A woman needs a man, as the feminist and social activist Irina Dunn once said, like a fish needs a bicycle. Unless, of course, she’s interested in making a baby, in which case a man can often be a useful addition to the process. That’s because humans, like most other animals, need to breed to reproduce – but that it's not the only option. There are plenty of species that can produce offspring without mating: sharks can do it, as can snakes and Komodo dragons.
And, it turns out, so can California condors. A new paper published in the Journal of Heredity has revealed for the first time that these critically endangered birds, once reduced to a population of just 22, have been boosting their numbers in an unconventional way: without the help of a male.
“I’ve told the story a few times, and I still get goosebumps” laughed Oliver Ryder, Kleberg Endowed Director of Conservation Genetics at San Diego Zoo, where the phenomenon was discovered. “It was just like – wow!”
Like so many of the best breakthroughs, it happened by accident.
The fact that California condors are able to reproduce like this is just the latest revelation from San Diego Zoo Wildlife Alliance’s three decades of California condor recovery research. Previous discoveries from the institution have already upended our understanding of the mammoth birds: when the last wild condors were taken into captivity back in 1987, there was no way of sexing individuals and the species was thought to be monogamous. Neither is true today.
“As part of [the conservation] effort, we were asked to … identify a method to sex the birds,” Ryder told IFLScience. “Male condors look like female condors.”
Luckily – or not so luckily, if you’re a condor – there’s one big problem when it comes to the species recovery: lead poisoning. Researchers would need a blood sample from every condor to measure the extent of the issue, Ryder explained – samples which could also handily reveal the sex and lineage of the bird.
“They were going to be paired for reproduction,” Ryder told IFLScience. “We didn’t want to pair closely related individuals – as it turned out, we now know that a couple of the birds who were brought in from the wild were [in a] parent-offspring relationship. We wanted to avoid that.”
As the conservation effort took off, condors were gradually released into the wild – more than half of the world’s 500 or so California condors today live in wilderness sites across California and Mexico – but researchers continued to collect blood samples and track genealogy. But the more information they gathered, the more chaos they found: mix-ups in labeling, misidentified parents, and the scandalous discovery that the condors are not, in fact, monogamous.
“We decided [out of] an abundance of caution to just look at the parentage of all of the condors in the program,” Ryder said. “Whether they were in managed care, or out in the wild.”
But there were two chicks that confused the researchers. They had been born to females housed with one male, so working out their family tree should have been a cinch. But genetic analysis told a different story: their mothers’ resident male was not their father. In fact, none of the male condors were.
“I was headed home, I had my backpack on and was headed to the parking lot, and [study co-author Leona Chemnick] said, ‘can I talk to you about the condor parentage, there’s something strange going on,’” Ryder explained.
When Chemnick explained the problem, Ryder had just one question.
“I said, are they males?” he told IFLScience. “She said yes, and I said ‘you’ve just discovered parthenogenesis in California condors.’ … There’s really no other plausible eplanation.
“That was the last thing in our minds,” he said.
This would be big news in any species, but for the California condors, already struggling to survive, it has big implications. Asexual reproduction, the paper notes, “could assist range expansion when populations are at very low densities,” and “when the majority of population recruitment is due to sexual reproduction, [it] may contribute to reducing genetic load via purging of deleterious mutation” – both of which would be valuable advantages to the effort to reintroduce the condor to the wild.
Unfortunately for the researchers, the chicks that resulted from this phenomenon are both dead – and although they lived for years, they were plagued by bad health. Ryder cautioned against blaming their virgin births for that, however: it’s “a good question,” he told IFLScience, but not one that they can answer yet.
“It’s only two birds,” he said, “and we didn’t really realize they were special until after they died. There was no special scrutiny of them. But genetically, if they had a lethal gene … they wouldn’t have happened. We wouldn’t have seen them at all.”
While there’s still a lot of work to be done – the team is already working on sequencing the entire genome of the California condors to try to figure out exactly how the parthenotes came about – the discovery of successful parthenogenesis in a previously unknown, critically endangered species stands as a reminder that there’s still a whole lot we don’t understand about the natural world.
“We only found this because we were doing this incredibly detailed pedigree analysis of the whole condor genealogy,” Ryder told IFLScience. “How many species is this being done for? Really very few … maybe this is going on around us, and we don’t notice because we didn’t think to look.”
“We didn’t know life could do this, and lo and behold it does. It happened. It didn’t happen once, it happened twice,” he added. “Don’t take nature for granted. There are wonders beneath the surface that we are yet to fathom.”
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