Speaker 1: Welcome to Stuff to Blow Your Mind production of My
Speaker 1: Heart Radio. Hey, welcome to Stuff to Blow Your Mind.
Speaker 1: My name is Robert Manam and I'm Joe McCormick, and
Speaker 1: we're back with part two of our series on the
Speaker 1: reptiles of the Galapagos Islands. Now, in the previous episode,
Speaker 1: we focused mainly on the marine iguana, or as as
Speaker 1: they were often referred to early on those hideous creatures,
Speaker 1: those stupid, awful, sluggish lizards. We we mounted a defense
Speaker 1: of the marine iguana. But today we are here to
Speaker 1: talk about the Galapagos tortoise. And I wanted to kick
Speaker 1: things off by reading a passage from Charles Darwin in
Speaker 1: the Voyage of the Beagle. Darwin, of course, was not
Speaker 1: just a great scientist, but a really wonderful writer. And
Speaker 1: I think this this will help set the scene. So
Speaker 1: are you ready to hear about Darwin's first vision of
Speaker 1: San Cristobul Island, then then what they called Chatham Island. Yeah,
Speaker 1: let's let's hear from from old Charles. And this is
Speaker 1: part of a narrative of when he slept ashore one
Speaker 1: night on the island, So off the boat, Darwin writes
Speaker 1: the entire surface of this part of the island seems
Speaker 1: to have been permeated like a sieve by the subterranean vapors.
Speaker 1: Here and there the lava, whilst soft, has been blown
Speaker 1: into great bubbles, and in other parts the tops of
Speaker 1: cavern similarly formed of fallen in, leaving circular pits with
Speaker 1: steep sides from the regular form of the many craters.
Speaker 1: They gave to the country an artificial appearance which vividly
Speaker 1: reminded me of those parts of Staffordshire where the great
Speaker 1: iron foundries are most numerous. The day was growing hot,
Speaker 1: and the scrambling over the rough surface and through the
Speaker 1: intricate thickets was very fatiguing, but I was well repaid
Speaker 1: by the strange clopian scene. As I was walking along,
Speaker 1: I met two large tortoises, each of which must have
Speaker 1: weighed at least two hundred pounds. One was eating a
Speaker 1: piece of cactus, and as I approached it stared at
Speaker 1: me and slowly walked away. The other gave a deep
Speaker 1: hiss and drew in its head. These huge reptiles, surrounded
Speaker 1: by the black lava, the leafless shrubs and large cacti,
Speaker 1: seemed to my fancy like some Antediluvian animals. The few
Speaker 1: dull colored birds cared no more for me than they
Speaker 1: did for the great tortoises. So Darwin transported to a
Speaker 1: time from before Noah's flood by the vision of these bizarre,
Speaker 1: gigantic tortoises crawling around on the on the lava. Yes,
Speaker 1: this is the great SCENEY paints here and um and yeah.
Speaker 1: As I mentioned in the first episode, I was. I
Speaker 1: was fortunate enough to get to travel to the Galapico
Speaker 1: Highlands uh to to a couple of months ago in
Speaker 1: San Cristobo Island was one of the islands that I
Speaker 1: got to visit, and this was pretty much the the
Speaker 1: the experience I had with my family walking through one
Speaker 1: of the uh the areas they had set aside for
Speaker 1: these magnificent tortoises. They're just they just they walk around
Speaker 1: as if yeah, as if you you don't matter, unless
Speaker 1: you get a little too close for their liking, in
Speaker 1: which case they'll often be this hiss and this retraction
Speaker 1: of their head. I mean, their heads don't retract in
Speaker 1: the same way that say, a box turtle does, but
Speaker 1: they're able to sort of pull their head in a bit.
Speaker 1: But that the hissing that Darwin is describing here. It
Speaker 1: does have a very i don't know, neumatic kind of
Speaker 1: quality to it. It feels it sounds like some sort
Speaker 1: of machinery um. And indeed, that's that's kind of more
Speaker 1: what it is, as opposed to like the hiss you
Speaker 1: might hear from a house cat or something. And one
Speaker 1: of the things that I kept thinking about while encountering
Speaker 1: them is that they already move with this kind of hookey,
Speaker 1: jerky kind of um locomotion. They already move like they
Speaker 1: are elaborate mechanical creatures created for practical effects for a
Speaker 1: nineteen nineties UH science fiction feature. And then they also
Speaker 1: make this hissing sound to move part of their anatomy.
Speaker 1: So it almost creates this feeling of am I really
Speaker 1: seeing real animals or is this an elaborate hoax these animatronics? Yeah, yeah, yeah,
Speaker 1: they they feel almost like animatronics, But of course they're
Speaker 1: they're they're they're quite alive, and they're quite but that's
Speaker 1: that's part of their strangeness. And they just the awe
Speaker 1: of watching these giant creatures walk around, slowly, eat and
Speaker 1: occasionally have some startling interactions. Now I'm I'm greatly envious
Speaker 1: of the opportunity you got to see these animals in person.
Speaker 1: But I trust that you did not do what Darwin
Speaker 1: did upon encountering these beasts and try to ride them.
Speaker 1: Absolutely not know they're the only time the time we
Speaker 1: were forced to get uncomfortably close with one of these
Speaker 1: situations of the area that we were walking through had
Speaker 1: a path, and you're supposed to stay on the path
Speaker 1: and keep your distance from the tortoises. Sometimes, though, the
Speaker 1: tortoises will just get on the path and you have
Speaker 1: to find your way around them, and uh, they don't
Speaker 1: necessarily like that, but no, we we kept our distance, um,
Speaker 1: and and you want to keep your distance because yeah,
Speaker 1: if you get a little too close, they're gonna stop
Speaker 1: interacting with their environment for a little bit. And if
Speaker 1: you don't want to watch that, you want to watch
Speaker 1: them eat and and rampage around and uh, you know
Speaker 1: occasionally have these fabulous stare downs between two males which
Speaker 1: I don't know, we may we may describe this later,
Speaker 1: So maybe I shouldn't get into that just yet. Yeah, yeah,
Speaker 1: we can talk about the mock fights later on. So
Speaker 1: the Galapa ghost tortoise is I think you would say
Speaker 1: originally the dominant land herbivore of the Galapagos Islands, which
Speaker 1: makes them kind of unique because there's pretty much nowhere,
Speaker 1: nowhere else us on Earth now where the dominant land
Speaker 1: herbivore is a reptile. Uh So, these are very unique
Speaker 1: and beautiful creatures, and the Galapos tortoise stands out so
Speaker 1: much among the endemic fauna that it's actually the origin
Speaker 1: of the archipelago's name in one way or another. There's
Speaker 1: a little bit of nitpicking on that, but basically it
Speaker 1: goes like this. By the fifteen seventies, these islands had
Speaker 1: already appeared on at least a couple of European maps.
Speaker 1: The one I saw named was by a Flemish cartographer
Speaker 1: named Abraham or Talias, and it named the islands Insula
Speaker 1: de los Galapagos or meaning Islands of the Tortoises. Now,
Speaker 1: the nitpicking about the terminology I've read is what exactly
Speaker 1: the word galapago or Galapagos originally meant. According to a
Speaker 1: book that I'm going to reference multiple times in this episode,
Speaker 1: Galapagos and Natural History, second Edition by John Creature and
Speaker 1: Kevin Loft Lend from Princeton University Press that editions out
Speaker 1: just two. They write that the origin of the name
Speaker 1: of the islands is an old Spanish word, galapago, which
Speaker 1: was a name for a specific type of saddle. So
Speaker 1: there's like, you know, a saddle you'd use on a horse.
Speaker 1: I guess that has a kind of upturned front. That
Speaker 1: was a galapago. And some, but not all, of the
Speaker 1: Galapagos tortoises have saddle shaped shells. Others have a more
Speaker 1: straightforward dome. And we can talk about the evolutionary reasons
Speaker 1: for those differences later on. But when Tamas de Brelonga
Speaker 1: landed on the islands in fifteen thirty five, a story
Speaker 1: we talked about in the previous episode. After this, he
Speaker 1: wrote a letter to the king in which he observed
Speaker 1: describing the animals of the island. He observed Muccio's lobos
Speaker 1: marinos meaning many sea lions, tortugas meaning sea turtles, iguanas,
Speaker 1: and Galapagos, and the author's right that this is probably
Speaker 1: a reference to the tortoises and their saddle shaped shells
Speaker 1: rather than to literal saddles being on the island. This
Speaker 1: is a solid observation that thankfully still holds true today
Speaker 1: Muccio's lobos Marinosto is iguanas and uh and and tortoises. Yes, yeah,
Speaker 1: the seed line, I mean the Muccio lobos marinos. Uh.
Speaker 1: That was probably the most astounding of all when you're
Speaker 1: near the coast, because they're everywhere, and they'll see sometimes laying.
Speaker 1: They'll be like a male that's come up and he's
Speaker 1: like laying in the street, or they they love park benches.
Speaker 1: There are a lot of fun to wide well. The
Speaker 1: difference in the Spanish name. I guess if it's lobo
Speaker 1: marino that would mean sea wolf, not sea lion, right,
Speaker 1: But that that heightens the kind of implicit comedy of
Speaker 1: naming these animals after what you would think of as
Speaker 1: a more actively voracious land predator, whereas you know, I
Speaker 1: guess when they're on the land, they're not quite so threatening.
Speaker 1: Is maybe a wolf for a lion would seem yeah,
Speaker 1: I mean, well, on one hand, yeah, you have some
Speaker 1: of the little tiny islands there as least one that's
Speaker 1: named for the wolf for the lobos, and of course
Speaker 1: that's why, because the sea lions are hanging out there,
Speaker 1: and yeah, on the on the on the beach, they're
Speaker 1: they're often quite docile, and you see people getting way
Speaker 1: too close to them in some cases. But the big males,
Speaker 1: of course are very territorial about hanging onto their bit
Speaker 1: of property and their um and their females. Uh you know,
Speaker 1: they're their their beach real estate, and so there of
Speaker 1: course always they're continuously loudly um sending the alarm and
Speaker 1: occasionally chasing off other males. So there's there's a lot
Speaker 1: of drama if you just sit back and watch that
Speaker 1: the sea lions, and I imagine that listeners from other
Speaker 1: parts of the world can attest to this as well. Yes, yes,
Speaker 1: keep your distance, folks, I mean, observe, but but there's
Speaker 1: no reason to get in the sea lions space, though
Speaker 1: sometimes in my experience of sea lion will come for
Speaker 1: your space. I was just seated away from sea lions
Speaker 1: and then here comes this female and she's just howling
Speaker 1: about something and insists on taking my spot on a
Speaker 1: log and I'm like this, you're the chairs. And then
Speaker 1: she just hangs out on the log for a few
Speaker 1: minutes and then leaves it. I don't know. So you're
Speaker 1: just trying to make a point. So if you have
Speaker 1: never seen the Galapagos tortoises before. You can easily find
Speaker 1: lots of pictures of them, but to briefly describe the adults,
Speaker 1: there are many different species scattered across the different islands.
Speaker 1: Maybe we can get into the exact numbers on that
Speaker 1: in a bit, but generally what they all have in
Speaker 1: common is that they're very large. They have large shells,
Speaker 1: some species with rounded dome tops, others with the saddle
Speaker 1: shape that Burlonga probably observed, which are typically turned up
Speaker 1: in the front to have a kind of big notch
Speaker 1: above the animal's head and neck. They have long, dry,
Speaker 1: wrinkly necks which are surprisingly slim, almost I dare say
Speaker 1: snake like in a way. They have blunt, round snouts
Speaker 1: and a beak like mouth with no teeth, and everywhere
Speaker 1: you can see their their skin. In between the shell
Speaker 1: parts there is typically a lot of leathery, wrinkly flesh,
Speaker 1: which just makes them look like old people. Yeah, they
Speaker 1: have this kind of appearance of of a cute, shriveled
Speaker 1: old person. Vase. Uh, They're they're very They're very sweet
Speaker 1: too to look at. Um. It's it's it's kind of
Speaker 1: hard to to not anthropomorphize them as such. Even in
Speaker 1: and that of course, can become complicated when you start
Speaker 1: considering like the full range of their um, of their
Speaker 1: lifestyle and the way that they they live and reproduce
Speaker 1: and so forth. Uh. It never pays to anthropomorphizes creatures
Speaker 1: too much. Yeah. Now, one thing many of us today
Speaker 1: might not appreciate, even if you go to the Galapagos
Speaker 1: today or if you see you know, good nature documentary
Speaker 1: footage from there, is how many tortoises there were when
Speaker 1: people first arrived, before the animals had any natural predators
Speaker 1: other than the threat post hatchlings by the Galapagos hawk. Uh,
Speaker 1: this place was swarming with tortoises. And to try to
Speaker 1: get a picture of that, uh, I wanted to cite
Speaker 1: some some basically math work that Creature in Laughlin do
Speaker 1: in their book. So they're talking about the reproductive rates
Speaker 1: of these tortoises. So they say, if if a female
Speaker 1: tortoise has more than two young that survive into adulthood,
Speaker 1: the tortoise population will grow, so she has replaced both
Speaker 1: her and her mate, and if she has more than one,
Speaker 1: the population will grow. And they say, now, consider that
Speaker 1: a female tortoise may conservatively lay five to tin eggs
Speaker 1: annually for perhaps eighty years or more. So just uh,
Speaker 1: for a very conservative estimate, they say, Okay, imagine she
Speaker 1: averages one annual clutch and there's just three eggs in it.
Speaker 1: That's kind of a small estimate. But there's just three
Speaker 1: eggs per clutch. That's more than two hundred eggs in
Speaker 1: a single adult female tortoises lifetime. Uh, they say, realist stically,
Speaker 1: the numbers probably a multiple of that. So they're gonna
Speaker 1: have a lot of young and there before humans arrive
Speaker 1: and bring their invasive species with them, before they bring
Speaker 1: dogs and pigs and stuff. There is not significant predation
Speaker 1: at any life cycle part of the life cycle of
Speaker 1: a tortoise. Uh. There's some minor predation by like hawks
Speaker 1: of the babies, but most of them are going to
Speaker 1: grow and become reproducing adults. Yeah, it's pretty amazing. Amazing.
Speaker 1: I asked one of the guides about, you know, how
Speaker 1: long are the females reproductive? Because you see some very
Speaker 1: he was pointed that my guide here was pointing out
Speaker 1: the various really old tortoises. But because you can sort
Speaker 1: of tell by looking at the shells the way that
Speaker 1: um the line, like for a while, you can sort
Speaker 1: of it's not like you can count the rings exactly,
Speaker 1: but you can sort of see the rings in the
Speaker 1: patterns on their shell. But eventually there's kind of like
Speaker 1: a smoothing out that occurs, and those are the really
Speaker 1: old ones. Um And and the guy was like, yeah,
Speaker 1: we're we're not entirely sure, but it seems like they're
Speaker 1: reproductively active for pretty much most of their lives, which
Speaker 1: is the astounding thank thank Yeah, it's it's amazing. And
Speaker 1: so the authors of this book end up concluding that
Speaker 1: before humans arrived and and brought these invasive predators with
Speaker 1: them and started harvesting the tortoises themselves, which is a
Speaker 1: sad fact we'll talk about in a moment um, the
Speaker 1: tortoises were just just profuse. They were everywhere. They say,
Speaker 1: there's a conservative estimate of a total population of two
Speaker 1: hundred and fifty thousand tortoises just on this small group
Speaker 1: of islands. But of course today, um, all of these
Speaker 1: tortoise populations are at least vulnerable, and some are up
Speaker 1: to critically endangered. And and that's after a significant bounce
Speaker 1: back in some cases for you know, after conservation effort,
Speaker 1: it's kicked in. So what happened to these tortoises. Well,
Speaker 1: one thing that happened is uh is something Darwin talks
Speaker 1: about in his Passage and Voyage of the Beagle. Before
Speaker 1: he even really gets to ecological observations about the tortoises,
Speaker 1: he writes at length about people eating them. So, in
Speaker 1: describing the small human colony on what was then Charles
Speaker 1: Island what today is called Floriana Island, so Darwin writes,
Speaker 1: in the woods there are many wild pigs and goats.
Speaker 1: Now remember those are not native to the islands, but
Speaker 1: introduced by humans. Darwin goes on, But the staple article
Speaker 1: of animal food is supplied by the tortoises. Their numbers
Speaker 1: have of course been greatly reduced in this island, but
Speaker 1: the people yet count on two days hunting, giving them
Speaker 1: food for the rest of the week. It is said
Speaker 1: that formerly single vessels have taken away as many as
Speaker 1: seven hundred, and that the ship's company of a frigate
Speaker 1: some years since brought down in one day two tortoises
Speaker 1: to the beach. And this brings us to a very
Speaker 1: sad fact about the human use of tortoises. Here that
Speaker 1: tortoises were of course very good meat sources for sailing
Speaker 1: vessels um, but this was especially due to the fact
Speaker 1: that because turtles have a very slow metabolism, and they
Speaker 1: could be loaded into the ship alive and then would
Speaker 1: survive for an extremely long time without food or water
Speaker 1: in the hold. And it's important to remember that, of course,
Speaker 1: ships at the time didn't have refrigerators or freezers or
Speaker 1: other sophisticated food preservation techniques beyond things like you know,
Speaker 1: the nuclear options salting. Yeah. Yeah, So this is this
Speaker 1: is quite sad to picture because on one hand, it's
Speaker 1: it's not like these tortoises were wandering around on deck. No,
Speaker 1: they they were stuffed below i think generally upside down
Speaker 1: and just stored away as living casks of food because
Speaker 1: they could live for up to a year without food
Speaker 1: or water, which is just crazy to think about, but
Speaker 1: also just unimaginally cruel to imagine them down there. And
Speaker 1: on top of this, one of the other troublesome things
Speaker 1: about this for the tortoises is that the sailors would
Speaker 1: tend to grab the tortoises they could easily carry back
Speaker 1: to the ship, which meant that they tended to focus
Speaker 1: on the smaller tortoises and leave the bigger ones. This
Speaker 1: meant that they were favoring female tortoises over male tortoises,
Speaker 1: and I guess to a certain extent also younger male tortoises,
Speaker 1: but certainly skewing more towards female tortoises, thus destabilizing the
Speaker 1: species even more than if they had managed more of
Speaker 1: a fifty fifty split between the tortoise genders. Yeah. So,
Speaker 1: unfortunately a lot of tortoises were removed from the islands
Speaker 1: that way, but also they just remained a a live
Speaker 1: meat source for hunting by the locals. And Darwin tells
Speaker 1: many interesting stories about this. Uh. For example, he writes
Speaker 1: about a time that he went up to one of
Speaker 1: the highland regions of one of the islands, and he
Speaker 1: hung out in a hovel that had been built by
Speaker 1: two men there who were who spent their their time
Speaker 1: hunting tortoises. And so he visits these guys and he
Speaker 1: sleeps there in the hovel one night. Um and what
Speaker 1: did he eat while he was there, Well, exclusively tortoise meat.
Speaker 1: That was the entire menu, about which he says, quote
Speaker 1: the breastplate roasted as the gauchos do carne conquero, which
Speaker 1: I think means meat with leather with the flesh on.
Speaker 1: It is very good, and the young tortoises make excellent soup,
Speaker 1: but otherwise the meat, to my taste, is indifferent. Well,
Speaker 1: there you go. Also taking harvesting the young tortoises. That's
Speaker 1: great as well, but they apparently these these the adult tortoises,
Speaker 1: are an amazing food source because of their immense size,
Speaker 1: and Darwin recounts the story told to him by a Mr. Lawson,
Speaker 1: who is an Englishman who was vice governor of the
Speaker 1: Charles Island Colony, saying that some tortoises, when caught, required
Speaker 1: six to eight men just to lift them off the
Speaker 1: ground and would provide up to two hundred pounds of
Speaker 1: me eat. Darwin also later describes a strange operation performed
Speaker 1: by the hunters. He says that you know they didn't
Speaker 1: always kill a tortoise. He said that while the tortoises
Speaker 1: meat is used both fresh and salted. Uh, the tortoises
Speaker 1: are also important for providing oil. That's right, reptile lard
Speaker 1: and oil that I think could be used for for
Speaker 1: food purposes. But also for just like like like lamp purposes.
Speaker 1: I believe. Yeah, it's it's said that in the old days,
Speaker 1: the larger towns of the Galapagos would have their streets
Speaker 1: would have been lit with tortoise oil. Bizarre though, I
Speaker 1: guess we're more familiar with that from like whale oil
Speaker 1: and stuff. Um. But yeah, So if if a tortoise
Speaker 1: will not provide enough oil, it is apparently not worth
Speaker 1: killing to the hunters. So Darwin writes, quote, when a
Speaker 1: tortoise is caught, the man makes a slit in the
Speaker 1: skin near its tail so as to see inside its
Speaker 1: body whether the fat under the dorsal plate is thick.
Speaker 1: If it's not, the animal is liberated, and it is
Speaker 1: said to recover soon from this strange operation. In order
Speaker 1: to secure the tortoise, it is not sufficient to turn
Speaker 1: them like a turtle, for they are often able to
Speaker 1: get on their legs again. And I think this is
Speaker 1: something that will come up later, because there are some
Speaker 1: situations where these tortoises often do end up flipped on
Speaker 1: their backs, even under natural circumstances, and they need to
Speaker 1: be able to flip back over and get back to business.
Speaker 1: I did not get to see that happen. Thankfully, I
Speaker 1: don't want to see a tortoise in distress. No, we're
Speaker 1: not going to ask you the quiz from the blade
Speaker 1: runner test. So what do these tortoises eat to grow
Speaker 1: so big? Well, it turns out in reality, they just
Speaker 1: they eat plants. These are entirely herbivorous creatures. There are
Speaker 1: turtles and tortoises that eat other things, but these tortoises
Speaker 1: are entirely plant eaters, and so especially in the lowlands,
Speaker 1: especially the the saddleback tortoises, will eat succulent cactus. This
Speaker 1: is something Darwin identifies. He says they especially favor the
Speaker 1: cactus if they live in the low and arid parts
Speaker 1: of the islands where there is little or no water.
Speaker 1: Of course the cactus becomes a principal water source, but
Speaker 1: also they eat tree leaves and berries as well as
Speaker 1: green lichen UH and their diet somewhat depends on which
Speaker 1: species they are and which part of the islands which
Speaker 1: microclimate they inhabit. Like the ones that live higher up
Speaker 1: in the UH the highlands with more lush vegetation probably
Speaker 1: feed on more leafy stuff, and the ones that live
Speaker 1: more in the arid regions probably feed on more cactus. Yeah,
Speaker 1: the ones I got to actually observe in the in
Speaker 1: the wild as it were on San Cristobule and on
Speaker 1: Santa Cruz Island. They they were definitely eating the leafy
Speaker 1: green stuff. But I got to see plenty of the cacti,
Speaker 1: which of course have coexisted with the tortoises long enough
Speaker 1: that they have they have particular adaptations, like they have
Speaker 1: been changed by cohabitation with the tortoise as well. And
Speaker 1: the most remarkable of these are the ones that they
Speaker 1: basically seemed to grow up like trees and then branch
Speaker 1: out because they're trying to reach and they're reaching an
Speaker 1: optimal height at which they're hopefully above the reach of
Speaker 1: the tortoise. There is one type of cactus that there's
Speaker 1: a great picture of in this book by Creature in
Speaker 1: Laughlin I've been talking about. It's called a candelabray cactus,
Speaker 1: and I thought it was beautiful because the branches look
Speaker 1: to me like giant green tarantula legs. They kind of
Speaker 1: have these lobes that look like little hairy legs segments
Speaker 1: on a large spider. Yeah. Yeah, And it's a nice
Speaker 1: picture too, because you gotta you gotta flamingo in there. Um.
Speaker 1: I did get to see a few flamingos on Seymour Island,
Speaker 1: I believe. But the tortoises just generally seemed to eat
Speaker 1: all kinds of foods that would look to us quite hostile. So,
Speaker 1: of course the the ones in the lowlands are gonna
Speaker 1: eat a lot of cactus, but they also apparently eat
Speaker 1: plenty of poison apple or men's nillo, which is toxic.
Speaker 1: It has a sap that is poisonous to other creatures.
Speaker 1: But uh, and I think it can can cause blistering
Speaker 1: if you touch it. But apparently the tortoises just chow
Speaker 1: down on this stuff, doesn't bother them. Yeah. On on
Speaker 1: San Cristoble Island, of the area where we're encountering the tortoises,
Speaker 1: they had signs everywhere, do not touch the apples, do
Speaker 1: not certainly do not eat the apples. Leave this to
Speaker 1: the tortoises. Now, coming back to Darwin's writing on the tortoises,
Speaker 1: he also observes their relationship with water. He says they're notable,
Speaker 1: of course for their ability to survive without water for
Speaker 1: a very long time, but when they get access to water.
Speaker 1: They go hog wild. They love it, the spring water
Speaker 1: and the mud puddles. They'll just get in there and
Speaker 1: and settle in uh, sometimes for days at a time.
Speaker 1: And when they when they're drinking, they will just gulp
Speaker 1: huge mouthfuls of water for a long time. And Darwin
Speaker 1: even this leads into him writing a really bizarre and
Speaker 1: it out that I had to share. So he says, quote,
Speaker 1: for some time after a visit to the springs, their
Speaker 1: urinary bladders are distended with fluid which is said to
Speaker 1: gradually which is said to gradually decrease in volume and
Speaker 1: to become less pure. The inhabitants, when walking in the
Speaker 1: lower district and overcome with thirst, often take advantage of
Speaker 1: this circumstance and drink the contents of the bladder if full.
Speaker 1: In one tortoise I saw killed, the fluid was quite
Speaker 1: limpid and had only a very slightly bitter taste. The inhabitants, however,
Speaker 1: always first drink the water in the pericardium, which is
Speaker 1: the membrane I believe as surrounding the heart tissue, which
Speaker 1: is described as being best. So that's right, drinking the
Speaker 1: water from a tortoise's heart or from a tortoise's bladder,
Speaker 1: and Darwin tasted the tortoise bladder water. I guess I
Speaker 1: should be happy for this, that they're using all parts
Speaker 1: of the tortoise conceivably in doing this, But of course
Speaker 1: this is still kind of sad to imagine. Yeah, but
Speaker 1: also from just a purely anatomical level, this is of
Speaker 1: course amazing. Now Darwin goes on to talk about how
Speaker 1: impressed he is by the long determined journeys that some
Speaker 1: of these tortoises make between uh. He believes what the
Speaker 1: point of these journeys is is between highland water sources
Speaker 1: and usual breeding grounds in the lower districts. I don't
Speaker 1: know if that holds up as the main reason for
Speaker 1: these journeys today, uh, though I do think some of
Speaker 1: these uh tortoises do make journeys between the highlands and
Speaker 1: the lowlands for the purpose of depositing eggs the females
Speaker 1: do after mating season. But there are also journeys I
Speaker 1: think having to do with with food resources in the
Speaker 1: different seasons and so forth. But anyway, Darwin says, you know,
Speaker 1: although the tortoises are pretty slow in their movements, you
Speaker 1: would be surprised how much ground they cover over time
Speaker 1: due to sheer determination. He estimates that they're going to
Speaker 1: move sixty yards in ten minutes, which is three hundred
Speaker 1: and sixty yards in an hour, or about four miles
Speaker 1: a day. Yeah, it's pretty remarkable, and of course nowadays,
Speaker 1: of course that everything has been shifted around a bit. Uh.
Speaker 1: You know all these invasive species, not only the such
Speaker 1: harmful invasive species as UH pigs and UH and goats
Speaker 1: that were introduced and then their populations have been dealt
Speaker 1: with the varying degrees, but you also have, of course,
Speaker 1: have plants to think about, um. And so in some
Speaker 1: cases you have things like berries that are that are
Speaker 1: now grown in the Galapagos and may occur wild in
Speaker 1: some cases, and of course the tortoises love those even
Speaker 1: though they are not native, and so you may see
Speaker 1: that uh interfere with their their movements a bit. But yeah, basically,
Speaker 1: through modern conservation and through modern tracking technology, you can
Speaker 1: actually see all of these tortoise movements plotted out on
Speaker 1: maps and it's quite impressive. UM. I think there their
Speaker 1: movements in these cases help illustrate why they're so crucial
Speaker 1: for the island ecosystem that they thrive in. They eat
Speaker 1: so much and they're slow, they do cover a lot
Speaker 1: of ground and defecate to spread speeds, spread seeds rather uh.
Speaker 1: And this is very much in line with other megafauna
Speaker 1: that you encounter in in other ecosystems as well as
Speaker 1: the Remember, if you think back to our episode on
Speaker 1: our episodes on the giant moa bird, which of course
Speaker 1: is extinct, but would have we still see like the
Speaker 1: footprint of their ecological importance in the areas that they
Speaker 1: occupied because they were vital for consuming plants and the
Speaker 1: spreading those seeds through defecation. Yeah, there is a great
Speaker 1: passage in the book by Creature in Laughlin where they
Speaker 1: talk about the importance of the tortoise in spreading a
Speaker 1: type a species of wild Galapagos tomato plant which apparently
Speaker 1: it only the seeds only germinate under very specific conditions,
Speaker 1: such as being exposed to acid for a long period
Speaker 1: of time. Now, how does that happen? What happens in
Speaker 1: the digestive system of the tortoise. So like they take
Speaker 1: this in, the seed gets exposed to the acid within
Speaker 1: the digestive juices and then it gets it travels with
Speaker 1: the tortoise along ways away from its original location, so
Speaker 1: that's also good for dispersal. And then once the tortoise
Speaker 1: poops it out, it of course has a bunch of
Speaker 1: nutritious fecal matters surrounding it to help it grow. Yeah,
Speaker 1: I've got I did get to poke uh some some
Speaker 1: tortoise dung with a stick, my son and I did,
Speaker 1: and we got to look all in there. It's a uh,
Speaker 1: you know, quite fascinating. Um. I think some stats would
Speaker 1: really help drive home though. While the tortoises so great
Speaker 1: at this and I got these from Seed Dispersal by
Speaker 1: Galapagos Tortoises by Blake at All, published in the Journal
Speaker 1: of Biogeography from so In this particular survey, the researchers
Speaker 1: looked at one and twenty fresh dung piles in both
Speaker 1: agricultural and national park land. They found seeds from more
Speaker 1: than forty five plant species in these dung piles, eleven
Speaker 1: of which were from introduced species. Is you know, like
Speaker 1: various berries and whatnot. A per tortoise average of four
Speaker 1: hundred and sixty four seeds and two point eight species
Speaker 1: per dung pile was detected. Now, this is where it
Speaker 1: gets kind of interesting because Okay, we've already established that, yes,
Speaker 1: they eat a lot, they travel farther than you might think,
Speaker 1: but how how long does it take for them to
Speaker 1: process their food? Uh, things go a little slower with
Speaker 1: with the Galapagos tortoises. The mean digesta retention time for
Speaker 1: a tortoise is twelve days, but twenty eight day retention
Speaker 1: times have been reported. So that's the that's the time
Speaker 1: it takes for the food that they've consumed to process
Speaker 1: through their body and become done, so they can really
Speaker 1: cover some ground in that time. Yeah. During that time,
Speaker 1: according to this paper, the tortoise may travel between three
Speaker 1: hundred and ninety four and four thousand, three hundred fifty
Speaker 1: five meters on the high end, that's two point seven
Speaker 1: miles or four point three kilometers. So you can see
Speaker 1: how these hortises would play an incredibly important role in
Speaker 1: helping the reproduction and dispersal of local flora. Yeah. Absolutely,
Speaker 1: I mean within it, as with any species, they don't
Speaker 1: they're not existing in isolation. In their ecosystem. They have
Speaker 1: a role, they have a they have a place in it,
Speaker 1: and if if you disrupt them, if you disrupt their
Speaker 1: numbers or in the very worst case scenarios. If they
Speaker 1: their extinction is brought about, Uh, then there is there's
Speaker 1: something missing. There's you end up pulling the carpet out
Speaker 1: from everything. And unlike with with the parlor trick, all
Speaker 1: the plates and the dishes are not necessarily going to
Speaker 1: stay standing up. Now. Uh, we've been talking about a
Speaker 1: lot of the predation and hunting of these tortoises. But
Speaker 1: barring that, how do tortoises die? What happens? Uh? Well,
Speaker 1: Darwin writes, quote the young tortoises as soon as they
Speaker 1: are hatched, fall praying great numbers to the carry and
Speaker 1: feeding buzzard. I think that would actually be referring probably
Speaker 1: to the galapagost hawk um, unless he's talking about some
Speaker 1: other species that that came in after humans arrived. But
Speaker 1: Darwin goes on, the old ones seemed to die generally
Speaker 1: from accidents, as from falling down precipices. At least several
Speaker 1: of the inhabitants told me that they never found one
Speaker 1: dead without some evident cause, which that kind of gave
Speaker 1: me a shiver. Yeah, yeah, I mean it's it's it's
Speaker 1: just impressive how long they live. Um that Now to
Speaker 1: the first point about predation is worth pointing out the
Speaker 1: tortoise sanctuaries that are up and running now. They care
Speaker 1: for the little ones to protect them from you know,
Speaker 1: not only the hawk, but also all these these these
Speaker 1: introduced species that maybe about UM once they get big enough.
Speaker 1: Though yeah, there's there's only really three ways they're going
Speaker 1: to die old age eventually, UM, accident vehicular especially of
Speaker 1: course being the main threat though UM on the glactos items.
Speaker 1: Today a lot of a lot of you know, laws
Speaker 1: and messaging have been put in place to prevent this
Speaker 1: from occurring. And then of course in the past human
Speaker 1: hunting was the big thing. Now you mentioned they can
Speaker 1: die of old age, of course they do, but that
Speaker 1: can take a good long while. I was reading about
Speaker 1: this in a Creature in Laughlin, and uh they say
Speaker 1: that it's possible, though we have no way to know
Speaker 1: for sure, that there may be tortoises still alive on
Speaker 1: the islands that were present when Darwin visited in eighteen
Speaker 1: thirty five. And Uh. A Galapagos tortoise named Harriet lived
Speaker 1: to an estimated age of a hundred and seventy five
Speaker 1: before she died in an Australian zoo in two thousand six,
Speaker 1: so they can live a long long time. Yeah, I've
Speaker 1: also I was doing some crunching on this as well.
Speaker 1: I think one of the sources I was looking at
Speaker 1: had listed like a hundred and seventy one years as
Speaker 1: being like I wanted to the the oldest stage is
Speaker 1: known for the tortoises. And even if you're just gonna
Speaker 1: go go with that, if you consider the idea that
Speaker 1: you have a tortoise born in eighteen thirty five when
Speaker 1: Darwin is visiting, if it lived a hundred and seventy
Speaker 1: one years, it would live to the year two thousand
Speaker 1: and six, which is just crazy to think about the
Speaker 1: idea that just one tortoise lifetime would bridge our time
Speaker 1: to the time of Darwin, and that a single tortoise
Speaker 1: lifetime could encompass basically the two worst centuries of the
Speaker 1: the impact of humanity on Glapacos tortoise numbers as well. Now,
Speaker 1: again not to come back too much to the the
Speaker 1: horrors of human tortoise interaction, but yeah, there are these
Speaker 1: accounts you read too of like times when uh roads
Speaker 1: to various villages were just aligned with like the bones
Speaker 1: or the shells of of these creatures. Um it was
Speaker 1: it was a rough time to be a glapacost tortoise. Yes,
Speaker 1: uh no, Now I think it's worth talking about Galapagos
Speaker 1: tortoise mating and reproduction, in which there's some interesting stuff. Uh.
Speaker 1: For one thing I was reading about. Uh maybe we
Speaker 1: can get to the actual mating in a minute, But
Speaker 1: first I was reading a section in uh in Creature
Speaker 1: in Laughlin about the nests and egg laying of the
Speaker 1: glopaost tortoise. So mating season typically occurs during the rainy season,
Speaker 1: and after having made it, a female tortoise will generally
Speaker 1: travel toward the arid lowlands to build a nest. Darwin
Speaker 1: has a section about this where he correctly observes that
Speaker 1: they will seek out arid sandy soil to dig a
Speaker 1: nest in. But then he says others. He says, sometimes
Speaker 1: they will just drop their eggs wherever, like in a precipice,
Speaker 1: like in a crevice in the rocks. I didn't find
Speaker 1: any other evidence of that, so maybe that was true
Speaker 1: when he was there, But I'm not aware of other
Speaker 1: evidence for that other than what Darwin says. But uh,
Speaker 1: generally what they do is they're gonna dig down in
Speaker 1: the arid regions now, and for the saddleback tortoises, which
Speaker 1: tend to live more in the lowlands, this is not
Speaker 1: much of a trip, but for the domed tortoises it
Speaker 1: can be a really great journey down from the highlands
Speaker 1: into the place where they're going to lay the lay
Speaker 1: the eggs, and the eggs are laid sometime between June
Speaker 1: and December. A clutch can contain anywhere from like two
Speaker 1: to twenty eggs. The eggs are sort of billiard ball
Speaker 1: sized or maybe a little bit larger. And the nest
Speaker 1: building process is what interested me because apparently it involves
Speaker 1: a good bit of p So the tortoise will find
Speaker 1: a spot in the soil and she will dig a
Speaker 1: hole about thirty centimeters deep, scooping the earth out with
Speaker 1: her hind legs, and this is a a an involved
Speaker 1: process that can take up to about twelve hours, and
Speaker 1: the tortoise will often urinate on the soil in order
Speaker 1: to soften it for digging. But the mother tortoise, after
Speaker 1: she lays her eggs in the hole and covers it up,
Speaker 1: then also peas on the soil again to form a
Speaker 1: kind of cement layer. In it. This is interesting. We've
Speaker 1: we've we've discussed a number of different like nest building,
Speaker 1: egg laying scenarios over the years, but I don't remember
Speaker 1: one that was so urine intensive. Yeah, there may be
Speaker 1: other species that do p cement, but this is the
Speaker 1: first time I remember reading about this. Uh So, anyway,
Speaker 1: the the eggs incubate in the cemented earth for like
Speaker 1: four to eight months, where the sex of the hatchling
Speaker 1: is ultimately determined by the temperature which the egg incubates.
Speaker 1: This kind of interesting. It's not chromosome ely determined as
Speaker 1: it is for some other animals. And uh So, afterwards
Speaker 1: they dig their way out of the nest to begin
Speaker 1: their lives. And of course this is the most vulnerable
Speaker 1: time for a Galapagos tortoise when they're a hatchling, but
Speaker 1: they are the ones that survived make it out. They
Speaker 1: they find food, they avoid predators, and they eventually grow up,
Speaker 1: though apparently the growing up also takes a good bit
Speaker 1: of time. The tortoises do everything pretty slow, including reaching maturity.
Speaker 1: I've read that they don't reach sexual maturity until several
Speaker 1: decades later. The mating itself is also kind of interesting.
Speaker 1: Because the basically consists of the mails chasing the females
Speaker 1: around until they can corner them. But then there's also,
Speaker 1: given that these are large shelled creatures, there the male's
Speaker 1: shell has like an intention on the bottom that allows
Speaker 1: for it to mount the female, because otherwise, like unless
Speaker 1: there was some arrangement of the shells in this capacity,
Speaker 1: that they would not be compatible. Right. And there was
Speaker 1: also a fact I came across that I thought was
Speaker 1: funny in in this book they talked about how the
Speaker 1: larger size of the Galapagos tortoise can make the physical
Speaker 1: active mating sometimes kind of cumbersome and laborious, and the
Speaker 1: authors note that quote, males often slide off, sometimes even inadvertently,
Speaker 1: landing upside down, at which point they must right themselves
Speaker 1: and try again, which I don't know if it's juvenile
Speaker 1: that I found that funny, but I did. The authors
Speaker 1: also note that the male tortoises sometimes get confused. For example,
Speaker 1: they try to mate with large rocks. Well, that's just
Speaker 1: in and of itself funny. We we can't help but
Speaker 1: laugh at that. But there's also surprising for these very
Speaker 1: slow moving animals, there is some surprisingly fierce competition between
Speaker 1: males for access to mates, and Darwin notes this. He
Speaker 1: says during breeding season, you can hear the mails emit
Speaker 1: what he calls a horse roar, and I think this
Speaker 1: roar is probably indicative of of male on male competition,
Speaker 1: which sometimes leads to these mock fights where they will
Speaker 1: raise their necks up at each other. Rob. I think
Speaker 1: you actually maybe saw one of these going on. Yes,
Speaker 1: I got to see this happen and I actually got
Speaker 1: to film it. Uh able to my wife was like, quick,
Speaker 1: get your get your camera out and make sure you're
Speaker 1: getting this, and so I did. Uh. Yeah. It's amazing
Speaker 1: to watch because you'll have these two lumbering giants that
Speaker 1: are kind of on a on a collision course with
Speaker 1: each other, and you're like, what's gonna happen, What's gonna happen?
Speaker 1: And then as they get closer, they'll both rear their
Speaker 1: heads up and they'll have the showdown. That doesn't it
Speaker 1: does not come to blows or bites or anything like that,
Speaker 1: but it is a competition to see who to determine
Speaker 1: who is the tallest and the tallest tortoise, who are
Speaker 1: the one that can raise its head up the highest
Speaker 1: he's the winner, and the other one accepts defeat and
Speaker 1: carries on. And that's that's as violent as it seems
Speaker 1: to get. But it's it's spectacular to watch. And yeah,
Speaker 1: this was the finest nature footage I have ever captured
Speaker 1: or will ever capture. Now, one last thing I wanted
Speaker 1: to read from Darwin here where he's talking about the
Speaker 1: tortoise's reaction to humans. This is another infamous section from
Speaker 1: the Voyage of the Beagle chapter. Darwin says, I was
Speaker 1: always amused when overtaking one of these great monsters, as
Speaker 1: it was quietly pacing along, to see how suddenly the
Speaker 1: instant I passed, it would draw in its head and
Speaker 1: legs and, uttering a deep hiss, fall to the ground
Speaker 1: with a heavy sound, as if struck dead. I frequently
Speaker 1: got on their backs, and then giving a few raps
Speaker 1: on the hinder part of the shells, they would rise
Speaker 1: up and walk away. But I found it very difficult
Speaker 1: to keep my balance. Oh, Charles, no doing why you're
Speaker 1: writing a tortoise? Um? I mean it is kind of
Speaker 1: I mean it based on this account, the tortoise is
Speaker 1: doing exactly what you know I observed in all these
Speaker 1: sources say they do if someone gets too close or
Speaker 1: something is too close. But it is kind of interesting
Speaker 1: this added detail that apparently eventually the tortoise is like, Okay,
Speaker 1: I guess this weird British man is not going away.
Speaker 1: I have things to do in places to be I'm
Speaker 1: just gonna start walking around with him on there and
Speaker 1: maybe I can sort of shake him off. Yeah, and
Speaker 1: this is actually not an isolated report. Again, we are
Speaker 1: not recommending writing the tortoises, but other other people talk
Speaker 1: about how well you can get on their backs and
Speaker 1: ride them and they'll just go about their business. And
Speaker 1: this is apparently a common occurrence. Um there was a
Speaker 1: common occurrence back in the day. Sometimes they say you
Speaker 1: can get two people on one of these tortoise shells
Speaker 1: and just ride them and they'll do their thing, like
Speaker 1: you know, they don't seem uh, they don't seem bothered. Now,
Speaker 1: I'm sure that puts extra strain on their must holes
Speaker 1: and their energy requirements and all that, so it's not
Speaker 1: like okay to do. But just showing the strength of
Speaker 1: the tortoise and how powerful and huge this animal is
Speaker 1: that it could just continue on its way trying to
Speaker 1: graze with like multiple humans riding on its back. Poor creatures. Uh. Yeah, again,
Speaker 1: do not do not attempt to don't do not get
Speaker 1: close to the tortoises, and do not ride them. Now
Speaker 1: we have a fair amount of variety with the Glaucos
Speaker 1: tortoises that they're all of the genus Chillonitis. And you
Speaker 1: get into some discussion about the different varieties, like the
Speaker 1: exact variety count. Uh. And then we have two that
Speaker 1: are definitely extinct. Uh. There's the Floridana Island subspecies that's
Speaker 1: thought to have been hunted do extinction by I think
Speaker 1: eighteen fifty when Darwin visited. This is up with the
Speaker 1: one we only describe seeing their bones. The Penta Island
Speaker 1: species is extinct, as with the death of Lonesome George,
Speaker 1: who was of course famous for being the last of
Speaker 1: his variety. Um, he died, and that it was seemingly
Speaker 1: it for this variety of tortoise. Yeah, I've read that
Speaker 1: there are either twelve or thirteen extant uh species. Yeah,
Speaker 1: thank thank so. Coming back to the challenges that tortoises
Speaker 1: faced during the age of humans, we've we've they're thoroughly discussed.
Speaker 1: I think the human hunting and human harvesting of tortoises
Speaker 1: at least for our purposes here. Um. But of course
Speaker 1: they are all these invasive species that humans introduced. And
Speaker 1: while we are dealing with cases in some cases where
Speaker 1: you'll have animals directly going after young tortoises, uh, there
Speaker 1: are also other ways that these creatures were harmful and
Speaker 1: are and can still be harmful to the native glacial
Speaker 1: those tortoises. Right. And in fact, one example of this
Speaker 1: came up in some episodes we did back in October
Speaker 1: on goats, right, the the issue of goats competing for
Speaker 1: resources with tortoises. That's right. Again. Goats, as we discussed,
Speaker 1: are amazing at what they do at roaming around finding
Speaker 1: audits of vegetation to consume. And yeah, they're they're ultimately
Speaker 1: better at it than tortoises. They're more thorough than the
Speaker 1: tortoises and uh and and ultimately so thorough that they
Speaker 1: can be even more disruptive to like the h to
Speaker 1: the ground itself, like you know, getting in there and
Speaker 1: actually making it unstable. So that's that's one thing to consider.
Speaker 1: Also when you're dealing with any creature that lays its
Speaker 1: eggs in the ground. Uh, Not only do you have
Speaker 1: to worry with certain species, like especially pigs and rats
Speaker 1: going after those eggs and then going after the young. Potentially,
Speaker 1: you also have to deal with cattle because there are
Speaker 1: are still cattle on the on the islands, and cattle
Speaker 1: were brought to the islands and cattle aren't in us.
Speaker 1: Did in really eating those tortoise eggs, but they will
Speaker 1: definitely step on those tortoise eggs if they happen to
Speaker 1: be ranging in the same area. Now, in the previous episode,
Speaker 1: we talked about some hypotheses about how marine iguanas first
Speaker 1: arrived on the Galapagos Islands, probably via some kind of
Speaker 1: rafting from the mainland. Is that also the idea of
Speaker 1: what likely happened with the ancestral tortoises. That's my understanding
Speaker 1: based on the sources I was looking at, and based
Speaker 1: on conversations with with some of the the naturalist and
Speaker 1: guides in the Glapicos Islands, that the idea is that
Speaker 1: it would have been much the same tortoises in South America,
Speaker 1: swept up in river floods, washed out with vegetation which
Speaker 1: they were able to raft on and uh and reaching
Speaker 1: these far flung islands. So it's amazing to imagine these
Speaker 1: extremely unlikely, kind of one off events that allowed the
Speaker 1: population of each island because it's not something you see
Speaker 1: happening every day. But know, all it takes is a
Speaker 1: is a small seed population to get there and then wow,
Speaker 1: what's this. You know, there's there's all these food resources
Speaker 1: and no predators and you can really boom once you arrive. Yeah.
Speaker 1: And I'm not sure if the numbers on this are
Speaker 1: you know, certified as it were, but it seems like
Speaker 1: the first Glava Coast tortoises probably reached the islands two
Speaker 1: to three million years ago via rafting. Uh. They would
Speaker 1: have probably arrived on the eastern islands of Espanola and
Speaker 1: San Cristobil first and then spread west from there. Uh
Speaker 1: So it's uh, yeah, it's interesting to think about now.
Speaker 1: The the other question that I guess came up from
Speaker 1: me in the in this was like how big were
Speaker 1: these tortoises when they first arrived, Because at least some
Speaker 1: sources out there make the case that they were already
Speaker 1: big and that they were already quote unquote gigantic um.
Speaker 1: While plenty of other sources also discussed glab of Coast
Speaker 1: tortoises as a case of island gigantism. Yeah, so island
Speaker 1: gigantism is uh something that often occurs. There's uh known
Speaker 1: as island dwarf is AM and island gigantism. These kind
Speaker 1: of runaway pressures on the size of animals that can
Speaker 1: that can really bulk them up or shrink them down
Speaker 1: when they're on an in a contained ecosystem like an island.
Speaker 1: And I don't think we know exactly what all the
Speaker 1: pressures would be, but you could imagine something like, well,
Speaker 1: maybe there is always sexual selection on say the size
Speaker 1: of adult male tortoises, to make them bigger and bigger,
Speaker 1: because the bigger you are, the more likely a female
Speaker 1: is to be receptive to mating. So there's sexual selection
Speaker 1: driving them to be bigger. But then there's naturally some
Speaker 1: kind of other pressure that wants to keep their size smaller.
Speaker 1: You know, like you there's that advantage in being bigger,
Speaker 1: but once you're bigger, maybe you're more at risk of predation,
Speaker 1: or it's harder to thermoregulate or something like that. And
Speaker 1: you can imagine cases where you get on an island
Speaker 1: and suddenly those other pressures are relieved and so you
Speaker 1: can just keep getting bigger and bigger than you would
Speaker 1: have been allowed to on the mainland. Yeah, yeah, I guess.
Speaker 1: On the On the on the like supporting the idea
Speaker 1: that they were already big, there is uh. There is,
Speaker 1: of course fossil evidence of of gigantic tortoises existing on
Speaker 1: I think every continent except Australia and Antarctica um at
Speaker 1: some point in the past, so it's not like these
Speaker 1: forms only emerged on on various islands island environments. But
Speaker 1: but I don't know. On the other hand, it seems
Speaker 1: like plenty of sources are discussing this as gigantism. One
Speaker 1: paper I was looking at this is from Jaffee at All,
Speaker 1: from a two thousand and eleven paper in the Royal
Speaker 1: Society Biology Letters, the Evolution of island gigantism and Body
Speaker 1: size Variation in Tortoises and Turtles UM. They point out
Speaker 1: that they do point out that quote the other evolutionary
Speaker 1: determinants of size diversity in Chelonians are protly understood, but
Speaker 1: they also point out that Chelonians spans some four orders
Speaker 1: of magnitude in their sizes, and that there is quote
Speaker 1: a pronounced relationship between habitat and optimal body size. Also
Speaker 1: worth noting that the apparently the closest living relative to
Speaker 1: the Galapacos tortoise is not a direct ancestor of those tortoises,
Speaker 1: but it is a really it is itself a relatively
Speaker 1: small bodied variety of tortoise that's found in South America,
Speaker 1: the Chaco tortoise, I believe it is called now. I
Speaker 1: also mentioned that there there are other giant tortoises still
Speaker 1: in the world outside of the Glapacos. Uh. These would
Speaker 1: be giant tortoises that survived in the Western Indian Ocean
Speaker 1: in the form of aldabra giant tortoises. Yeah. And I
Speaker 1: believe when Darwin arrived he thought that these were the
Speaker 1: same species, like that the ones on the Galapacos were
Speaker 1: the same as those, or at least the same as
Speaker 1: some other island gigantic tortoise he was aware of. I
Speaker 1: think it would have been those, because those are the
Speaker 1: only other ones I know of. Um, and he he
Speaker 1: was mistaken in that, in fact that they're just uh,
Speaker 1: they're different parallel forms of of gigantic tortoises. But one
Speaker 1: last thing I wanted to talk about with these tortoises
Speaker 1: before we we wrap up today is the differences in
Speaker 1: the shell shapes, because we mentioned earlier that some species
Speaker 1: have more dome shaped shells and some have these saddle
Speaker 1: shaped shells, and there are also intermediate species that have
Speaker 1: sort of somewhere in between. UH. Creature and Laughlin have
Speaker 1: a great section on this in their chapter on the tortoises,
Speaker 1: and UH and I wanted to talk about it a bit.
Speaker 1: So one of the questions is why, uh, you can
Speaker 1: observe some things that might lead to these differences. The
Speaker 1: tortoises with the domed shells tend to live more in
Speaker 1: the highlands and around calledera rims, where vegetation is much
Speaker 1: thicker and lush all the time, whereas the ones with
Speaker 1: the saddle backed shells tend to live more or even
Speaker 1: exclusively in the lowlands, where conditions are more often dry.
Speaker 1: Of course, the differences in these shell is that, well,
Speaker 1: as the domed ones are more just kind of like
Speaker 1: an upturned cup over the over the reptiles back the
Speaker 1: saddle back tortoises, their shell tends to have like a
Speaker 1: relief area above the head and neck. It's almost like
Speaker 1: a like a collar that's pulled back. And there are
Speaker 1: some other differences to the domed tortoises tend to have
Speaker 1: a larger body size but shorter legs and necks, whereas
Speaker 1: the saddle back tortoises tend to be smaller overall but
Speaker 1: have longer legs and longer necks. Now, I remember in
Speaker 1: the last episode when we talked about the marine iguanas,
Speaker 1: and we were trying to come up with the the
Speaker 1: biological explanation for why the iguana kept returning out of
Speaker 1: the water after Darwin threw it in, even though you
Speaker 1: know it's got to go in the water all the
Speaker 1: time to to eat, So why doesn't it just stay
Speaker 1: in the water to stay away from him? Uh? And
Speaker 1: the answer we came up with that the Darwin did
Speaker 1: not land on himself is that is probably for thermoregulation
Speaker 1: and reasons because the water is cold and it was
Speaker 1: removing heat from the iguana's body, and the iguana needs
Speaker 1: to get back up on land to heat back up.
Speaker 1: I think a good explanation for one of the explanations
Speaker 1: for the different body plans of these different tortoises probably
Speaker 1: also has to do with reptile thermoregulation with the the
Speaker 1: regulation of body temperature, because of course, animals with a
Speaker 1: larger body volume also tend to retain more heat because
Speaker 1: they have less surface area proportional to their volume. So
Speaker 1: if you're living in a cold place and you're trying
Speaker 1: to retain body heat, it's easier to do that if
Speaker 1: you're bigger. You've got there's just more body in there
Speaker 1: and less relatively less surface area, and vice versa. It's
Speaker 1: easier to cool off if you're smaller because a bigger
Speaker 1: percent of your body is surface area that you can
Speaker 1: lose heat through. This would seem to correlate with the
Speaker 1: observation and that the domed tortoises, which live up in
Speaker 1: the highlands where it tends to be a little bit cooler,
Speaker 1: tend to have a larger body size, but also shorter
Speaker 1: legs and necks, so less extremities poke poking out that
Speaker 1: can lose heat, whereas these saddleback tortoises tend to be
Speaker 1: smaller overall, with longer legs and longer necks, and they
Speaker 1: live down in the lowlands where things tend to be hotter. Yeah, yeah, now,
Speaker 1: most of the tortoises I got to observe. We're definitely
Speaker 1: in highland environments. But uh, yeah, their their relationship with
Speaker 1: temperature is is notable as well. Uh. In one case,
Speaker 1: you know, we've got to go out and see these
Speaker 1: tortoises out there in this um uh this this uh
Speaker 1: this highland area, and it was early enough in the
Speaker 1: day that some of them were essentially sleeping in. They
Speaker 1: were still bedded down in the mud where they could
Speaker 1: they could, you know, keep their temperature relatively stable throughout
Speaker 1: the night. And some were already getting up to begin
Speaker 1: their their day of eating. Others just weren't quite ready yet.
Speaker 1: Oh yeah. And I've read that these tortoises just love
Speaker 1: the mud, like they love to get in the mud puddles,
Speaker 1: and they'll just hang out there for days sometimes. Yeah,
Speaker 1: so that you'll see them trooping around, and you on
Speaker 1: one level, they kind of look like bulldozers because it
Speaker 1: just covered with mud, and of course they've been eating too.
Speaker 1: There are lots of pictures you included one here of
Speaker 1: one with just this spectacularly messy face from all the
Speaker 1: vegetation and or fruits it's been consumed. It's just smeared
Speaker 1: all over. It's like one of those gross baby pictures
Speaker 1: where the baby just they've been faced down in a
Speaker 1: plate of spaghetti. Yeah, and their face, the face of
Speaker 1: the the Glabcoast tortoise does kind of look like like
Speaker 1: old baby. Um, so it really matches up with that well.
Speaker 1: But there are other differences in the environments that might
Speaker 1: explain the different body plans of these tortoise species. So uh,
Speaker 1: A lot of it probably has to do with vegetation, right.
Speaker 1: Domed tortoises tend to live in more lush highlands with
Speaker 1: dense undergrowth, and uh a creature and offline right quote.
Speaker 1: The domed shells, smoothly rounded as they are, may prove
Speaker 1: adaptive as the tortoises move tank like through dense plant cover,
Speaker 1: which is of course also the animal's food source. On
Speaker 1: the other hand, saddle type shells with a large forward
Speaker 1: notch can actually become snagged in low vegetation, impeding the
Speaker 1: movement of the tortoise. Saddle shells are not very adaptive
Speaker 1: in low dense vegetation, so it's just going to be
Speaker 1: easier to move around with a more rounded shell uh.
Speaker 1: In in all that thick brush in the in the
Speaker 1: upper highland forest regions, whereas if you had the saddle
Speaker 1: shell with the you know, the upturned sort of collar
Speaker 1: in the front. Yeah, that just be getting hooked on
Speaker 1: stuff all the time. And I mean they are little bulldozers.
Speaker 1: They can tear stuff up, like for instance, Uh, you know,
Speaker 1: they're gonna be limits. They could continue to be be
Speaker 1: slowed down or I guess stuck in vegetation. But uh,
Speaker 1: to give one example that I was told about, do
Speaker 1: you have again individuals who are still ranching in these
Speaker 1: in these parts of the highland, they have cows. Um,
Speaker 1: they need to contain those cows. But if they're gonna
Speaker 1: be tortoises moving through, they're gonna they're just gonna take
Speaker 1: down your barbed wire fence or your your whatever kind
Speaker 1: of fencing you have. So in many cases they'll have
Speaker 1: the fencing, they'll have this big gap at the bottom
Speaker 1: that will allow a tortoise to move through because that
Speaker 1: way you still get to have your fence and the
Speaker 1: tortoise won't won't tear it down when it makes a
Speaker 1: bee line for whatever wherever it's going. Unfortunately, the cows
Speaker 1: can't crawl under yeah, I guess not. It did raise
Speaker 1: some questions like well can they Yeah, can the cow
Speaker 1: what about really short cows? I don't know, but apparently
Speaker 1: it works. But the final thing with the difference between
Speaker 1: the domed tortoises and the saddlebacks is probably food sources
Speaker 1: as well, because again, the domed ones are going to
Speaker 1: be munching on a lot of you know, lush, low
Speaker 1: lying vegetation. Uh so you know that that that's just
Speaker 1: that's okay to have a normal kind of dome dome
Speaker 1: shaped shell for that. But the saddleback tortoises, which live
Speaker 1: in the more arid lowlands, are going to be eating cacti,
Speaker 1: often tall cacti that they need to reach up to
Speaker 1: get to, and so the upturned front of the shell
Speaker 1: allows more room to raise the neck, and of course,
Speaker 1: of course, as I said as well, they've got longer
Speaker 1: necks and longer legs to help reach. Robin, I think
Speaker 1: you said you observe stuff about those cactuses sort of
Speaker 1: reacting to that by growing taller and taller to try
Speaker 1: to escape the munching tortoises. Yeah. Yeah, And it's it's
Speaker 1: remarkable to see because yeah, here's this um, here's this
Speaker 1: cactus that has evolved thrive alongside the tortoises and it
Speaker 1: ends up Yeah, it ends up feeling more like a
Speaker 1: tree than a cactus, if that makes sense. Um, yeah,
Speaker 1: it's a remarkable ecosystem. All right, So there you have it.
Speaker 1: Hopefully we gave just at least a nice snapshot, a
Speaker 1: nice overview of the Galapgos tortoise. Uh. There. Obviously there's
Speaker 1: a lot of search out there about these creatures, so
Speaker 1: perhaps there's there are some details that we managed to
Speaker 1: leave out. If you think that we left out something
Speaker 1: that is particularly exciting, then right in. We'd love to
Speaker 1: hear about it. We'd love to see it for ourselves
Speaker 1: and to share it in a future listener mail. Likewise,
Speaker 1: as I mentioned the first one, if you've traveled to
Speaker 1: the Labcost Islands, if you if you live on the
Speaker 1: Galabicost Islands or or are an Ecuadorian, we would also
Speaker 1: love to hear from you. We love your thoughts on
Speaker 1: these fabulous creatures that we've discussed here, or any of
Speaker 1: the other creatures of the Glabgost Islands. I'm always excited
Speaker 1: to hear more. Just a reminder to everybody that that's
Speaker 1: stuff to blow your mind. Publishes its core episodes on
Speaker 1: Tuesdays and Thursdays and the Stuff to Blow Your Mind
Speaker 1: podcast feed We have booster mail episodes on Mondays, a
Speaker 1: short form artifact or monster fact episode on Wednesdays, and
Speaker 1: on Fridays we set aside most serious concerns and just
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Speaker 1: Max Williams. If you would like to get in touch
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