Rarely has a birth been so anticipated, or the wait so suspenseful. On March 24, for the first time in 16 years, the Smithsonian’s National Zoo’s Conservation and Research Center celebrated the birth of clouded leopard cubs.

The cubs weigh about half a pound each and are in good health. Because female clouded leopards sometimes harm their cubs, the newborns were promptly removed from their mother, two-year-old Jao Chu, and placed in an incubator. They will be hand-raised by staff at the Conservation and Research Center in Front Royal, Virginia.

The Smithsonian is widely recognized as the leader in conservation and research of clouded leopards. Since 1978, more than 70 clouded leopard cubs have been born at the Conservation and Research Center. But the last litter was born there in 1993, and no clouded leopards have been born at any North American zoo or conservation facility for the past six years. These cubs are the result of a new approach to clouded leopard reproduction, and represent hope for a species threatened by extinction.

Clouded leopards are so secretive that their current range can only be guessed at and population estimates vary widely. Scientists say 10,000 or fewer of the wild cats remain in the forests of Southeast Asia and surrounding islands.

The smallest of the big cats, clouded leopards weigh just 30 to 50 pounds and are about five feet long—although approximately half of that is tail. Their short legs, long tails and oversized paws help them balance on small branches, and their flexible ankles allow them to run down trees headfirst. The cloud-like pattern of their coats gives them their name, and helps them disappear into the shadows of the forest.

Despite their well-camouflaged coats and elusive nature, many clouded leopards are killed by poachers for their pelts. Poaching, combined with development-driven deforestation and habitat fragmentation, has made the clouded leopard one of Asia’s most endangered cats.

“We are the champions of this species,” says Dr. JoGayle Howard, who heads up the Smithsonian’s clouded leopard conservation program. It organizes and leads research on the cat’s behavior, hormonal cycles, reproductive physiology, natural history and more. “You can’t just do one little piece and hope to save a species,” says Howard.

The National Zoo has partnered with the Nashville Zoo and the Zoological Park Organization of Thailand to launch the Thailand Clouded Leopard Consortium and a clouded leopard breeding program at Thailand’s Khao Kheow Open Zoo on the outskirts of Bangkok. Since its inception in 2002, the consortium has produced 32 surviving cubs, all hand-raised, including Jao Chu and her mate, Hannibal.

Breeding clouded leopards is not as simple as combining a male and a female. Male clouded leopards have a gruesome record of attacking, maiming and sometimes killing potential female partners. The attacks come without warning, and the results are often fatal. While they still don’t understand the reasons behind the attacks, Howard and her team have learned to reduce the risk. In fact, their efforts to understand and prevent male aggression are what led to this birth.

Most cat species will not breed if the male and female are raised together. But, providing further evidence that clouded leopards are like no other cat, raising a pair together seems to be the only thing that does work for this species. “We now know that introductions work best with very young males who are just six months old” explains Ken Lang, the Conservation and Research Center’s mammal unit supervisor. Historically, most of the attacks occurred when already mature males were introduced to potential partners. This aggression is much less common if future pairs are allowed to mature together.

Hannibal and Jao Chu were introduced in Thailand when they were about six months old. The two grew up together and arrived at the Front Royal center in February 2008. They are now the only compatible pair among the Conservation and Research Center’s 12 clouded leopards. Their cubs prove that the technique works, and the implications for breeding more clouded leopards are “huge,” says Howard.

The cubs’ genes may be their most valuable trait. There are only about 75 clouded leopards in North American’s captive population, and many of these animals are too old or too closely related to be successfully bred. The new cubs' parents, however, are only one or two generations removed from the wild, so they are likely to carry genes that are different from those in the North American clouded leopard population. With any luck, each of the new cubs will be paired with a future partner by the time they are six months old.

In fact, Howard is already thinking about potential partners for the cubs. The North American Clouded Leopard Species Survival Plan, which coordinates breeding among the captive population, makes pairing recommendations based on the genetics and pedigree of each cat. These two cubs, with their wild genes, will be in high demand.

In the meantime, Howard and her team are not slowing down. “We just keep going,” says Howard, who credits thirty-years of science-based clouded leopard research for this birth. “It takes science, it takes research to understand a difficult species like this.” In fact, the Smithsonian’s Conservation and Research Center has ambitious plans for a multi-million-dollar clouded leopard breeding and research facility. Once completed, the facility will be able to house ten pairs of clouded leopards. Perhaps one or both of Jao Chu’s cubs will eventually produce their own cubs here.

But the National Zoo may not have to wait nearly that long to celebrate their next clouded leopard birth. Last week, just as the Conservation and Research Center’s staff began to organize a 24-hour birth-watch for Jao Chu, the Zoo’s second clouded leopard pair was spotted mating. The two—Mook and Tai—have mated before, but have never produced cubs. Howard is hopeful this time, saying the interaction appeared to be successful and the female “seemed more relaxed” than in the past.

For now, Howard and her team remain focused on the cubs. “Getting through the first week will be big,” she says. “Getting through the second week will be bigger. Every day’s a milestone.”