Day of the Condor? : Genetic ‘Fingerprinting’ Could Help Breeders Keep Birds From Extinction

As an electric nest nurtures the egg that holds 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 of the eggs produced without breeders knowing how closely the parents are related.

Knowing the family trees of the 27 remaining condors 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--most commonly 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 pioneers in the world trying to apply this breakthrough in human genetics to endangered animals.

Ecstatic is the word Bill Toone, curator of birds at the Wild Animal Park, uses to describe his reaction when he learned late last year that San Diego scientists had successfully made useful genetic fingerprints of the condors.

Significant to Survival

“It has the potential of contributing very significantly to the long-term survival of the species,” Toone said.

“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 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 the zoo’s breeding work.

Statistical Approach

“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 fingerprinting 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 a captive-breeding triumph. (Genetic fingerprinting of the two parents-to-be will have to wait until after breeding season, 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 much as possible, 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 are unclear.

Inbreeding Detrimental

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, as well as with pygmy chimpanzees.

With the chimps, Ryder tested the genetic fingerprints against the much more tedious chromosome studies done earlier to determine paternity of an animal.

Vernon’s In, Kevin’s Out

Holding some fingerprint patterns up to the light, he pointed to the line patterns of the daughter, Lenore, next to those of her mother and her two possible fathers, Vernon and Kevin. Any lines that her mother didn’t have must have come from Lenore’s father.

“You can go through here and find 12 bands that qualify Vernon and exclude Kevin,” Ryder said. “It’s really elegant data that just pounds it in about who the father of this chimp is.”

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 around the country. But in many cases that will be enough to produce DNA fingerprints for them, 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 quite closely related, and they would have to be paired anyway, Toone said.

Will Affect Pairings

“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 around the country, genetic fingerprinting also is proving 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.”

Other Species Affected

The zoo group is behind the Species Survival Plan, an effort to preserve 37, so far, endangered species worldwide. Currently, 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 rethought.

As wildlife habitats shrink, more and more animals are being forced into isolated genetic “islands,” Ryder said. Fingerprinting might help scientists determine whether such islands are too inbred to be genetically viable populations that can be saved, he said.

Though such applications for the technique are in the future, its potential is sparking increasing interest, Ryder said.

CALIFORNIA CONDOR GENE POOL

The parentage of all the mating pairs is unknown, making it difficult to determine which of the younger birds would best be mated. Breeding close relatives could increase genetic problems and further jeopardize the condors’ chances to escape extinction.

PAIR ONE

Fertile egg laid March 3, now in incubator.

PAIR TWO (male dead)

6 surviving offspring, one of which has fathered a bird by the female in Pair Three.

PAIR THREE (male dead)

5 surviving offspring

PAIR FOUR (female dead)

4 surviving offspring

PAIR FIVE (both dead)

2 surviving offspring

PAIR SIX (female dead)

1 surviving offspring

Fourteen of the birds are at the San Diego Wild Animal Park and 13 are at the Los Angeles Zoo. There are two other, unmated birds whose parentage is also unknown.