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Speaker 1: Approximately one percent of all bird species are total jerks. No,

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Speaker 1: approximately one percent of all bird species are not seagulls.

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Speaker 1: They're what are called interspecific brood parasites. And fine, they're

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Speaker 1: not really jerks, but evolution has endowed them with a

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Speaker 1: profoundly jerk like strategy. You see, interspecific brood parasites put

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Speaker 1: their eggs into the nests of other species, often without

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Speaker 1: them knowing it, and to add insult to injury, the

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Speaker 1: parasitic birds often damage the host nest as well. For example,

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Speaker 1: just in case the parents of the parasitized nest can count,

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Speaker 1: the brood parasite takes one of the host eggs out

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Speaker 1: of the nest and yeats it overboard. Now the nest

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Speaker 1: has the same number of eggs as it did before

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Speaker 1: the doting parents went out to grab a quick snack,

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Speaker 1: but those eggs is not their own, and then the

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Speaker 1: brood parasite mom typically SCRAMs, leaving the host parents to

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Speaker 1: do the difficult job of raising the kids. How did

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Speaker 1: this dead beat parenting strategy evolve? And why can't the

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Speaker 1: host species seem to figure out what's happening and fight back.

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Speaker 1: On today's episode, We're going to dig into interspecific brood parasitism,

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Speaker 1: and I'm going to be absolutely thrilled to be combining

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Speaker 1: some of my favorite topics, animal behavior and parasitism. Welcome

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Speaker 1: to Daniel and Kelly's parasitic Universe. Hi.

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Speaker 2: I'm Daniel. I'm a particle physicist, and I have zero

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Speaker 2: tolerance for parasites.

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Speaker 1: Hello. I'm Kelly Waitersmith. I study parasites and space, and

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Speaker 1: I have all the time in the world for parasites.

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Speaker 2: Right, Kelly, with then my question for you today is

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Speaker 2: how many non human species are there in your brood?

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Speaker 1: Oh, you're asking me about pets. You've already asked me

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Speaker 1: about pets. You just found a different way to ask

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Speaker 1: or I guess you know you need an update, right

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Speaker 1: because you asked me this a couple of weeks ago,

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Speaker 1: and the number changes regularly.

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Speaker 2: But now I'm framing them as parasites on Kelly's goodwill.

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Speaker 1: Oh, Oh, probably just my dog Biscuit, because she's been

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Speaker 1: she's been a real handful lately. But no, she's a

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Speaker 1: good girl. I've got a goose that's been trying to

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Speaker 1: bite me lately. I don't appreciate.

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Speaker 2: That that wasn't in the terms of service you got

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Speaker 2: when you got the goose.

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Speaker 1: Now, yeah, we used to call him Jacques Goostow and

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Speaker 1: we thought that was really cute. But now we call

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Speaker 1: him Schmaltz because we're thinking he might become Christmas dinner

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Speaker 1: because he has become very aggressive, So just Schmaltz.

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Speaker 2: Wow, what lesson do you think your kids take from

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Speaker 2: that sort of change in status based on behavior?

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Speaker 1: Well, hmm, that's interesting, based on I don't necessarily want

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Speaker 1: them to take the message that based on behavior these

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Speaker 1: things happen. But I am okay with the fact that

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Speaker 1: they live on a farm and they need to understand

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Speaker 1: where their food comes from, although they've insisted that they

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Speaker 1: won't eat it. But will I was gonna make a

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Speaker 1: joke about them going hungry on Christmas, but I wouldn't

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Speaker 1: do that to them.

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Speaker 2: Well, I think that's a pretty powerful incentive. You know,

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Speaker 2: behave well or you're not going to be here for dinner.

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Speaker 2: You're going to be part of dinner.

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Speaker 1: Yeah, but you know, this isn't an episode on cannibalism,

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Speaker 1: so it really doesn't extend to the family eiting.

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Speaker 2: We already got the pull out.

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Speaker 1: Your bingo cars. But I am under the impression that

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Speaker 1: all of your pets are cherished family members and that

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Speaker 1: none of them you would consider parasites.

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Speaker 2: No, none of our pets are parasites. Currently. We have

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Speaker 2: a dog who lives in our house, and we have

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Speaker 2: a horse who doesn't live in our house. But my

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Speaker 2: daughter Hazel considers part of the family.

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Speaker 1: Oh yeah, I do. I I shouldn't. Well, I'm not

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Speaker 1: going to go down that. I shouldn't have said anything

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Speaker 1: bad about Biscuit. She's been chewing on her feet a

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Speaker 1: lot lately, but we got to get her to the vet.

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Speaker 1: That's my fault.

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Speaker 2: They're doing their best.

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Speaker 1: Yeah, yeah, yeah, yeah, Bescaus, she's a good girl.

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Speaker 2: She's the best girl.

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Speaker 1: Yeah yeah yeah.

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Speaker 2: But today we're not talking about pets we love, who

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Speaker 2: we've welcomed intentionally into our family, even if they do

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Speaker 2: cross the species barrier. We're talking about something much more sinister,

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Speaker 2: aren't we.

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Speaker 1: We are. Actually I should have talked about my livestock

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Speaker 1: guardian dog who choose on our goats, because that's that

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Speaker 1: shouldn't happen.

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Speaker 2: That's sort of how the goats feel about that.

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Speaker 1: They don't they don't love it. Although we've got one

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Speaker 1: goat who kind of spaces out when it's happening, and

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Speaker 1: it doesn't really seem to mind so much because she

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Speaker 1: really likes food and she's just kind of chewing on

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Speaker 1: the grass and he's just playing. But anyway, okay, So, yes,

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Speaker 1: interspecific brood parasitism.

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Speaker 2: Interspecific is a complicated word. It just means cross species.

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Speaker 1: Right, yes, it does. It means yeah, between species. And actually,

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Speaker 1: so when you know, when you say interspecific brood parasitism,

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Speaker 1: it's fun to watch people try to break the different

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Speaker 1: pieces down to try to figure out what it means.

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Speaker 1: And so this is a perfect transition actually to the

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Speaker 1: questions that we asked the listeners. So let's go ahead

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Speaker 1: and see how they broke it down. So I asked

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Speaker 1: our listeners who are willing to volunteer to answer questions

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Speaker 1: for us, what is interspecific brewed parasitism? And I'd like

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Speaker 1: to mention here that you're probably not going to hear

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Speaker 1: as many voices from women as I would like for

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Speaker 1: us to be hearing. And so I would like to

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Speaker 1: make yet another plea for women to please go ahead

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Speaker 1: and answer these questions. It's okay if we don't know

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Speaker 1: the answers, or you know, some of us probably do

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Speaker 1: know the answers. But even if you don't know, add

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Speaker 1: your voice to the chorus of or you know, just

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Speaker 1: go ahead and guess I would like some more women voices.

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Speaker 1: So anyway, let's go ahead and hear what answers we got.

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Speaker 3: It is when a animal family builds up a herd

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Speaker 3: immunity to a certain parasite.

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Speaker 2: I have no idea, you guys got me.

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Speaker 4: Look sure where it is, but it sounds like a

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Speaker 4: parasot that invites the nest and the zombifores the young

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Speaker 4: ones in there.

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Speaker 1: I think the bird lays into eggle, moves its egg

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Speaker 1: into a different bird's nest, and gets that other bird

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Speaker 1: to raise its young, or something like that.

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Speaker 2: I think.

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Speaker 5: I think interspecific brood parasitism is when a parasitic animal

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Speaker 5: fools a different animal species into taking care of its

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Speaker 5: eggs are offspring. And I only know this because my

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Speaker 5: daughters and I watched the PBS Nature documentary on this

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Speaker 5: subject a couple of years ago.

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Speaker 6: I think of broods like egg clutches of species relying

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Speaker 6: on the egg clutches of other species in order to

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Speaker 6: exist and thrive.

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Speaker 7: Probably an interspecies specific parasite or a parasite that goes

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Speaker 7: after a specific species. But the word brood makes me

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Speaker 7: feel like the parasites.

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Speaker 2: Are brooding within their.

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Speaker 3: Host interspecific parasit a brudhism is a tongue twister and

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Speaker 3: something to do with I don't even know what a

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Speaker 3: brood is, like an ipa.

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Speaker 4: I think we're talking about animals like cuckoos. I remember

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Speaker 4: hearing them a lot when I was a child. I'm

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Speaker 4: thinking there was something a bit ikey about their nesting behavior. However,

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Speaker 4: I expect the science here is really interesting.

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Speaker 6: Maybe it's how parasites select for specific characteristics in a

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Speaker 6: host population, or maybe even that parasites doing that guide

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Speaker 6: the evolution of the host population. Either way, I'm sure

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Speaker 6: Kelly's gonna tell us really excitedly.

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Speaker 2: These are great answers, and I'd have to say I

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Speaker 2: don't think I would do very well either here because

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Speaker 2: the phrase interspecific to me hits on the specific instead

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Speaker 2: of species, and so I'm thinking like interspecific as opposed

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Speaker 2: to like inter general, Like what does that even mean?

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Speaker 2: Interspecific is hard for my brain, and brood is not

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Speaker 2: a word I typically use to describe, like people in

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Speaker 2: my species. Who I'm taken care of.

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Speaker 1: Oh, well, you know I went was that an Ohio thing? No,

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Speaker 1: I guess not. But like, so, you know, when I

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Speaker 1: was an undergrad, I thought I was going to go

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Speaker 1: to med school, and then I was like, you know what,

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Speaker 1: I could never deliver to someone the news that like

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Speaker 1: their kid didn't make it. That's not for me. Yeah,

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Speaker 1: And then I decided I was going to go to

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Speaker 1: VET school, and then I was like, you know what,

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Speaker 1: I could never deliver to someone the news that their

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Speaker 1: dog didn't make it, so like, that's not for me either.

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Speaker 1: And then I took an animal behavior class, and I

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Speaker 1: was like, this is what I'm going to do with

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Speaker 1: the rest of my life. And then I ended up

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Speaker 1: going to grad school for behavioral ecology, which is trying

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Speaker 1: to understand, you know, why animals do what they do

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Speaker 1: in the wild. And so that's where I came across

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Speaker 1: the word brood. And so I do think of, you know,

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Speaker 1: my children as my brood. But I probably would not

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Speaker 1: have thought of that had I not gone to grad

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Speaker 1: school for behavioral ecology.

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Speaker 2: Because brood to me implies some sort of like dark

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Speaker 2: Gothic mood, like he stands at the parapet of his castle,

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Speaker 2: brooding over his future or something.

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Speaker 1: Yes, as a goth kid, I had heard the word

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Speaker 1: yes in that way. Yeah.

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Speaker 2: So this is an especially tricky phrase because each word

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Speaker 2: on its own has several meetings with very different contexts,

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Speaker 2: and so putting them all together in the right order,

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Speaker 2: it's tricky stuff. So tell us, Kelly, what the heck

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Speaker 2: is this? Break it down for us in basic English.

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Speaker 1: Okay, So, first of all, I want to note the

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Speaker 1: reason that we are enjoying this amazing topic today is

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Speaker 1: because a listener named Daniel saw a New York Times

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Speaker 1: article on brown headed cowbirds that have this strategy and

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Speaker 1: he wanted to know more. So that's what we're going

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Speaker 1: to talk about today. So, interspecific brood parasitism is when

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Speaker 1: one organism tricks or coerces a parent of a different

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Speaker 1: species into caring for their offspring.

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Speaker 2: So this is not Biscuit being taken care of by you,

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Speaker 2: because that's something you did intentionally. Yeah, add Biscuit to

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Speaker 2: your brood.

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Speaker 1: That's right. I knew that I was adding Biscuit to

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Speaker 1: my brood. I love Biscuit very much. I wish she

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Speaker 1: didn't have allergies. We're working on it. She's great.

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Speaker 2: What about the fact that dogs are like selected for

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Speaker 2: to be cute and to like, you know, pull on

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Speaker 2: your heart strings and effectively emotionally manipulate their way into

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Speaker 2: your Does that count?

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Speaker 1: No, it doesn't. Like you still you're still choosing to join,

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Speaker 1: you know, and like kids are well, I was gonna

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Speaker 1: say kids are cute, but not all kids are cute,

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Speaker 1: but we still love them.

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Speaker 2: I can't believe you just said that on the record.

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Speaker 2: I mean, I totally agree with you. Some kids to

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Speaker 2: collect Winston Churchill or Richard Nixon, but I would never

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Speaker 2: have said that. Oh my god, I just said it.

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Speaker 1: Also, yeah, yeah, yeah, but we love them anyway, right,

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Speaker 1: you don't have to be cute to be absolutely amazing

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Speaker 1: and loved. And so the point with parasitism is you're

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Speaker 1: essentially being tricked or coerced. And Okay, so we're gonna

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Speaker 1: start with my favorite example, and almost all examples involve birds,

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Speaker 1: and so the bird people out there are going to

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Speaker 1: be like, how dare you start with an example that's

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Speaker 1: not birds? But look at people. The fact of the

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Speaker 1: matter is, like number one, I'm a parasite person. But

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Speaker 1: after being a parasite person. I'm a fish person, and

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Speaker 1: so it's gonna be a fish example. So we're going

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Speaker 1: to talk about the cuckoo catfish. All right. So down

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Speaker 1: in Africa there are these cicklids and these are the

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Speaker 1: host species.

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Speaker 2: So this is what's a clid.

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Speaker 1: A cyclid is a fish, and like Africa is sort

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Speaker 1: of famous for their ciclids, these are species that sort

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Speaker 1: of like radiated. There's loads of different species. A bunch

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Speaker 1: of evolutionary biolog just go down to Africa to try

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Speaker 1: to figure out why there's so many different species of

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Speaker 1: this kind of fish in Africa and how they've managed

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Speaker 1: to like fill all of these different niches. So it's

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Speaker 1: just a species that you find in lakes in Africa.

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Speaker 2: Okay, what does it look like? Roughly?

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Speaker 1: H it looks like a fish. You may have gone

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Speaker 1: to a pet store and you can you've seen convict cyclids,

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Speaker 1: Like there's ciclids are a very popular fresh water fish

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Speaker 1: species that you can find at pet stores. And this

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Speaker 1: is like a different species than what you've seen at

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Speaker 1: pet stores, but it's got like the same body shape.

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Speaker 2: Okay.

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Speaker 1: One of them does this amazing thing where they lay

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Speaker 1: eggs and then they stick them in their mouths.

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Speaker 2: On purpose, on purpose, hold them in their mouth to like,

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Speaker 2: you know, keep them safe or something.

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Speaker 1: Yes, they're called mouth brooders.

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Speaker 2: Whoa.

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Speaker 1: And so like these mouth routers they pick up the eggs.

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Speaker 2: Not the same as mouth breathers, right, that's a totally

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Speaker 2: different kind of thing.

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Speaker 1: That's me when I have a cold. These are mouth ruders, okay.

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Speaker 1: And so they pop the eggs in their mouth. The

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Speaker 1: eggs hatch and the fish can swim in and out

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Speaker 1: of the mouth. And so when the fish want to go,

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Speaker 1: like get some food, they'll swim out and they'll like

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Speaker 1: eat little things that are in the water. And then

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Speaker 1: when a predator comes, they swim into mom's mouth for safety.

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Speaker 1: And sometimes Mom will like open her mouth and create

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Speaker 1: an inflow of water to like, you know, help them

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Speaker 1: get in when she sees a predator. And so, like

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Speaker 1: the mouth is a safe place for these little babies.

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Speaker 2: And how do they avoid being eaten? Or how does

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Speaker 2: mom eat with her babies in her mouth?

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Speaker 1: I believe mom ejects the babies when it's time for

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Speaker 1: her to eat ice. And so yeah, like, so the babies,

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Speaker 1: you know, when they're in the egg stage, she might

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Speaker 1: sort of like spit them under a rock for a

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Speaker 1: little while and then go and get a snack and

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Speaker 1: then suck them all back up again. And I'm not

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Speaker 1: an expert on the mouth bruders.

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Speaker 2: It's amazing to me though, that like things other species

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Speaker 2: do sound gross to me, like spitting your babies under

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Speaker 2: a rock from your mouth, but things that our species do,

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Speaker 2: like you know, creating milk from your body and feeding

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Speaker 2: it to your baby, that's not gross to me at all.

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Speaker 2: So it's amazing how your instincts are just like totally parochial.

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Speaker 1: Yes, I will note that Zach stayed on the side

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Speaker 1: of the blanket near my head when labor was happening,

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Speaker 1: and so human birth is pretty gross too.

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Speaker 2: So well, I guess it depends on the husband, because

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Speaker 2: when Hazel was being born and Katuna was having a

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Speaker 2: c section, they were like, please stay on that side,

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Speaker 2: and I was like, you're opening up my wife to

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Speaker 2: pull out my daughter, like I'm gonna watch, and I did,

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Speaker 2: and it was fascinating.

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Speaker 1: I would have been watching, Yeah, yeah, I would have

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Speaker 1: been watching. And then they went to hand Zac the

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Speaker 1: umbilical cord and they're like, do you want to cut?

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Speaker 2: And he was like, yes, that's what I pay you

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Speaker 2: guys for.

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Speaker 7: Yeah.

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Speaker 1: No, wipe that thing off and give it to me

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Speaker 1: when it's clean. But he was very supportive through the

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Speaker 1: whole thing.

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Speaker 2: Interesting for a man whose office is a disaster that

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Speaker 2: he only wants clean things handed to.

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Speaker 1: Yes. Yes, well we're all still trying to understand the

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Speaker 1: emotional support Dorito's bag. But anyway, yes, exactly.

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Speaker 2: All right, So we have this mom who has babies

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Speaker 2: and keeps them in her mouth. Yes, and then that's

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Speaker 2: the host.

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Speaker 1: That's the host. Yes. And so the parasite is called

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Speaker 1: the cuckoo catfish. Who And you know, I think a

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Speaker 1: lot of us have seen catfishes. They've got those like whiskers,

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Speaker 1: they move around on the ground.

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Speaker 2: This one they're good and sandwiches.

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Speaker 1: Hell, sure, sure. This one's kind of tiny. It's like white.

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Speaker 1: It's got some speckles. That doesn't really matter. The point

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Speaker 1: is it's like a tiny catfish.

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Speaker 2: Okay.

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Speaker 1: And so these catfish try to eat the host eggs. Okay.

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Speaker 1: So like when the hosts are first laying the eggs,

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Speaker 1: they have to lay them on the sand before the

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Speaker 1: mom can get them in her mouth. And so well,

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Speaker 1: the eggs are being laid on the sand and getting fertilized.

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Speaker 1: The catfish are going around and trying to eat them,

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Speaker 1: and the parents are freaking out and they're trying to

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Speaker 1: get the catfish to leave, and they're like, go away,

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Speaker 1: go away. And while they're distracted and trying to chase

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Speaker 1: the catfish away, the catfish lay some of their own

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Speaker 1: eggs in amongst the host eggs. Wow, And so then

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Speaker 1: the catfish go away, and so the mom is like, okay, fine,

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Speaker 1: they're gone, Thank goodness. And of course I'm being super

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Speaker 1: anthropomorphic here. Who knows what the mom is thinking. It

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Speaker 1: might just be like, I don't know how smartfish are.

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Speaker 1: So anyway, the mom eventually goes to acquire all of

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Speaker 1: the eggs and she sucks them all up into her mouth,

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Speaker 1: and she has accumulated her eggs and the eggs of

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Speaker 1: the parasitic catfish.

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Speaker 2: I see. So they're not replaced, they're just in addition.

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Speaker 1: They're in addition, right. But the catfish eggs hatch first,

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Speaker 1: so they're like set to hatch faster, and so the

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Speaker 1: catfish eggs hatch before the host eggs hatch. But when

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Speaker 1: the host hatch, the catfish are there ready for a snack.

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Speaker 1: Oh yeah. And so as all the host eggs are hatching,

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Speaker 1: the catfish are eating them one by one.

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Speaker 2: Oh my gosh.

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Speaker 1: And so in a lot of cases, none of the

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Speaker 1: host babies will survive. They will all become catfish snacks,

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Speaker 1: and the parents will spend a significant amount of their

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Speaker 1: energy protecting the catfish babies. So the catfish babies will

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Speaker 1: like leave the mouth. But then when a predator comes,

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Speaker 1: they'll swim towards the you know, the parasitized mom, and

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Speaker 1: the mom will open her mouth to give them a

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Speaker 1: place to hide. Because the mom, you know, recognizes anything

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Speaker 1: that swims out of her mouth as her offspring, and

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Speaker 1: so she has been tricked.

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Speaker 2: Wow. Crazy, that is crazy. Can I ask you how

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Speaker 2: I'm supposed to feel about this? Because I have all

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Speaker 2: of these emotions. When I watch like nature documentaries, I

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Speaker 2: always end up like rooting for one animal. But I

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Speaker 2: find that like, if I'm watching the documentary about cheetahs,

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Speaker 2: I'm rooting for the cheetah as it chases the antelope.

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Speaker 2: If I'm watching the antelope documentary, I'm rooting for the antelope.

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Speaker 2: And I'm like, you, dang, cheetah, what are you doing?

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Speaker 2: So what am I supposed to feel here because it

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Speaker 2: feels like one of these is getting tricked. It feels unfair.

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Speaker 1: Yeah, in all cases, you should be rooting for the

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Speaker 1: tapeworm that lives in all of those animals. But no,

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Speaker 1: you didn't see it coming. But yeah, I'm nature is

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Speaker 1: just it's complicated. There's no clear answer, like I you know,

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Speaker 1: I feel that way also, like when you know, when

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Speaker 1: I'm watching the antelope documentary and the antelope gets away,

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Speaker 1: I'm like, oh, you know, I'm happy with that antelope,

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Speaker 1: but that cheetah maybe had babies that aren't getting fed,

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Speaker 1: and nature is you know, it's not Life isn't fair,

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Speaker 1: especially if you are, you know, living out in the wild.

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Speaker 2: But I feel like parasitism is especially emotionally fraught. Was

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Speaker 2: that what attracted you to this field? Or are you

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Speaker 2: totally impervious to all of that emotion?

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Speaker 1: Oh? Interesting, No, I'm not impervious to the emotion. And like,

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Speaker 1: you know, especially when it's humans who are getting infected,

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Speaker 1: Like I'm totally on board with, yeah, trying to eradicate

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Speaker 1: the parasites that are her people, and.

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Speaker 2: Not just trying to eradicate them, but like feeling angry

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Speaker 2: at them.

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Speaker 1: Yes, yeah, feeling angry at them judgmental, yes, But I

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Speaker 1: also but I still have like a begrudging respect for

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Speaker 1: for example, a species like what was the speci. John

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Speaker 1: Hawden was telling us about a species of parasite that

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Speaker 1: is in our body and is able to essentially like

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Speaker 1: rip proteins off of like our cells and stick it

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Speaker 1: on itself and essentially we're like, uh, you know, host

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Speaker 1: coat to escape from us. And in our Zombie Fish episode,

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Speaker 1: we were talking about trematodes that go through snails and

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Speaker 1: fish and birds, and then they also have a phase

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Speaker 1: where they're swimming through the water. Like imagine being able

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Speaker 1: to succeed in environments that are that different.

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Speaker 2: It's impressive.

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Speaker 1: And you've got immune systems that are trying to attack

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Speaker 1: you in those different kinds of hosts, Like, that's kind

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Speaker 1: of incredible that evolution has come up with solutions in

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Speaker 1: all of those different environments. And so I am begrudgingly

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Speaker 1: impressed with their abilities. And so anyway, I'm amazed with

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Speaker 1: the solutions evolution has come up with for complicated problems.

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Speaker 1: But you know, I don't think that the suffering is

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Speaker 1: funny or wonderful, and especially when it's people, but it

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Speaker 1: still is kind of amazing. It is amazing unless it's

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Speaker 1: happening to people, then it's sticks.

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Speaker 2: Yeah, And I think it's probably misguided to put yourself

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Speaker 2: on one side of it or the other, or to

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Speaker 2: assert like moral superiority or inferiority to one side of

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Speaker 2: these battles, because you know, who knows what these animals

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Speaker 2: are thinking, that they really have choices to make anyway.

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Speaker 2: In the end, we're like really imposing a lot of

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Speaker 2: human values and emotions on these things, which is something

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Speaker 2: weirdly we do, right, Like I impose human emotions on

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Speaker 2: my dog. I interpret my dog's emotions in the context

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Speaker 2: of humanity, And so here I'm like really feeling for

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Speaker 2: the mom, Like not only has she lost her babies,

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Speaker 2: she ended up taking care of the babies that killed

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Speaker 2: her babies.

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Speaker 1: Yeah, I know. And you know what's kind of weird

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Speaker 1: is that, you know, we have all of this human baggage,

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Speaker 1: and we sort of care differently depending on what species

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Speaker 1: we're talking about. So when I was talking about the fish,

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Speaker 1: I didn't feel that bad for the cicklid. They kind

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Speaker 1: of got like empty, vapid looks in their eyes.

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Speaker 2: Your impersonation of the sicklid mom was not especially empathetic.

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Speaker 1: I have to say, yeah, I'm sorry, but like, but

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Speaker 1: we're about to talk about birds and when I when

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Speaker 1: I see the bird babies getting yeated out of the nest,

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Speaker 1: then I feel bad and I don't know why, and

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Speaker 1: it's kind of arbitrary, and humans are arbitrary.

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Speaker 6: I guess.

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Speaker 2: Well, then let's take a break and when we come back,

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Speaker 2: we'll hear about more examples of interspecific brood parasitism, ones

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Speaker 2: that make even Kelly feel bad.

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Speaker 8: Even Kelly, Okay, we're back, and we're talking about species

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Speaker 8: that trick other species.

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Speaker 2: Moms into taking care of their youth for them. Why

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Speaker 2: can't they take care of their own babies, Kelly? What's

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Speaker 2: wrong with them?

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Speaker 1: Well that's a great question. So you know, evolution has

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Speaker 1: now sent them down this path where they can't take

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Speaker 1: care of them anymore because they don't need to. There's

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Speaker 1: this other strategy where they can get somebody else to

435
00:21:26,160 --> 00:21:28,520
Speaker 1: do it. And so to me, the question isn't why

436
00:21:28,560 --> 00:21:30,840
Speaker 1: can't they take care of their own babies anymore? The

437
00:21:30,920 --> 00:21:34,919
Speaker 1: question is why are the host parents allowing this to

438
00:21:34,960 --> 00:21:38,480
Speaker 1: happen to themselves? Which sounds very much like victim blaming, but.

439
00:21:39,880 --> 00:21:41,800
Speaker 2: It why were you wearing that?

440
00:21:41,960 --> 00:21:45,360
Speaker 1: Huh oh? Yeah right, I'm feeling uncomfortable about the phrasing already,

441
00:21:45,640 --> 00:21:48,120
Speaker 1: But so let's walk through. So a big part of

442
00:21:48,359 --> 00:21:51,840
Speaker 1: the way scientists think about this question is how much

443
00:21:51,920 --> 00:21:54,840
Speaker 1: pressure does it put on the host in terms of costs,

444
00:21:54,880 --> 00:21:59,199
Speaker 1: like how much how many babies essentially are they losing

445
00:21:59,280 --> 00:22:01,800
Speaker 1: in a season because this is happening to them, okay,

446
00:22:01,880 --> 00:22:04,879
Speaker 1: And it turns out the answer is it depends a

447
00:22:05,040 --> 00:22:09,159
Speaker 1: lot on what a surprise, Yeah, right, on the details.

448
00:22:09,560 --> 00:22:12,359
Speaker 1: So let's talk about the common cuckoo first, because this

449
00:22:12,400 --> 00:22:15,399
Speaker 1: is one of the most well studied examples, and for

450
00:22:15,440 --> 00:22:18,919
Speaker 1: a common cuckoo, you lose a lot if a common

451
00:22:18,960 --> 00:22:21,480
Speaker 1: cuckoo lays eggs in your nest. Some folks may have

452
00:22:21,520 --> 00:22:24,679
Speaker 1: seen videos of this, because these videos kind of really

453
00:22:24,680 --> 00:22:27,800
Speaker 1: make the rounds when they start getting some traction. But so,

454
00:22:27,880 --> 00:22:30,640
Speaker 1: a common cuckoo will lay an egg in the nest

455
00:22:30,760 --> 00:22:32,920
Speaker 1: of a bird that's much smaller than it is when

456
00:22:33,119 --> 00:22:36,280
Speaker 1: that bird is like off collecting food or something, okay,

457
00:22:36,560 --> 00:22:39,879
Speaker 1: And when the egg hatches, the egg tends to hatch

458
00:22:39,960 --> 00:22:43,639
Speaker 1: again before the host egg hatches, and while that chick

459
00:22:43,720 --> 00:22:47,320
Speaker 1: is still like completely naked, no feathers. It's at the

460
00:22:47,359 --> 00:22:49,960
Speaker 1: stage where it's still like sort of trembling, trying to

461
00:22:50,000 --> 00:22:52,720
Speaker 1: get its body in order. Like its eyes are still closed.

462
00:22:52,800 --> 00:22:54,600
Speaker 2: It feels like a helpless babe or something.

463
00:22:54,680 --> 00:22:57,160
Speaker 1: Yeah, right, you'd imagine like, well, this couldn't do any

464
00:22:57,200 --> 00:22:59,280
Speaker 1: harm at all. Someone needs to take care of this

465
00:22:59,359 --> 00:23:03,000
Speaker 1: poor little bit. It fumbles around the nest and when

466
00:23:03,000 --> 00:23:06,520
Speaker 1: it feels another egg, it puts its back up to

467
00:23:06,600 --> 00:23:08,960
Speaker 1: the egg, lifts its butt up.

468
00:23:09,160 --> 00:23:10,880
Speaker 2: Uh oh, the music just got dark.

469
00:23:11,160 --> 00:23:14,800
Speaker 1: Yeah, gets the egg up on its back, lifts it

470
00:23:14,880 --> 00:23:18,080
Speaker 1: up over the side, and then pushes its neck back

471
00:23:18,200 --> 00:23:21,600
Speaker 1: to throw it over the side of the nest. What

472
00:23:22,320 --> 00:23:25,480
Speaker 1: And it does that over and over and over again

473
00:23:25,920 --> 00:23:28,439
Speaker 1: until it is the only thing in that nest.

474
00:23:28,800 --> 00:23:32,520
Speaker 2: I'm imagining like security footage of some hospital where they

475
00:23:32,560 --> 00:23:34,920
Speaker 2: have the babies in those little trays and like one

476
00:23:34,960 --> 00:23:37,360
Speaker 2: baby is crawling around like pushing all the other babies

477
00:23:37,400 --> 00:23:39,600
Speaker 2: out of the trays. That's the moral equivalent of what's

478
00:23:39,600 --> 00:23:40,360
Speaker 2: happening here, right.

479
00:23:40,520 --> 00:23:44,000
Speaker 1: Oh, yeah, that sounds somehow, that sounds way worse. Again.

480
00:23:44,040 --> 00:23:46,919
Speaker 1: We're back to the humans having different sets of values

481
00:23:47,000 --> 00:23:49,199
Speaker 1: depending on the species. You're talking about, but yes, that

482
00:23:49,200 --> 00:23:50,080
Speaker 1: would be the equivalent.

483
00:23:50,240 --> 00:23:52,280
Speaker 2: So here the cuckoo doesn't just want to be taken

484
00:23:52,320 --> 00:23:55,120
Speaker 2: care of by the mom. It wants like exclusive access.

485
00:23:55,200 --> 00:23:57,600
Speaker 2: Is that because of the food limitation. It's like want

486
00:23:57,640 --> 00:23:59,639
Speaker 2: a bigger share of breakfast?

487
00:23:59,800 --> 00:24:01,600
Speaker 1: Yeah? Yeah, And it is going to grow to be

488
00:24:01,880 --> 00:24:05,560
Speaker 1: much bigger than its host parent, and so it needs

489
00:24:05,640 --> 00:24:07,800
Speaker 1: a lot of food. And if it does happen that

490
00:24:07,920 --> 00:24:11,280
Speaker 1: some of the eggs do hatch before the baby gets

491
00:24:11,280 --> 00:24:13,600
Speaker 1: a chance to push the eggs out, then it will

492
00:24:13,600 --> 00:24:15,280
Speaker 1: just go ahead and push the babies out of the nest.

493
00:24:15,880 --> 00:24:16,760
Speaker 1: It's kind of horrible.

494
00:24:16,880 --> 00:24:19,080
Speaker 2: Is there no limit to what these cuckoos will do?

495
00:24:19,359 --> 00:24:23,000
Speaker 1: I know, I know, darn you cuckoos. And so sometimes

496
00:24:23,080 --> 00:24:25,960
Speaker 1: these babies will grow to be like three times bigger

497
00:24:26,000 --> 00:24:29,200
Speaker 1: than the parents that are frantically trying to feed it. Wow,

498
00:24:29,480 --> 00:24:31,520
Speaker 1: which is crazy, Like you'll see it. It's like, you know,

499
00:24:31,600 --> 00:24:33,879
Speaker 1: the baby cuckoo is like spilling out of the nest

500
00:24:34,160 --> 00:24:36,520
Speaker 1: and the parents are still frantically trying to shove food

501
00:24:36,560 --> 00:24:38,280
Speaker 1: in its mouth as it screams at them like.

502
00:24:38,240 --> 00:24:40,920
Speaker 2: Fe me me, and there's nothing in the parent's brain.

503
00:24:41,040 --> 00:24:44,200
Speaker 2: It's like something is weird here. Or trigger some sort

504
00:24:44,200 --> 00:24:47,119
Speaker 2: of response to it recognizes that it's not its own baby.

505
00:24:47,400 --> 00:24:50,560
Speaker 1: Yeah, all right, So here is where evolutionary biologists gets

506
00:24:50,560 --> 00:24:54,160
Speaker 1: super excited about this system, right, because that should be happening. Yeah,

507
00:24:54,280 --> 00:24:57,360
Speaker 1: and so this has become a really sort of exciting

508
00:24:57,400 --> 00:25:00,560
Speaker 1: system for studying co evolution. And so that is when

509
00:25:00,600 --> 00:25:04,080
Speaker 1: you get evolution happening with both the host and the parasite.

510
00:25:04,119 --> 00:25:06,320
Speaker 1: So what should be happening here is that the host

511
00:25:06,400 --> 00:25:10,040
Speaker 1: should be figuring out some way to detect the cuckoo

512
00:25:10,080 --> 00:25:12,320
Speaker 1: egg so they can throw it out of the nest.

513
00:25:12,840 --> 00:25:14,960
Speaker 1: And then the cuckoo should end up with some way

514
00:25:15,000 --> 00:25:17,520
Speaker 1: to make it harder for the host to detect the

515
00:25:17,520 --> 00:25:19,760
Speaker 1: cuckoo egg, and then you should ends up with this

516
00:25:19,960 --> 00:25:22,960
Speaker 1: arms race where you keep getting the host getting better

517
00:25:23,000 --> 00:25:26,560
Speaker 1: at evicting the cuckoo and the cuckoo getting better at

518
00:25:26,800 --> 00:25:28,639
Speaker 1: tricking the host, and back and forth.

519
00:25:28,720 --> 00:25:31,119
Speaker 2: Yeah, that makes perfect sense. And so is that what

520
00:25:31,200 --> 00:25:34,359
Speaker 2: happens is the cuckoo like developing techniques that it knows

521
00:25:34,400 --> 00:25:38,359
Speaker 2: will take advantage of like weaknesses in the host bird brain.

522
00:25:38,720 --> 00:25:42,679
Speaker 1: Okay, so I sent a picture to you in the outline, Oh,

523
00:25:42,720 --> 00:25:44,639
Speaker 1: and I want you to scroll down.

524
00:25:44,720 --> 00:25:46,680
Speaker 2: Okay, scroll and scroll and scroll in.

525
00:25:46,920 --> 00:25:50,280
Speaker 1: I've shared with Daniel a photo where the top row

526
00:25:50,359 --> 00:25:53,680
Speaker 1: are all eggs that were made by cuckoos, and it's like.

527
00:25:53,640 --> 00:25:56,199
Speaker 2: A bunch of different eggs, is like green and orange

528
00:25:56,320 --> 00:25:59,040
Speaker 2: and ones with squiggles on them and spots, very very

529
00:25:59,080 --> 00:26:00,640
Speaker 2: different kinds of eggs.

530
00:26:00,280 --> 00:26:02,320
Speaker 1: Very different kinds of eggs. And then the bottom row

531
00:26:02,440 --> 00:26:04,879
Speaker 1: are all the host eggs that they're trying to match.

532
00:26:05,200 --> 00:26:08,280
Speaker 2: Wait, those are not from the same species. That's crazy.

533
00:26:08,320 --> 00:26:11,800
Speaker 2: They match exactly. They look like, detail for detail the

534
00:26:11,880 --> 00:26:14,240
Speaker 2: same as the original eggs are.

535
00:26:14,560 --> 00:26:16,560
Speaker 1: Are you just being nice to me or do you

536
00:26:16,600 --> 00:26:18,359
Speaker 1: mean it? Because I think they're pretty good matches.

537
00:26:18,520 --> 00:26:19,600
Speaker 2: They're incredible matches.

538
00:26:19,680 --> 00:26:19,840
Speaker 4: Yeah.

539
00:26:19,880 --> 00:26:21,960
Speaker 2: I mean maybe they're a little bigger or a little

540
00:26:22,000 --> 00:26:25,360
Speaker 2: smaller or whatever. And I don't know what the variation is,

541
00:26:25,880 --> 00:26:29,520
Speaker 2: but the difference between the host and the cuckoo is

542
00:26:29,600 --> 00:26:32,400
Speaker 2: much smaller than the difference between the different species. Yeah,

543
00:26:32,440 --> 00:26:33,720
Speaker 2: so they're pretty good matches, you know.

544
00:26:33,920 --> 00:26:37,080
Speaker 1: Yeah, they're pretty good matches. And there are stories about,

545
00:26:37,160 --> 00:26:40,439
Speaker 1: you know, evolutionary ecologists going out into the field and

546
00:26:40,480 --> 00:26:42,240
Speaker 1: looking at a nest and being like, Okay, I just

547
00:26:42,280 --> 00:26:44,520
Speaker 1: saw a cuckoo lay an egg in here, which one

548
00:26:44,560 --> 00:26:47,439
Speaker 1: is the cuckoo egg and which one is the one

549
00:26:47,480 --> 00:26:48,880
Speaker 1: you know that was laid by the hosts?

550
00:26:49,080 --> 00:26:51,520
Speaker 2: All right, So the cuckoos know that the hosts are

551
00:26:51,520 --> 00:26:53,639
Speaker 2: looking out for this, and they're doing their best to

552
00:26:53,680 --> 00:26:54,880
Speaker 2: camouflage their babies.

553
00:26:55,080 --> 00:26:57,440
Speaker 1: Yeah, and by doing their best, essentially, what we mean

554
00:26:57,600 --> 00:26:59,760
Speaker 1: is that, you know, there's a lot of cuckoos laying

555
00:26:59,760 --> 00:27:03,640
Speaker 1: a lot lot of eggs. Randomly, a cuckoo will lay

556
00:27:03,640 --> 00:27:06,160
Speaker 1: an egg that happens to be a shade or two

557
00:27:06,240 --> 00:27:08,920
Speaker 1: that's a little bit closer, and that egg is less

558
00:27:08,960 --> 00:27:11,520
Speaker 1: likely to be rejected, so that female makes a lot

559
00:27:11,560 --> 00:27:13,800
Speaker 1: more babies that make it to the next generation, and

560
00:27:13,840 --> 00:27:16,120
Speaker 1: their egg also tends to match a little bit more.

561
00:27:16,280 --> 00:27:16,399
Speaker 3: Right.

562
00:27:16,400 --> 00:27:21,160
Speaker 2: There's no intentionality or design here, it's just natural selection, right.

563
00:27:21,040 --> 00:27:25,080
Speaker 1: Yes, exactly, And so over time, these cuckoos have ended

564
00:27:25,160 --> 00:27:28,200
Speaker 1: up with eggs that do an amazing job of matching

565
00:27:28,600 --> 00:27:32,679
Speaker 1: these increasingly complex eggs that their hosts are making, and

566
00:27:32,760 --> 00:27:37,440
Speaker 1: so they have essentially made it very costly for the

567
00:27:37,480 --> 00:27:42,280
Speaker 1: moms to eject an egg from the nest. And so

568
00:27:43,000 --> 00:27:45,840
Speaker 1: there have been cases where, you know, scientists have been

569
00:27:45,840 --> 00:27:48,359
Speaker 1: watching a nest and a mom has looked at the

570
00:27:48,440 --> 00:27:51,040
Speaker 1: eggs in the nest, and you know, presumably you know,

571
00:27:51,119 --> 00:27:53,040
Speaker 1: we don't know what the moms are thinking, but they've

572
00:27:53,080 --> 00:27:56,439
Speaker 1: ejected an egg, and we've seen that a cuckoo has

573
00:27:56,520 --> 00:27:58,560
Speaker 1: laid an egg. We know which one was the cuckoo egg.

574
00:27:58,640 --> 00:28:01,040
Speaker 1: And she ejected her own egg and not the cuckoo egg.

575
00:28:01,119 --> 00:28:03,360
Speaker 2: Oh that's even more tragic.

576
00:28:03,160 --> 00:28:07,280
Speaker 1: I know, right, So mistakes get made, Mistakes get made.

577
00:28:07,920 --> 00:28:09,880
Speaker 2: Well, so when the dad comes back and the mom

578
00:28:10,000 --> 00:28:12,120
Speaker 2: is like, by the way, I killed one of our babies.

579
00:28:12,400 --> 00:28:15,359
Speaker 2: Mistakes were made. Do you think he's could accept that

580
00:28:15,520 --> 00:28:16,359
Speaker 2: passive voice?

581
00:28:16,720 --> 00:28:20,480
Speaker 1: Well, you know, the secret at Daniel is they don't

582
00:28:20,520 --> 00:28:22,280
Speaker 1: actually talk to each other like that.

583
00:28:23,560 --> 00:28:25,560
Speaker 2: Oh I see, So you're saying that's the secret to

584
00:28:25,640 --> 00:28:28,200
Speaker 2: marital harmony is just stop talking to each other.

585
00:28:28,240 --> 00:28:32,040
Speaker 1: That's right. Low communication ability, that's the key.

586
00:28:32,200 --> 00:28:34,520
Speaker 2: This is not a marriage advice podcast, by.

587
00:28:34,440 --> 00:28:36,760
Speaker 1: The way, that's right, that's right. Yes, please go somewhere

588
00:28:36,760 --> 00:28:39,000
Speaker 1: else for that where we're going to get you in trouble.

589
00:28:39,400 --> 00:28:42,160
Speaker 1: But parents will start using other information in the environment.

590
00:28:42,280 --> 00:28:44,760
Speaker 1: So you know, scientists will go out there and they

591
00:28:44,800 --> 00:28:49,240
Speaker 1: will like put a mimic cuckoo egg in a bird's

592
00:28:49,280 --> 00:28:52,800
Speaker 1: nest and they'll note that, like the birds won't respond

593
00:28:52,840 --> 00:28:55,239
Speaker 1: to it. They'll like look at their nest and they

594
00:28:55,280 --> 00:28:59,040
Speaker 1: won't eject any eggs. But if you put a stuffed

595
00:28:59,040 --> 00:29:03,760
Speaker 1: cuckoo near their nest, they'll be like, oh, those jerks

596
00:29:03,800 --> 00:29:08,240
Speaker 1: are around, they might be, and then they'll start ejecting eggs.

597
00:29:08,320 --> 00:29:10,560
Speaker 1: And so, you know, they're trying to collect at your information,

598
00:29:10,680 --> 00:29:13,440
Speaker 1: like how high is the risk are there cuckoos in

599
00:29:13,480 --> 00:29:15,400
Speaker 1: the area. If so, maybe I'm going to have to

600
00:29:15,440 --> 00:29:18,080
Speaker 1: take a closer look at my eggs boy, And so

601
00:29:18,160 --> 00:29:20,520
Speaker 1: you know, it's not like they're just sort of passively

602
00:29:20,560 --> 00:29:24,440
Speaker 1: accepting things. They're constantly looking collecting information about risk. Sometimes

603
00:29:24,480 --> 00:29:27,440
Speaker 1: they're making mistakes. It's getting increasingly complicated.

604
00:29:27,560 --> 00:29:30,760
Speaker 2: Wow, but what about the scenario we talked about originally

605
00:29:31,080 --> 00:29:33,160
Speaker 2: where now you have this cuckoo and it's growing and

606
00:29:33,200 --> 00:29:35,920
Speaker 2: it's like much bigger than your own babies. Isn't that

607
00:29:35,960 --> 00:29:38,520
Speaker 2: a clear signal? How can the cuckoos continue to be

608
00:29:38,600 --> 00:29:41,560
Speaker 2: fed by the mom when they're so outrageously big.

609
00:29:41,840 --> 00:29:44,520
Speaker 1: Yeah, So there are examples in some systems or with

610
00:29:44,600 --> 00:29:47,680
Speaker 1: some of the two hundred plus hosts of common cuckoos

611
00:29:48,080 --> 00:29:51,640
Speaker 1: where the hatchling will get rejected at that stage where

612
00:29:51,680 --> 00:29:55,200
Speaker 1: like a mom or dad or whatever will be like, ah,

613
00:29:55,640 --> 00:29:58,000
Speaker 1: darn it, you know, we thought we had this figured out,

614
00:29:58,040 --> 00:30:00,160
Speaker 1: but you are clearly not our own, and the just

615
00:30:00,200 --> 00:30:04,760
Speaker 1: abandon the nest. But there's also selection for cuckoo offspring

616
00:30:05,280 --> 00:30:10,640
Speaker 1: to like have the features that the parents are looking for. So,

617
00:30:10,680 --> 00:30:14,320
Speaker 1: for example, some offspring have very particular markings inside of

618
00:30:14,360 --> 00:30:17,480
Speaker 1: their mouths that the parents queue in on when they're

619
00:30:17,520 --> 00:30:21,160
Speaker 1: bringing food, and they can be you know, like orange splotches,

620
00:30:21,240 --> 00:30:23,880
Speaker 1: and so sometimes cuckoos will have like these very species

621
00:30:23,920 --> 00:30:26,600
Speaker 1: specific markings on the inside of their mouths. And I

622
00:30:26,600 --> 00:30:29,080
Speaker 1: forget if this is common cuckoos in particular or other

623
00:30:29,200 --> 00:30:31,800
Speaker 1: species of cuckoos, because there's a lot of cuckoo species

624
00:30:31,840 --> 00:30:34,520
Speaker 1: with a lot of different strategies. But there is also

625
00:30:34,520 --> 00:30:37,600
Speaker 1: an arms race at various other stages. So yes, there's

626
00:30:37,640 --> 00:30:40,320
Speaker 1: the egg recognition stage, but then there's also the hatchling

627
00:30:40,360 --> 00:30:43,280
Speaker 1: recognition stage. Yeah, there's a lot going on. And so

628
00:30:43,560 --> 00:30:46,600
Speaker 1: not only does it vary depending on like how well

629
00:30:46,680 --> 00:30:50,120
Speaker 1: the eggs match or how well the hatchling matches, but

630
00:30:50,200 --> 00:30:55,320
Speaker 1: there's also pressure depending on how bad the situation is

631
00:30:55,360 --> 00:30:57,160
Speaker 1: for the parents. So like if you've got a common

632
00:30:57,200 --> 00:31:00,720
Speaker 1: cuckoo hatchling that's going to throw all your eggs out.

633
00:31:01,080 --> 00:31:03,400
Speaker 1: There's a lot of pressure to get that right. But

634
00:31:03,920 --> 00:31:07,200
Speaker 1: sometimes there are some other species of birds that will

635
00:31:07,240 --> 00:31:11,160
Speaker 1: like lay one egg in your nest, they won't throw

636
00:31:11,200 --> 00:31:14,280
Speaker 1: your eggs out, and their offspring will take about as

637
00:31:14,360 --> 00:31:17,480
Speaker 1: much energy as the rest, and so the parents still

638
00:31:17,520 --> 00:31:20,360
Speaker 1: get all of their babies that will hatch out. Maybe

639
00:31:20,360 --> 00:31:21,960
Speaker 1: they all get a little bit less food than they

640
00:31:21,960 --> 00:31:24,480
Speaker 1: would have otherwise, but in that case there's a lot

641
00:31:24,560 --> 00:31:27,760
Speaker 1: less like selective pressure to figure out which egg doesn't

642
00:31:27,760 --> 00:31:31,640
Speaker 1: belong and kick out the intruder, because you know your

643
00:31:31,640 --> 00:31:33,920
Speaker 1: babies are still going to survive. So we see a

644
00:31:33,920 --> 00:31:37,280
Speaker 1: lot of variability depending on what the parasite species is

645
00:31:37,320 --> 00:31:39,000
Speaker 1: and what it does to the host, on whether or

646
00:31:39,080 --> 00:31:41,400
Speaker 1: not hosts are just like they tolerate what's going to

647
00:31:41,440 --> 00:31:44,040
Speaker 1: happen to them, or if they're like actively trying to

648
00:31:44,080 --> 00:31:47,240
Speaker 1: fight back against you know, the presence of parasites in

649
00:31:47,240 --> 00:31:47,800
Speaker 1: the area.

650
00:31:47,840 --> 00:31:49,800
Speaker 2: And for birds, is it both moms and dads that

651
00:31:49,800 --> 00:31:52,160
Speaker 2: are feeding the babies. Do they both need to evolve

652
00:31:52,200 --> 00:31:54,120
Speaker 2: this or the dad's involved? How does that work?

653
00:31:54,280 --> 00:31:56,959
Speaker 1: Depends on the species. Sometimes the dads are involved. Sometimes

654
00:31:56,960 --> 00:32:00,240
Speaker 1: the dads aren't involved. I think in general the pressure

655
00:32:00,280 --> 00:32:03,040
Speaker 1: is more on the moms. And so there's a big

656
00:32:03,160 --> 00:32:06,480
Speaker 1: question in the field how do the parents figure out

657
00:32:06,520 --> 00:32:09,800
Speaker 1: what their eggs should look like? So initially there was

658
00:32:09,960 --> 00:32:13,520
Speaker 1: this idea that maybe moms figure out what their eggs

659
00:32:13,640 --> 00:32:17,160
Speaker 1: should look like by like the very first egg they

660
00:32:17,160 --> 00:32:19,560
Speaker 1: see in their nest. They will like imprint on that

661
00:32:19,680 --> 00:32:21,480
Speaker 1: and use that as a template for the rest of

662
00:32:21,520 --> 00:32:23,760
Speaker 1: their lives. But if they make the nest and the

663
00:32:23,880 --> 00:32:25,600
Speaker 1: very first thing that shows up in their nest is

664
00:32:25,640 --> 00:32:27,880
Speaker 1: a cuckoo egg, is that going to mess things up

665
00:32:27,880 --> 00:32:30,080
Speaker 1: for the rest of their lives. And it turns out

666
00:32:30,080 --> 00:32:31,920
Speaker 1: that's probably not how it works. It looks like maybe

667
00:32:31,960 --> 00:32:35,000
Speaker 1: at the beginning of every season for like this, for

668
00:32:35,200 --> 00:32:37,040
Speaker 1: some of the species that we've looked at the very

669
00:32:37,080 --> 00:32:40,120
Speaker 1: first egg that they lay, they turn around and they're like,

670
00:32:40,480 --> 00:32:41,240
Speaker 1: that's what I do.

671
00:32:42,080 --> 00:32:44,000
Speaker 2: That just came out of me. So that's that's a me.

672
00:32:44,560 --> 00:32:48,760
Speaker 1: That's a me. That's a me. Uh And it's not

673
00:32:48,800 --> 00:32:51,720
Speaker 1: like it's monogrammed or something. But like, and the problem is,

674
00:32:51,760 --> 00:32:54,800
Speaker 1: you know, like you mentioned, there's variability, and so you know,

675
00:32:54,840 --> 00:32:56,920
Speaker 1: you hope that's a pretty good representation of what you're

676
00:32:56,960 --> 00:32:59,280
Speaker 1: going to be doing that season, But that seems to

677
00:32:59,320 --> 00:32:59,920
Speaker 1: be kind of how.

678
00:32:59,840 --> 00:33:02,280
Speaker 2: They do it, and the pressures must be complicated also

679
00:33:02,400 --> 00:33:05,600
Speaker 2: because like, if the cuckoo is too successful, then it's

680
00:33:05,680 --> 00:33:08,200
Speaker 2: essentially going to kill off the host, right then there'll

681
00:33:08,200 --> 00:33:11,000
Speaker 2: be no host babies to grow up to be tricked

682
00:33:11,080 --> 00:33:14,520
Speaker 2: parents to raise the next generation of cuckoos. So isn't

683
00:33:14,520 --> 00:33:16,520
Speaker 2: there pressure for the cuckoos to not push all the

684
00:33:16,560 --> 00:33:17,760
Speaker 2: other babies out of the nest.

685
00:33:17,920 --> 00:33:20,520
Speaker 1: So in situations like that, you can get cycling. So

686
00:33:20,560 --> 00:33:22,760
Speaker 1: if you do end up with a whole lot of

687
00:33:22,800 --> 00:33:25,680
Speaker 1: cuckoos one year, then the next year there's just not

688
00:33:25,840 --> 00:33:29,160
Speaker 1: going to be a lot of parents. Yes, there's not

689
00:33:29,160 --> 00:33:31,040
Speaker 1: going to be a lot of host nests that you

690
00:33:31,120 --> 00:33:33,080
Speaker 1: can lay eggs, and so a lot of cuckoos are

691
00:33:33,120 --> 00:33:35,120
Speaker 1: just not going to be successful. So there won't be

692
00:33:35,120 --> 00:33:37,440
Speaker 1: a lot of cuckoos the year after that or you know,

693
00:33:37,480 --> 00:33:40,120
Speaker 1: five years after that or something, depending on how long

694
00:33:40,160 --> 00:33:41,000
Speaker 1: the cycling takes.

695
00:33:41,120 --> 00:33:42,760
Speaker 2: So it's self regulating that, Yeah, it's.

696
00:33:42,640 --> 00:33:43,600
Speaker 1: Self regulating that way.

697
00:33:43,680 --> 00:33:44,120
Speaker 2: Interesting.

698
00:33:44,880 --> 00:33:47,280
Speaker 1: I'm sure there are some cases where cuckoos, for example,

699
00:33:47,320 --> 00:33:50,800
Speaker 1: have driven local species locally to you know, extinction. Or

700
00:33:50,840 --> 00:33:55,000
Speaker 1: extirpation now, and that at the cuckoos again, that's right,

701
00:33:55,040 --> 00:33:57,600
Speaker 1: But usually my sense is that usually you would get

702
00:33:57,880 --> 00:33:58,800
Speaker 1: something like cycling.

703
00:33:59,040 --> 00:34:01,040
Speaker 2: And I don't even know what a cuckoo looks like.

704
00:34:01,160 --> 00:34:04,800
Speaker 2: Is it cute? Because weirdly that affects my emotional reaction here.

705
00:34:06,280 --> 00:34:09,359
Speaker 1: It's pretty cute. Yeah, I mean, yeah, it's pretty cute.

706
00:34:09,360 --> 00:34:11,640
Speaker 1: It's got like bars on its chest, something that it's

707
00:34:11,719 --> 00:34:15,640
Speaker 1: kind of meant to mimic some raptors, so that warblers,

708
00:34:16,480 --> 00:34:18,720
Speaker 1: we'll leave it alone a little bit rather than mobbing

709
00:34:18,719 --> 00:34:21,719
Speaker 1: it because they're scared of it, at least initially, and

710
00:34:21,719 --> 00:34:23,680
Speaker 1: then they realize, oh, you're a cuckoo. You're not gonna

711
00:34:23,680 --> 00:34:25,400
Speaker 1: eat me. I hate you, and then they'll try to

712
00:34:25,440 --> 00:34:26,000
Speaker 1: chase it away.

713
00:34:26,880 --> 00:34:29,279
Speaker 2: All right, let's take a break, and when we come back,

714
00:34:29,320 --> 00:34:33,000
Speaker 2: we'll hear about why sometimes birds might even tolerate these

715
00:34:33,000 --> 00:34:56,120
Speaker 2: invaders in their nests even when they do discover them. Okay,

716
00:34:56,200 --> 00:35:00,439
Speaker 2: we're back, and we're talking about interspecific breed parasitism, when

717
00:35:00,560 --> 00:35:04,759
Speaker 2: birds or fish are tricked into raising birds of another species.

718
00:35:05,360 --> 00:35:07,960
Speaker 2: And we've heard all about the clever tricks cuckoos use

719
00:35:08,360 --> 00:35:11,560
Speaker 2: and other birds used to avoid being spotted. But you

720
00:35:11,560 --> 00:35:15,399
Speaker 2: were also telling me Kelly about the mafia hypothesis that

721
00:35:15,440 --> 00:35:18,600
Speaker 2: there's an idea for why these birds might actually tolerate

722
00:35:19,000 --> 00:35:21,280
Speaker 2: these invaders in their nest. What is that all about?

723
00:35:21,520 --> 00:35:24,359
Speaker 1: Yeah, so one person noted, like, you know, wow, there's

724
00:35:24,360 --> 00:35:26,799
Speaker 1: a lot of instances where it really seems like a

725
00:35:26,800 --> 00:35:29,480
Speaker 1: host bird should have been able to notice that there

726
00:35:29,520 --> 00:35:32,000
Speaker 1: was a like parasitic egg in its nest, it should

727
00:35:32,000 --> 00:35:35,280
Speaker 1: have thrown it out, but it didn't. What other reason

728
00:35:35,320 --> 00:35:37,799
Speaker 1: could we come up with for why a host bird

729
00:35:37,920 --> 00:35:41,560
Speaker 1: might tolerate it? And one idea that I believe it

730
00:35:41,560 --> 00:35:45,120
Speaker 1: was a matsahave came up with, was that maybe they're

731
00:35:45,120 --> 00:35:48,879
Speaker 1: being coerced. Maybe it's sort of like a mafia sort

732
00:35:48,920 --> 00:35:51,160
Speaker 1: of thing where if they were to kick it out,

733
00:35:51,600 --> 00:35:54,560
Speaker 1: if they were to destroy the parasite eggs, then the

734
00:35:54,680 --> 00:35:58,719
Speaker 1: parents would come back and would like take retribution in

735
00:35:58,760 --> 00:36:01,840
Speaker 1: some way. Oh and there've actually been a couple tests

736
00:36:01,840 --> 00:36:05,120
Speaker 1: of this. So, for example, brown headed cowbirds, which you

737
00:36:05,120 --> 00:36:12,160
Speaker 1: can find in the United States, they parasitize prothenatterie warblers

738
00:36:12,600 --> 00:36:15,480
Speaker 1: I'm just gonna call them warblers because nobody wants to

739
00:36:15,480 --> 00:36:17,719
Speaker 1: hear me stumble over that again. And there was this

740
00:36:17,760 --> 00:36:22,720
Speaker 1: experiment where they had these greased poles with nest boxes

741
00:36:22,800 --> 00:36:24,880
Speaker 1: up top. And the reason it's important to know they

742
00:36:24,880 --> 00:36:28,040
Speaker 1: had greased poles is because snakes and small mammals couldn't

743
00:36:28,080 --> 00:36:31,480
Speaker 1: get up the greased poles to eat the eggs. And

744
00:36:31,560 --> 00:36:34,160
Speaker 1: so now you can sort of control predation and know

745
00:36:34,480 --> 00:36:37,000
Speaker 1: what got the eggs, because the only thing that could

746
00:36:37,040 --> 00:36:38,920
Speaker 1: steal the eggs from the nest would be things that

747
00:36:38,960 --> 00:36:42,239
Speaker 1: could fly up there. Okay, all right, So they had

748
00:36:42,280 --> 00:36:45,759
Speaker 1: three different treatments. They knew that cowbirds had laid their

749
00:36:45,760 --> 00:36:49,520
Speaker 1: eggs in each of the warbler nests. In the first treatment,

750
00:36:49,920 --> 00:36:53,480
Speaker 1: they removed the cowbird egg, so the parasite egg was

751
00:36:53,520 --> 00:36:57,840
Speaker 1: taken out. In the second treatment, they left the cowbird

752
00:36:57,880 --> 00:37:02,520
Speaker 1: egg in there. Their treatment, they took out the cowbird egg,

753
00:37:03,040 --> 00:37:05,360
Speaker 1: and then they narrowed the hole a little bit so

754
00:37:05,440 --> 00:37:08,560
Speaker 1: the warblers could still get in, but the cowbirds, which

755
00:37:08,560 --> 00:37:11,080
Speaker 1: are bigger, couldn't get in anymore.

756
00:37:10,719 --> 00:37:11,120
Speaker 2: All right.

757
00:37:11,600 --> 00:37:13,520
Speaker 1: And then they looked to see what happened to the

758
00:37:13,560 --> 00:37:15,920
Speaker 1: host eggs which had been left in all of the

759
00:37:15,960 --> 00:37:19,840
Speaker 1: nest boxes. And what they found was that the nests

760
00:37:20,040 --> 00:37:22,520
Speaker 1: where they had removed the cowbird.

761
00:37:22,000 --> 00:37:23,840
Speaker 2: Eggs the invading eggs.

762
00:37:23,480 --> 00:37:29,359
Speaker 1: The invading eggs, the host eggs had been destroyed when

763
00:37:29,400 --> 00:37:32,920
Speaker 1: a cowbird egg was removed, but that didn't happen when

764
00:37:32,960 --> 00:37:36,800
Speaker 1: the cowbird egg was removed, But the cowbirds couldn't get

765
00:37:36,960 --> 00:37:39,799
Speaker 1: into the nest because the hole had been narrowed, and

766
00:37:40,200 --> 00:37:42,960
Speaker 1: it didn't happen when the cowbird egg was left in

767
00:37:43,040 --> 00:37:46,520
Speaker 1: the nest. And so it really looked like the cowbirds

768
00:37:46,520 --> 00:37:52,320
Speaker 1: were coming back and taking retribution on the warblers. You

769
00:37:52,520 --> 00:37:55,239
Speaker 1: presume they thought the warblers had removed the eggs and

770
00:37:55,239 --> 00:37:58,520
Speaker 1: they were taking retribution. And why would they do that. Well,

771
00:37:58,960 --> 00:38:04,160
Speaker 1: when the warbler nest fails, they'll remove everything from that

772
00:38:04,320 --> 00:38:07,920
Speaker 1: nest and start over again. And when they start over again,

773
00:38:08,760 --> 00:38:11,960
Speaker 1: they're probably gonna accept the cowbird egg the next time,

774
00:38:12,400 --> 00:38:15,440
Speaker 1: and if they don't, they'll get attacked again. And so

775
00:38:15,560 --> 00:38:18,799
Speaker 1: this is the cowbird's way of saying, Hey, you've got

776
00:38:18,800 --> 00:38:21,920
Speaker 1: another chance, make the right decision the next time.

777
00:38:22,600 --> 00:38:25,040
Speaker 2: Awfully nice nest you've got here, be a shame if

778
00:38:25,040 --> 00:38:26,239
Speaker 2: something more to happen to it.

779
00:38:26,480 --> 00:38:30,000
Speaker 1: That's right, exactly, I see. There have been some other

780
00:38:30,040 --> 00:38:32,480
Speaker 1: experiments that people have done that have gotten similar results.

781
00:38:32,520 --> 00:38:35,759
Speaker 1: There's also some evidence of what we call farming. And

782
00:38:35,800 --> 00:38:39,320
Speaker 1: the idea here is that if a parasitic bird arrives

783
00:38:39,360 --> 00:38:42,080
Speaker 1: too late in a season and the eggs are about

784
00:38:42,120 --> 00:38:44,480
Speaker 1: to hatch, like the host eggs are about to hatch,

785
00:38:44,840 --> 00:38:47,040
Speaker 1: that would be bad for them because their babies need

786
00:38:47,040 --> 00:38:49,799
Speaker 1: that head start, and so they'll go through and they'll

787
00:38:49,840 --> 00:38:52,279
Speaker 1: destroy a bunch of nests, so the parents have to

788
00:38:52,280 --> 00:38:55,040
Speaker 1: start over again. And when the parents start over again,

789
00:38:55,400 --> 00:38:57,799
Speaker 1: they'll go and lay their eggs in those nests. And

790
00:38:57,840 --> 00:39:01,120
Speaker 1: so they call that farming because they're essentially like creating

791
00:39:01,200 --> 00:39:03,959
Speaker 1: resources for themselves that they'll be able to use because

792
00:39:04,000 --> 00:39:05,640
Speaker 1: now they're at the right stage at the right time.

793
00:39:05,960 --> 00:39:09,799
Speaker 2: And this implies somehow that the host bird, the one

794
00:39:09,840 --> 00:39:13,000
Speaker 2: that destroyed the invading eggs the first time and not

795
00:39:13,160 --> 00:39:16,359
Speaker 2: the second time, has like learned this, you know, because

796
00:39:16,400 --> 00:39:19,240
Speaker 2: like in the mafia example, you're very clear, you're like, look,

797
00:39:19,320 --> 00:39:21,080
Speaker 2: I'm going to bust up your shop if you don't

798
00:39:21,080 --> 00:39:24,480
Speaker 2: pay the protection money or whatever. But there's no conversation

799
00:39:24,600 --> 00:39:28,080
Speaker 2: between these birds. So the host has to effectively learn

800
00:39:28,239 --> 00:39:31,520
Speaker 2: this behavior. This is like negative reinforcement of this behavior.

801
00:39:31,719 --> 00:39:33,520
Speaker 2: That's something that these birds are capable of.

802
00:39:33,719 --> 00:39:35,600
Speaker 1: It seems that they are. I would bet that not

803
00:39:35,719 --> 00:39:38,319
Speaker 1: all species catch on, and I would bet that some

804
00:39:38,960 --> 00:39:42,319
Speaker 1: couples need to learn the lesson more than once. And

805
00:39:42,360 --> 00:39:44,800
Speaker 1: I should note that we don't always see this happening.

806
00:39:44,840 --> 00:39:49,080
Speaker 1: Not all bird species that do interspecific breed parasitism use

807
00:39:49,120 --> 00:39:52,959
Speaker 1: this mafia strategy. Yeah, and we don't always even see

808
00:39:53,000 --> 00:39:56,719
Speaker 1: the species that do this using the mafia strategy all

809
00:39:56,760 --> 00:39:58,959
Speaker 1: the time. And so I think a lot of these

810
00:39:59,320 --> 00:40:01,920
Speaker 1: parasitic birds will lay their eggs in a bunch of

811
00:40:01,920 --> 00:40:04,719
Speaker 1: different nests, and so some years maybe they're like, oh,

812
00:40:04,760 --> 00:40:06,160
Speaker 1: you know what, I've laid one hundred eggs and one

813
00:40:06,200 --> 00:40:07,960
Speaker 1: hundred different nests. I don't need to watch them all.

814
00:40:07,960 --> 00:40:11,520
Speaker 1: This was a great year for me, but it But

815
00:40:11,640 --> 00:40:13,680
Speaker 1: in some years where maybe the stakes are higher, they

816
00:40:13,760 --> 00:40:16,040
Speaker 1: might be like watching a little bit more closely, you know.

817
00:40:16,520 --> 00:40:19,879
Speaker 1: So yeah, I'm guessing it doesn't always go according to plan.

818
00:40:19,960 --> 00:40:21,480
Speaker 1: But there are some years where they give it a

819
00:40:21,480 --> 00:40:24,759
Speaker 1: shot and hope that the message sticks and other years

820
00:40:24,760 --> 00:40:26,200
Speaker 1: where it doesn't work as well.

821
00:40:26,360 --> 00:40:28,840
Speaker 2: And so just so that I understand, this is not

822
00:40:28,960 --> 00:40:33,359
Speaker 2: a selection thing where you're just choosing the nests where

823
00:40:33,400 --> 00:40:38,040
Speaker 2: you don't get destroyed by cutting off the reproduction path

824
00:40:38,160 --> 00:40:40,600
Speaker 2: of those that have destroyed it. You're really teaching these

825
00:40:40,600 --> 00:40:43,600
Speaker 2: birds that if you destroy the invading eggs, we will

826
00:40:43,600 --> 00:40:46,520
Speaker 2: also destroy your eggs. So this is like within the

827
00:40:46,560 --> 00:40:50,640
Speaker 2: life cycle of an individual bird, not like within generations

828
00:40:50,680 --> 00:40:51,239
Speaker 2: of that host.

829
00:40:51,440 --> 00:40:53,560
Speaker 1: That's right, Yeah, this is within the So for some

830
00:40:53,800 --> 00:40:56,680
Speaker 1: bird species, they're able to have multiple nests in a year,

831
00:40:57,320 --> 00:41:00,600
Speaker 1: and if their nest gets destroyed early in the year,

832
00:41:01,200 --> 00:41:03,680
Speaker 1: then they're able to start a new nest sooner, and

833
00:41:03,719 --> 00:41:05,799
Speaker 1: maybe they can go through more cycles, or maybe they

834
00:41:05,800 --> 00:41:10,480
Speaker 1: can just do one cycle if their nest goes through

835
00:41:10,520 --> 00:41:12,799
Speaker 1: the normal timing, but maybe they can get two in

836
00:41:12,840 --> 00:41:15,080
Speaker 1: there if the first one is destroyed and they restart.

837
00:41:15,360 --> 00:41:17,359
Speaker 2: And to really convince yourself with this, wouldn't you want

838
00:41:17,360 --> 00:41:20,880
Speaker 2: to do something like analyze the behavior of the birds

839
00:41:20,920 --> 00:41:23,680
Speaker 2: who had their nest destroyed relative to those who didn't,

840
00:41:23,680 --> 00:41:27,239
Speaker 2: to see if they're like less likely to kick out

841
00:41:27,280 --> 00:41:28,240
Speaker 2: the invading eggs.

842
00:41:29,000 --> 00:41:31,640
Speaker 1: Yes, right, So you are wanting to know how well

843
00:41:31,680 --> 00:41:34,520
Speaker 1: this strategy works. Yeah, yeah, it would be great to

844
00:41:34,560 --> 00:41:37,520
Speaker 1: know how well the strategy works, as opposed to just

845
00:41:38,120 --> 00:41:43,239
Speaker 1: saying that like brown headed cowbirds are real jerks. Yes, yeah,

846
00:41:43,280 --> 00:41:44,879
Speaker 1: it would be great to have those data. I'm under

847
00:41:44,880 --> 00:41:46,640
Speaker 1: the impression that we don't have those data, and that

848
00:41:46,640 --> 00:41:49,120
Speaker 1: the people who have done the follow up work have

849
00:41:49,239 --> 00:41:52,120
Speaker 1: been like, wow, well we didn't actually see it happen

850
00:41:52,160 --> 00:41:54,040
Speaker 1: at all this time, and so maybe it's sort of

851
00:41:54,080 --> 00:41:54,680
Speaker 1: a rare thing.

852
00:41:55,080 --> 00:41:58,320
Speaker 2: Interesting. Yes, so we're at the cutting edge of understanding

853
00:41:58,440 --> 00:41:59,800
Speaker 2: mafia behavior in birds.

854
00:42:00,120 --> 00:42:02,560
Speaker 1: Yes, and maybe we will end up discovering actually, this

855
00:42:02,600 --> 00:42:04,360
Speaker 1: is the thing that happens pretty rarely. And maybe it

856
00:42:04,400 --> 00:42:07,440
Speaker 1: happens pretty rarely because birds aren't brilliant. They don't pick

857
00:42:07,480 --> 00:42:08,320
Speaker 1: it up real fast.

858
00:42:11,080 --> 00:42:13,080
Speaker 2: Are you whispering in case birds are listening and you

859
00:42:13,080 --> 00:42:13,960
Speaker 2: don't hurt their feelings?

860
00:42:14,040 --> 00:42:16,200
Speaker 1: Yeah, well I don't want them to attack me, you know,

861
00:42:16,400 --> 00:42:18,440
Speaker 1: like maybe they'll go after my kids.

862
00:42:18,800 --> 00:42:19,520
Speaker 2: Oh my gosh.

863
00:42:19,560 --> 00:42:20,439
Speaker 1: Yeah, yah, it'd be bad.

864
00:42:20,520 --> 00:42:22,360
Speaker 2: And so how rare is this? Like what fraction of

865
00:42:22,400 --> 00:42:25,120
Speaker 2: bird species or fish species do this?

866
00:42:25,560 --> 00:42:28,560
Speaker 1: So it has been most thoroughly studied in birds, like

867
00:42:28,640 --> 00:42:31,120
Speaker 1: it's been a little bit studied in fish. Some insects

868
00:42:31,160 --> 00:42:34,080
Speaker 1: do it. It's like scattered around the animal kingdom, but

869
00:42:34,200 --> 00:42:36,520
Speaker 1: in birds it's gotten the most attention, and about one

870
00:42:36,560 --> 00:42:39,960
Speaker 1: percent of bird species seem to do it. Wow, it

871
00:42:40,000 --> 00:42:42,600
Speaker 1: looks like it's popped up about seven times.

872
00:42:43,120 --> 00:42:44,399
Speaker 2: Seven times? What do you mean?

873
00:42:44,520 --> 00:42:46,800
Speaker 1: So, if you look at like the tree of life

874
00:42:47,040 --> 00:42:49,400
Speaker 1: and you've sort of started at the branch where birds

875
00:42:49,440 --> 00:42:52,759
Speaker 1: pop up or along seven of the branches, this strategy

876
00:42:52,960 --> 00:42:54,960
Speaker 1: of laying your egg in the nest of a different

877
00:42:54,960 --> 00:42:58,640
Speaker 1: species has developed, and then there's been like speciation where

878
00:42:58,680 --> 00:43:00,520
Speaker 1: you get more species that do it and they keep

879
00:43:00,560 --> 00:43:01,640
Speaker 1: this strategy with them.

880
00:43:02,000 --> 00:43:03,799
Speaker 2: Oh I see. So you're saying it's not just like

881
00:43:04,200 --> 00:43:07,000
Speaker 2: one branch of birds do this and all the branches

882
00:43:07,080 --> 00:43:09,200
Speaker 2: of birds that do it today come from that same branch.

883
00:43:09,200 --> 00:43:12,680
Speaker 2: You're saying it evolved independently seven different places on the tree.

884
00:43:12,719 --> 00:43:13,440
Speaker 2: That's incredible.

885
00:43:13,520 --> 00:43:15,120
Speaker 1: Yeah. Right, And so then one of the things that

886
00:43:15,160 --> 00:43:17,680
Speaker 1: people have been trying to figure out is what were

887
00:43:17,760 --> 00:43:21,520
Speaker 1: the birds doing before they started this strategy? And so yeah,

888
00:43:21,640 --> 00:43:23,640
Speaker 1: one of the ideas is that maybe they were doing

889
00:43:23,719 --> 00:43:27,280
Speaker 1: what we call conspecific brood parasitism, which is to say,

890
00:43:27,719 --> 00:43:30,960
Speaker 1: there were laying their eggs in the nest of other

891
00:43:31,000 --> 00:43:32,440
Speaker 1: members of the same species.

892
00:43:32,680 --> 00:43:33,160
Speaker 2: Oh.

893
00:43:33,200 --> 00:43:36,719
Speaker 1: So, for example, wood ducks will nest in tree cavities,

894
00:43:36,760 --> 00:43:38,839
Speaker 1: so like if there's a hole in a tree, wood

895
00:43:38,880 --> 00:43:40,879
Speaker 1: ducks will lay their eggs in there. But if there's

896
00:43:40,920 --> 00:43:44,400
Speaker 1: not enough wood cavities that season and there's too many ducks,

897
00:43:44,640 --> 00:43:47,320
Speaker 1: sometimes two females will lay their eggs in the same tree,

898
00:43:47,600 --> 00:43:50,799
Speaker 1: and one female will evict the other. But maybe she

899
00:43:50,800 --> 00:43:52,080
Speaker 1: can't tell that. I don't know if it's that she

900
00:43:52,080 --> 00:43:54,680
Speaker 1: can't tell the difference between all of the eggs or what,

901
00:43:54,880 --> 00:43:58,360
Speaker 1: but she will sit on and raise all of the

902
00:43:58,360 --> 00:44:01,440
Speaker 1: eggs and the chicks that were in that tree cavity. Okay,

903
00:44:01,560 --> 00:44:05,040
Speaker 1: And so the idea is that maybe over time, you know,

904
00:44:05,200 --> 00:44:08,080
Speaker 1: females started laying eggs and nest cavities, and instead of

905
00:44:08,120 --> 00:44:10,560
Speaker 1: fighting to be the winner, they were just like, oh no,

906
00:44:10,800 --> 00:44:13,759
Speaker 1: I lost, you can you can raise all of these.

907
00:44:14,280 --> 00:44:17,239
Speaker 1: And then maybe they just started like laying eggs in

908
00:44:17,280 --> 00:44:20,640
Speaker 1: other places and letting other maybe even other duck species

909
00:44:20,840 --> 00:44:24,879
Speaker 1: raise their young. So you could imagine it's starting that way.

910
00:44:25,440 --> 00:44:29,400
Speaker 1: Another example are American coots. They're duck like things, but

911
00:44:29,480 --> 00:44:34,440
Speaker 1: they're extra kind of unattractive. Sorry coots, but females that

912
00:44:34,520 --> 00:44:38,000
Speaker 1: can't get nest sites tend to lay their eggs in

913
00:44:38,040 --> 00:44:39,200
Speaker 1: the nest of other females.

914
00:44:39,400 --> 00:44:42,920
Speaker 2: What do you mean unattractive? They look cute? Oh yeah, Okay, now,

915
00:44:42,960 --> 00:44:44,839
Speaker 2: I'm zooming it a little bit. Yeah, it's a little

916
00:44:44,840 --> 00:44:45,279
Speaker 2: bit of a vult.

917
00:44:45,440 --> 00:44:48,520
Speaker 1: Yeah, yeah, I still like them. I still like them.

918
00:44:49,560 --> 00:44:51,560
Speaker 1: But anyway, so females who couldn't get their own nest

919
00:44:51,640 --> 00:44:53,960
Speaker 1: will lay their eggs in the nests of other females,

920
00:44:54,160 --> 00:44:56,560
Speaker 1: or females who have gotten their own nest, but they

921
00:44:56,680 --> 00:44:58,880
Speaker 1: like have made a bunch of eggs, and they're like,

922
00:44:58,960 --> 00:45:01,000
Speaker 1: I can't really raise any more kids, but it can

923
00:45:01,120 --> 00:45:04,040
Speaker 1: make more eggs, and they'll go ahead and lay their

924
00:45:04,160 --> 00:45:07,000
Speaker 1: excess eggs in the nests of other females. Like you,

925
00:45:07,239 --> 00:45:09,080
Speaker 1: you know, you could imagine that maybe you could go

926
00:45:09,160 --> 00:45:11,759
Speaker 1: from that strategy where you fill up your nest and

927
00:45:11,760 --> 00:45:13,120
Speaker 1: then maybe you see if you can get some of

928
00:45:13,120 --> 00:45:16,279
Speaker 1: your eggs in the nest of another species, and you know,

929
00:45:16,320 --> 00:45:18,520
Speaker 1: you just try some stuff out and maybe that's the

930
00:45:18,600 --> 00:45:23,160
Speaker 1: path through which interspecific brood parasitism arose.

931
00:45:23,400 --> 00:45:25,640
Speaker 2: But for that to happen, for it to be passed down,

932
00:45:25,920 --> 00:45:28,680
Speaker 2: for that behavior to exist also in your children, it

933
00:45:28,719 --> 00:45:31,759
Speaker 2: has to be genetic, right, So there's something in these

934
00:45:31,840 --> 00:45:34,279
Speaker 2: genes that have been tweaked that chaines the behavior of

935
00:45:34,320 --> 00:45:37,640
Speaker 2: the birds to accept this kind of scenario or to

936
00:45:37,680 --> 00:45:38,720
Speaker 2: attempt this kind.

937
00:45:38,520 --> 00:45:40,879
Speaker 1: Of approach, Yeah, exactly, but you can imagine it being

938
00:45:41,200 --> 00:45:44,840
Speaker 1: less of a jump. If you are genetically encoded to

939
00:45:45,320 --> 00:45:48,080
Speaker 1: lay your eggs in the nest of another individual of

940
00:45:48,120 --> 00:45:51,799
Speaker 1: the same species, and then you lay your eggs in

941
00:45:51,800 --> 00:45:53,839
Speaker 1: the nest of an individual of a different species, then

942
00:45:53,880 --> 00:45:57,120
Speaker 1: to go from I'm laying my eggs in my own

943
00:45:57,200 --> 00:46:00,640
Speaker 1: nest and then jumping to nominal laying my eggs in

944
00:46:00,640 --> 00:46:04,480
Speaker 1: a totally different species nest. But actually, when you like

945
00:46:05,040 --> 00:46:07,920
Speaker 1: look at the genomes of all of these different species

946
00:46:08,040 --> 00:46:10,239
Speaker 1: and you look at where they differ, and you try

947
00:46:10,280 --> 00:46:13,080
Speaker 1: to like make a tree of life based on you know,

948
00:46:13,239 --> 00:46:17,280
Speaker 1: what those codes say, it looks like most of the time,

949
00:46:17,600 --> 00:46:22,400
Speaker 1: maybe every time, but once that jump went through like

950
00:46:22,600 --> 00:46:25,799
Speaker 1: normal parental care, so like they were sitting on their

951
00:46:25,800 --> 00:46:30,280
Speaker 1: own nest, their own babies, and then the next step

952
00:46:30,520 --> 00:46:33,760
Speaker 1: was they were laying eggs in the nest of another species.

953
00:46:33,960 --> 00:46:36,560
Speaker 1: And wow, we're not quite sure how that jump happened,

954
00:46:36,600 --> 00:46:39,120
Speaker 1: and so there's you know, a lot of research going

955
00:46:39,120 --> 00:46:41,879
Speaker 1: into trying to understand that. But for a long time

956
00:46:41,920 --> 00:46:44,520
Speaker 1: we thought there was probably this intermediate step, but we

957
00:46:44,560 --> 00:46:47,040
Speaker 1: don't have any evidence to support that hypothesis. So now

958
00:46:47,040 --> 00:46:51,160
Speaker 1: we're changing the way we think about it and doing

959
00:46:51,200 --> 00:46:52,320
Speaker 1: some more research.

960
00:46:52,040 --> 00:46:53,839
Speaker 2: And there doesn't have to be an intermediate step.

961
00:46:53,880 --> 00:46:54,000
Speaker 3: Right.

962
00:46:54,040 --> 00:46:56,799
Speaker 2: If you can go in one generation from just being

963
00:46:56,840 --> 00:47:01,080
Speaker 2: parental to laying your eggs in another and it works,

964
00:47:01,160 --> 00:47:03,919
Speaker 2: then it's going to be reinforced by selection. Right.

965
00:47:04,120 --> 00:47:05,440
Speaker 1: So it's a little hard for me to imagine that

966
00:47:05,480 --> 00:47:08,480
Speaker 1: in one generation there was a jump, but as long

967
00:47:08,520 --> 00:47:12,880
Speaker 1: as that behavior was somehow encoded in a way that

968
00:47:12,960 --> 00:47:15,719
Speaker 1: could be passed either through learning, like maybe you saw

969
00:47:15,760 --> 00:47:18,120
Speaker 1: your mom do it and so you do it, or

970
00:47:18,160 --> 00:47:20,200
Speaker 1: maybe like imprinting was genetically encoded.

971
00:47:20,360 --> 00:47:21,680
Speaker 2: But how can you see your mom do it if

972
00:47:21,680 --> 00:47:23,080
Speaker 2: you're raised by another mom?

973
00:47:23,320 --> 00:47:25,839
Speaker 1: Right, yeah, right, So maybe it wasn't that you saw

974
00:47:25,840 --> 00:47:27,799
Speaker 1: your mom do it. Maybe it was just when you

975
00:47:27,840 --> 00:47:31,319
Speaker 1: were hatched in the nest of another species, you saw

976
00:47:31,360 --> 00:47:32,640
Speaker 1: that species and you were.

977
00:47:32,560 --> 00:47:34,680
Speaker 2: Like, oh, this is where the eggs go.

978
00:47:35,080 --> 00:47:37,880
Speaker 1: This is where eggs go. Right, And so that was

979
00:47:37,960 --> 00:47:41,160
Speaker 1: like the thing that took one generation for the you know,

980
00:47:41,520 --> 00:47:42,400
Speaker 1: the change to happen.

981
00:47:42,560 --> 00:47:44,960
Speaker 2: Hold on a second, I just had a complete realignment

982
00:47:45,120 --> 00:47:48,600
Speaker 2: of my emotional connection because now I'm like, maybe cuckoos

983
00:47:48,880 --> 00:47:52,239
Speaker 2: think that they are this other species and they're just

984
00:47:52,280 --> 00:47:54,359
Speaker 2: going there because that's how it works, you know, that's

985
00:47:54,360 --> 00:47:56,640
Speaker 2: how they grew up. They were raised by this other

986
00:47:56,719 --> 00:47:58,560
Speaker 2: kind of mom, and so that's what they want for

987
00:47:58,600 --> 00:47:59,200
Speaker 2: their babies.

988
00:47:59,320 --> 00:48:01,440
Speaker 1: But they're still hill and their brothers and sisters. Though

989
00:48:01,480 --> 00:48:06,880
Speaker 1: if they think that that's still that's still not okay. Yeah, right,

990
00:48:07,360 --> 00:48:09,000
Speaker 1: we got like, I don't know, twenty five percent of

991
00:48:09,040 --> 00:48:12,239
Speaker 1: the way there or something. Anyway, I think this is

992
00:48:12,280 --> 00:48:15,600
Speaker 1: fascinating and it's really interesting as a way to study

993
00:48:15,640 --> 00:48:18,640
Speaker 1: like evolution between parasites and hosts and you know, sort

994
00:48:18,680 --> 00:48:21,799
Speaker 1: of like how this arm race works and how one

995
00:48:21,880 --> 00:48:24,640
Speaker 1: sort of tries to counter the effects of the other,

996
00:48:25,120 --> 00:48:27,720
Speaker 1: and it's just kind of crazy the solutions that evolution

997
00:48:27,800 --> 00:48:30,239
Speaker 1: has come up with. Like I will post on our

998
00:48:30,280 --> 00:48:34,040
Speaker 1: blue Sky account and our Discord channel and our Instagram account.

999
00:48:34,239 --> 00:48:37,000
Speaker 1: I'll link to like a picture of the cuckoo eggs

1000
00:48:37,360 --> 00:48:40,240
Speaker 1: and the host eggs that I showed to Daniel because

1001
00:48:40,280 --> 00:48:43,160
Speaker 1: it is incredible to me how close the match is.

1002
00:48:43,880 --> 00:48:45,719
Speaker 1: And we didn't even talk about the genetics, Like it

1003
00:48:45,760 --> 00:48:48,880
Speaker 1: looks like genetic information you only get from females, so

1004
00:48:49,160 --> 00:48:50,799
Speaker 1: you know, I'll be really quick about this, but like

1005
00:48:50,840 --> 00:48:56,160
Speaker 1: in humans, females are have the XX chromosomes and males

1006
00:48:56,200 --> 00:49:00,600
Speaker 1: have x Y. But in ducks the males are zz

1007
00:49:01,120 --> 00:49:05,200
Speaker 1: and the females are ZW, so they have different chromosomes.

1008
00:49:05,200 --> 00:49:08,759
Speaker 1: But the females are the ones that have two different chromosomes.

1009
00:49:09,480 --> 00:49:13,120
Speaker 1: So if the females are the ones that are continuously

1010
00:49:13,280 --> 00:49:16,600
Speaker 1: like picking a certain kind of host species to end

1011
00:49:16,640 --> 00:49:20,360
Speaker 1: up in their nest over time, the genetic information about

1012
00:49:20,360 --> 00:49:22,839
Speaker 1: what the eggs look like could get passed on the

1013
00:49:23,000 --> 00:49:26,839
Speaker 1: W chromosome. And that's how you can have one species

1014
00:49:26,960 --> 00:49:29,920
Speaker 1: that produces eggs that look super different and match a

1015
00:49:29,920 --> 00:49:34,839
Speaker 1: bunch of different species host species, egg coloration patterns, and

1016
00:49:35,440 --> 00:49:39,680
Speaker 1: you get your genetic information in your mitochondria from your mom.

1017
00:49:40,000 --> 00:49:43,480
Speaker 1: So that's another way egg color and pattern information could

1018
00:49:43,520 --> 00:49:47,160
Speaker 1: get passed through mom. And anyway, it's absolutely fascinating how

1019
00:49:47,160 --> 00:49:49,760
Speaker 1: they manage to color match all of these so closely.

1020
00:49:50,640 --> 00:49:54,000
Speaker 1: And I just think it's super neat. Evolution's weird and

1021
00:49:54,080 --> 00:49:55,719
Speaker 1: doesn't care about your feelings.

1022
00:49:56,080 --> 00:49:58,640
Speaker 2: Yeah, well, let's go out on a limb. What do

1023
00:49:58,640 --> 00:50:02,680
Speaker 2: you think is the future of interspecific brood parasitism If

1024
00:50:02,719 --> 00:50:04,680
Speaker 2: birds went from like I'm gonna have another mom, take

1025
00:50:04,719 --> 00:50:07,480
Speaker 2: care of my babies in the same species too, then

1026
00:50:07,520 --> 00:50:11,040
Speaker 2: eventually to another species. In a million years, Are we

1027
00:50:11,080 --> 00:50:14,200
Speaker 2: going to have like elephants taking care of bird babies?

1028
00:50:14,520 --> 00:50:18,799
Speaker 1: Hmmm, uh, you know, I don't necessarily, it doesn't really

1029
00:50:18,840 --> 00:50:21,880
Speaker 1: work necessarily like work that way, Like it doesn't have

1030
00:50:22,040 --> 00:50:25,000
Speaker 1: to like become more extreme or more species don't necessarily

1031
00:50:25,080 --> 00:50:25,640
Speaker 1: have to do it.

1032
00:50:25,680 --> 00:50:28,760
Speaker 2: Over time, We're I'm gonna have antelopes raising cheetababies or something.

1033
00:50:28,880 --> 00:50:31,880
Speaker 1: Yeah, No, I don't think so. I don't think that'll happen,

1034
00:50:32,080 --> 00:50:35,080
Speaker 1: you know. I think it's it's possible that some interspecific

1035
00:50:35,160 --> 00:50:39,680
Speaker 1: brood parasites will drive the hosts that they were parasitizing,

1036
00:50:39,960 --> 00:50:44,200
Speaker 1: like to extinction, or maybe they'll switch to a different

1037
00:50:44,239 --> 00:50:48,080
Speaker 1: host species if their other host species is like the

1038
00:50:48,120 --> 00:50:51,920
Speaker 1: population numbers are getting low. But I'm not expecting that,

1039
00:50:52,040 --> 00:50:54,719
Speaker 1: like next year I will be raising cuckoos and I

1040
00:50:54,719 --> 00:50:57,040
Speaker 1: won't realize they're not human babies.

1041
00:50:58,640 --> 00:51:01,480
Speaker 2: All right, And if any of our listeners are warblers,

1042
00:51:01,640 --> 00:51:04,160
Speaker 2: maybe you know, go out there and check on those

1043
00:51:04,160 --> 00:51:06,520
Speaker 2: babies and make sure you're not racing cuckoos. And let's

1044
00:51:06,560 --> 00:51:09,359
Speaker 2: hate you want to, in which case, more power to you,

1045
00:51:09,400 --> 00:51:12,040
Speaker 2: because nature tells us that there's all kinds of families

1046
00:51:12,040 --> 00:51:12,479
Speaker 2: out there.

1047
00:51:12,719 --> 00:51:22,320
Speaker 1: That's right, all right, Until next time, everyone. Daniel and

1048
00:51:22,440 --> 00:51:26,359
Speaker 1: Kelly's Extraordinary Universe is produced by iHeartRadio. We would love

1049
00:51:26,400 --> 00:51:27,200
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1050
00:51:27,320 --> 00:51:30,239
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1051
00:51:30,480 --> 00:51:33,120
Speaker 2: have about this Extraordinary Universe.

1052
00:51:33,200 --> 00:51:36,160
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1053
00:51:36,160 --> 00:51:39,160
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1054
00:51:39,200 --> 00:51:39,600
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1055
00:51:39,880 --> 00:51:43,399
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1056
00:51:43,440 --> 00:51:46,640
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1057
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1058
00:51:47,880 --> 00:51:51,680
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1059
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1060
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1061
00:51:55,880 --> 00:51:57,440
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