A California condor at the San Diego Zoo. Photo courtesy of the zoo

Researchers at the San Diego Zoo announced Thursday the discovery of asexual reproduction by two California condors in a breeding program for the once nearly extinct birds.

During a routine analysis of biological samples from two chicks in the San Diego Zoo Wildlife Alliance’s program, scientists confirmed that each was genetically related to the respective female condor that laid the egg, but neither chick was genetically related to a male the females were housed with.

In other words, both chicks were biologically fatherless, and accounted for the first two instances of asexual reproduction, or parthenogenesis, to be confirmed in the California condor species.

The discovery was officially reported this week in the Journal of Heredity, an academic publication of the American Genetic Association.

Parthenogenesis is a natural form of asexual reproduction in which an embryo that is not fertilized by sperm continues to develop, containing only genetic materials of the mother. It occurs naturally in some plants, insects, fish, amphibians, reptiles and very rarely birds.

“This is truly an amazing discovery,” said Oliver Ryder, director of conservation genetics at the 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.”

Both of the females had also produced numerous offspring with their mates—one had 11 chicks, while the other was paired with a male for over 20 years and had 23 chicks. The latter pair reproduced two more times following the parthenogenesis.

“Unlike other examples of avian parthenogenesis, these two occurrences are not explained by the absence of a suitable male,” said Cynthia Steiner, associate director for the conservation research division at San Diego Zoo Wildlife Alliance.

The team plans on continuing future genetic studies in the hopes of identifying other parthenogenetic cases. “These findings now raise questions about whether this might occur undetected in other species,” Ryder said.

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Chris Jennewein

Chris Jennewein is Editor & Publisher of Times of San Diego.