How the California condor escaped extinction — and a genetic bottleneck

After coming back from the brink of extinction, the genome of the California condor is surprisingly diverse, according to a new study.

The birds were once extinct in the wild, and in 1982 there remained only 22 California condors in captivity. But thanks to some emergency conservation efforts, there are now more than 300 of the animals in the wild, with another 200 in captivity.

"The individuals in the wild seem to be doing well. They are nesting successfully and raising young and expanding their territory on their own and reclaiming parts of their former range," Jacqueline Robinson told Quirks & Quarks host Bob McDonald.

The study is the first to map out the genome of this largest species of land bird in North America, as a way to monitor their health as the population continues to recover. It was published in the journal Current Biology.

Saved by historically high populations

Robinson is a postdoctoral scholar in the Institute for Human Genetics at the University of California San Francisco. She said that when population sizes become very small, there's a risk that subsequent generations could suffer from genetic diseases caused by inbreeding.

"Inbreeding tends to cause an increase in the prevalence of genetic disorders that are caused by mutations that are recessive. And what that means is that if you have one copy of this mutation, there's no real impact. But if two copies of that mutation are inherited in a single individual, then the trait or disease will manifest," said Robinson.

Another concern is the loss of genetic variation, which can affect how the species is able to adapt to its environment over time. 

Robinson and her colleagues studied the genome of two California condors and looked for signs of inbreeding by analyzing the maternal and paternal genetic lines for similarities. They found some evidence of inbreeding, but this came from before the captive breeding program started in the 1980s, and it was not as much as they had expected.

"There was actually quite high genetic diversity," she said.

It hasn't been easy and it's been a decades-long effort at this point, but it's paid off.- Dr. Jacqueline Robinson, UCSF

Robinson added that from the diversity in their genome it seems likely that historically, California condor populations would have been in the tens of thousands, ranging across the contiguous United States. 

"I wasn't expecting to see very high levels of genetic diversity in California condors, but it makes sense when we consider the long term evolutionary history," she said. "Genetic diversity, it takes a long time to build up. And apart from inbreeding, it would take a fairly long time for it to be completely lost just due to small population size."

Informing future conservation efforts

By mapping out the genome, researchers can now use this data as a baseline to monitor the species moving forward.

"Things like feces or discarded feathers, we can get biological material from that, sequence those genomes, and find out if there's inbreeding in the wild or if there are individuals that are migrating between different populations near different release sites," said Robinson.

Ultimately, she adds that this is yet another promising sign for the future success of the California condor.

"I think that there's reason to be optimistic that California condors, the population can grow in the future and they can live alongside humans," she said.

"It hasn't been easy, and it's been a decades-long effort at this point, but it's paid off."

Produced and written by Amanda Buckiewicz.