interpretations of that. As I recall now on the issue
(49:51):
of marine iguana evolution, I was looking at another source.
This is from Martin Wakelski in a two thousand and
five edition of the Royal Society paper entitled Evolution of
body Size in Galapagoes marine Iguanas, and I found this
one interesting because the author here lays out one possible
model for how the Marinea iguanas evolved. So, first of all,
(50:13):
iguanas arrived, according to this theoretical model, in the Galapagoes,
perhaps ten to fifteen million years ago from South America
via rafting, so swept out to see floating on some
vegetation and so forth, and then being cast on this
strange island. And once they're there, it becomes clear eventually
(50:35):
here that in the intertidal zone there's plenty of food
for iguanas, but it's not on the land, it's the
algae in the water. Initially, the iguanas are going to
have to depend on low tides to get to the food,
so the tide goes down, iguanas are daring to get
down in there and go after the algae, and so
(50:57):
there's going to but from there that's where we're going
to be to see the selection pressure towards larger bodies
for thermal inertia and also the ability to anchor themselves
in the surf, as well as these other adaptations that
we mentioned, like the bigger claws ultimately the shorter snout
as well. That's going to be part of their their
forging behaviors. They essentially like rub their faces against the
(51:20):
rocks to gnaw off the algae as well as the
like swimming morphological changes.
Speaker 2 (51:26):
Interesting.
Speaker 1 (51:26):
Yeah, there's and there's there's actually a lot of a
lot of work that comes out related to the marine iguanas,
Like there's no shortage of papers. There's one from twenty
twenty one that I was looking at, Cranial Anatomy of
the Galapagos Marine Iguana by Paparella and Caldwell in the
American Association for Anatomy, and they point out some of
(51:48):
the you know, the key changes just to the head
of the creature of VI. It's evolution modified configuration of
the snout and nasal chamber, increased muscle attachments in the
temporal post orbital region of the skull, and and also
the teeth as well. So all of this is coming
seems to revolve around what they're feeding on and how
(52:09):
they're feeding on and how that's affecting just like the
overall shape and even like the muscles of the head.
Speaker 2 (52:16):
And I imagine they would make some guesses from this
about how far back in time the marine iguanas had
these evolutionary changes.
Speaker 1 (52:25):
Yeah, one of the authors here, Paparella, I found this
is actually I believe from another paper. But I saw
this author saying that arguing elsewhere for an iguana colonization
of the ancient Galapagos Islands as far back as twenty
to twenty five million years ago. And I think in
this we're getting into into this idea of not only
the existing Galapagos Island, but these like pre existing Galapagos islands,
(52:50):
the ones that, like you said, have now been lost
and are submerged. Wrote that like this we would have
like an initial dispersal followed by constant short range hopping
from older to newer islands. So you know, they get
a foothole in one place and then they can spread
to these other islands much more easily. And then as
(53:10):
new islands emerge, that opens up new places for them
to be. And of course as old islands die away,
then so do the populations of those islands or they
you know, they're forced to disperse to newer islands. And
Joe from that paper about the shape of their heads,
I included this wonderful image, this one. I think I
didn't get this out of the paper itself, but this
(53:32):
was I believe from a like a Twitter post by
the American Association for anatomy. It's out there if anyone
wants to look it up for themselves. But yeah, you
see very very high definition close up on both the
head of the marine iguana, and then also a comparison
of the skull, which I thought was just very insightful
(53:53):
looking at these, because you know, it just looks it
looks very much unlike a lot of the lizard skulls
you might see, Like glancing at it, you might not
even think of it as a lizard's call. I mean,
it doesn't look like a human skull or anything. It's distinct,
but you can clearly see like the changes that have
taken place here.
Speaker 2 (54:12):
Yeah, the blunt snout and the density of it, I
mean almost you could imagine it being more of a
turtle skull or again, I mean it looks kind of
like Godzilla.
Speaker 1 (54:20):
Yeah, it's like Godzilla, and I like how they kind
of have. You see, especially in close up like these,
there's real sense of iguana lips, you know.
Speaker 2 (54:29):
Yeah, you also get a really good look up inside
the nostrils.
Speaker 1 (54:33):
Yeah, this, of course is a specimen. This is a
dead iguana that Joe and I are gawking at here,
but still beautiful specimen but yeah, the marine iguanas are
are special creatures. And I think I don't even have
to tell anyone this. It's this is not new information. Uh.
(54:55):
There have been so many documentaries that of course have
covered the Galacos Islands that have caught brilliant footage of them.
They are a standout species that they've been highlighted in
various shows over time, or you've no doubt seen articles
about them or see them popping up in the lists.
So so yeah, nothing nothing new in me saying that
these animals are great. But like all these things, yeah,
(55:15):
if you get to see them in person, if you
have that chance, take that opportunity, because they're pretty remarkable.
Speaker 2 (55:21):
I would like to see the iguana puppy pile. Hey,
we haven't even touched on the most famous reptiles of
the Galapagos, and I think we're gonna have to do
that in the next episode.
Speaker 1 (55:33):
That's right, the Galapagoes tortoise. Yeah, we're going to come
back in the next episode of of this journey to
discuss these fabulous creatures. I mean, it makes sense that
they'd come in second. They are slower, but they're they're
very remarkable in their own way, so be sure to
come back for that episode. In the meantime, we'd love
(55:54):
to hear from you if you have thoughts about Marine
iguanas you know firsthand or docum menory based. If you're
a resident of Ecuador the Glavigos Islands, certainly we would
love to hear from you on all of this. If
you want to hear more Stuff to Blow Your Mind,
I'll just remind you that core episodes of the show
publish on Tuesdays and Thursdays, and the Stuff to Blow
(56:14):
Your Mind podcast feed on Mondays. We do listener mail.
On Wednesdays we do a short form artifact or monster fact,
and on Fridays we do Weird House Cinema. That's our
time to set aside most of the serious science and
so forth and just talk about a strange film.
Speaker 2 (56:28):
Huge thanks to our audio producer, Max Williams. If you
would like to get in touch with us with feedback
on this episode or any other, to suggest a topic
for the future, or just to say hello, you can
email us at contact at Stuff to Blow your Mind
dot com.
Speaker 3 (56:51):
Stuff to Blow Your Mind is production of iHeartRadio. For
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