And while this has been seen in other vertebrates and even birds, these are believed to be the first recorded instances in birds when the females had access to a mate, researchers said.
The exceptional hatchings — the first of which happened in the early 2000s and the second later that decade — were noted only when researchers analyzed biological samples from condors at a breeding program run by the San Diego Zoo Wildlife Alliance, the group said.
The female condors in question were continuously housed with a fertile male in the alliance’s breeding program, and each had numerous other chicks with their mates. But recent genetic testing found two anomalies.
“It just hit us in the face. We only confirmed it because of the normal genetic studies we do to prove parentage,” Oliver Ryder, the alliance’s director of conservation genetics, said in a news release.
“Our results showed that both eggs possessed the expected male ZZ sex chromosomes, but all markers were only inherited from their dams (mothers), verifying our findings.”
One chick died in 2003 shortly before its second birthday; the other died in 2017 days before it turned 8, researchers said.
Scientists also saw the beginnings of asexual reproduction in finches in a 2008 study, and in domestic pigeons in a 1924 study — but the eggs did not hatch, the journal report reads.
Researchers believe the condor findings stand out, when compared to other instances in birds.
“Unlike other examples of avian parthenogenesis, these two occurrences are not explained by the absence of a suitable male,” Cynthia Steiner, associate director of the alliance’s conservation research division, said.
The San Diego Zoo Wildlife Alliance, a nonprofit conservation organization at the San Diego Zoo and the San Diego Zoo Safari Park, says it hopes to identify other cases of asexual reproduction.
“These findings now raise questions about whether this might occur undetected in other species,” Ryder said.
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