California Endangered Vultures Can Reproduce Asexually, Research Finds


Conservation geneticists working to conserve endangered California vultures have discovered two examples of chicks hatching from unfertilized eggs – the first known cases of virgin births within the species.

This finding included A study published Thursday in The Journal of Heredity, which is particularly noteworthy because such cases are unusual among birds.

Parthenogenesis, the process by which female animals produce embryos that are not fertilized by sperm, is more common among vertebrate species such as fish or lizards. Before the findings were made public on Thursday, other known examples of parthenogenesis among birds were limited to turkeys, finches and domestic pigeons, according to the San Diego Zoo Wildlife Alliance.

“Parthenogenesis is considered a rare phenomenon in birds,” said Oliver Ryder, co-author of the study and director of conservation genetics at the San Diego Zoo Wildlife Alliance. “We discovered it in California vultures because we have such a detailed lineage analysis of the entire population.”

California vultures have long been an endangered species, with the world population dropping to just 23 in 1982. According to the U.S. Fish and Wildlife Service. At this point, the agency has removed all known California vultures from the wild and bred them in captivity.

Samantha Wisely, a conservation geneticist at the University of Florida who was not involved in the study, said the species, which was 504 bird in 2020, has been closely watched and studied for decades, leading to discoveries like the one published Thursday.

The need to identify birds by sex to develop a successful breeding program led to the discovery of two chicks.

Years ago, Dr. Ryder was asked to develop a system for determining the sex of California vultures in captivity because males and females look the same. He also needed to identify close relatives among the birds so that the relatives did not mate. So he created a genetic database for all California vultures.

In 2013, Dr. Ryder’s team noticed some inconsistencies in the database, which led to a reanalysis of all captive birds. Dr. Ryder’s team discovered two male chicks, one born in 2001 and the other in 2009, and did not fit any of the genetic profiles of the males. This meant that none of the male vultures were fathering them.

“There was no paternal contribution,” said Dr. ryder “They just got genetic information from their mother.”

The final clue that these chicks developed from parthenogenesis was that they were both males. Due to the genetic makeup of birds, self-reproducing female vultures can only give birth to male vultures.

Dr. In the past, parthenogenesis was thought of as a somewhat hopeless form of reproduction, occurring when females occur in low male populations or environments with few members of their own species, Wisely said.

However, vultures in captivity mated with males in an enclosure but still reproduced via parthenogenesis.

Dr. According to Ryder, the discovery of “virgin births” in such a closely watched bird population is leading scientists to wonder whether more birds reproduce through parthenogenesis in the wild than previously believed.

Dr. “For other species, it seems like a last-ditch effort to save themselves,” Wisely said. “It will be really interesting for the birds to know the context in which it takes place in the wild.”

Another interesting aspect of parthenogenesis is that lethal genetic traits cannot be passed on from the mother.

Still, Dr. Some less favorable traits may still appear in offspring, Ryder said.

“Maybe they don’t carry the good-looking genes or anything,” he said.



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