SAN PASQUAL VALLEY - Call it Match.com for rare and endangered species. When an Indian rhino was born last year at the San Diego Zoo's Wild Animal Park in the rural San Pasqual Valley east of Escondido, jubilant park officials noted that the calf's birth had increased an endangered species' population by one.

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The calf, a male named Surat that will turn 1 on Oct. 1, was the product of a breeding program that sounds very much like the popular Match.com online dating service for humans looking for ideal mates.

Borrowing an approach used by professional matchmakers, park scientists and keepers said in recent interviews that they used an extensive database that lists the characteristics of every Indian rhino housed in a zoo or similar facility in North America to find the perfect mating couple.

Arun and Goalpara, an 18-year-old male and a 20-year-old female, respectively, emerged as the top candidates - they were both already at the park - and the match eventually resulted in Surat's birth.

The rhino database, which has helped produce 92 white rhinos and 54 Indian rhinos at the park since it opened in 1972, is just one of more than 450 registries that exist for rare and endangered species. Also known as stud books, the databases are maintained by the national Association of Zoos and Aquariums, a Maryland-based organization that accredits animal institutions in North America.

All 216 of the association's members use the databases to decide which rare or endangered species of animal they will breed, according to several association members.

Dr. Bob Wiese, director of animal collections at the Wild Animal Park and the person in charge of its breeding programs, helped develop the stud books and is now considered to be one of the leading experts on endangered species genetics.

"It's the ultimate dating service," he said of the databases.

"Basically, it's a family tree of all these animals in the computer. Based on that, we can tell which ones have the rarest genetic family lines. We try to breed those first."

Park actively breeding

Run by the Zoological Society of San Diego, which also operates the San Diego Zoo, the animal park is home to 79 endangered species of mammals and 37 endangered bird species.

Park spokeswoman Yadira Galindo said Przewalski's horses, the California condor, and types of antelopes known as bongos and Arabian oryx are some of the other species whose populations have been boosted with the help of breeding programs in place at the animal park. She said offspring often are reintroduced into the wild but that some animals become part of the breeding programs.

Wiese said efforts to expand endangered species' populations often are complicated because any one zoo may have just a few members of a particular endangered species, and that in many cases, those animals are too closely related for breeding.

Breeding any animals with the same or close blood lines raises the potential for birth defects and other genetic problems, said Wiese, who added that the stud books are designed to minimize inbreeding and keep endangered species' gene pools as diverse as possible.

Brandie Smith, interim director of conservation and science for the zoos and aquarium association, said that, like national registries that track bloodlines for pedigreed dogs and horses, the endangered species stud books were started decades ago. She said they now contain extensive information about several generations of animals housed at zoos and similar institutions that are association members.

Logistics and ownership

Birth, breeding and death dates, and information about parents, siblings and other relatives are among the details compiled in the databases, she said.

Association members have agreed to work together to make the best breeding matches possible, and they often exchange or loan animals if it helps increase the species' population, said Smith.

"Sometimes a zoo will work on its own," she said. "But if you want to maintain a species in a long-term program, you have to have a big gene pool."

Wiese said the participants' commitment to coordinating their efforts often means zoos must shuffle animals around when a new breeding program starts up or a stud book identifies male-female mates that are in different parts of the country. Advisory panels assigned to monitor specific species therefore make breeding recommendations at least a year in advance to give participants time to work out the logistics, he said.

The Wild Animal Park recently hosted a meeting for a panel that suggested potential mates for lion cubs born at the facility last year, for example. Ties within their own pride meant the youngsters would be breeding with siblings and other relatives if they stayed at the park, Wiese said.

Zoos and aquariums that own the animals earmarked for breeding have the final say on whether the animals breed and also what becomes of any offspring, said Wiese. Animal ownership disputes are virtually nonexistent, he said.

"Technically, somebody owns them," Wiese said about animals that are loaned out. "But for the benefit of the program, everyone has agreed they're going to do the right thing and we'll just loan them (around)."

Preventing new births

The flip side of the matchmaking equation is the need to prevent animals viewed as inappropriate mates from reproducing. Wiese said that occurs more often than people might think.

"Most of the (advisory) recommendations are 'do not breed' because animals can reproduce a lot more than they need to perpetuate their population," he said, citing the lack of predators, major disease and other threats in a captive environment. "In most cases, we would run out of space if we allowed them to breed uncontrolled."

Wiese said the Wild Animal Park employs a variety of methods to keep its animal populations in check, including long-term Norplant implants that release hormones that keep the ovaries from releasing eggs in orangutans and gorillas, and contraceptives mixed into the feed or injected into the bodies of other animals.

Castrating and spaying are some of the more permanent solutions. However, Wiese said the simplest approach is sometimes the easiest.

"If they're solitary animals in the wild, we can just keep the male and females separate," he said. Or we keep the males in one exhibit and the females in another. That solves that problem."

Contact staff writer Andrea Moss at (760) 739-6654 or amoss@nctimes.com.