SAN DIEGO (KGTV) — San Diego Zoo Wildlife Alliance officials announced Thursday that researchers have confirmed that two California condor chicks that had hatched years ago did so from unfertilized eggs, a potentially game-changing discovery for wildlife genetics and conversation.
In a study published this week in the Journal of Heredity, researchers said during a routine analysis of biological samples of two California condors in SDZWA's breeding program, the two chicks were found to be genetically related to the respective female condor, also known as a "dam," that laid the eggs from which they each hatched, but were biologically fatherless.
Neither bird was genetically related to a male and accounted for the first two instances of asexual reproduction in the California condor species, according to SDZWA.
SDZWA said the two dams that laid the eggs were continuously housed with fertile male partners, making the discovery all the more astonishing. Both females had also had numerous offspring with their mates, including 11 chicks by one and 23 chicks by the other.
Sadly, the chicks passed away, one in 2003 at the age of 2 and the other in 2017 at the age of 8, according to SDZWA.
"This is truly an amazing discovery," said Oliver Ryder, Kleberg Endowed Director of Conservation Genetics at San Diego Zoo Wildlife Alliance. "We were not exactly looking for evidence of parthenogenesis, it just hit us in the face. We only confirmed it because of the normal genetic studies we do to prove parentage. Our results showed that both eggs possessed the expected male ZZ sex chromosomes, but all markers were only inherited from their dams, verifying our findings."
Parthenogenesis is a natural form of asexual reproduction where an embryo that is not fertilized by sperm continues to develop, containing only the genetic materials of the mother. The resulting offspring are called "parthenotes." This process is relatively rare in birds and normally seen in females with no access to fertile males.
"We believe that our findings represent the first instance of facultative avian parthenogenesis in a wild bird species, where both a male and a female are housed together," said Cynthia Steiner, associate director for the conservation research division at San Diego Zoo Wildlife Alliance. "Still, unlike other examples of avian parthenogenesis, these two occurrences are not explained by the absence of a suitable male."
