‘Big surprise’: California condors reproduce without mating

California condors, a critically endangered species, can reproduce without mating, a new study by conservation scientists at the San Diego Zoo Wildlife Alliance has found.

The unexpected discovery came during a routine analysis of biological samples from the California condors in the zoo’s decades-long breeding programme, the scientists found that two condor chicks had hatched from unfertilised eggs.

“It came as a big surprise, to be honest. We didn’t expect to find any of this,” Cynthia Steiner, associate director for the alliance’s conservation research division, told Reuters news agency.

Steiner is also a co-author of the study published last week in the Journal of Heredity, the official publication of the American Genetic Association.

Scientists confirmed that each condor chick was genetically related to its mother but neither bird was genetically related to a male.

The two birds represent the first two instances of asexual reproduction, or parthenogenesis, to be confirmed in the California condor species, the zoo said.

The California condor is one of the world’s rarest bird species. It was proclaimed extinct in the wild in the 1980s, but has been gradually reintroduced through breeding and conservation efforts.

Steiner said there are now about 500 living condors, about 200 in captivity and 300 in the wild.

The bird is the largest species in North America, with a wingspan of about 2.5 to 3 metres (8.2 to 9.8 feet).

‘Rare discovery’

Steiner said the recent finding is particularly significant because asexual reproduction is rarely found in birds.

“This is a very rare discovery because it’s not well-known in birds in general,” she said. “So it’s known in other species, in reptiles and in fish, but in birds, it’s very rare, in particular in wild species.”

She added the discovery was also jolting because both female birds in question were continuously housed with fertile male partners and had already produced chicks while paired with a male.

Asexual reproduction has never before been confirmed in any avian species where the female bird had access to a mate.

“At some point they decided, for some reason, to go into asexual reproduction as well,” Steiner said.

Both chicks were underweight when they hatched, Steiner said. One was released into the wild and died at the age of two in 2003, while the other survived for eight years in captivity and died in 2017.

She hopes to keep studying asexual reproduction in the birds to see if it continues now that there are more condors in the wild.

“We just want to know how often this phenomenon might be happening now that the population is expanding instead of contracting as before in the 1980s,” she said.