SEATTLE (AP) - A Seattle zoo's 20-year quest to use artificial insemination to make a baby elephant has been called cruel by some critics who say more than 50 unsuccessful attempts was enough.

Studies show artificial insemination is a longshot but Woodland Park Zoo officials said the procedures were necessary because the future of captive elephants is in crisis, The Seattle Times reported Monday.

Activists for years have called on the zoo to stop trying to impregnate the adult elephant named Chai.

Bruce Bohmke, the zoo's deputy director, said artificial insemination is the best option for breeding zoo elephants in the United States. Elephants are rarely imported from the wild, and shipping elephants to breed out of state is time-consuming and disruptive to the animal.

The insemination process is complex. Female elephants are fertile just three times a year, and scientists haven't perfected a way to freeze elephant sperm. This limits viability to a window of 24 hours.

Still, Bohmke says the effort is worth it.

"It's about saving elephants for us," said Bohmke, who sits on a committee that oversees management and reproduction of elephants in zoos accredited by the Association of Zoos and Aquariums. "Somebody needs to tell their story. And we believe strongly that seeing an animal in captivity has a huge impact."

A 2004 study in the journal Zoo Biology found Asian elephants in North America are particularly vulnerable because of low fertility rates. According to the study, which the zoo cites, the population could die out in 50 years without significant intervention.

Using an artificial insemination technique developed during the 1990s, an elephant named Shanti at the National Zoo in Washington, D.C., was among the first to conceive after six attempts, according to the study. She gave birth to a male calf in 2001.

In U.S. zoos, only two Asian elephants conceived from the method are alive today, Shanti's baby and another in New Mexico. The numbers are higher for African elephants, with nine now living in zoos.

What gives hope to Woodland Park officials is that artificial insemination did result in one pregnancy for Chai in 2008, but she miscarried in her first trimester.

Animal activists have pressed the zoo for years to stop breeding Chai and transfer all three of its female elephants to a sanctuary.

In June, two women filed an appeal after a King County Superior Court judge dismissed their lawsuit aimed at stopping the city from using taxpayer money for the Woodland Park Zoo. Last year, the city contributed $6.4 million toward the zoo's $31 million budget.

Activists' complaints included inadequate space; using Chai and another elephant that once lived at the zoo as "breeding factories;" and potentially exposing a calf to the elephant herpes virus, which in 2007 killed Chai's only baby, Hansa, who had been conceived naturally.

Zoo officials say their elephants get the best care possible.

Chai came to the Pacific Northwest in 1980 at age 1, a gift from Thai Airways International to celebrate its new Bangkok-Tokyo-Seattle route. Chai was noticeably mellow and even-tempered. Over time, the elephant's age, docility, and an ovulation cycle made her the zoo's best breeding candidate.

In 1992, she underwent her first procedure. Since then, Chai has undergone at least 50 attempts, according to zoo records.

Chai delivered once, after being sent across the country in 1998 to mate with a bull at Dickerson Park Zoo in Springfield, Mo. The U.S. Department of Agriculture, which oversees the Animal Welfare Act, later filed a complaint against Dickerson for allegedly abusing Chai. Dickerson neither admitted nor denied it, and settled by paying a $5,000 penalty.

Chai came back to Seattle, pregnant with Hansa, who was born on Nov. 3, 2000.

The baby was an instant hit. People lined up for hours to catch a glimpse of the adorable calf romping around the barn. Attendance tripled the first month; in her first year, overall attendance jumped 13 percent.

A contest to name her drew more than 27,000 entries. The winning name, Hansa, means "supreme happiness" in Thai.

In 2007, at 6½ years old, Hansa was found dead in the elephant barn after an eight-day illness. Doctors determined she'd died from a previously unrecognized virus of elephant herpes.

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