My Welcome to Stuff to Blow Your Mind production of My Heart Radio. Hey you welcome to Stuff to Blow your Mind. My name is Robert Lamb and I'm Joe McCormick, and today we're beginning a series of episodes on the reptiles of the Galapacos Islands. And rob this is not a topic we just landed on randomly. This is related to your recent travels, right. Yeah. I had the great pleasure and the good fortune to visit some of the islands of the glap Coos Archipella go back in October. It was a fantastic family trip that we've been planning for a long time and we meant to do before the pandemic and then obviously we had to reschedule. But yeah, this is this is one of the top trips I've ever had the privilege to make. And now, certainly I was visiting as a tourist, but but one of the things about the Glapos Islands that I love is so much of the tour is um there is about the natural beauty of the place. It's about the environments, it's about the animals and um. And so if you're you're going all the way to the Galapagos Islands. You you probably want to see some reptiles, you probably want to see some birds, etcetera. And they really facilitate that. The local guides are are all terrific, all the ones that that I interacted with, a very knowledgeable of everything going on there. And yeah, it was a trip just unlike any other, especially when when 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. It's 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 they'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 Galapicos Islands that um that that that feels less 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 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. Um, you know, creeping up for a close look at this animal or another, 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 place where animals don't seem to flee from humans because there they come from many generations of animals without natural land predators. Yeah. Yeah, and uh, I believe that is the case with the Clap of Coasts. So let's let's introduce everybody to the to the clap Coost Islands. If you're not familiar with the clap of Coost Archipelago, it is a chain of islands in the eastern Pacific Ocean, roughly nine sixty six kilometers or six hundred miles off the coast of Ecuador. It consists of thirteen major 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 with the Hawaiian islands, the islands here and the Galapaos 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 galapaost islands, but I've seen it very a bit. The Galapa Ghost Conservatory says quote probably no more than five million years with the younger volcanically active westernmost islands perhaps as young as hundreds of thousands of years old, but the idea that none of the islands there today are are more than five million years old. According to some of the dates that I was looking at me at least sighted dates, but just sort of casting a wide net. I did see some other dates out there, so um, you know, I can only speak to the ones I'm sighting here. Well, estimates very a bit, but it also depends on what you're counting as the Galapa Coost Islands. For example, I was reading a passage in a book Galapagos a Natural History, second Edition by John Creature and Kevin Laughlin from Princeton University Press. That new edition is just just out this year in two and there is a section in 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 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 sea mounts in the eastern part of the archipelago. Well, Creature and Laughlin right 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. Uh and the the authors here site a 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 ranged from between five to nine million years, which is older than any of the existing Galapagos islands today. So to read from this passage quote, 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 albeit accidental dispersal, new islands forming over the hot spot will be colonized even as old islands a road and disappear beneath the sea from whence they came. So normally you're talking about island 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 the case of the Galapagos, uh, A lot of the evidence of the earliest colonization by animals could be under the waves. It could just be lost because those islands aren't there anymore. M Yeah, there's sort of the lost animal kingdoms of the globos potentially. Now when we're we're talking about the the modern day Galapkos islands, uh, some of the main ones, just to mention them real quick. You have Isabella, which is the largest. You have Santiago, Uh, Fernandina, you have Santa Cruz, you have San Cristobil. I only really visited Santa Cruz and San Cristobul and a couple of smaller, unoccupied um by humans islands that were quite fascinating. And one of the things about these islands, and you've often encountered this with with volcanic highland formations is that they're defined by steep out elevation changes and the resulting islands that contain multiple microclimates due to this, So a visit to even a single Glabacos island is an encounter with multiple and varied ecosystems. Right, So you'll get different climates and different vegetation and so forth at different elevations on the island. So uh and 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 foraging up in the highlands. Yeah. Yeah, So it's any one of these islands, you'll have, you know, have sort of desert environments, you'll have highland lush environments, you'll have coastal and Ironman's 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 for a while, because I think it's a nice sort of touchtone to compare, especially since we've we've talked about those islands on the show before as well. Um So when it comes to Hawaii, as we've discussed before, you have such geographic isolation that with those islands, so there are actually no native land reptiles or amphibians there. So anything in the categorization of reptiler 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 Glabcost Islands for a few different reasons. So as far as humans go, first human contact with Glavicos comes a bit later. We're talking about fifty five versus Hawaii's betwe Queen. And also Hawaii is a greater distance from the nearest continental land mass and I shouldn't know that, I think I pointed this on the 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 yeah, exactly three hundred years before Darwin did. By the way, yeah, thank thank 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 Thomas de Borlonga who was a bishop. He eventually served as the bishop of the Colony of Panama, and I've read it alleged in several sources that Burlongo was responsible for introducing bananas 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 is responsible for bringing bananas over, but I'm not sure what the original source of this claim is. Anyway. In five Blonga was traveling by ship from Panama to Peru to help sort out some kind of horrible sounding squabble between the conquistador Francisco Pizzarro and another conquistador over land and spoils after their conquest of the the Inca Empire. So Berlonga is on the way down to try to help sort this out, but as 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 see by strong ocean currents, and just when supplies, including fresh water, are about to run out, the crew sites land. Their prayers have been answered, but like so many early visitors, the 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 one to continue the search for water. Unfortunately, on the way they were once again be calmed 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 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 bbe in his book galapagost World's End, A published nine BB rights. In their extremity, they had recourse to a plant which has saved many a thirsty man and animal, And by chewing the fruit and juicy stalks of the cactus, they kept themselves alive. They took a page from the tortoise playbook there. Yeah, uh, 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 stones, brutal doom metal bishop uh. And then Babe goes 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 Babe has taken a little liberty with the storytelling there, but all plausible, you know, given the given the local of flora and fauna. Yeah, desolate beaches, weird sea lions hanging about, Well, I guess they sea lions generally described her as weird. They would have certainly been exposed to sea lions already, But in my book, sea lions are inherently strange but also very amusing to watch. 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 a spring water and as little pools collected in cup shaped depressions in the rocks. 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. Burlonga made a number of observations while on the island, writing, according to an eight eight four translation of his letters, that the animals of the Galapagos were quote so silly that they not know how to flee uh, and that as a result, wild animals were easily caught in the hand. Well, that does match up, I think with the reality of visiting the Glabicos 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, um like, they don't necessarily understand what we are and they're not threatened by us unless we get too close, and then a lot of these animals will let you know. So, yeah, don't 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. Now, Rob, you mentioned that the tourism at the Galapagos today is almost entirely centered around the islands 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, right right, Um, Yeah, and yeah, I mainly mean, yeah, you're not gonna find that. You're not gonna 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, um, you know that there is there is culture there. There's some some great restaurants, there's there's great local culture and the people who live there. Uh. We were on the whole very friendly and uh and I loved interacting with them quite a bit. But yeah, it's when people go to the Galapacos. I mean, the main selling point, the big deal for for everyone seems to be the natural world that is available to you there. 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 anymore than they would have claimed Hell for Spain. M I haven't read this novel, but I did see it in bookstore. There was a nice bookstore on one of the islands and the Collapacos, and they had it there. They were probably had several Darwin related books, and then they had Vanagats Glapacos, and I was tempted to pick it up, but then I was like, I don't know if I'm in the mid for post apocalyptic literature at the moment. 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, uh, 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 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 rated coastal settlements on the mainland. Yeah. Yeah, when when it comes to the human history of the clab because it's easy to sort of think, oh, well, Darwin, uh and then you sort of fast forward to today. But yeah, there's a lot of bloody history there. It was this It was an extreme location that, like you said, I didn't have a lot seemingly to offer except as a place of refuge for people engaged in various bloody activities. Sometimes it seemed like a place for utopia, utopian ideals, and um, 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. Uh. 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. That's that's that's funny because they're on Sant Christoble Island. You know, there's like a statue of of of Charles Darwin in the ship with his hand out and I had I got my picture made with this, of course, but there, yeah, there statutes of Darwin all over the islands. Nice. Um 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 not cool. Yeah, that's not the quote that's like on a plaque. Besides this, h Now, regarding uh, 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 were sure about but They're all kinds of interesting arguments about whether or not others had been there before, and their theories of contact regarding the Inca's Pacific peoples and so forth. But I think all of these are speculative and the the evidence is questionable there. There was certainly no permanent human settlement in pre Columbian times, and the earliest arrivals by humans appeared to be by accident. Yeah, you get into that situation though, where if earlier people's 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 uh, the reptiles, which is going to be the main thing we're talking about in these episodes. Um. Again, the Hawaiian Islands no native reptiles, but we have these fascinating examples of reptiles on the Galapacos Um. So while while while reptiles never had the chance to to reach the Hawaiian Islands on their own, the Glaphicos Islands are in just the right position. It seems to have been gifted some wandering um lost at sea reptiles. Uh. And yet at the same time, isolated enough that they were able to evolve their unmolested for a very long time. Um. 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. 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 in the main examples of terrestrial reptiles reaching the Galapagos Islands, they tend to involve rafting. They tend to involve animals being um, just swept out to see via rivers in South America. And then you know, 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. Well, this sounds like a perfect transition to the marine iguana. Robbert, you ready, Yeah, let's talk about the marine iguana. Probably not the most famous denizen of the islands, but at least number two. Yeah, yeah, and certainly maybe the most uh salient in my brain because specifically, to come back to Darwin, Charles Darwin's discussion of the marine iguana or scientific name ambly Rinkus Chris Tatis and the Voyage of the Beagle has long stuck in my head. So of course, the Voyage of the Beagle is the common name used to refer to the published writings of Charles Darwin after his sales on on the HMS Beagle with Captain fitz Roy and this, uh, 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 with which Darwin treats these animals. Uh. So I want to read a few selections as we go about here from this passage in the Beagle with some abridge mints. 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 ten yards inshore. It is a hideous looking creature of a dirty black color, stupid and sluggish in its movements. Uh. And in his journal he refers to them initially as quote, large, disgusting, clumsy lizards. Well, I mean they do lay around in clumps um, which I could imagine some seeing this as being kind of gross looking. But in the same in this, on the same note, the way they kind of lounge around. Sometimes they seem oddly human in the way like one al sometimes have an arm slung over the shoulder of another. Like it's like it's too like it's an old married couple 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. So early chroniclers often used 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 quotes a description by a previous author, a Captain Colnett, who visited the Galapagos, who says, in the part of his 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. Colne 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. And I'm gonna 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. Yeah, they do look kind of like jumps, but I think in a good way. I often we often thought that they looked kind of like tiny Godzilla's. Something about the the shape of their their heads and their snouts and of course the little, uh you know, protrusions on the top of their head give them kind of a a kaiju appearance, and um that and there's so many things about them that there's just a lot of times that 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 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's kind of wait until whatever did is it has moved on, and then they'll keep going. So there's is kind of like laid back care free of energy to these creatures. They're kind of wasted away again in Margaritaville. Yeah. Yeah, by the way, you mentioned their stubby little snouts. That's actually what the genus name means, ambly Rincus means blunt snout. Ah. Well, we'll come back to that blunt snout of that. Thank However, to come back to Darwin's writings on the marine iguana. His unseemly anti iguana prejudice aside, he does make some correct observations about them. For example, Captain Colnett remember said that they go a fishing and 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 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. Yeah, I mean this is this is spot on, of course, and then we'll get into into it more in a bit. But but yeah, and it's also very observable if you're watching the creatures, because sometimes they're going to be uh, eating algae that's under the water and perhaps out of you. But other times it's it's algae, especially as the tides change, it's like partially and partially out of the water, so you can see them they're munching, grazing on the alergae on the rock. So 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 two 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, about herbivores eating animals accidentally or even sometimes on purpose. Yeah. But after introducing them, Darwin goes on to describe the animals in detail, describing their movement. It's 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 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 formed the coast. In such situations, 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 make a living there. 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 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 deep 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 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 all out on the dry rocks and shuffled away as quickly as it could. I several times called 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. Uh. Now, this is indeed a really odd bit of behavior, right, yeah, so it would seem. Um. Now, before we get into that, I want to just mentioned I want to want to make two comments about Darwin's writing here. First of all, I do get the impression that perhaps Darwin was not a cat person or had 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 be there, So strange. Um. But 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 uh, these these lizards. It's a swim about because it's I mean, it's it's unlike anything you see with any other species on the planet. There's this this graceful, indeed serpentine movement to them. There whatever awkwardness you might observe on the land is not present in the water. And it's yeah, it's like watching a strange aquatic little dragon move about. 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. Yeah, but with their their heads up in a 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. I agree, and having seen not in person, but seen plenty of you know, video of it. They are beautiful when they're swimming. But to come back to this odd behavior or 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 a guess about why it 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 urged by a fixed and hereditary instinct that the shore is its place 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. Yeah, yeah, it would seem to be a decent theory. And in eat on land that nothing really messes with them except when they're smaller, and when they're smaller, they're you know, like 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 uh maturity, Uh yeah, they can just bask where they want. Nothing's gonna mess with them. Yeah, well, at least in the ancestral environment of the glass. Now introduced dogs and pigs and all that stuff that humans brought there will prey on them, right, So I decided to follow up on this and see has there been any subsequent research about this behavior in marine iguanas that could confirm or deny Darwin's guests about the evolutionary reasoning there. And I found a paper that addresses exactly this topic. It is by Edmund As 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 teen sixty nine, and it seems that sharks do occasionally eat the iguanas as Darwin guest. A report of the contents of shark's stomachs in nineteen o 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 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 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. So if it's not a fear of sharks, what explains this behavior, Well, I would venture I guess I'd say it it has to do with temperature, that they're their thermic reasons at play here. 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 is 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 their reptiles h to read from Hobson, citing another researcher named Bartholomew quote. Bartholomew in nineteen sixty six offered a more plausible explanation. After noting that iguana is 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 would you're taken from the rocks and thrown into the water immediately returned to land, simply because they are reluctant to cool off. Uh 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. Uh And Rob, I think you'll know exactly what I'm talking about here. When humans are trying to come up with explanations for 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 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 explained tons about the natural world. It's just our brains just don't jump to those things as quickly when we're looking for a hy Yeah. I think modern reptile enthusiasts, especially any who have engaged in keeping of reptiles, they'll be pretty quick to tell you, oh, yeah, temperature is important, temperature regulation. Uh, you know, the lizards, snakes, they want their warm places and and they're certainly going to realize that. But yeah, this is an easy, easy trap to fall into. I should also say I did. I did go into the water in the Galapagos snorkeling once, and it is to me a non iguana quite cold. So I can I can in some way at least understand how they feel about it. 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. Yeah, And I think 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, to too cold. I wish to get out. It's not time it's not time out. 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, um, it's it's very fascinating, especially again thinking of them as this this 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 All from Tleven published in p. Los one. They point out here that that lizards make up of all reptiles, but very few lizard species compared to say, turtles and snakes are present in our oceans, and this is this isn't getting so much into the issue of prehistoric aquatic reptiles, which do include extinct squamates like the mosasaur. The mososaurs which were actually distant relatives of modern iguanas and monitor lizards. We're pretty fascinating of themselves. They were gigantic, They reached links of up to twelve meters or forty feet. Uh. They swam in earths 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. Uh, though I'm not sure it's it's this is certain. There's some various studies out there about possible egg finds of the mosasaurs. But it's worth mentioning here to drive home the difference between today's marine reptiles and those of the past, especially you know, thinking about sea turtles, thinking too, about the marine iguana. These are animals that um to varying degrees, are great in the water, but they still must return to shore to complete some vital stage of their um of their life, certainly with sea turtles, with 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 um and this includes the Western Pacific mangrove monitor, which is a carnivore. But as the authors here point out, the galapagost marine iguana is the most aquatic of all extants lizards. It basques, 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 squa mate that's actually able to exploit the research 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 Glabos Island islands, to be sure, including seven smaller species and three species of land iguanas in the genus um Conelphus. 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 Galapa those 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. Uh not not even even locals don't usually get to see this creature. The first thing that popped into my head is it looks kind of like a hot dog. Yeah, yeah, it's you know, it's it's it's it's especially it's an iguana pink. But yeah, they're these are these are rare and beautiful creatures. But again, the marine iguana is the real standout here. The other guanas are a lot of fun to watch too, if you if you visit, but 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 out virtually every island of the Galapacos, Thank thank so. Coming back to the question, how did any of these lizards get to the far flung Galabicos 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 by river floods, and carried out to the Galapagos, and again this is where the Galapagos is 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 actually can breed with one another to produce hybrids. So hybrids have been reported. According to rest Moodsen, 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 there it's been pointed out there not above at least trying out the odds grape scrap of this, that or the other. And perhaps that accounts for the 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 hind gut has evolved to thrive on the algae. Like they're they're bound to the algae. This is not just a this is not just a 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 we mentioned their flattened tail. That's one of the adaptations. Um and uh. And it's 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 a limited webbing on their feet, which I saw kind of a two different takes on this, and the literature is 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 little bit, but let's not overstress its importance. Well, I'm no marine iguana expert, but I 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. 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 if you're observing one from the shore, or if you're looking at images or footage of them, or or if you're snorkeling and get to see one underwater. I did not get to see one underwater firsthand, but either way, when they're feeding, they're often in an area where 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 gonna need to keep from being swept up anyway. So yeah, they got to have those powerful claws to aid them. That's not an easy lifestyle, like crawling out of the surf onto rocks. I mean, think about how dangerous, how dangerous it would be to try the land a boat or even just swim up onto jagged rocks as the tide is coming in and out. Yeah, for sure. Um I was also Now this is something I was told by one of the guides in the Colabkos Island, who again are are very um 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 find things and so forth. It 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. It. And then it should also be noted we we touched on this earlier, but there's the whole regulation of their body temperature. Uh. And this is key because again the water is 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, uh there, and it is backed up in the the paper those reading recently, is that in order to go into the water, they kind of have to power up, so like they're powering they're 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's time to go into the water to forage for food, and they make that bee line, but it's only then, only only then, and they're not going to be thrown in early by some deranged Englishmen and and if something should get in their way while they're just gonna wait patiently for a little bit. But they're they've got a place to be. Uh, it is time to go into the water and feed. So it's a constant trade off of managing different energy resources in the body. You've got, you know, your your thermal energy, like you need to bask on the land to uh, 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. Yeah. Now when they're in the water, their heartbeats also reduced 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, uh, 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 found in the four larger iguanas they have salt glands um that helped them process an abundance of salt should it be in the body. But with the 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 that they basically blasting salt out of their nostrils as they lounge about on their rocks. And as they're doing this to 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 look to their heads. They got the salt snot on their Yeah, you know, uh, this comes back to something else Darwin said. He was like, uh, there, you know, you can back them into a corner and you can catch them. 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. Yes, I was. I remember reading this as well, because I was when we were in the glab because I pulled up the text, was reading it, and yeah, there is this um accusation that they're doing it defensively. Uh, and yeah, this does not seem to be the case. No, they they're just doing it. Maybe they're doing it. I guess. I guess it's probably this. I have no data on this, but I guess it's possible that if someone has 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 of self defense measure. That's right up there with a in defensive vomiting. Yeah. Yeah, there's a lot of back and forth on that, right. I think we've discussed that, like, is a is like a vulture vomiting in order to like free up room, uh and you know, make itself lighter so it can take off and get away. Is it 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 they're they're various interpretations of that. As I recall now on the issue of marine iguana evolution, I was looking at another source. This was from Martin Wakelski in a two thousand five edition of the Royal Society paper entitled Evolution of body size in Galapagos Marine Iguanas. And I found this one interesting because the author here lays out one possible model for how the marine iguana is evolved. So, first of all, iguanas arrived according to this this um, this theoretical model in the Galapa goes perhaps ten to fifteen million years ago from South America via rafting, so swept out to see floating on some veget tasition and so forth, and then being cast on this strange island. And once they're there it becomes clear eventually here that in the inter title zone there's plenty of food for iguanas, but it's not on the land, it's the algae in the water. Uh. Initially, the iguanas are going to have to depend on low tides to get to the food. So the tide goes down, iguanas are are daring to to get down in there and go after the algae. And so there's going to but from there, that's where we're gonna begin 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 clause ultimately the shorter snout as well. Uh, that's going to be a part of their their foraging behavior as they essentially like rub their their faces against the rocks to gnaw off the algae, as well as the like swimming morphological changes. Interest. 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 one that I was looking at, Cranial Anatomy of the Glabos marine Iguana by Paparella and calledwell in the American Association for Anatomy, and uh, they point out some of the you know, the key changes just to the head of the creature of viets evolution, uh, modified configuration of the snout and nasal chamber, increased muscle attachments in the temporal post orbital region of the skull and UH didn't, and also the teeth as well. So all this is coming seems to revolve around what they're feeding on and how they're feeding on it, and how that's affecting UH, just like the overall shape and even like the the muscles of the head. And I imagine they would make some guesses from this about how far back in in time the marine Iguanas had these evolutionary changes. Yeah, that one of the authors here, Paparella. I found this is actually I belief from another paper, but I saw this author saying that arguing elsewhere for an iguana colonization of the ancient Collapos Islands as far back as million years ago. And I think in this we're getting into, uh into into this idea of not only the the existing Galapicos Island, but these like pre existing Collapicos islands, the ones that, like you said, have now been lost and are submerged. Um Uh wrote that like this, we would have had like an initial dispersal followed by constant short range hopping from older to newer islands. So you know, they get a foothold on one place and then they can they can spread to these other islands much more easily. And then as new islands emerged, 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 that paper about the shape of their heads, I included at this wonderful image, this one. I think I didn't get this out of the paper itself, but this was I believe from a uh like a Twitter post by the American Association for Anatomy. It's out there if anyone wants to look it up for themselves. But uh 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 looking at these, because you know, if it just looks, it looks very much unlike a lot of the lizard skulls you might see, like, like glancing at it, you might not even think of it as a lizard scull, mean, doesn't look like a human skull or anything. Um, it's distinct, but you can clearly see like the changes that have taken place here. Yeah, the blunt snout and the density of it, I mean almost you can imagine it being more of a turtle skull. Or again, I mean it looks kind of like Godzilla. Yeah, it's like Godzilla. And I like how they kind of have you see, especially in close up that like these there's real sense of iguana lips, you know. Yeah, you also get a really good look up inside the nostrils. Yeah, this of course is a specimen. This is a dead iguana that Joe and I are galking at here. Um, but still beautiful specimen. But yeah, the Marina iguanas are our special creatures. And I don't I think I don't even have to tell anyone this. This is not new information. Uh. There have been so many documentaries that of course have covered the Galakos Islands that have caught brilliant footage of them. They are a standout species that they've been highlighted in in various shows over time, or you've 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 but like all these things, you have if you get to see them in person. If you have that chance, take that that opportunity, because they're they're pretty remarkable. 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. That's right, the Galapa goes towards us. We're gonna come back in the next episode of of this journey to discuss uh, 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 to hear from you if you have thoughts about Marine iguanas um you know, firsthand or documentary based. If you're a resident of of Ecuador the Glavacos island, 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 in the Stuff to Blow Your Mind podcast feed on Monday's We Do Listener Mail, on Wednesday's We Do a short form artifact or monster Fact, and on Friday's We Do Weird How Cinema. That's our time to set aside most of the serious science and so forth in just talk about a strange film. 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. Stuff to Blow Your Mind is production of I Heart Radio. For more podcasts for my heart Radio, visit the iHeart Radio app, Apple Podcasts, or wherever you listening to your favorite shows.