It was a moment of hushed expectancy at Omaha's Henry Doorly Zoo. A team of 20 veterinarians, neonatologists and reproductive specialists crowded into an operating room one morning last month as a cesarean section was being performed on a 9-year-old Siberian tiger named Nicole. Staff veterinarian Dr. Doug Armstrong, 39, pulled out one, then another and finally a third newborn cub, each weighing a little less than three pounds. The third cub—a white male—died two hours later from respiratory' problems, but the two amber-colored cubs—a male and a female—thrived from the start. Because of the anesthetic, the tiger cubs were asleep on arrival.

The cubs may have slept through the experience, but not so the scientific community. While it is not unusual for tigers to be born in captivity, there was nothing ordinary about what took place back in mid-January. That was when Nicole was implanted with 15 artificially fertilized embryos. The unprecedented delivery of the world's first test-tube tigers 109 days later "had us flying pretty high." says Dr. Lee Simmons, 52, Doorly's director.

This first successful reproduction through in vitro fertilization of a big cat capped 15 years of research. Adapting a technique used on domestic cats, hormones were injected into Nicole and two female Bengal tigers to induce ovulation. Ripened eggs were extracted from the two Bengal tigresses and mixed in a petri dish with sperm, collected from a white tiger, to produce the 15 embryos.

In the days after their birth the cubs were bottle-fed five times a day, first on Nicole's antibody-rich milk and now on a special formula. The surrogate mother never bonded with her cubs and will have no role in their upbringing. The cubs, who will stay at Doorly for the foreseeable future, have not been given names.

Far more than just a biological curiosity, Omaha's success could have profound implications for saving endangered species—by taking lab-produced embryos, frozen in liquid nitrogen, for implantation in the wild. The Doorly team hopes to test the technique on the diminishing tiger stock of Asia and later on lions, pumas, cheetahs and other beasts. Still, thrilled though they are, the Omaha scientists are trying not to lionize their accomplishment. From a big cat's perspective, notes Simmons, "Perhaps there should be more fun to procreation."