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California Condors reproduce without a male. A first.

A California condor is shown at the San Diego Zoo Global Wildlife Conservancy in this undated photo.
A California condor is shown at the San Diego Zoo Global Wildlife Conservancy in this undated photo.

San Diego Zoo Wildlife Alliance officials used genetic testing to uncover evidence that at least two condors have reared offspring that only have one parent.

San Diego Zoo Wildlife Alliance researchers have uncovered the first ever case of condor reproduction by just a single parent.

California Condors reproduce without a male. A first.

Speaker 1: (00:00)

We already know that the California condor is an audacious species. The birds boldly bounced back from near extinction. 30 years ago to a population of hundreds today flying free over the American Southwest. But wildlife researchers have now confirmed that California Condors have made a reproductive breakthrough by producing offspring that have no father it's called parthenogenesis. It's been seen in other bird species, but never before in the condor, the finding has startled wildlife experts and made movie buffs recall the female only reproduction of baby dinosaurs in Jurassic park, Johnny Mayez KPBS environment, reporter Eric Anderson, Eric, welcome to the program.

Speaker 2: (00:46)

Thank you, Maureen. Remember life will find a way as Jeff Goldbloom said,

Speaker 1: (00:51)

Apparently it does. I'm wondering, how did researchers confirm that these two condor chicks had only one parent?

Speaker 2: (01:00)

Well, the researcher is do something with the Condors that they don't have a chance to do with a lot of other endangered species. And that is they test them genetically, uh, because all of the Condors are brought in, uh, from the wild back in the 1980s, they've been able to basically identify each condor or the majority of the Condors, uh, through their genetic testing program. And they do that for a very simple reason. Uh, they want to be able to keep that population, which was so small to begin with just 22 birds, uh, genetically diverse. In other words, they want, they want to make sure that, uh, the right birds are meeting with each other so that it increases the diversity of the species so that they have a better chance, uh, to be resilient in the future. Uh, and that when the herd gets bigger, like it is now, or when the flock gets bigger, like it is now, uh, then they'll be much more resilient to anything they might face.

Speaker 1: (01:58)

So if they find that the genomes are identical to the mothers, does that mean there was no male involved in their development?

Speaker 2: (02:05)

Well, here's what happens typically when you look at a genome, any genome, a parent of a human baby, you'd look at that genome. And you say, look, these are traits that came from the mother. These are traits that came from the father and the resulting genome of the child is sort of a blend of the two. What they found in these cases is that the genomes of the children of two separate Condors, the male children of two separate Condors, uh, was exactly the same as the genome of the mother. And the only explanation for that is that there was no father involved in the fertilization process.

Speaker 1: (02:40)

How does parthenogenesis work? I mean, do we understand it?

Speaker 2: (02:46)

It's a very good question and I'm not sure that there's a full understanding of exactly how it works, but, uh, we do know that it does happen. Um, in other species, we know that, um, there is some, there are dinosaurs in Jurassic park, as we all know reptiles, it happens in it. And also it's been known to happen in birds. But the thing with the birds is it usually find it in settings where, uh, all the birds in an enclosure might be female. So there's no chance for contact with a male and yet they still produce offspring. Now, what they found is that some of the birds that were allowed to grow to term this way, weren't viable. They weren't very strong, genetically this, in this particular case, in the Condors, um, these two birds are, uh, from all intents and purposes, normal male condor. So, uh, this hasn't affected them, uh, the offspring in any negative way.

Speaker 1: (03:45)

And as you say, this type of female only asexual reproduction, not only is it rare, but it's even more startling because in this instance there were male Condors present. Can you tell us more about that?

Speaker 2: (03:57)

Yeah. Uh, this is something that puzzled the researchers when they, uh, found this, uh, uh NAMMily um, because the females that were involved, the two mother Condors that were, that were involved in this were in the same enclosure with fertile males. So they had an opportunity. And yet, um, as it happened, they went ahead and reproduced, uh, without the help of the male condor and, and the researchers really don't have an answer as to why, uh, that is the case.

Speaker 1: (04:28)

So if condor is, could achieve parthenogenesis, why do they almost go extinct 30 years ago,

Speaker 2: (04:36)

The conduits were under extreme environmental pressure. Uh, their range was shrinking. They were, uh, interacting more with, uh, people and, and their big, large birds, which makes them big, large, uh, targets in some ways. And so the population went down parthenogenesis I don't think is, uh, uh, really, uh, uh, huge, uh, reproductive tool. There are a couple of things you have to recognize about parthenogenesis now the females, uh, can lay and fertilize an egg on their own as the researchers have proven, but the, the, but the chick that they'll raise will always be a male. And that's because, uh, the male Condors carry the sex hormone, right? So without fertilization, you can't have a female condor born, so that's kind of a dead end road over the term. What's interesting in one of the researchers talked to me about was this idea that maybe it's a mechanism for the species to eliminate, uh, um, unhealthy traits from a population. So if, uh, a number of males are, have this deleterious, uh, gene expression in their genome that can kind of skip over, uh, allowing them to reproduce and they can themselves, and then those males will die off. And the ones that are produced by the female only sperm, uh, would take their place and, and, and reproduce naturally. So that's one possibility, but, uh, you know, the, the, the information is so new that they haven't had a really, a good chance to, to say exactly why it happens and what the long-term impact might be.

Speaker 1: (06:20)

As you explained, researchers have an abundance of genetic information on the California condor, which makes me think that if they had the kind of complete genetic information about other species that they have on the California condor, might they find that parthenogenesis happens more often in other species?

Speaker 2: (06:41)

Um, I think that's a fair assumption to make, uh, you know, we don't have all of the, the entire genetic library of crows or the entire genetic library, uh, of, uh, other large birds like Eagles, but we do have, uh, pretty much the entire genetic library of the California condor. And so findings like this, uh, can be made the only way you would. I, you know, be able to tell in other species, without these genetic markers is through observation, and then you'd have to have them in some kind of a contained area where they don't have exposure, and then they still raise viable, uh, eggs. Uh, so it's much more complicated and, and really, um, it's kind of a stroke of luck that they have this huge genetic resource available so that they can make this finding and then perhaps understand, uh, what, how this functions within the species and how it helps, uh, propagate that species over the longterm.

Speaker 1: (07:42)

I've been speaking with KPBS environment reporter Eric Anderson. Thank you so much.

Speaker 2: (07:48)

My pleasure.

Routine genetic testing revealed that two unrelated condors only had one parent. Their eggs were not fertilized by male sperm. Basically the females did not need a male condor to produce a viable offspring. It was like something taken from the movies.

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“You’re implying that a group composed entirely of female animals will … breed?” asked actor BD Wong in the 1993 film Jurassic Park.

“I’m simply saying that life finds a way,” answered the character played by Jeff Goldblum.

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“It hit us in the face,” said Oliver Ryder, a geneticist with the San Diego Zoo Wildlife Alliance. “We weren’t looking for it. We didn’t expect it.”

Genetic testing of the captive and wild population of California Condors is a regular occurrence as researchers work to maintain genetic diversity in the endangered species.

The world’s largest flying bird nearly went extinct 30 years ago, when the population sank to just 22 birds.

Conservationists moved ahead with a controversial breeding plan that called for all the condors to be captured. The last free bird was caught in 1987.

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California condor
Ken Bohn / San Diego Zoo Wildlife Alliance
A California condor is shown in this undated photo.

Those researchers have since been vindicated, because the current population is over 500 birds, with more than 300 flying free in California, Arizona and Mexico.

Because scientists had contact with all the individuals of the species, they have been able to build a genetic library of the condors.

It was during routine genetic testing that the anomaly was found.

“We couldn’t believe that this is something that was really happening,” said Cynthis Steiner a researcher at the San Diego Zoo Wildlife Alliance. “And so when we were working in the lab we were repeating the genotyping processes. Getting all the genetic information multiple times to make sure that we were not making any mistakes, to be honest.”

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When they saw that the genomes of the mothers and the male chicks were the same, it confirmed reproduction without fertilization, called parthenogenesis.

“It happened twice when the population was small,” Ryder said. “Will it happen again when the population gets bigger. I think that’s an important question.”

These are the first known cases of parthenogenesis in California condors and it’s the first time genetic testing has confirmed the phenomenon.

The development is also unique because there were fertile males present but the asexual reproduction happened anyway.

In other bird species where asexual reproduction has occurred, it usually happened because there were no males.

“Knowing that this is not a random individual we found, this is two individuals, from two separate families that were able to be generated using parthenogenesis we might think this is not as uncommon as we thought before,” said Steiner.

The California condor is the largest flying bird in the world with wingspans that can reach nine feet.

California Condors reproduce without a male. A first.