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Speaker 1: Towards the Island of Christmas, and all across the land

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Speaker 1: the red crabs were flowing across root Street and sand

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Speaker 1: like a red tide of scuttling, claw snapping doom. They

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Speaker 1: streamed through my front door and into my rooms. Meanwhile,

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Speaker 1: in the forests the giants, they're crawled coconut crabs, hulking

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Speaker 1: monsters with claws. They hunted for carrion crab bird and

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Speaker 1: ratted and gobbled it up, rancid, sinew and fat. Welcome

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Speaker 1: to Stuff to Blow your Mind from how Stuff Works

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Speaker 1: dot Com. Hey, welcome to Stuff to Blow your Mind.

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Speaker 1: My name is Robert Lamb, and I'm Joe McCormick, and

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Speaker 1: getting in that holiday spirit. We're gonna be talking about

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Speaker 1: crab Horror. Yes, this is this pair of episodes. I've

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Speaker 1: been looking forward to all year. This has been my

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Speaker 1: my goal. I forget when, but earlier in the year

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Speaker 1: I was reading about Christmas Island and and the various

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Speaker 1: creatures that that call it home, and I realized, we

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Speaker 1: have to do this episode for Christmas, even though this

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Speaker 1: really has nothing to do with Christmas, no, virtually nothing

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Speaker 1: to do with Christmas, though I do enjoy um like

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Speaker 1: forcing decapods upon Christmas and uh and and and at

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Speaker 1: least in my mind, allowing them to take over the

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Speaker 1: holiday decapods with bows of all? Is it bows? I

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Speaker 1: should have said clause of glory? Either way, I appreciate

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Speaker 1: the holiday zeal. Now, so we're going to be going

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Speaker 1: to crab Horror Island, and there are many wonderful movies

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Speaker 1: and maybe we'll save it for next time to talk

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Speaker 1: about our favorite Crab Island movies. But the giant crab

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Speaker 1: is one of my favorite kind of movie monsters, and

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Speaker 1: they've always got to have their own island of terror,

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Speaker 1: right right, and and so in discussing Christmas Island and

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Speaker 1: these two episodes, we're going to talk about crabs or

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Speaker 1: you know, decapods anyway that are either enormous, uh, singularly

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Speaker 1: and enormous or collectively enormous. I think the first episode

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Speaker 1: we're going to focus on the collectively enormous, and the

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Speaker 1: second episode will focus on the decapods who are individually enormous. Now,

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Speaker 1: this first episode is going to focus on the Christmas

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Speaker 1: Island Red crab. Robert, will you take me on a

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Speaker 1: mystical adventure to crab Horror Island? Yes, we're talking about

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Speaker 1: Christmas Island, so named. It's in the Indian Ocean, about

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Speaker 1: three hundred and fifty kilometers or two hundred and twenty

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Speaker 1: miles south of Java and Sumatra and around uh, let's

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Speaker 1: see one thou fifty kilometers or nine hundred and sixty

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Speaker 1: miles northwest of the closest point on the Australian mainland.

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Speaker 1: Technically part of Australia though right it is an Australian

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Speaker 1: external territory. It has an area of a hundred five

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Speaker 1: square kilometers or fifty two square miles, so not huge, No,

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Speaker 1: not a big place at all. It's a very old,

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Speaker 1: though very old volcanic seamount island. It was first visited

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Speaker 1: by Europeans in sixty three Captain William Minors of the

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Speaker 1: Royal Mary and English East India Company vessel. He just

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Speaker 1: named the island when he sailed past it on Christmas

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Speaker 1: Day of that year. That's that's the only Christmas high

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Speaker 1: end there he didn't find, you know, and naturally occurring

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Speaker 1: Christmas tree there. Uh, there's no wasn't where the elf

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Speaker 1: workshop was exactly. There's there's nothing else about it except

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Speaker 1: it was Christmas Day when he found it. It could

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Speaker 1: have easily it could have easily turned out to be

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Speaker 1: Christmas Eve Island or Boxing Day Island or Halloween Island.

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Speaker 1: That would perhaps be a little more appropriate. Yeah. Uh So.

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Speaker 1: One of the cool things about this place is that

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Speaker 1: when when they were able to take a closer look

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Speaker 1: at it, they realized that it was uninhabited, at least

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Speaker 1: by humans. So it's obvious that what makes this island

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Speaker 1: unique is not anything about the indigenous culture or anything,

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Speaker 1: since it was apparently uninhabited originally, but it was not

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Speaker 1: uninhabited by wildlife. Fest we've made clear the wildlife there

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Speaker 1: was of a terrific scuttling variety, oh correct. And one

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Speaker 1: of the really cool things about the scuttling life on

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Speaker 1: Christmas Island it is that so much of it is

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Speaker 1: on Christmas Island. We're talking about land crabs, crabs that

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Speaker 1: need only returned to the water to mate, but mostly

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Speaker 1: live on land. And you'll find these elsewhere. To be sure,

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Speaker 1: this is not the only place land crabs can be found.

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Speaker 1: Uh And we're we're talking about both true crabs as

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Speaker 1: well as hermit crabs here. Hermit crabs are decapods, but

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Speaker 1: not true crabs. But forgive us as we as we

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Speaker 1: talk about them in these episodes, I will probably end

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Speaker 1: up calling them both crabs in the unofficial sense. The

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Speaker 1: Christmas Island is home to more land crabs than anywhere

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Speaker 1: else on Earth. We're talking more than twenty terrestrial and

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Speaker 1: semi terrestrial crabs species, plus a hundred and sixties species

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Speaker 1: or thereabouts in the reefs and shallows around the island. Yeah,

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Speaker 1: so Robert tell me a little bit about crabs. Well,

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Speaker 1: just to refresh everybody, crabs are crustaceans. But we should

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Speaker 1: be clear that again, there are true crabs of the

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Speaker 1: decapoda soap order bracci ura, which means small tail um,

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Speaker 1: which references their smaller abdomen. And then there are the

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Speaker 1: ano mora or mixed tail crabs, which included hermits and

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Speaker 1: as we'll discuss later in the second episode, robber crabs.

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Speaker 1: But still again we're often going to refer to them

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Speaker 1: both as crabs in the unofficial sense. And these were

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Speaker 1: these are ancient creatures. These were the first animals to

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Speaker 1: develop true legs, none of those false legs. Yeah, I mean,

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Speaker 1: we we've talked about crabs on the show before. I

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Speaker 1: think back to our episode about Carl Sagan and the

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Speaker 1: Samurai Crabs. So so hopefully everyone is is on board

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Speaker 1: for two more episodes of of crab based content. But

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Speaker 1: so it's not just the varieties of crab and crab

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Speaker 1: like creatures that live on Christmas Island that make it

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Speaker 1: crab Island Earth, Uh, it is is the number of

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Speaker 1: a particular species of crab there, the Christmas Silelan red crab,

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Speaker 1: where there are supposedly tens of millions of these crabs

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Speaker 1: on the island. And this is not a big island. Remember,

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Speaker 1: it's a hundred thirty five square kilometers, right, a small island.

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Speaker 1: And yet yeah, I've seen the figures of like fifty

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Speaker 1: million of these creatures living, living in the forest, living,

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Speaker 1: you know, pretty much all over the island. And that's

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Speaker 1: a reduced number. I remember we watched a documentary about

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Speaker 1: the island from the nineteen eighties that suggested, at the

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Speaker 1: time it was believed that there were over a hundred

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Speaker 1: million of the crabs. They're right. That was a night

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Speaker 1: David Attenborough narrated special titled Kingdom of the Crab, great title,

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Speaker 1: and that's a great one to watch if you get

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Speaker 1: a chance, because it really shows off what makes this

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Speaker 1: island visually astounding, but it's the sheer numbers of the

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Speaker 1: crabs and the Christmas Island red crab is pretty much

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Speaker 1: found only on Christmas Island. Yeah, I think maybe on

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Speaker 1: another nearby island or island group, but they're not found

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Speaker 1: like all over the place. So I do want to

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Speaker 1: come back to the human history for a little bit

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Speaker 1: where we we explore the red uh crab in depth.

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Speaker 1: So the most you know, essential thing about human history

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Speaker 1: of Christmas Island is that for the longest there seems

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Speaker 1: to have been none. It is a geographically isolated place

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Speaker 1: now from everything I've read so far, and it's always

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Speaker 1: possible on missing something, but there's no evidence that humans

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Speaker 1: ever visited the place before the seventeenth century. See this.

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Speaker 1: Despite Java being again only two miles away, it's a

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Speaker 1: short enough distance for modern humans anyway that boats of

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Speaker 1: asylum seekers frequently make it their point of destination in

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Speaker 1: reaching Australia, because again it's an Australian external territory, So

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Speaker 1: if you reach Christmas Island, you are, you know, in

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Speaker 1: a legal sense, in Australia. However, it's also worth pointing

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Speaker 1: out that the seas can be deadly uh, surrounding Christmas Island,

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Speaker 1: and there are stories out there boats of asylum seekers

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Speaker 1: breaking on the rocky coast with lethal results. I think

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Speaker 1: I've read about this in cases of the early visitors

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Speaker 1: to the island. Also that you know, it was kind

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Speaker 1: of dangerous to land there. And for example, there was

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Speaker 1: one case where I read that a crew was driven

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Speaker 1: to land there because there was scurvy on the ship

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Speaker 1: and it was only because the disease had gotten so

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Speaker 1: bad that they risked trying to land. Yeah, that's sort

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Speaker 1: of the typical story book reasons for landing on an

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Speaker 1: uninhabited island with a strange crab population. Yeah, but out

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Speaker 1: of the scurvy pan into the crabs. Yeah, and you

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Speaker 1: know it, but but it is. It is weird to

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Speaker 1: think about places like this, places where where humans just

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Speaker 1: didn't take up residents. And of course you have to,

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Speaker 1: of course realize that moving to an isolated island is

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Speaker 1: a difficult proposition, like you've really got to have a

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Speaker 1: reason to go there and a reason to stay there,

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Speaker 1: and a way to um to to safely arrived there

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Speaker 1: as well. But still, you know, it's enough to make

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Speaker 1: one wonder. For instance, Homo Erectus or a Java Man

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Speaker 1: lived on the island of Java, relatively close by one

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Speaker 1: point seven million years ago. Humans practiced agriculture there on

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Speaker 1: Java as early as b C. Java was known to

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Speaker 1: traders and other powers. The Kingdom of Mataram ruled there

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Speaker 1: until they lost power to the Dutch East India Company

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Speaker 1: in seventy nine and became a vassal state of the

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Speaker 1: company UM, a statement that I think really drives home

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Speaker 1: the power of the East India Company UM, the idea

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Speaker 1: that you would have a vassal state to a corporation.

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Speaker 1: But that's a job. My point is that I just

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Speaker 1: find it so enthralling that this island remained either free

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Speaker 1: of human contact for so long or only encountered minimal influence.

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Speaker 1: You know. It's I guess it's possible that it's at

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Speaker 1: some point somebody wound up there by purpose or accident

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Speaker 1: and didn't didn't stay long enough to leave a footprint,

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Speaker 1: you know. Galapagos Islands or another example of this, though

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Speaker 1: there there have been at least disputed claims of Inca

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Speaker 1: artifacts found on the Galapacos Islands, perhaps due to Inca

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Speaker 1: sailors being blown off course. The statials in the Indian

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Speaker 1: Ocean and are another example of islands that were uninhabited

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Speaker 1: through most of recorded history, though they may have been

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Speaker 1: visited by early seafares as well, depending on who you

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Speaker 1: talked to. But with Christmas Island, I found no such thing,

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Speaker 1: and not even a crackpot theory. So it really does

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Speaker 1: seem as if humans, not even the Vikings, went their

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Speaker 1: theory by no Vikings or anything. So it really does

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Speaker 1: seem that nobody visited it until the seventeenth century, with

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Speaker 1: the earliest sighting I think having occurred in sixteen fifteen.

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Speaker 1: Now after that, of course, it actually did become an

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Speaker 1: economically significant island because of mineral deposits discovered there. That's right.

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Speaker 1: It was explored by British naturalist John Murray, and this

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Speaker 1: was eighteen seventy two. He discovered that there were phosphate

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Speaker 1: deposits on the island, which would play a key role

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Speaker 1: in the island's future. Exportation of phosphate begin in eighteen

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Speaker 1: by the Christmas Island Phosphate Company, and this activity led

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Speaker 1: to the loss of twenty of the island's rainforest area. Yeah, Now,

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Speaker 1: phosphate was important in the late eight hundreds because it

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Speaker 1: had been discovered by that time that phosphate, when treated

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Speaker 1: with sulfuric acid, could be used as an ingredient in

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Speaker 1: plant food, and of course synthetic fertilizers became very important

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Speaker 1: in the development of commercial agriculture at scale, and so

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Speaker 1: now there was a reason and economic reason for people

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Speaker 1: to not only go to Christmas Island but to work there,

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Speaker 1: and so settlement began in the eighteen eighties. Uh later on,

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Speaker 1: during the Second World War there was a Japanese occupation

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Speaker 1: of the island from ninety five, and in the post

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Speaker 1: war period it was administered by Singapore, which was then

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Speaker 1: a British colony, and then Australia purchased the island for

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Speaker 1: two point nine million pounds on January one, nineteen fifty

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Speaker 1: eight day that's known as Territory Day on Christmas Island.

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Speaker 1: Today it has around I've read two thousand full time

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Speaker 1: human residents and the ethnic makeup is mostly Chinese in

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Speaker 1: meleay Um originally brought in for labor. Now a big

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Speaker 1: poor scan of the land of the island today is

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Speaker 1: basically a national park. It's like a big wildlife preservation area. Yeah,

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Speaker 1: two thirds of its land mass are national park. Now,

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Speaker 1: and a big part of the wildlife significance here is

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Speaker 1: the Christmas Island red crabs. So I guess we should

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Speaker 1: dive headfirst into a puddle of crabs after we come

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Speaker 1: back from a break. Alright, we're back, so it is

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Speaker 1: time to dive into a pit of crabs. The Christmas

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Speaker 1: Island red crab or get Karcodia natalis. And these are

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Speaker 1: crabs that live, as we mentioned earlier, primarily not in

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Speaker 1: the ocean, not even on the shoreline, but in inland forests.

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Speaker 1: So if you picture Christmas Island, it's sort of a

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Speaker 1: terraced rainforest. It's a you know, volcanic island. It's got

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Speaker 1: some steep slopes that go up onto rainforest covered terraces,

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Speaker 1: and the crabs go all the way up into the

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Speaker 1: forests and make their burrows inland. Yeah, we're talking against

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Speaker 1: something like fifty million of these a little land well

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Speaker 1: ers uh in the forest chewing up leaf litter. And

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Speaker 1: here on Christmas Island they are the chief decay agents

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Speaker 1: for that leaf litter. I've seen estimates of something like

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Speaker 1: four thousand crabs per acre to keep the leaf litter down. Yes,

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Speaker 1: and they primarily feed on plant matter like you say,

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Speaker 1: so that is going to be leaf litter. It's also

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Speaker 1: things like fallen fruits and seeds, flowers, et cetera. But

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Speaker 1: they're also crabs after all, so you might not be

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Speaker 1: surprised to learn that they are opportunistic omnivores. My favorite

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Speaker 1: pairs of words. So if you get a little bit

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Speaker 1: of meat from say another dead red crab or something

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Speaker 1: like that presenting itself, this is a legitimate score, and

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Speaker 1: they will say, gentlemen, get that in my mouth parts.

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Speaker 1: It's time to masticate. But the crabs are important for

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Speaker 1: the maintenance of the ecosystem in multiple ways. So they

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Speaker 1: clear the forest floor of like leaf litter, but also

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Speaker 1: saplings and flowers other plants that would create dense underbrush,

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Speaker 1: and so they keep the forest floors lean, and this

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Speaker 1: actually helps contribute to forest biodiversity. They also prevent the

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Speaker 1: soil from being packed too densely because of the burrows

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Speaker 1: they dig. They're like natural soil tillers. They turn the soil,

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Speaker 1: and this also helps contribute to forest biodiversity. But so

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Speaker 1: we might have a pretty good sense of what the

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Speaker 1: life of an ocean dwelling crab is like. What is

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Speaker 1: the life of a land crab like crabs, as you

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Speaker 1: can imagine, in between chewing up things in their environment

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Speaker 1: and eating it, they have to stay moist and this means,

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Speaker 1: for one thing, staying out of the direct sun. So

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Speaker 1: the red crabs on Christmas Island like to stay in

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Speaker 1: the shady forests and they live in these dugout burrows

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Speaker 1: that they can hide from the sun in and they

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Speaker 1: have guilt chambers that have adapted for terrestrial life. They

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Speaker 1: have to keep them moist, and they also I love this,

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Speaker 1: they have to manually wet their eye stalks. Yes, I

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Speaker 1: love this. It's pretty cool to watch if you can

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Speaker 1: find video of this. So their eyes talks emerge from

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Speaker 1: little cups in their carapace, and they don't have eyelids

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Speaker 1: of course, and by the way, just try to imagine

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Speaker 1: life without eyelids. Kind of a terror. So they wet

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Speaker 1: and wash their eyes by filling their eye cups up

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Speaker 1: with drops of water and then dipping their eyestalks down

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Speaker 1: into the cups to rinse them off. Yeah. I think

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Speaker 1: this is This is one of the great things about

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Speaker 1: watching any crab close up, but especially with the Christmas

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Speaker 1: crabs is those tiny little sort of methodical movements that

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Speaker 1: you see take place with their mouth parts and their

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Speaker 1: their eyes stalks totally. Now, despite their life in the woods,

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Speaker 1: they still have to return to the sea to spawn,

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Speaker 1: and this results in a vast scuttling migration that is

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Speaker 1: truly unlike anything else on earth. This is why you

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Speaker 1: will you will see. You know, there's so many different

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Speaker 1: documentaries about Christmas Island. That's why there's so much great

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Speaker 1: footage because they they go on these enormous migrations and

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Speaker 1: we're talking a several kilometer journey each year. Yeah, this

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Speaker 1: is crab Apocalypse. This is where the real show is

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Speaker 1: on Christmas Eye. And so around the beginning of the

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Speaker 1: rainy season, which is sometime October through December, the red

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Speaker 1: crabs begin this migration for their breeding cycle. And the

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Speaker 1: migration begins with the males, usually the biggest males, who

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Speaker 1: will crawl out over land from their forest burrows to

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Speaker 1: the shore where they're going to eventually get there and

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Speaker 1: dig new burrows for mating. And as the males make

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Speaker 1: this journey, the females eventually joined them in the journey

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Speaker 1: and they march towards the sea. Now, once the crabs

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Speaker 1: reached the shore, but before they dig their burrows to mate, uh,

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Speaker 1: they typically wash themselves off in seawater, though strangely enough,

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Speaker 1: they have to be careful not to get fully sucked

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Speaker 1: out into the sea because these are land dwelling crabs.

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Speaker 1: This is how they've evolved, and they can neither breathe underwater,

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Speaker 1: nor can they swim very well. These are crabs who

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Speaker 1: are not very good at being crabs. Yeah, so the

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Speaker 1: truly aquatic crabs in the neighborhood are just probably watching

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Speaker 1: this in halfing at them. But there's so many of them.

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Speaker 1: How could you laugh at them? Because they could really

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Speaker 1: gang up on you if they got a hold of

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Speaker 1: your right But so they would rinse themselves off in

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Speaker 1: the sea water. And then the males dig the burrows. Now,

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Speaker 1: sometimes when they dig the burrows, usually they'll go up

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Speaker 1: a little bit from the beach and one of the

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Speaker 1: forested areas just right by the beach, and they'll dig

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Speaker 1: these burrows. And sometimes the males have to defend their

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Speaker 1: burrows from other males, who of course think, hey, why

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Speaker 1: dig one when you can just claim somebody else's. So

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Speaker 1: there are sometimes these fights and dominance displays, a lot

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Speaker 1: of claw waving to keep the burrows secure, and then

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Speaker 1: of course the females come in and they will find

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Speaker 1: a male with a burrow and initiate the mating. And

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Speaker 1: by the way, if you've never watched crabs mating before,

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Speaker 1: it's one of the funnier looking types of animal sex.

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Speaker 1: I think it's just crabs look funny no matter what

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Speaker 1: they're doing. But also if you can just watch their

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Speaker 1: eyes while they're mating, it's really something special. It's you know,

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Speaker 1: it's like two googly eyed robots trying to be sexy

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Speaker 1: at each other and then throwing some claws and swiveling

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Speaker 1: mouth parts. It's just awesome. Now you mentioned the waving

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Speaker 1: of the clause, I want to I was reading a

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Speaker 1: little bit about crab clause in Douglas j Imland's book

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Speaker 1: Animal Weapons. Uh and he goes. He spends a little

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Speaker 1: bit of time talking about, you know, how these are

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Speaker 1: high energy adaptations packed with powerful muscles. They need to

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Speaker 1: be able to break through the exo skeletons of of

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00:18:22,400 --> 00:18:25,840
Speaker 1: rival males in many cases. Uh And he mostly looks

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Speaker 1: at fiddler crabs in this book. But but, but it's

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Speaker 1: interesting stuff. The economics of not only having growing, evolving

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Speaker 1: gigantic class, but waving them around, because that's that's part

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Speaker 1: of having the cleaving clause or a claw, is to

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Speaker 1: wave that sucker around, yeah, or like flexing your muscles,

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Speaker 1: like showing off the guns. Yeah, you have to show

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Speaker 1: off the guns. That's that's part of having them, right. Yeah.

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Speaker 1: So the female will generally find a male and a

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Speaker 1: male with the borrow and they will mate, and then

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Speaker 1: after mating, what the males do is they just pack

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Speaker 1: up and headback inland. Their work is done, and they

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Speaker 1: leave the females by themselves in the seaside burrows. And

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Speaker 1: there's another interesting thing about this. Okay, so the red

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Speaker 1: crabs are sort of moon worshiping druids. The breeding migration

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Speaker 1: has to be timed exactly according to the cycle of

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Speaker 1: the moon because the cycle of the moon affects the tides.

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Speaker 1: So the adult crabs arrive at the shore and then

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Speaker 1: they mate, and after mating, the females produce eggs within

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Speaker 1: about three days, and then they remain in their burrows

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Speaker 1: for another twelve or thirteen days. And after this they

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Speaker 1: emerge from the hole in the ground and they release

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Speaker 1: their eggs into the sea water. And it has to

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Speaker 1: be timed exactly at the turn of high tide as

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Speaker 1: the moon goes from its last quarter to a new moon.

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Speaker 1: And this is because it's when the tide conditions are

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Speaker 1: just right to be releasing uh the young. But if

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00:19:50,960 --> 00:19:54,359
Speaker 1: the migration is delayed by weather so that breeding can't

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00:19:54,359 --> 00:19:56,680
Speaker 1: be timed exactly right with the phases of the moon,

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Speaker 1: the crabs will just wait. They'll just wait until the

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Speaker 1: next month to breed because it's not it's not going

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Speaker 1: the moon isn't right. So when the time is right,

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00:20:05,000 --> 00:20:07,879
Speaker 1: the females release their eggs acts, which looks kind of

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00:20:07,920 --> 00:20:10,480
Speaker 1: like a weird foamy sponge that they carry on the

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00:20:10,560 --> 00:20:13,320
Speaker 1: underside of their bodies. They release these eggs acts into

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Speaker 1: the water. Yet again, I can't help but notice that

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Speaker 1: my wonder at these animals is combined with hilarity on

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Speaker 1: seeing this, because in some cases, the female crabs have

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Speaker 1: to release their eggs into like rough surf while clinging

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Speaker 1: to rocks above the water, and they're trying to be

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Speaker 1: careful not to fall in. And when you see footage

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Speaker 1: of this, the way they're just frantically shaking their bodies

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Speaker 1: to knock the eggs acts off, dumping thousands of eggs

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Speaker 1: off a cliff. I can't help but laugh. It's funny.

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Speaker 1: And then also sometimes they'll they'll go into the surf

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Speaker 1: on a beach and you'll see them like raising their

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Speaker 1: claws and shaking their bodies, like get off, just dumping

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Speaker 1: all these eggs off into the water. I don't know,

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Speaker 1: it's it's funny to me. Well, by human comparisons, they're

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00:20:58,480 --> 00:21:01,399
Speaker 1: maybe not great moms, but by but by Christmas Island

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00:21:01,440 --> 00:21:05,000
Speaker 1: Red Crab standards, moms of the Year. Yeah, exactly, and

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Speaker 1: that this does make me think about the ways that

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00:21:07,320 --> 00:21:09,840
Speaker 1: we anthropomorphize good parenting. I want to come back to

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00:21:09,880 --> 00:21:12,600
Speaker 1: that in just a minute. So the eggs are released

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Speaker 1: into the surf and they hatch pretty much immediately, and

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00:21:15,280 --> 00:21:18,200
Speaker 1: then you've got these hatchling crab larvae that live in

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Speaker 1: the water for about a month, transforming through large larval stages,

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Speaker 1: and then they returned the shore in this seething foam

385
00:21:26,800 --> 00:21:29,919
Speaker 1: of what looks like pink ants. This is also just

386
00:21:30,000 --> 00:21:33,399
Speaker 1: astonishing to see, like the original migration from the forest

387
00:21:33,440 --> 00:21:36,800
Speaker 1: to the shore with the beaches and rocks covered in

388
00:21:36,880 --> 00:21:42,760
Speaker 1: this surging pink shag carpet of tiny millimeter sized baby crabs.

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Speaker 1: And then they molt, and immediately after molting, they they

390
00:21:46,200 --> 00:21:49,159
Speaker 1: are committed to an air breathing life on land, and

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00:21:49,200 --> 00:21:52,680
Speaker 1: they travel inland to do as their ancestors did before them.

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Speaker 1: And this growth from about a five millimeter baby crab

393
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Speaker 1: stage to adulthood usually takes about four years, during which

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00:21:58,920 --> 00:22:01,959
Speaker 1: time they mostly tend to hide out undercover until they

395
00:22:02,000 --> 00:22:05,080
Speaker 1: get big enough to fend for themselves. But yeah, back

396
00:22:05,080 --> 00:22:08,520
Speaker 1: to this idea about the way we look at non

397
00:22:08,680 --> 00:22:12,000
Speaker 1: human animals and tend to to judge their parenting. I mean,

398
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Speaker 1: that's inherently what I was doing when I think it's

399
00:22:14,200 --> 00:22:17,520
Speaker 1: funny just watching the mother crabs chuck their eggs off

400
00:22:17,520 --> 00:22:22,639
Speaker 1: a cliff. But it's like it's hilarious watching a crab

401
00:22:22,760 --> 00:22:25,320
Speaker 1: vigorously shake its body to knock all the eggs off

402
00:22:25,359 --> 00:22:28,760
Speaker 1: and stuff. But it's because we've so deeply internalized the

403
00:22:28,800 --> 00:22:32,640
Speaker 1: brood protection tendencies of mammals. Mammals tend to keep their

404
00:22:32,680 --> 00:22:35,520
Speaker 1: offspring close and take care of them for for like

405
00:22:35,560 --> 00:22:38,720
Speaker 1: extended periods of time while they mature, and that would

406
00:22:38,760 --> 00:22:41,480
Speaker 1: make no sense for crabs to do. First of all,

407
00:22:41,520 --> 00:22:43,560
Speaker 1: of course, it is just mechanically the case, because the

408
00:22:43,600 --> 00:22:46,800
Speaker 1: eggs need to hatch in the water. That's what chemically

409
00:22:46,880 --> 00:22:51,280
Speaker 1: and mechanically they do, but also mathematically, the parents have

410
00:22:51,359 --> 00:22:55,359
Speaker 1: a totally different relationship with their offspring. Mammals tend to produce,

411
00:22:55,440 --> 00:22:58,320
Speaker 1: you know, relatively small numbers of offspring and invest a

412
00:22:58,320 --> 00:23:01,520
Speaker 1: lot of energy into caring for and protecting them. But

413
00:23:01,600 --> 00:23:03,280
Speaker 1: I was trying to do a little bit of rough

414
00:23:03,359 --> 00:23:06,119
Speaker 1: math about the red crabs. So let's assume there are

415
00:23:06,160 --> 00:23:09,679
Speaker 1: fifty million adult red crabs on the island, and then

416
00:23:09,720 --> 00:23:12,359
Speaker 1: you've got mated pairs, and each mated pair of adult

417
00:23:12,359 --> 00:23:15,600
Speaker 1: crabs produces tens of thousands of eggs. I've seen a

418
00:23:15,680 --> 00:23:19,520
Speaker 1: common figure of a hundred thousand eggs per female crab sited.

419
00:23:19,880 --> 00:23:23,399
Speaker 1: So if fifty million crabs made it and produced twenty

420
00:23:23,400 --> 00:23:26,680
Speaker 1: five million eggs sponges, and each of those had a

421
00:23:26,760 --> 00:23:30,200
Speaker 1: hundred thousand eggs in it, and all those eggs survived

422
00:23:30,200 --> 00:23:35,640
Speaker 1: to adulthood, that would be two trillion, five hundred billion crabs. Now,

423
00:23:35,760 --> 00:23:39,040
Speaker 1: Christmas Island is about a hundred and thirty five square kilometers.

424
00:23:39,080 --> 00:23:41,240
Speaker 1: If my math is right, this means that just after

425
00:23:41,520 --> 00:23:44,600
Speaker 1: one year there would be a Christmas Island would have

426
00:23:44,760 --> 00:23:49,000
Speaker 1: eighteen point five billion crabs per square kilometer. So you're saying,

427
00:23:49,400 --> 00:23:52,800
Speaker 1: as a red crab mom, you have to be willing

428
00:23:52,840 --> 00:23:54,520
Speaker 1: to let some of those crabs go because you have

429
00:23:55,160 --> 00:23:57,400
Speaker 1: you have the numbers on your side, right. I mean,

430
00:23:57,440 --> 00:24:00,159
Speaker 1: it's just a totally different way of of have a

431
00:24:00,200 --> 00:24:04,040
Speaker 1: relationship between generations, right. They're going for for numbers. You know,

432
00:24:04,080 --> 00:24:07,560
Speaker 1: it's quantity rather than quality. And it's just impossible for

433
00:24:07,600 --> 00:24:10,639
Speaker 1: all those young to sustainably survive. Even if a decent

434
00:24:10,680 --> 00:24:13,919
Speaker 1: fraction of them survived, it would be ridiculous. Only a

435
00:24:13,920 --> 00:24:16,960
Speaker 1: tiny fraction of them can possibly make it to adulthood

436
00:24:17,040 --> 00:24:21,040
Speaker 1: in any ecologically sustainable way. And so most that get

437
00:24:21,080 --> 00:24:23,879
Speaker 1: dumped out into the water to hatch never make it

438
00:24:23,920 --> 00:24:26,160
Speaker 1: back to shore alive. They get washed out to sea,

439
00:24:26,280 --> 00:24:30,520
Speaker 1: never to return. Apparently, whale sharks migrate to the Christmas

440
00:24:30,600 --> 00:24:33,679
Speaker 1: Island area to eat red crab larvae when they hatch,

441
00:24:34,200 --> 00:24:36,280
Speaker 1: and among those that do make it back to the

442
00:24:36,320 --> 00:24:39,280
Speaker 1: beach in that in that you know foamy pink shag

443
00:24:39,359 --> 00:24:42,160
Speaker 1: carpet I mentioned, they're obviously going to be pretty easy

444
00:24:42,240 --> 00:24:44,760
Speaker 1: prey at that stage too. You can even sometimes see

445
00:24:44,800 --> 00:24:47,520
Speaker 1: I've seen footage of this of adult red crabs just

446
00:24:47,600 --> 00:24:51,480
Speaker 1: kind of shoveling clawfulls of young red crabs into their mouths,

447
00:24:51,840 --> 00:24:54,080
Speaker 1: because hey, what are the chances that these are mine?

448
00:24:54,160 --> 00:24:56,760
Speaker 1: It's pretty slim. Again, it's a numbers game. Well. Plus,

449
00:24:56,800 --> 00:24:58,680
Speaker 1: it's like they're just against so many of them. It's

450
00:24:58,680 --> 00:25:02,240
Speaker 1: like if you make way too much a pancake batter, Uh,

451
00:25:02,280 --> 00:25:05,280
Speaker 1: you may treat yourself to a few spoonfuls of unclid

452
00:25:05,359 --> 00:25:08,920
Speaker 1: pancake batter. I mean, why not, it's there. You can

453
00:25:08,920 --> 00:25:11,479
Speaker 1: only make so many pancakes. You can make similar argument.

454
00:25:11,480 --> 00:25:13,600
Speaker 1: You'd be like, look, if I made all of this

455
00:25:13,680 --> 00:25:16,680
Speaker 1: into pancakes, our house would be packed with pancakes six

456
00:25:16,680 --> 00:25:21,280
Speaker 1: ft high exactly. But anyway, given this kind of life cycle,

457
00:25:21,320 --> 00:25:23,280
Speaker 1: in these kind of odds, the way to be a

458
00:25:23,320 --> 00:25:26,199
Speaker 1: good parent is to do exactly what the female crabs do.

459
00:25:26,560 --> 00:25:28,880
Speaker 1: They shake them off into the water where they've got

460
00:25:28,880 --> 00:25:31,120
Speaker 1: a chance, and then they call it a day. There's

461
00:25:31,160 --> 00:25:33,000
Speaker 1: nothing more you can do at that point. And if

462
00:25:33,080 --> 00:25:35,840
Speaker 1: somehow you were still around when they hatched and molted,

463
00:25:35,880 --> 00:25:38,800
Speaker 1: who knows, you might just gobble them up. So, despite

464
00:25:38,800 --> 00:25:41,959
Speaker 1: how funny it looks, I rebuke my instincts. I do

465
00:25:42,080 --> 00:25:44,359
Speaker 1: not think that the red crabs are bad parents. I

466
00:25:44,400 --> 00:25:47,119
Speaker 1: think they're awesome crab parents. All right, we're gonna take

467
00:25:47,160 --> 00:25:48,639
Speaker 1: a quick break, and when we come back, we're going

468
00:25:48,720 --> 00:25:50,440
Speaker 1: to get into the human element. What happens when we

469
00:25:50,480 --> 00:25:55,960
Speaker 1: have the human element to the red crab element. Thank alright,

470
00:25:55,960 --> 00:25:59,560
Speaker 1: we're back now. We discussed earlier how crazy these migrations are.

471
00:25:59,800 --> 00:26:02,879
Speaker 1: You when the island can, sometimes in areas, become just

472
00:26:03,000 --> 00:26:06,040
Speaker 1: thick with crabs that are moving from forest to shore

473
00:26:06,200 --> 00:26:09,800
Speaker 1: or returning from shore to forest. And this doesn't even

474
00:26:09,880 --> 00:26:13,160
Speaker 1: take into consideration the fact that sometimes there are multiple

475
00:26:13,240 --> 00:26:16,920
Speaker 1: waves of migration during the same year. So you've got

476
00:26:17,040 --> 00:26:20,000
Speaker 1: crabs going both ways. Like one set of crabs they

477
00:26:20,000 --> 00:26:22,680
Speaker 1: moved down to the shore, and then there's another, uh

478
00:26:22,720 --> 00:26:25,439
Speaker 1: you know, trigger of the rainy season, another set of

479
00:26:25,480 --> 00:26:28,040
Speaker 1: crabs they start moving to the shore, and then the

480
00:26:28,040 --> 00:26:30,200
Speaker 1: other ones are going home. So you can have crabs

481
00:26:30,240 --> 00:26:32,280
Speaker 1: going this way, crabs going that way. There on the

482
00:26:32,320 --> 00:26:35,439
Speaker 1: golf course, there on the streets, there in the grocery store.

483
00:26:35,520 --> 00:26:39,560
Speaker 1: I mean, it can become quite thick with crabs on

484
00:26:39,680 --> 00:26:43,400
Speaker 1: Christmas Island. And yet there are people here, that's right,

485
00:26:43,480 --> 00:26:47,520
Speaker 1: and those people have vehicles that they also have pets. Uh,

486
00:26:47,800 --> 00:26:49,719
Speaker 1: we'll get into some of those complications in a bit,

487
00:26:49,760 --> 00:26:52,919
Speaker 1: but just the roads. You're talking about something like a

488
00:26:53,000 --> 00:26:56,480
Speaker 1: million crabs a year crushed by road traffic on Christmas Island,

489
00:26:56,840 --> 00:26:59,240
Speaker 1: but that's still only gonna shake out to something like

490
00:26:59,320 --> 00:27:02,600
Speaker 1: one percent of the population. And the dead, by the way,

491
00:27:02,600 --> 00:27:06,399
Speaker 1: are apparently swiftly cannibalized. Again, crabs. Crabs are gonna do

492
00:27:06,400 --> 00:27:08,639
Speaker 1: what crabs are gonna do. No. I mentioned earlier that

493
00:27:08,680 --> 00:27:12,440
Speaker 1: there's this great old British TV documentary called Kingdom of

494
00:27:12,480 --> 00:27:16,919
Speaker 1: the Crabs and narrated by David Attenborough from nineteen I think, yeah,

495
00:27:16,960 --> 00:27:19,960
Speaker 1: that was the same year that we got John Carpenters

496
00:27:20,000 --> 00:27:24,280
Speaker 1: They Live, Killer Clowns from Outer Space, The Blob the remake,

497
00:27:24,359 --> 00:27:26,760
Speaker 1: the really cool eighties remake, as well as of course

498
00:27:26,840 --> 00:27:29,040
Speaker 1: Mac and Me. Well, this is right up there with those.

499
00:27:29,320 --> 00:27:31,119
Speaker 1: But it's got so many great moments. And one of

500
00:27:31,160 --> 00:27:34,200
Speaker 1: the best moments from it is when you're watching hundreds

501
00:27:34,200 --> 00:27:37,879
Speaker 1: of crabs scuttling across a pair of railroad tracks and

502
00:27:37,880 --> 00:27:41,960
Speaker 1: then a train emerges in the background and it's barreling

503
00:27:41,960 --> 00:27:45,720
Speaker 1: towards the crab crossing, and then the crabs show no

504
00:27:45,840 --> 00:27:47,800
Speaker 1: sign of getting out of the way, and then the

505
00:27:47,840 --> 00:27:51,600
Speaker 1: train conductor starts blowing his horn at the crabs as

506
00:27:51,640 --> 00:27:54,840
Speaker 1: if that's going to deter them. I guess it's like

507
00:27:54,840 --> 00:27:56,960
Speaker 1: when people like they stop in the road because the

508
00:27:57,000 --> 00:27:59,320
Speaker 1: turtle is crossing and they honked their horn at it.

509
00:28:00,040 --> 00:28:04,720
Speaker 1: I never actually haunt my hornets, they squirrels, chipmunks, but

510
00:28:04,760 --> 00:28:07,840
Speaker 1: I will almost wreck my vehicle to avoid them. But

511
00:28:07,920 --> 00:28:10,160
Speaker 1: I I guess that's human nature. Like you don't want

512
00:28:10,200 --> 00:28:13,159
Speaker 1: to squish crabs unnecessarily. I mean maybe some people do.

513
00:28:13,720 --> 00:28:15,360
Speaker 1: There are probably a few people on the island who

514
00:28:15,400 --> 00:28:16,760
Speaker 1: kind of get off on it. Well, I've read that

515
00:28:16,800 --> 00:28:20,520
Speaker 1: it can. It can also hurt your tires. Yeah, you

516
00:28:20,560 --> 00:28:23,240
Speaker 1: have people with flat tires due to the crabs. Probably

517
00:28:23,280 --> 00:28:28,399
Speaker 1: hurts trains less, probably, Uh. But the humans have had

518
00:28:28,440 --> 00:28:31,720
Speaker 1: to put in place many steps to help the crabs

519
00:28:31,800 --> 00:28:35,040
Speaker 1: cope with roads and tracks and the other ways that

520
00:28:35,160 --> 00:28:39,000
Speaker 1: we have unfortunately disrupted their migration zones. I mean, it's

521
00:28:39,000 --> 00:28:41,360
Speaker 1: not the crabs fault, right, They didn't ask us to

522
00:28:41,400 --> 00:28:44,680
Speaker 1: put a road there, but railroad tracks there to do

523
00:28:44,800 --> 00:28:47,640
Speaker 1: all that kind of stuff. So these adaptations are are

524
00:28:47,640 --> 00:28:50,560
Speaker 1: pretty interesting. They include barriers of course around the edges

525
00:28:50,560 --> 00:28:52,800
Speaker 1: of roads and put walls around the roads to keep

526
00:28:52,840 --> 00:28:55,840
Speaker 1: the crabs from walking onto the roads, and these lead

527
00:28:55,960 --> 00:28:59,400
Speaker 1: to sort of crab funnels that route the crabs to

528
00:28:59,520 --> 00:29:03,440
Speaker 1: specially designs safe crossings, so you might have an underpass

529
00:29:03,560 --> 00:29:06,080
Speaker 1: with a great on top of it, or even there's

530
00:29:06,120 --> 00:29:10,200
Speaker 1: even a five meter high crab bridge climbable by crab

531
00:29:10,480 --> 00:29:12,960
Speaker 1: to help them over one stretch of road. Oh yeah,

532
00:29:12,960 --> 00:29:14,560
Speaker 1: and you included a picture of these in our notes.

533
00:29:14,560 --> 00:29:17,120
Speaker 1: It's pretty incredible because it looks like one of the

534
00:29:17,560 --> 00:29:22,360
Speaker 1: recognizers those enemy ships in the Tron movies. Yeah, it

535
00:29:22,400 --> 00:29:24,680
Speaker 1: looks like like that the big clamp that comes down

536
00:29:24,720 --> 00:29:27,240
Speaker 1: on top of you, right, except instead of being made

537
00:29:27,240 --> 00:29:31,000
Speaker 1: out of brightly colored light, it's covered in brightly colored

538
00:29:31,000 --> 00:29:35,560
Speaker 1: red crabs right now. Interestingly enough, early accounts of Christmas

539
00:29:35,560 --> 00:29:39,440
Speaker 1: Island make no real mention of the crab hoardz. So

540
00:29:40,360 --> 00:29:42,240
Speaker 1: you could you can look at that one of two ways, right, Well,

541
00:29:42,760 --> 00:29:45,320
Speaker 1: either it didn't occur in this at least with the

542
00:29:45,360 --> 00:29:48,600
Speaker 1: same at the same level, or they just forgot to

543
00:29:48,640 --> 00:29:52,360
Speaker 1: mention it, which seems unlikely, but maybe they didn't witness it. Well,

544
00:29:52,440 --> 00:29:56,760
Speaker 1: it's true too, but there is this suspected link between

545
00:29:57,360 --> 00:30:01,800
Speaker 1: the current levels and the decent levels of of of

546
00:30:01,840 --> 00:30:06,080
Speaker 1: the red crab population with the extinction of two species

547
00:30:06,120 --> 00:30:10,760
Speaker 1: of rat that were on the island when Europeans first arrived.

548
00:30:11,400 --> 00:30:13,680
Speaker 1: And uh, and it's possible that these two species of

549
00:30:13,760 --> 00:30:18,240
Speaker 1: rat may have kept the populations more in check. What

550
00:30:18,320 --> 00:30:21,880
Speaker 1: are these rats alright? One is called mcclear's rat or

551
00:30:22,240 --> 00:30:26,160
Speaker 1: memor Rattis McCleary and the other is the bulldog rat

552
00:30:26,720 --> 00:30:31,360
Speaker 1: or Rattus nativitatis. And those are just two of only

553
00:30:31,520 --> 00:30:35,520
Speaker 1: five native mammal species on Christmas Island to have been

554
00:30:35,520 --> 00:30:39,000
Speaker 1: officially listed as extinct since human showed up. That being

555
00:30:39,080 --> 00:30:42,920
Speaker 1: both of these rats, and the reason that they went extinct,

556
00:30:42,960 --> 00:30:46,200
Speaker 1: it's it's probably because exotic rodents were brought in by

557
00:30:46,240 --> 00:30:49,720
Speaker 1: early human colonizers or brought in. I would say they

558
00:30:49,920 --> 00:30:53,200
Speaker 1: just came along with let rats do. Okay, So the

559
00:30:53,240 --> 00:30:57,240
Speaker 1: ideas that humans brought different kinds of rodents, those rodents

560
00:30:57,280 --> 00:31:00,760
Speaker 1: out competed the native rodents, but those rodents weren't as

561
00:31:00,840 --> 00:31:04,479
Speaker 1: much of a competition with the red crabs. Well, it's

562
00:31:04,520 --> 00:31:07,720
Speaker 1: more than just outcompete as apparently like straight up killed

563
00:31:07,720 --> 00:31:10,680
Speaker 1: them off with illness. It was looking at a two

564
00:31:10,680 --> 00:31:14,680
Speaker 1: thousand eight study published in PLS one, and they pointed

565
00:31:14,680 --> 00:31:16,920
Speaker 1: out that there seems to be a direct cause here

566
00:31:16,920 --> 00:31:19,640
Speaker 1: and it seems to be disease. They collected DNA samples

567
00:31:19,880 --> 00:31:23,600
Speaker 1: from the islands now extinct native rats via late nineteenth

568
00:31:23,600 --> 00:31:27,240
Speaker 1: and early twentieth century museum specimens, and they attributed the

569
00:31:27,280 --> 00:31:31,600
Speaker 1: extinction event here to ship jumping black rats infected with

570
00:31:31,680 --> 00:31:37,800
Speaker 1: the protozoan Tripenasoma louizy, an organism that is related to

571
00:31:37,840 --> 00:31:41,480
Speaker 1: an organism that causes sleeping sickness in humans. And indeed,

572
00:31:42,160 --> 00:31:46,360
Speaker 1: native Island rats were seen to stagger around following the

573
00:31:46,440 --> 00:31:51,120
Speaker 1: arrival of the s S Hindustan in eight and this

574
00:31:51,400 --> 00:31:55,080
Speaker 1: protozoan is light is likely spread by fleas, so we

575
00:31:55,160 --> 00:31:57,360
Speaker 1: have you know, it's a similar situation that we've seen

576
00:31:57,480 --> 00:32:01,680
Speaker 1: with certainly with with human populations and UH and other organisms,

577
00:32:01,720 --> 00:32:05,480
Speaker 1: where an exotic variant brought in a parasite that the

578
00:32:06,080 --> 00:32:08,560
Speaker 1: UH that the native inhabitants were just simply unable to

579
00:32:08,600 --> 00:32:12,960
Speaker 1: deal with. Now, in terms of other native Christmas Island mammals,

580
00:32:13,680 --> 00:32:15,800
Speaker 1: others have had a tough time as well. The Christmas

581
00:32:15,800 --> 00:32:21,760
Speaker 1: Island shrew is critically endangered. There's also a particular bat

582
00:32:22,440 --> 00:32:30,240
Speaker 1: the Christmas Island PIPISTRELLI, Yes, thank you for helping that one. Now,

583
00:32:30,280 --> 00:32:33,720
Speaker 1: it's it's name. It is a cute name, a cute

584
00:32:33,840 --> 00:32:37,560
Speaker 1: name for a bat. It's critically endangered, if not outright extinct,

585
00:32:37,640 --> 00:32:41,520
Speaker 1: and apparently the reasoning behind that is is not completely understood.

586
00:32:41,800 --> 00:32:45,000
Speaker 1: There's also the Christmas Island flying fox, which is another

587
00:32:45,040 --> 00:32:48,240
Speaker 1: type of bat. It is also in decline for unknown reasons.

588
00:32:48,800 --> 00:32:51,600
Speaker 1: And then you have the exotic mammals. We've already mentioned

589
00:32:51,680 --> 00:32:54,240
Speaker 1: black rats, but you also have a house mice, you

590
00:32:54,280 --> 00:32:57,280
Speaker 1: have feral cats and wild dogs. Now do we know

591
00:32:57,600 --> 00:33:00,959
Speaker 1: what the explicit relationship between that change in the mammal

592
00:33:01,040 --> 00:33:05,479
Speaker 1: populations and the surge and crabs is. The belief is

593
00:33:05,600 --> 00:33:09,400
Speaker 1: that those populated the original populations of rodents were helping

594
00:33:09,400 --> 00:33:12,960
Speaker 1: to keep the population of crabs in check, and apparently

595
00:33:13,080 --> 00:33:16,600
Speaker 1: the the the exotic mammals have not been able to

596
00:33:16,640 --> 00:33:19,600
Speaker 1: keep their numbers in check the same in the same rate.

597
00:33:19,800 --> 00:33:23,680
Speaker 1: I see, So they're not adapted to to crab Island, right, Yeah,

598
00:33:23,840 --> 00:33:26,840
Speaker 1: it's it's one of those situations where again you just

599
00:33:26,840 --> 00:33:30,080
Speaker 1: see humans show up in the unbalanced things. Now, in

600
00:33:30,120 --> 00:33:32,880
Speaker 1: the case of the red crabs, it would almost seem

601
00:33:32,960 --> 00:33:36,080
Speaker 1: like the unbalancing made more spectacle right, Like the reason

602
00:33:36,080 --> 00:33:38,120
Speaker 1: we're talking about Christmas Island is because we have this

603
00:33:38,320 --> 00:33:42,920
Speaker 1: enormous surge that arguably might not be the same level

604
00:33:43,680 --> 00:33:46,640
Speaker 1: if we had also not managed to kill off two

605
00:33:46,640 --> 00:33:50,440
Speaker 1: whole species of rodents on the island. True, and there's

606
00:33:50,440 --> 00:33:53,560
Speaker 1: going to be even more stuff along those lines coming up.

607
00:33:53,600 --> 00:33:57,080
Speaker 1: So there are actually multiple ongoing threats to the life

608
00:33:57,080 --> 00:34:00,000
Speaker 1: cycle of these amazing animals. If if you care about

609
00:34:00,000 --> 00:34:03,880
Speaker 1: out the beauty of the crab army scuttling through the forests,

610
00:34:04,160 --> 00:34:07,560
Speaker 1: you should care about these issues. One is climate related.

611
00:34:07,680 --> 00:34:12,360
Speaker 1: So there is a paper from in Global Change Biology

612
00:34:12,400 --> 00:34:16,400
Speaker 1: called Linking l Neino Local rainfall and migration timing in

613
00:34:16,440 --> 00:34:20,160
Speaker 1: a tropical migratory species by Alison K. Shaw and Catherine A.

614
00:34:20,280 --> 00:34:24,240
Speaker 1: Kelly and the authors here find that species whose mating

615
00:34:24,400 --> 00:34:28,440
Speaker 1: and migratory behaviors are determined by weather, like the Christmas

616
00:34:28,480 --> 00:34:31,799
Speaker 1: Island red crab, remember it's the it's certain things about

617
00:34:31,840 --> 00:34:34,680
Speaker 1: the beginning of the rainy season that tell them time

618
00:34:34,719 --> 00:34:37,719
Speaker 1: to go to the beach and mate. Uh, they will

619
00:34:37,760 --> 00:34:41,680
Speaker 1: probably be adversely affected by the way climate change is

620
00:34:41,840 --> 00:34:45,360
Speaker 1: upsetting normal weather patterns that were used to so the

621
00:34:45,360 --> 00:34:48,120
Speaker 1: author's write quote. We find that the timing of the

622
00:34:48,160 --> 00:34:52,000
Speaker 1: annual crab breeding migration is closely related to the amount

623
00:34:52,040 --> 00:34:56,600
Speaker 1: of rain that falls during a migration window period prior

624
00:34:56,640 --> 00:34:59,960
Speaker 1: to potential egg release dates, which is in turn really

625
00:35:00,000 --> 00:35:03,320
Speaker 1: added to the Southern oscillation index and atmospheric l ne

626
00:35:03,400 --> 00:35:08,120
Speaker 1: NEO Southern oscillation index. As reproduction in this species is

627
00:35:08,200 --> 00:35:12,680
Speaker 1: conditional on successful migration, they don't reproduce if they don't migrate,

628
00:35:13,200 --> 00:35:17,040
Speaker 1: major changes in migration patterns could have detrimental consequences for

629
00:35:17,080 --> 00:35:20,520
Speaker 1: the survival of the species. So, in other words, climate

630
00:35:20,600 --> 00:35:23,279
Speaker 1: change messes around with the amount of timing of the

631
00:35:23,400 --> 00:35:26,719
Speaker 1: rainfall on Christmas Island, and then the crabs get the

632
00:35:26,719 --> 00:35:29,520
Speaker 1: short end of the stick and could find themselves unable

633
00:35:29,560 --> 00:35:33,120
Speaker 1: to use their normal migration and breeding instincts in order

634
00:35:33,160 --> 00:35:35,840
Speaker 1: to produce the next generation. And this could also have

635
00:35:35,920 --> 00:35:39,080
Speaker 1: follow on effects with the animals that depend on these

636
00:35:39,320 --> 00:35:42,560
Speaker 1: migratory animals for food, like the Christmas Island red crab

637
00:35:42,920 --> 00:35:45,359
Speaker 1: is sort of a keystone species on the island in

638
00:35:45,400 --> 00:35:48,080
Speaker 1: many ways. One of the things we already mentioned is

639
00:35:48,120 --> 00:35:51,080
Speaker 1: that those whale sharks come to eat the Christmas Island

640
00:35:51,080 --> 00:35:53,920
Speaker 1: red crab larvae in the water. But another thing is,

641
00:35:54,040 --> 00:35:56,840
Speaker 1: as we mentioned, they maintain the state of the forest

642
00:35:56,960 --> 00:36:00,719
Speaker 1: by clearing leaf litter and clearing out other plants in

643
00:36:00,760 --> 00:36:03,960
Speaker 1: the undergrowth of the forest, and you know, and by

644
00:36:03,960 --> 00:36:07,840
Speaker 1: turning the soil right. Yeah, they're they're aerators. Now, there

645
00:36:08,040 --> 00:36:11,200
Speaker 1: is another culprit that is putting the Christmas Island red

646
00:36:11,239 --> 00:36:15,640
Speaker 1: crabs at risk, and that is yellow crazy ants crazy ants. Again,

647
00:36:15,920 --> 00:36:18,960
Speaker 1: it's different crazy ants somewhat. So we did an episode

648
00:36:19,000 --> 00:36:21,480
Speaker 1: about crazy ants before, but that was focused on a

649
00:36:21,520 --> 00:36:24,440
Speaker 1: completely different animal. We were mainly talking about the raspberry

650
00:36:24,480 --> 00:36:28,239
Speaker 1: crazy ant of the genus Nylandria. The yellow ant is

651
00:36:28,400 --> 00:36:32,719
Speaker 1: a totally different genus. It's an apolo lepus gracillips and

652
00:36:32,880 --> 00:36:36,120
Speaker 1: these are ants with a slender body, long legs, and

653
00:36:36,239 --> 00:36:40,240
Speaker 1: like the crazy ants in genus Nylanderia, they're also easily

654
00:36:40,239 --> 00:36:43,160
Speaker 1: recognized by these movement patterns that give them their name.

655
00:36:43,200 --> 00:36:47,239
Speaker 1: Their motion is sometimes described as frantic or erratic or crazy,

656
00:36:47,520 --> 00:36:50,840
Speaker 1: and like raspberry crazy ants, these ants can also form

657
00:36:50,920 --> 00:36:54,400
Speaker 1: what are known as super colonies, which means they build

658
00:36:54,480 --> 00:36:58,520
Speaker 1: separate but friendly nests which do not attack one another

659
00:36:58,920 --> 00:37:01,960
Speaker 1: and form a kind of web of allied ant armies

660
00:37:02,000 --> 00:37:04,960
Speaker 1: that can easily overwhelm the habitats that they spread to,

661
00:37:05,560 --> 00:37:09,520
Speaker 1: and so they're considered a very problematic invasive species like

662
00:37:09,600 --> 00:37:12,880
Speaker 1: other crazy ants. Also, they spray formic acid as a

663
00:37:12,960 --> 00:37:17,040
Speaker 1: defensive and offensive biological weapon, and formic acid is a

664
00:37:17,080 --> 00:37:21,720
Speaker 1: powerful chemical. Uh, it's apparently a potent poison against land crabs.

665
00:37:21,719 --> 00:37:24,040
Speaker 1: So you can imagine a bunch of ants come up

666
00:37:24,080 --> 00:37:26,759
Speaker 1: against one of these Christmas Island red crabs and the

667
00:37:26,840 --> 00:37:30,680
Speaker 1: ants spray formic acid in its eyes, in the segment

668
00:37:30,800 --> 00:37:33,440
Speaker 1: joints of the crabs, so you know, like getting in

669
00:37:33,480 --> 00:37:36,560
Speaker 1: the leg joints, and this can leave the crabs unable

670
00:37:36,640 --> 00:37:39,359
Speaker 1: to move or to survive. And then after the crabs die,

671
00:37:39,400 --> 00:37:41,479
Speaker 1: of course, the ants get a feast of crab meat

672
00:37:41,760 --> 00:37:44,359
Speaker 1: and this has had a huge impact on crab populations.

673
00:37:44,400 --> 00:37:47,360
Speaker 1: It's been estimated that in the last fifteen years the

674
00:37:47,440 --> 00:37:50,359
Speaker 1: ants have reduced the crab populations on the island by

675
00:37:50,360 --> 00:37:54,120
Speaker 1: as much as so local land crabs have been put

676
00:37:54,120 --> 00:37:58,080
Speaker 1: severely at risk by the yellow crazy ants. Interestingly, the

677
00:37:58,160 --> 00:38:01,680
Speaker 1: yellow crazy ants exist it on the island for many decades.

678
00:38:01,719 --> 00:38:04,080
Speaker 1: I think they were introduced sometime in the first half

679
00:38:04,080 --> 00:38:06,520
Speaker 1: of the twentieth century. I've seen estimates in the nineteen

680
00:38:06,560 --> 00:38:09,560
Speaker 1: teens or twenties around then. Uh, And they were on

681
00:38:09,600 --> 00:38:13,799
Speaker 1: the island a long time before they became so destructive

682
00:38:13,840 --> 00:38:17,480
Speaker 1: to the land crabs beginning around the nineteen nineties. So

683
00:38:17,520 --> 00:38:21,360
Speaker 1: what changed around the nineteen nineties. I was reading a

684
00:38:21,480 --> 00:38:24,719
Speaker 1: report that was put together by Parks Australia together with

685
00:38:24,800 --> 00:38:28,400
Speaker 1: Latrobe University, and it appears that it was only in

686
00:38:28,440 --> 00:38:32,319
Speaker 1: the nineteen nineties or so that these massive super colonies

687
00:38:32,360 --> 00:38:36,560
Speaker 1: of yellow crazy ants began forming. So what caused that change?

688
00:38:36,600 --> 00:38:39,960
Speaker 1: What happened then? H the author's point to the emergence

689
00:38:40,040 --> 00:38:44,239
Speaker 1: of a mutualism actually a symbiotic relationship, and this is

690
00:38:44,280 --> 00:38:47,520
Speaker 1: a mutualism between the yellow crazy ants and another group

691
00:38:47,560 --> 00:38:51,680
Speaker 1: of insects called scale insects. So it's like the like

692
00:38:51,760 --> 00:38:55,799
Speaker 1: the two enemies, they they forged a truce and and

693
00:38:55,840 --> 00:38:58,719
Speaker 1: then we're united against the forces of the crab. Yes,

694
00:38:59,239 --> 00:39:03,040
Speaker 1: so another non native species, the scale insects. What they

695
00:39:03,080 --> 00:39:06,320
Speaker 1: do is they cling to plant stems and they suck

696
00:39:06,400 --> 00:39:09,120
Speaker 1: the sap from the plants for energy, and they produce

697
00:39:09,239 --> 00:39:13,560
Speaker 1: a sugary waste product from their anal pores in the process.

698
00:39:13,600 --> 00:39:17,000
Speaker 1: And the ants love this sugary poop, they go straight

699
00:39:17,000 --> 00:39:19,319
Speaker 1: to the anal pores and they eat it up. So

700
00:39:19,400 --> 00:39:23,439
Speaker 1: they have formed this mutualistic protective relationship with the tree

701
00:39:23,520 --> 00:39:27,160
Speaker 1: sucking candy poopers. The scale insects suck from the trees,

702
00:39:27,320 --> 00:39:30,680
Speaker 1: they produce sugary poop. The yellow the yellow crazy ants

703
00:39:30,719 --> 00:39:34,200
Speaker 1: eat the sugary poop and they protect the scale insects.

704
00:39:34,239 --> 00:39:37,560
Speaker 1: And it appears that this emerging symbiosis between the yellow

705
00:39:37,600 --> 00:39:40,839
Speaker 1: crazy ants and the scale insects is related to the

706
00:39:40,880 --> 00:39:45,759
Speaker 1: ant's ability to form these ecologically devastating super colonies. But

707
00:39:46,080 --> 00:39:49,120
Speaker 1: here's so, then you take the question one step back, Well,

708
00:39:49,160 --> 00:39:52,520
Speaker 1: what caused this mutualism to begin in the first place. Uh,

709
00:39:52,560 --> 00:39:55,719
Speaker 1: the authors of this report don't know. They speculate that

710
00:39:55,920 --> 00:39:59,759
Speaker 1: changing rainfall patterns on Christmas Island, we're putting stress on

711
00:40:00,040 --> 00:40:04,360
Speaker 1: freeze and this made the sap more concentrated, which means

712
00:40:04,440 --> 00:40:07,799
Speaker 1: it's even more sugary goodness for the scale insects. And

713
00:40:07,880 --> 00:40:12,239
Speaker 1: this increases the population of the scale insects, which produces

714
00:40:12,320 --> 00:40:15,520
Speaker 1: more delicious sugary poop for their yellow ant friends, which

715
00:40:15,560 --> 00:40:18,560
Speaker 1: means more ants to protect the scale insects, which means

716
00:40:18,600 --> 00:40:21,239
Speaker 1: even more scale insects and then you get this dangerous

717
00:40:21,280 --> 00:40:25,000
Speaker 1: feedback loop. It's this is all Christmas Island is in

718
00:40:25,040 --> 00:40:28,800
Speaker 1: so many ways. This uh, this wonderful look at the

719
00:40:29,960 --> 00:40:34,200
Speaker 1: horrible cascading effects of colonialism, of human intervention in general,

720
00:40:34,239 --> 00:40:37,040
Speaker 1: I mean at the macroscopic climate level and at the

721
00:40:37,120 --> 00:40:40,600
Speaker 1: local invasive level. Yet like at every level, we have

722
00:40:40,719 --> 00:40:43,440
Speaker 1: messed with this island. And we messed it with it

723
00:40:43,480 --> 00:40:45,239
Speaker 1: in one way, and now we're messing with it in

724
00:40:45,280 --> 00:40:47,560
Speaker 1: a different way, and and now in fact we're gonna

725
00:40:47,640 --> 00:40:49,840
Speaker 1: keep messing with it in order to try to fix

726
00:40:49,920 --> 00:40:53,520
Speaker 1: part of what we did. Because the question is can

727
00:40:53,600 --> 00:40:56,799
Speaker 1: anything be done to save these amazing red crabs. I mean,

728
00:40:56,840 --> 00:41:00,120
Speaker 1: these are it is a wonderful thing to see these

729
00:41:00,160 --> 00:41:02,600
Speaker 1: animals doing what they do. And so I was reading

730
00:41:02,600 --> 00:41:05,719
Speaker 1: an interesting article about this on the Conversation in UH

731
00:41:05,800 --> 00:41:10,480
Speaker 1: posted in by two Latrobe University professors Susan Lawler and

732
00:41:10,520 --> 00:41:14,319
Speaker 1: Peter Green, and apparently Parks Australia has been trying to

733
00:41:14,320 --> 00:41:17,240
Speaker 1: do all kinds of things to help the crabs survive

734
00:41:17,320 --> 00:41:19,640
Speaker 1: the crazy ants, or to knock the crazy ant super

735
00:41:19,640 --> 00:41:23,200
Speaker 1: colonies back, like they tried poison bading the ants by hand,

736
00:41:23,280 --> 00:41:26,279
Speaker 1: but apparently this is just not an efficient solution. In

737
00:41:26,800 --> 00:41:30,640
Speaker 1: sen they launched a new project, and this was killer wasps.

738
00:41:30,960 --> 00:41:33,399
Speaker 1: Like it tell me more so the killer wasps. They're

739
00:41:33,440 --> 00:41:36,640
Speaker 1: only about two millimeters long and they're naturally found in

740
00:41:36,640 --> 00:41:41,040
Speaker 1: India and Southeast Asia. They're called tach Cardiaphagus summer Villy

741
00:41:41,760 --> 00:41:45,719
Speaker 1: and the author selected this tiny wasp because it attacks

742
00:41:45,760 --> 00:41:49,520
Speaker 1: this specific species of scale insect that has formed the

743
00:41:49,600 --> 00:41:55,440
Speaker 1: mutualistic relationship with the crazy ants. Uh So, the wasp

744
00:41:55,520 --> 00:41:58,920
Speaker 1: is a parasitoid that lays its eggs in the body

745
00:41:59,040 --> 00:42:01,960
Speaker 1: of the female of this one species of scale insect,

746
00:42:02,320 --> 00:42:05,359
Speaker 1: which hatch into more wasps that lay more eggs in

747
00:42:05,400 --> 00:42:09,520
Speaker 1: these species of scale insects, and hopefully this will severely

748
00:42:09,560 --> 00:42:14,040
Speaker 1: control the population of this one particular species of scale insect,

749
00:42:14,080 --> 00:42:16,920
Speaker 1: which is also invasive on the island. Uh And the

750
00:42:16,960 --> 00:42:19,480
Speaker 1: authors note that they've had to be very cautious because

751
00:42:19,520 --> 00:42:22,839
Speaker 1: they cite examples that, you know, in the past, we've

752
00:42:22,840 --> 00:42:26,239
Speaker 1: tried to introduce animals to places in the hope that

753
00:42:26,280 --> 00:42:28,880
Speaker 1: they would control a pest problem, but then they became

754
00:42:28,920 --> 00:42:30,920
Speaker 1: a problem in their own right. They said, the example

755
00:42:30,960 --> 00:42:33,719
Speaker 1: of the cane toad in Australia, which was brought into

756
00:42:33,760 --> 00:42:36,480
Speaker 1: control cane beetles, but then it became its own kind

757
00:42:36,480 --> 00:42:40,239
Speaker 1: of problem. And I'm reminded, of course, of the old

758
00:42:40,320 --> 00:42:42,960
Speaker 1: nursery rhyme. There was an old lady who swallowed a fly, right,

759
00:42:43,440 --> 00:42:47,560
Speaker 1: and she's forced to keep swallowing progressively larger and parasitic

760
00:42:47,600 --> 00:42:50,839
Speaker 1: wasps and larger and more destructive organisms to try and

761
00:42:51,040 --> 00:42:53,200
Speaker 1: uh savor until if she dies at the end of

762
00:42:53,200 --> 00:42:56,080
Speaker 1: the song. Yeah, well, the authors, so we hope that

763
00:42:56,120 --> 00:42:59,960
Speaker 1: doesn't happen. The authors claim they performed rigorous research before

764
00:43:00,040 --> 00:43:02,839
Speaker 1: and uh they tested really hard to make sure this

765
00:43:02,880 --> 00:43:06,479
Speaker 1: wasp would not harm other local species, and they said,

766
00:43:06,560 --> 00:43:09,080
Speaker 1: you know, according to their tests, everything seemed to check out.

767
00:43:09,160 --> 00:43:12,839
Speaker 1: So they introduced the wasps in sixteen. And I checked

768
00:43:12,880 --> 00:43:15,160
Speaker 1: with a more recent news article on the wasp control

769
00:43:15,239 --> 00:43:18,600
Speaker 1: project from it looks like the effort is having early

770
00:43:18,640 --> 00:43:22,279
Speaker 1: markers for success. The wasps have become established, their range

771
00:43:22,280 --> 00:43:24,879
Speaker 1: is spreading, But we'll have to wait a few more

772
00:43:24,920 --> 00:43:27,800
Speaker 1: years before we see the full effect on the crab populations.

773
00:43:27,840 --> 00:43:29,760
Speaker 1: But I hope it works, and I hope it doesn't

774
00:43:29,800 --> 00:43:32,799
Speaker 1: have any unexpected effects. Less to become island of the

775
00:43:32,840 --> 00:43:35,640
Speaker 1: Wasps Kingdom of the Wasps. You don't want to have

776
00:43:35,719 --> 00:43:39,200
Speaker 1: to think about Crab Island needing to be protected. You

777
00:43:39,200 --> 00:43:42,760
Speaker 1: want to think that Crab Island is an armored, claw

778
00:43:42,880 --> 00:43:46,520
Speaker 1: wielding force to be reckoned with, and that it you know,

779
00:43:46,640 --> 00:43:50,239
Speaker 1: it can withstand anything on its own. But I don't know. Yeah,

780
00:43:50,360 --> 00:43:54,560
Speaker 1: natural populations or even unnatural populations are vulnerable. I mean,

781
00:43:54,640 --> 00:43:58,160
Speaker 1: look at Skull Island right King Kong's homeland. Oh, I

782
00:43:58,160 --> 00:44:01,760
Speaker 1: don't know anything about population dynam There a monster island

783
00:44:01,840 --> 00:44:08,279
Speaker 1: where all the giant Japanese monsters with That's clearly these

784
00:44:08,280 --> 00:44:10,120
Speaker 1: are places that need to be protected. We don't need

785
00:44:10,200 --> 00:44:11,719
Speaker 1: to go in there and try and defeat them with

786
00:44:11,719 --> 00:44:15,799
Speaker 1: our robots. Is there is there a crab kaiju? Yes?

787
00:44:15,840 --> 00:44:19,359
Speaker 1: There are. There are crab kaiju up the wazoo. Yes. Nice,

788
00:44:19,840 --> 00:44:23,080
Speaker 1: They have their own movies sometimes. Yeah, Godzillafat want to

789
00:44:23,120 --> 00:44:26,719
Speaker 1: forget its name? I cannot. I can never remember the

790
00:44:26,800 --> 00:44:31,239
Speaker 1: names of the adversary except that maybe it But yeah,

791
00:44:31,280 --> 00:44:33,120
Speaker 1: he fought a giant crab in one episode. It was

792
00:44:33,160 --> 00:44:35,440
Speaker 1: I finally remember it from my childhood. But we'll get

793
00:44:35,440 --> 00:44:37,640
Speaker 1: into We'll get into monster crabs a bit more in

794
00:44:37,680 --> 00:44:40,359
Speaker 1: the next episode of Stuff to Blow Your Mind, because

795
00:44:40,360 --> 00:44:44,440
Speaker 1: we will talk about another resident of Christmas Island that

796
00:44:44,600 --> 00:44:47,920
Speaker 1: is an enormous deco pod. In fact, that the largest

797
00:44:48,320 --> 00:44:52,120
Speaker 1: land crab that you will find on Earth. Now, naturally

798
00:44:52,120 --> 00:44:53,799
Speaker 1: we would love to hear from everybody out there. We

799
00:44:53,840 --> 00:44:57,080
Speaker 1: have listeners all over the world. I wonder if we

800
00:44:57,120 --> 00:45:01,040
Speaker 1: have just a single listener that lives on Christmas Island

801
00:45:02,120 --> 00:45:05,239
Speaker 1: if we do email us yes, Likewise, we have a

802
00:45:05,239 --> 00:45:08,319
Speaker 1: lot of Australian listeners uh and just listeners who have

803
00:45:08,480 --> 00:45:10,959
Speaker 1: traveled around the world. In general, if you have ever

804
00:45:11,080 --> 00:45:14,720
Speaker 1: been to Christmas Island and witnessed any of the species

805
00:45:14,760 --> 00:45:16,799
Speaker 1: we discussed here, or just I mean even if you've

806
00:45:16,800 --> 00:45:19,360
Speaker 1: just been there and you saw nothing at all, we

807
00:45:19,440 --> 00:45:21,560
Speaker 1: want to hear from you. Whatever you have to share

808
00:45:21,560 --> 00:45:25,160
Speaker 1: about Christmas Island would be gratefully appreciated. And in the meantime,

809
00:45:25,200 --> 00:45:26,759
Speaker 1: you can check out all the episodes of Stuff to

810
00:45:26,760 --> 00:45:28,919
Speaker 1: Blow Your Mind. It's Stuff to Blow your Mind dot com.

811
00:45:29,040 --> 00:45:31,759
Speaker 1: That's where you'll find all the episodes, links out to

812
00:45:31,760 --> 00:45:36,280
Speaker 1: our various social media accounts, including uh the discussion module,

813
00:45:36,400 --> 00:45:39,239
Speaker 1: which is our group on Facebook. Look up Stuff to

814
00:45:39,239 --> 00:45:42,080
Speaker 1: Blow your Mind Discussion Module and you can easily join

815
00:45:42,200 --> 00:45:45,200
Speaker 1: that and interact with other listeners as as as well

816
00:45:45,280 --> 00:45:48,359
Speaker 1: as Joe and myself. The website stuff to Blow Your

817
00:45:48,360 --> 00:45:50,800
Speaker 1: Mind dot com also has a link to our store

818
00:45:50,840 --> 00:45:55,480
Speaker 1: where you can buy some cool merchandise stickers, shirts, etcetera. Um,

819
00:45:55,560 --> 00:45:58,480
Speaker 1: it's probably probably a bit late now for for Christmas gifts,

820
00:45:58,640 --> 00:46:00,640
Speaker 1: at least for this Christmas. At hey, you can go

821
00:46:00,680 --> 00:46:03,520
Speaker 1: ahead and start start banking ahead for next year. It's

822
00:46:03,560 --> 00:46:05,040
Speaker 1: a great way to support the show, and if you

823
00:46:05,040 --> 00:46:07,600
Speaker 1: want to support the show without spending a dime, well

824
00:46:07,760 --> 00:46:10,040
Speaker 1: you can simply rate and review us wherever you have

825
00:46:10,120 --> 00:46:12,960
Speaker 1: the power to do so. Huge thanks as always to

826
00:46:13,040 --> 00:46:16,960
Speaker 1: our excellent audio producers Alex Williams and Torry Harrison. If

827
00:46:16,960 --> 00:46:18,800
Speaker 1: you would like to get in touch with this directly

828
00:46:18,840 --> 00:46:21,160
Speaker 1: to let us know feedback on this episode or any other,

829
00:46:21,360 --> 00:46:23,839
Speaker 1: to suggest topic for the future, or just to say hi,

830
00:46:23,960 --> 00:46:25,879
Speaker 1: let us know where you listen from that kind of thing,

831
00:46:26,120 --> 00:46:28,640
Speaker 1: you can email us at blow the Mind at how

832
00:46:28,719 --> 00:46:40,360
Speaker 1: stuff works dot com for more on this and thousands

833
00:46:40,360 --> 00:46:42,680
Speaker 1: of other topics. Is it how stuff works dot com

834
00:47:01,360 --> 00:47:03,239
Speaker 1: must as a tame baby a pro