The California condor can reproduce alone: the discovery at the San Diego Zoo, where two female condors have procreated without recourse to the male
Some animals do not need a mate to reproduce: it happens to sharks, stingrays, some lizards - including the Komodo Dragon. They call them "virgin births," or virgin births, and refer to parthenogenesis - an asexual mode of reproduction without fertilization typical of many plants and some animals.
A new study published in the Journal of Heredity today adds an unexpected new addition to the list of animals that can reproduce on their own: it's one of the most endangered species on the planet, the California condor.
An endangered species
For the first time, the research says, a female condor has reproduced without a male. This is a California condor specimen, which adds to the short and fascinating list of animals that do not need a mate to reproduce.
The observation was made possible as a result of the intense activity of Oliver Ryder and his colleague Leona Chemnick for the preservation of the species, among the most endangered of the entire planet.
In 1982, the California condors were a total of 22, virtually extinct. The efforts of the researchers, who bred them in captivity at the San Diego Zoo and released them into the wild, have resulted in a total population that now exceeds 500 individuals.
The selection of specimens to breed and the careful monitoring of the genetic data of all individual California condors raised in captivity have revealed to Ryder and Chemnick a fascinating reality, to say the least.
Chemnick discovered that two male condor specimens, identified in the studbook as SB260 and SB517, showed no genetic contribution from those adult males thought to be their parents.
The only possible solution is that they were conceived without any contribution from the male. The two female condors that gave birth to SB260 and SB517 basically did it all on their own.
Why reproduce without a mate
That some animals resort to parthenogenesis when they don't have a male available to mate with is a well-known fact: it's been observed in turkeys, chickens and the Chinese blue-breasted quail.
What's strange, according to the researchers, is that the two female condors that sired their own young had males available for fertilization. Which were not chosen, for some reason.
The first obvious question to unravel is: that the females decided not to use the males' genetic contribution for some reason related to the genetic success of the offspring? Unlikely, since the two condors generated by parthenogenesis did not live long enough to reproduce in turn.
SB260 lived only two years, while SB517 died before reaching eight years of age, when California condors can safely reach 60 years of age. What's more, the two female condors had already successfully mated with both "rejected" males - both before and after they chose to procreate on their own.
Ryder admits he still doesn't understand what happened in detail, but he's pretty sure it's more common than we think.
Reshma Ramachandran, of Mississippi State University, has been conducting parallel experiments on parthenogenesis in birds since 2018. The news from the San Diego Zoo doesn't surprise her: "I expect more such news now," the researcher says.
No one can rule out, Ryder says, that investigating the genetic makeup of any birds will find that "occasionally they may reproduce by parthenogenesis." "No one has yet studied this so thoroughly as to answer such questions," Ryder concludes.