Zoe purrs and grunts when she hears women talking. Just like any house cat wanting her ears scratched, she rubs against the chain-link fence invitingly.
But Zoe, who lives at the Smithsonian National Zoo's Conservation and Research Center in Front Royal, Virginia, is no kitty cat; she's a rare clouded leopard. And the specialists at the center are among the few animal experts in the world who have been able to get clouded leopards to breed without literally killing one another.
Since the zoo started its captive breeding program in 1978, 75 clouded leopard cubs have been born.
"The common theme is that these make horrible exhibit animals and you can't show them and they kill each other," said JoGayle Howard, National Zoo's animal fertility specialist.
Fewer than 10,000 clouded leopards are believed to survive in the wild. The breeding program may hold the key to the future of a species vanishing fast as its forest homes disappear and as poachers learn how to capture them.
For years the incredibly rare cats had frustrated zookeepers hoping to breed them. The males killed the females, sometimes almost instantly. Even if they could tolerate one another in a cage, they refused to breed. And they hid.
The Smithsonian staff overcame those problems through dogged patience, making one change after another to reduce the animals' stress, improve their health and get them in the mood for mating. These ranged from giving them trees to climb, to varying their diet and gradually getting them used to being together.
The clouded leopards are the smallest of the "great cats," just a meter long and weighing between 10 and 20 kilorams. Their large, grey paws and bowed legs make them well suited for climbing trees.
Named for the cloud-shaped grey and black markings on its short fur, the clouded leopard is found in southern China, Thailand, Malaysia and Indonesia's islands of Sumatra and Borneo.
DNA evidence suggests that the clouded leopard may be most closely related to the extinct sabre-tooth cat of North America - a legacy carried today in its unusually long canine teeth.
Killings at night
At the Smithsonian center, a small female purrs in an enclosure and meows frantically when carnivore specialist Ken Lang enters. After he scratches her, she goes back to trying to get the attention of the much larger male in the next cage.
"Obviously, with his bite, he'd kill her in a second," Lang said. He is trying to habituate the two, in the eventual hope of a mating.
The National Zoo team worked on one pair for a year, getting the male and female used to one another before they dared leave them alone together for a night. "That's when the killings occur, is at night," Howard said.
Lang, Howard and a few other experts, mostly in Thailand, have been studying clouded leopards for 20 years. They believe they are finally beginning to understand them, and what they are learning defies common wisdom about zoo animals.
"The biggest problem we have (in zoos) everywhere is the males kill the females," Howard said. "What is it that makes them so weird, that makes them kill their mates?"
It turned out that in zoos, the shy, tree-dwelling cats, were usually put next to the aggressive and loud tigers.
"It was bad for a clouded leopard to put it near something that can eat them," Howard said.
And they were put in typical cages, with concrete floors and nowhere to hide. "They love to go up," Howard says. "Let them climb, their stress hormones go down."
So in Thailand, the leopards' cages were fitted with large trees. As soon as they were moved away from the big cats, into cages with large tree limbs they could climb on, the stress hormone levels in their droppings plunged, the females started ovulating and the males began producing normal sperm.
The specialists also learned what to feed the leopards.
"The most common mistake with any carnivore, including cats, is you just throw in meat," Howard said. They need other nutrients, including calcium. So they worked with feed producers to formulate a special leopard chow.
And in perhaps the biggest rejection of conventional wisdom, the keepers and vets started hand-rearing the cubs. These cats are tame.
"We wanted to make sure that these moms would not kill them. So we pulled them. We found hand-rearing these cubs would help. They have been socialized to people," Howard said.
Few clouded leopards are on public display, but the National Zoo plans to feature some of its rare specimens in a new, treetop-level exhibit later this year. The Front Royal conservation facility is not open to the general public.
Howard, whose fame mainly lies in artificially inseminating the notoriously hard-to-breed giant pandas, says she does not consider this the pinnacle of her career. She is responsible for the conception of Tai Shan, the six-month-old panda cub currently basking in the oohs and aahs of visitors to the National Zoo in Washington, D.C.
She is more proud of the clouded leopards she has helped bring into the world. "Giant pandas are easy compared to clouded leopards," Howard said.