How can condors reproduce without a mate?

Female condors have managed to make baby condors without a male. How is this possible?
11 November 2021


A headshot of a condor



'How can a female condor produce fertile offspring without mating with a male condor?'


In order to answer this condor conundrum, Sally Le Page posed this question to molecular biologist, Nessa Carey.

Nessa - Right, so Huw, I take your flesh-eating duck and I raise you a parthenogenetic vulture. Parthenogenesis is the phrase we use for creating live young without mating. We've had hints before that this can happen in birds, but we've never seen it in species like condors and vultures, which are these huge, huge scavengers. The really weird thing about these female condors that did it, is they actually had access to fertile males. Normally we only see this thing in birds of producing eggs and young under extreme conditions where there's no males around. But this time there were males, it's just for some reason, the females decided not to bother with them.

Sally - So it wasn't that the condors didn't have a man, they just didn't want a man.

Nessa - They just didn't want a man. They just decided that this time the vulture sisters were doing it for themselves. And these two females, so it's happened twice, they laid eggs and those hatched, it was little male condors that came out. It seems like what happened was when the female first started producing an egg, normally you basically halve the amount of your DNA, because essentially each offspring gets half from mum and half from dad. But it looks like what the female did was she halved her DNA and then thought 'I'll not bother with dad. I'll just copy this. So that I end up with the right amount of DNA and then we'll have a new condor.' And they did it, and absolutely nobody knows why.

Sally - And did you say that the chick was male?

Nessa - Both chicks were male.

Sally - But surely this means that if they've got exactly the same genetic information as their mother, wouldn't they just be a clone?

Nessa - No, because birds are different from humans. In humans the male has an X chromosome and a Y chromosome, it's the Y chromosome that creates being a male. Whereas women are XX, they have two identical what we call sex chromosomes. Birds are the other way around. In birds, the male has the two sex chromosomes that are exactly the same and the female has what's called a Z and a W. In these particular cases, the females passed on two of the Z chromosomes and created new males. Isn't it weird? There you go flesh-eating ducks, take that.

Sally - That is incredible. John?

John - Could the dinosaurs have done the same if they're in a similar family?

Nessa - Well, yeah, that's a great question.

Sally - Isn't that what happened in Jurassic Park?

Nessa - Which is, as we all know, highly scientifically accurate. It's not. It's not. Spoiler. It's not. Birds are dinosaurs. Basically the dinosaurs didn't die out, they just changed into birds. So chances are maybe the dinosaurs did. We certainly know lizards do. You know those Komodo dragons? Those really big, terrifying lizards that bite you and you die from blood poisoning if you don't die from having your leg bitten off? Well, we certainly know that they can do the same thing. There's been females in zoos who couldn't get near a male and who have had created offspring. It's basically, if you put enough pressure on almost any animal, apart from mammals, they manage to do this, but mammals can't.

Sally - Why don't we all just do parthenogenesis? It sounds great.

Nessa - Well it certainly solves that problem of 'can you find a decent boyfriend?' If that's something that you're struggling with, if you can't find the proper baby daddy. Mammals can't because mammals have placentas and we have systems built in that mean that you have to have some of your DNA from a male and some of your DNA from a female. If you don't, the offspring can't develop properly. So you never ever get live offspring. It has been done once in mice, but that's because the scientists mucked about with the DNA.

Sally - That ruddy placenta getting in the way.

Nessa - I know, more trouble than it's worth.


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