Conservationists Trying Radical Ways to Preserve ‘Megaspecies’ : Wildlife: In Namibia, officials tranquilize rhinos and saw off their horns in an effort to discourage poachers. Tigers, elephants and gorillas also are on the brink of extinction.

A 2-ton black rhinoceros drops to the ground. A group of chain saw-wielding Namibians converge on the beast and slice off its distinctive horn.

It could have been a scene of wanton slaughter: Poachers often shoot rhinos for their horns, which are more valuable than gold or cocaine when sold for Far Eastern elixirs and Yemeni dagger handles.

But this rhino was dehorned to save its life. The enormous animal was felled by a wildlife official’s tranquilizer rifle for an operation based on the theory that hornless rhinos won’t be targets.

Only 2,000 black rhinos are left in all of Africa. Several hundred have had their horns officially severed and safely stored away.

Some wildlife experts believe that conservation of the planet’s megaspecies, such as tigers, elephants and gorillas, demands extraordinary strategies--beyond preserves, parks, zoos, captive-breeding programs and “frozen zoos” of sperm, ova and embryos.

This year the Convention on International Trade in Endangered Species (CITES) marks its 20th anniversary, and the 20-year-old U.S. Endangered Species Act is up for reauthorization.

Wildlife worldwide is threatened most by habitat destruction and poaching. The world’s few hundred mountain gorillas are also caught in the deadly cross-fire of Rwanda’s civil war. China’s giant panda populations have been decimated in the last decade despite multimillion-dollar conservation programs, according to renowned biologist George B. Schaller.

The World Wildlife Fund has put the black rhino, Siberian tiger, giant panda and Asiatic black bear on its newest “Ten Most Wanted” list of endangered species. The organization warns that wild tigers, which number only about 7,000 globally, could face extinction within 10 years without effective long-term protection.

CITES, whose 120 member nations can ban international commercial trade in endangered species, points to rebounding leopard populations as a major achievement, and to crashing rhino populations as a failure.

CITES’ controversial 1990 international ban on elephant-ivory trade “is one of the only success stories in conservation,” according to Cynthia Moss, longtime leader in African elephant research and conservation. By reducing the demand for ivory, she says, the poaching rate in Kenya, for example, has been cut 90%.

“The ban has to stay,” Moss contends. “The ban is the message. If it is lifted, elephants will be killed again for their ivory.”

Not everyone agrees. Critics like American author Raymond Bonner indict outside wildlife organizations for imposing such a ban on all African elephant countries. Bonner calls for “sustainable utilization.” Africans, he says, should be allowed to cull herds, eat the meat and sell the ivory at sensible levels.

To ensure their survival in some parts of Africa, elephants may be put to work. A major problem elephants may help alleviate in many regions, for example, is the tendency for thick bush vegetation to creep onto grazing land. Lions that attack cattle hide in the bush.

“Elephants are the architects of the savannas,” Moss says. “The combination of elephants and fire keep the savannas open. Even Masai chiefs in Kenya say, ‘Let’s get your elephants out there (outside Amboseli National Park) to clear the bush.’ ”

The unconventional African rhino-saving technique is caught on the horns of a dilemma. “We know nothing long-term about the effects on rhinos of frequent dehorning,” says Diana McMeekin, executive vice president of the African Wildlife Foundation in Washington. “Horns regenerate, but they seem to grow back increasingly frayed and fissured. We could have a whole population of rhinos looking like Peruvian guinea pigs.”

With National Geographic Society support, Joel Berger of the University of Nevada is in the Namib Desert assessing the ecological consequences of dehorning on the black rhino. Janet Rachlow, also of Nevada, is conducting similar studies on government-dehorned white rhino in Zimbabwe.

“There shouldn’t be a rush to declare this the one and only way to save rhinos,” McMeekin said. “It’s situational. Where the rhino habitat is dense bush, poachers could shoot to kill before knowing whether the animal has already been dehorned. On plateaus in Namibia, it may make sense to dehorn.”

“We don’t notice something until there’s a crisis,” McMeekin added. “We had known about the elephants for a long time, but look what it took to galvanize world action. It hadn’t dawned on us how serious the situation had become for the rhino. Then, when our focus shifted to the rhino, no one was watching the tigers. Now they are going down the tubes.”

Tigers appeal to the same type of markets as rhino. Fewer than 400 Siberian tigers, the world’s largest cats, survive in the wild. About 800 live in captivity. In a dramatic rescue in January, a pair of orphaned Siberian tiger cubs whose mother was probably killed for her body parts was flown thousands of miles from their homeland in the Russian Far East to safety at the Henry Doorly Zoo in Omaha, Neb.

Although the double-barreled weapon of poaching and forest clear-cutting menaces Siberian tigers, experts say poaching is the most immediate danger because of the Oriental medicinal market for tiger parts.

The tigers were relatively safe from this threat before the collapse of the Soviet Union. Subsequent relaxation of travel restrictions across the border between China and Russia made poaching easier.

In folk medicine practiced in China, Korea, Taiwan and Japan, tiger skins, skulls, genitals and even whiskers have healing powers. Tiger bones are pulverized and prescribed for rheumatism. Pulverized bones are also an essential ingredient of “tiger wine,” a Chinese export.

“A real problem for conservation of the tiger is combatting thousands, at least hundreds, of years of Oriental belief,” said wildlife ecologist Howard B. Quigley of Frostburg State University in Maryland. “It is culturally ingrained. China has proposed breeding tigers for their parts. That’s repugnant.”

One hope of saving the tiger is introducing more Western medicine into China, said Quigley, who is studying the Siberian tiger in a three-year U.S.-Russian project.

“Instead of using tiger bones,” he said, “they’ll use Tylenol.”