Day of the Condor? : Genetic ‘Fingerprinting’ May Help Save Endangered Birds

As an electric nest nurtures the first captive-bred California condor chick, researchers at the San Diego Zoo and Wild Animal Park have embarked on an ambitious program to use genetic “fingerprinting” to make that chick one of the last of its kind.

That is, they want to make it among the last eggs produced without breeders knowing how closely related its parents are to each other.

Knowing the 27 captive condors’ family trees is essential to prevent inbreeding problems and to give the animals a genetic edge when they are reintroduced into the wild, perhaps as early as 1993. Without it, future generations of condors might not have the genetic adaptability to survive in the wild.

The San Diego researchers hope that genetic fingerprinting--mostly used in humans to establish paternity or to identify crime suspects--will provide a powerful tool to assure the condors’ future. They are among a handful of scientists in the world trying to apply this breakthrough in human genetics to endangered animals.

‘Exciting Technique’

“It’s a very exciting technique. I can’t tell you how important it is to our program,” said Joseph J. Dowhan, coordinator of the condor project for the U.S. Fish and Wildlife Service.

A genetic fingerprint looks like a cross between an X-ray and the bar code on products at the supermarket. To make one, scientists extract the DNA from cells and chemically chop it up to see the different-size pieces that result from certain regions of the molecule. DNA is the chemical blueprint for all living things.

In 1985, a British scientist discovered that the relative sizes of these pieces can be translated into patterns of lines so distinctive that they identify the person from whom the DNA came. Because parents pass their unique DNA patterns on to their children in chromosomes, discovering matching DNA line patterns between two people indicates that they are related.

How many matching bands it takes to determine, for instance, whether animals are siblings or cousins is a question that remains to be resolved--and that will be crucial to zoo breeding work.

“It’s going to take a careful statistical approach, but individuals that share more of these bands are more likely to be closely related than ones that don’t,” said Oliver Ryder, the San Diego Zoo geneticist who is leading the effort.

The problem is that no one is sure that the wild-hatched parents of the egg laid March 3 are not so closely related--perhaps even brother and sister--that their offspring could be a genetic tragedy even while it is a captive breeding triumph. (Genetic fingerprinting of the two parents-to-be will have to wait until after breeding season ends, when blood can be drawn without interrupting their courtship.)

With only 27 condors known to be in existence, all of them at the San Diego and Los Angeles zoos, scientists need to assure that the birds reproduce as often as possible if the species is to survive, Ryder said.

Breeders know enough to worry that mating closely related animals would result in infertile eggs, unhatched eggs, chicks that die soon after hatching and adults that have trouble reproducing. But the familial lines of the birds is unclear.

Furthermore, inbreeding also would draw down the “gene pool,” the sum of hereditary characteristics available to future generations of condors.

“The ability to adapt to changing environments and to rebound from environmental onslaughts, the key to that is having the previously existing genetic variability in the population,” said Ryder, who works at the zoo’s Center for Reproduction of Endangered Species.

Ryder’s research group so far has used the new technique to develop genetic fingerprints on eight condors.

One of the most striking aspects of the work will come in doing genetic fingerprints of long-dead condors. Some are preserved in museums, and some survive only as tissue samples in labs throughout the country. But in many cases, that will be enough to produce DNA fingerprints, Ryder said.

Scientists might be able to track down hereditary trails beyond the seven to 14 genetic lines they think are represented in the adult “founder” birds now in captivity. Finding traces of a dead bird’s genetic structure in a still-living bird would provide a chance to re-establish that genetic line through careful breeding.

Conversely, the genetic fingerprints could bring the bad news that all the animals are closely related, and they would have to be paired anyway, Toone said.

“We have hypothesized pairings based on the assumptions that our founder birds are not related,” Toone said. “But we have no real way of knowing that. Now that we have the ability, that’s going to have a very distinct and significant impact on the pairings we would consider. We may find that we have no choice but to, say, pair cousins together. But it’s the sort of thing that, if we don’t have to do it, we’ll know that we have other options.”

In San Diego and at a handful of other genetics labs throughout the country, genetic fingerprinting also is proving to be useful in determining how to proceed with other species-rescue efforts, said Thomas J. Foose, conservation coordinator for the American Assn. of Zoological Parks and Aquariums, in Minneapolis.

“We’re trying to utilize it to clarify some pedigrees,” Foose said. “It’s also very critical that we try to elucidate just what the possible subspecies situations are for forms like the Sumatran rhino. That’s going to have great relevance to how we organize our programs.”

Foose’s group is behind the Species Survival Plan, an effort so far to preserve 37 endangered species worldwide. At present, its trappers are in Asia trying to capture 14 Sumatran rhinos for a breeding program.

The Sumatran rhino has three subspecies, but conservationists hope they are genetically similar enough to interbreed without making the offspring sterile, Foose said. If genetic fingerprinting determines they are not, the entire breeding plan will have to be re-examined.

For the condor, genetic fingerprinting is another tool to fight extinction. No one can know if the efforts will work.

“People ask us, ‘How do you know you’re in time?’ We don’t. The condor is so close to the edge, with so few birds in existence, that we don’t know,” Toone said. “Perhaps we’re already too late.”