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“Virgin births” discovered among California condors

During a routine analysis of biological samples from two male California condors in the San Diego Zoo Wildlife Alliance’s managed breeding program, a team of conservation scientists reported an amazing discovery that could have a significant impact on wildlife genetics and conservation science. Both male condors had DNA that was 100 percent of their mothers, and were thus biologically fatherless. 

This phenomenon is known as parthenogenesis and represents a natural form of asexual reproduction in which an embryo that is not fertilized by sperm continues to develop, containing only the mother’s genetic material. Parthenogenesis is very rare in birds, and usually occurs in females who have no access to males.

“This is truly an amazing discovery,” said study co-author Oliver Ryder, the 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. 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.” 

Previous examples of aviary parthenogenesis were only found domestic birds such as turkeys, finches, and domestic pigeons. Moreover, these birds did not have access to males. By contrast, the condor females had also produced a large number of offspring with their mates: one had 11 chicks, and the other – which was paired with a male for more than 20 years – had 23 chicks. 

“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 study co-author 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.”

Although these results represent only two documented cases in the condor population, the discovery could have important implications. Further research is needed to see whether parthenogenesis occurs in other condors, as well as in other species too.

The study is published in the Journal of Heredity. 

By Andrei Ionescu, Staff Writer

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