It is the first time that researchers have discovered that California condors can apparently also reproduce in this special way.
It’s an extraordinary discovery: condors that can reproduce virginally. Although it is a well-known phenomenon and there are several species that use this tactic, this is the first time that ‘parthenogenesis’ has been identified in California condors. “This is really an amazing discovery,” said researcher Oliver Ryder.
The California condor is a very impressive bird that can reach enormous size. For example, an adult condor can have a wingspan of three meters. Most of the time they spend hovering, with the animal looking for carrion to eat. The California condor is unfortunately one of the most endangered species in the world. For example, in December of 2015, only 435 were left alive worldwide. In 1987 there were even fewer; only 22. The United States government took drastic measures in 1987 to save this animal. All wild condors were captured to breed in captivity. Animals have subsequently been released back into the wild from captivity. This has led to the numbers steadily increasing again.
Parthenogenesis is a phenomenon whereby females can produce young without the involvement of a male. The virgin females spontaneously lay eggs or give birth to young. In parthenogenesis, the offspring are therefore completely genetically identical to the mother. Although this phenomenon is known to biologists, it is actually rare among birds. Only a few cases in domestic birds are known. For example, studies in 1965 and 1968 confirmed parthenogenesis in turkeys, and in 1924 and 2008, scientists observed the same thing in finches and domestic pigeons, although in the latter case the eggs ultimately failed to hatch.
Condors
But now we can add another bird species to the prestigious list: California condors. Researchers have discovered that two chicks, born in 2001 and 2009, hatched from the unfertilized eggs laid by two different mothers. The researchers made this astonishing discovery after analyzing biological samples from the chicks and genetically testing them. The study confirmed that the chicks were only related to the mother and not to a male.
Genetic study
“We weren’t even looking for evidence of parthenogenesis,” Ryder says. “We actually just ran into it. We found out because of normal genetic studies that we do to prove lineage. Our results then showed that both eggs possessed the expected male ZZ sex chromosomes, but all markers were only inherited from their mothers, confirming our findings.”
Males nearby
The story gets a little weirder. Because normally parthenogenesis is only seen in females who are not accompanied by males. But in the case of the California condors, there were fertile males nearby. Both females had also produced numerous offspring with their mates. For example, one female had eleven offspring. The other female had also mated with a fertile male for more than twenty years. Together they had produced as many as 23 chicks. This pair even reproduced twice after parthenogenesis. This is the first time that researchers have discovered that birds accompanied by fertile males also reproduce virginally.
Why the two ladies reproduced virginally is still a mystery. “Unlike previous cases, these two events cannot be explained by the absence of a suitable male,” notes study researcher Cynthia Steiner. Research continues, not least because the discovery could have significant demographic implications. In follow-up studies, the researchers hope to uncover several parthenogenetic cases. “These findings now raise questions as to whether parthenogenesis can also occur undetected in other species,” Ryder concludes.
Source material:
“San Diego Zoo Wildlife Alliance Conservation Scientists Report First Confirmed Hatchings of Two California Condor Chicks from Unfertilized Eggs – San Diego Zoo Wildlife Alliance
Image at the top of this article: Andrew James, San Diego Zoo