The tigers that slip through the leafy shadows of Zoo Atlanta are losing their grip in the wild, according to an international report released this week.

Sumatran tigers are killed for body parts and chased from their ranges by encroaching humans, the World Wildlife Fund reported Tuesday. The report warns that unimpeded poaching and habitat loss could be the "death knell" for the subspecies, on display at the zoo.

Courtesy of Zoo Atlanta (ENLARGE)

Jalal is a Sumatran tiger at Zoo Atlanta. An international report says Sumatran tigers are in extreme peril in the wild.

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The cat already is listed as critically endangered on the World Conservation Union's Red List of Threatened Species; an estimated 400 remain in the wild.

If nothing is done to save Panthera Tigris sumatrae, they may one day be seen only in zoos, said Leigh Henry, a WWF program officer.

"I have an 18-month-old daughter, and I'd like to think she could one day see one in the wild," said Henry, who works in TRAFFIC North America, a division of the WWF and World Conservation Union. The program specializes in animal trade.

The report did not surprise Megan Wilson, assistant curator of carnivores at Zoo Atlanta. The zoo has four Sumatran tigers and hopes to breed two. She is familiar with the loss of their habitat and the illegal trade in tiger parts.

"It's my hope that they will survive in the wild," said Wilson.

Yet laws enacted to protect the tiger have not worked because they aren't rigidly enforced, said WWF researchers. In 2006, they visited markets in 28 cities across Sumatra.

Posing as shoppers, they found more than 30 stores — 10 percent of the shops surveyed — trading in the big cats' teeth, claws, skin pieces, whiskers and bones. Twenty-three tigers likely were killed to supply the stores, the researchers estimated. A comparable survey, taken from 1999-2002, concluded that poachers had slain 52 tigers to supply stores with parts that were used for everything from folk medicine to aphrodisiacs.

The drop in estimated tiger deaths does not prove that Indonesian conservation laws are working, said Henry. It means that tigers are harder to poach: There aren't as many left.

"It's depressing," she said.

Vanishing land, cats

Tigers are a mainstay in North American zoos. Figures from the Association of Zoos and Aquariums show that 258 of the big cats live in AZA-accredited institutions. Almost half are the Amur, or Siberian, tigers that roam Russian forests.

Seventy-three of the North American population are Sumatrans. Zoos in Dallas, San Francisco, and Phoenix, as well as the National Zoo in Washington, house them.

Sumatrans are the smallest of the Tigris subspecies — the most distinct, too, brilliant orange and black. Their stripes stand like bare trees against sundown. At Zoo Atlanta, they often appear suddenly from a stand of hardwoods, crouch to drink, then fade again into the gloom.

They may vanish altogether in Indonesia, warned Ron Tilson, director of conservation for the Minnesota Zoo. Tilson heads the AZA's species survival plan, a program that oversees the breeding of captive tigers at zoos across the country. The SSP last year approved Zoo Atlanta's proposal to breed Sumatran tigers Kavi and Chelsea. Zoo officials hope the two will produce a litter this year.

Tilson also is co-author of "Tigers of the World." Published in 1988, the book reviewed the environmental, political and biological challenges facing the world's largest feline. The book, which has been rewritten to reflect changes in the past two decades, is about to be republished.

The revised "Tigers" has no good news for the Sumatran cats, he said.

"We know, for a fact, that in the last 20 years, half their habitat has been lost," he said. "As have half the tigers."

If the population continues to decline, he said, the tigers will lack the gene pool to sustain themselves. Sumatran tigers, like the vanished Javan and Bali tigers, will roar their last.