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Scientists at zoos nationwide are working to find a successful method of artificial insemination of Asian elephants so the world won't have to do without the mighty beasts.

Asian elephants are the smaller of the two species of elephants living today. Once, there were hundreds of species, but only Asian and African elephants have escaped extinction.Asian elephants have smaller ears than African elephants, and they have high foreheads with two prominent bumps. Their backs arch in the middle, and only males usually have tusks.

Asian elephants are an endangered species. Fewer than 25,000 are left in the wild. In the United States, about 130 Asian elephants live in zoos, a small number perform in circuses and a few are privately owned.

Since 1880, only 52 Asian elephants have been born in North American zoos, about half of them in the last eight years as breeding efforts intensified.

Although all of those births were the result of natural breeding, natural breeding is not an option for most zoos.

"There are few zoos capable of maintaining a bull elephant. They are large and difficult to manage, and they can be unruly at times," said Bruce Read, curator of large mammals at the St. Louis Zoo.

"You need heavily reinforced facilities with remote-controlled doors operated by a hydraulic system. Several years ago, we did have an African bull elephant (he died in 1972), but as a matter of safety the animals, we chose not to risk housing another bull."

In 1976, the London Zoo made the first attempt to artificially inseminate an elephant, and the Washington Park Zoo in Portland, Ore., has been doing research since 1974. Yet to date, no births have resulted from artificial insemination.

In artificial insemination, semen is collected from a male animal. Humans put the sperm into the reproductive tract of a female and hope that pregnancy results.

The St. Louis Zoo's most recent attempt at artificial insemination occurred in January, with an elephant named Carolyn.

"It will take five to six months after the artificial insemination procedure to tell if Carolyn is pregnant. You have to wait two full estrous (fertile) cycles to be sure, which is not really a long time, considering that elephants have a 22-month gestation," Read said.

Another research project is the Species Survival Plan, a national program under the auspices of the American Association of Zoological Parks and Aquariums. The association is a professional organization that coordinates conservation efforts on behalf of many endangered species.

"The zoos are cooperating in an attempt to save a number of endangered species," said Bill Boever, senior staff veterinarian and director of research at the St. Louis Zoo.

For a female elephant to get pregnant, sperm must be introduced during estrus, the fertile period of her cycle. But the fertile period in elephants is almost impossible for observers to determine.

"There is no sign from the animal," Boever said. So the zoo's scientists are looking for hormonal and microscopic clues.

"We looked at 43 different blood parameters before we found one that is a reliable indicator of estrus," Read said. "The consensus seems to be that elephants cycle about three times a year. Now we need to learn to detect when; we need to be able to predict the cycle and figure out the optimum time for insemination."

Fewer than a third of U.S. zoos have male elephants, and some are the wrong age for breeding. Balke noted that of the 23 Asian elephants that have been born in North American zoos since 1980, 17 are male and only six are female.

"That's one of the biggest issues with captive breeding and it may be a problem with artificial insemination, too the disproportionate number of males. If we continue to produce a lot of males, what will we do with them?"

Even though the 130 Asian elephants in American zoos have produced 23 calves in the last eight years, Read said that is not enough to maintain the population.

"The actual numbr of breeding bulls in this country is under 10," he said.

The elephants' size also puts pressure on zoos to find ways to use artificial insemination.

"Simple manipulation of an elephant is a major issue," Boever said. "With other species, if we knew of a place that had a male and we had a female, they would ship the male to our female for breeding. There is a lot of movement with other species, but elephants are difficult to move. And you also have to have the right facilities for breeding to take place."