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Like online dating sites for endangered species, many zoos use computerized matchmaking to mate animals in captivity in hopes of saving some of the world's most vulnerable creatures.

The tools of the trade range from frozen panda sperm through genetic databases to ultrasounds for hefty rhinos.

But like dating everywhere, it can be expensive, complicated and doesn't always work.

After more than three decades of efforts, some experts are taking a fresh look at modern breeding tactics. Zoos, they say, cannot keep pace with the high costs of shipping animals from one facility to another, as the loss of wild habitat pushes more creatures to the brink of extinction.

A movement to improve captive breeding began in the late 1970s, when scientists realized that some zoo-held baby giraffes, gazelles and deer were more likely to die if inbred.

"That really caused a sea change in zoos because they realized they had to be better at managing captive populations," said David Wildt, head of the Center for Species Survival at the Smithsonian National Zoo.

Today, survival plans exist for more than 500 species, including cheetahs, Asian elephants and black-footed ferrets.

The genetic data of captive specimens is fed into computers so scientists can determine the most diverse matches for each individual.

Sometimes the plans work, as for the scimitar-horned oryx, a graceful African antelope that was declared extinct in the wild in 2000 due to overhunting and habitat loss.

Thousands have been bred in captivity. Some have already been reintroduced in Tunisia, and there are plans to release more soon, according to the Sahara Conservation Fund.

China's giant panda breeding program has also been "extraordinarily successful," Wildt said.

China maintains a core population of captive pandas and rents some out to mate in zoos around the world, with the caveat that the animals must eventually return home.

"They only have one shot per year," said Pierre Comizzoli, a research scientist who works with the solitary bears at the National Zoo.

The 100-114 kg pandas rarely manage the position needed to conceive naturally, so zoo experts resort to artificial insemination.

Most years, the attempts have failed. One panda cub born in 2005 at the National Zoo has survived to adulthood. This year, experts for the first time used samples from two different bears, including one from a San Diego zoo.

A so-far healthy, baby giant panda was born on Aug 23 though its paternity will remain a mystery until the DNA tests come back. A second cub emerged stillborn a day later.

For other species, like the critically endangered Sumatran rhinoceros, inbreeding is now the only option left, US zookeepers say.

In the wild, as few as 100 remain in Indonesia and Malaysia. The females ovulate only if a potential mate is nearby - which isn't always the case.

A Cincinnati Zoo team began working with Sumatran rhinos in the 1990s and finally succeeded in getting a pair to breed in 2001, producing the world's first calf born in captivity in 112 years.

（中国日报网英语点津 Helen 编辑）

About the broadcaster:

Nelly Min is an editor at China Daily with more than 10 years of experience as a newspaper editor and photographer. She has worked at major newspapers in the U.S., including the Los Angeles Times and the Detroit Free Press. She is also fluent in Korean.