By Dan Klepal
The Cincinnati Enquirer

Terri Roth gives Emi, a Sumatran rhino, a piece of food Thursday in her pen at the Cincinnati Zoo. The Associated Press/TOM UHLMAN

The Cincinnati Zoo's pregnant Sumatran rhino, which made history with her first birth in 2001, is making history again - and at a critical time in the breed's existence.

Emi became the first Sumatran rhino in captivity to give birth in 112 years when Andalas was born. Her second calf is due in July.

But she has gotten through this pregnancy without the steroid hormone progesterone - an enormous success in a rare animal breeding program. Breeders used progesterone during Emi's first pregnancy to help make her uterus a receptive home for the embryo.

Many scientists don't consider the captive breeding program a success until a calf is produced without progesterone, said Terri Roth, vice president of animal sciences and director of the zoo's Center for Conservation and Research of Endangered Wildlife.

"Emi will be the first rhino in history to produce two calves in captivity and the first to produce a calf naturally," Roth said. "We wanted to give her one shot at carrying a pregnancy to term naturally."

Zoo officials turned to the synthetic drug, which should be produced naturally, after Emi had five miscarriages between 1997 and 2000. Sumatran rhinos are one of the most endangered mammals in the world, numbering less than 300. Emi's pregnancy this time around is particularly important after the sudden deaths of five Sumatran rhinos this winter at the Sungai Dusun preserve in Malaysia.

That reduced the number of captive Sumatran rhinos to eight - two of which are at the Cincinnati Zoo, and a third is Andalas, who now lives at the Los Angeles Zoo.

"Every new calf is a lifeline because the species is in such a critical state," Roth said.

Scientists at the zoo developed a program that made rhino breeding in captivity possible. It started in the early 1980s, as efforts to protect the Sumatran rhinos in the wild were failing.

Rhinos are critically endangered because of habitat loss and poachers, who kill them for their horns, which are believed to have medicinal value in some Asian cultures.

The initial challenge was getting males and females together. Sumatran rhinos only like to be around one another when it's time to mate.

Because females show no changes in behavior to indicate when they are receptive to breeding, zoo officials turned to science to determine when to put Emi and the male rhino, Ipuh, together.

By using ultrasound exams to determine ovarian follicle size, as well as blood samples to measure progesterone concentrations, scientists were able to determine when Emi was ready to mate.

Today, Emi is 337 days into her pregnancy, which typically lasts about 475 days. And she is doing well, with a strong fetal heartbeat and noticeable head and limb movement during ultrasound examinations of the 50-pound fetus. Andalas weighed 72 pounds at birth.

Paul Reinhart, who helps care for Emi and Ipuh, said Emi was a great mother the first time around.

"Some rhinos don't even recognize calves as their own," he said. "But within 10 minutes of Andalas' birth, she was licking him very gently and allowing him to nurse. There were a couple of times she even put herself between the baby and (zoo handlers)."

E-mail dklepal@enquirer.com