In a mountains desert along the Rio Grande a few months ago, U.S. agents arrested five men and seized a million dollars worth of goods smuggled over the Mexican border. The haul: 17,500 lynx, ring-tailed cat, gray fox and other pelts destined for European markets.

Last year, a leading Bogota newspaper exposed a massive underground traffic in endangered crocodile skins, parrots and snakes, smuggled from Colombia through Panama to Europe and Japan. Hugo Torrijos, brother of the former Panamanian leader, was implicated in the trade.

About the same time, six crowded crates of live animals - including leopards, tapirs, 50 baby macaque monkeys and 38 white-handed gibbons - were shipped from Vientiane, Laos, to Brussels. The cargo provoked an international outcry among conservationists because the rare gibbons, a species native to Thailand, could only have been smuggled across the Mekong River.

These three events are not isolated incidents. According to government officials in the United States, Africa, South America and Asia, they are part of a growing international scandal: The illegal traffic in endangered species. While there is a large legal trade in common animals such as mink, the growing traffic in endangered species is illegal because it breaks the law of countries where the animals are caught and violates the International Convention on Endangered Flora and Fauna, a treaty signed by 51 nations. The trade in rare plants and animals is a business involving hundreds of millions of dollars, corrupt public officials, "laundered" import documents, physical brutality to animals, and a cast of characters ranging from Somali poachers and New Guinea tribesmen to the sophisticated operators of organized crime rings.

"The profits in illegal wildlife are equivalent to profits in the drug trade," says U.S. Justice Department attorney Kenneth Berlin. "For a $1,000 investment, the smuggler can make ten grand."

Rhino horn - ground into powder for its mythical aphrodisiac attributes - brings $600 an ounce in the Far East, twice the price of gold. A woman's crocodile handbage costs $400 in West Germany. A majestic purple parrot known as a hyacinth macaw fetches $5,000 smuggled to the United States from Brazil. An endangered peregrine falcon is worth $10,000 to an Arab sheik.

The trade, coupled with increasing human destruction of jungles and other wildlife habitat, has brought hundreds of species to the edge of extinction: the Asian elephant, the Java rhino, the Bengal tiger, the Mexican green sea turtle, Australia's golden-shouldered parrot, Rwanda's mountain gorilla.

Moreover, the animal trade is a source of tension between Third World and industrialized countries. Africans and South Americans see it as yet another example of wealthy countries exploiting their resources and giving them little in return.

"It's a pretty dirty, sordid business," said Russell Train, president of the World Wildlife Fund. "A few dishonest dealers get rich, but it does not significantly help the economies of the developing countries."

Wildlife trading has probably existed since the stone age, but only recently has it reached the alarming point of devastating whole species. It can be traced, in the familiar pattern of the developing world, to the rise in population. The tribesman who must feed his family from an ever-shrinking resource base sees in ivory an easy profit.And American boom babies, now of age, are greedy for fashion furs and snakeskin sandals.

In 1976, the most recent statistics show, the United States imprted 91 million wildlife products - jewelry, handbags, coats, carvings; 32.5 million skins and hides; 34,000 trophies and 300,000 live birds. Of course, not all, nor even a majority of these items, are illegal. But U.S. officials are unable to estimate the magnitude of illegal trade. Much of it enters the country with phony documents masquerading as legal. A good deal slips in over the border or through poorly guarded customs ports.

The difficulty is determining what's legal. The same cat's skin may be illegal if it comes from a country which prohibits wildlife exports, or legal if it comes from a nation which encourages trade. And how to tell the difference between a watchband made from an endangered snake or one from a common snake? Between a rare orchid and an everyday variety?

The confusion leads to tangled problems of enforcement. The Environmental Defense Fund has recently spent hundreds of hours wading through the import documents attached to ivory shipments and has found that 80 percent are falsified or incorrectly filled out, for example, listing ivory from places like Hong Kong which have no elephants. Import documents are required to state the country of origin. EDF is preparing a lawsuit to force the government to keep better track of trade.

But it's a formidable task. U.S. attorneys, more concerned about drug trafficking and organized crime, are reluctant to prosecute wildlife smuggling. Judges are hesitant to slap fines or prison sentences on offenders. The complexity of gathering evidence is overwhelming - a single fur-smuggling case a few years ago required attorneys to analyze 60,000 documents. And, Fish and Wildlife Service agents, the men responsible, are more accustomed to chasing duck hunters out of season than analyzing the business records of multinational import firms. The result is uneven enforcement. For example, Wayne King of the New York Zoological Society says that New York City, one of eight approved ports for wildlife trade, has strict controls. "But I could drive a herd of elephants through Los Angeles and the Fish and Wildlife Service director there wouldn't give a damn."

It sounds discouraging, but there is reason for modest hope. The Justice Department recently set up a task force with new authority to investigate illegal trade. The U.S. World Wildlife Fund is raising money for a group called TRAFFIC USA to monitor the shipment of wildlife in and out of U.S. ports. And 51 countries have now signed the Convention on International Trade in Endangered Species, a comprehensive treaty that lists endangered species, sets up rules for trading, shipping and monitoring traffic. Drawn up in 1973, the treaty has only recently begun to have an impact. Signatory nations agree to ban exports of wildlife in danger of extinction. Rare species may be traded under strict regulations. However, more than half the world's countries, including major wildlife traders such as Japan, Belgium, Italy and Mexico, haven't ratified the pact.

Solomon Ole Sailbull, Tanzania's Minister for Natural Resources and Tourism, fears that "unless trade in endangered species is stopped, whole populations will disappear from the face of the earth."

The 1970s, Sailbull said, "have brought despair to wildlife conversion throughout Central and Eastern Africa. The rising prices of ivory, rhino horns, leopard and zebra skins increased profits to unprecedented levels . . . The bulk of poached products is smuggled out of the country and sold on international markets beyond our control. A large amount of public revenue goes into unscrupulous private pockets."

In Africa, the trade has spawned a new breed of poacher armed with machine guns, light aircraft and friends in high places.

While Tanzania has a fairly good enforcement record, Kenya has experienced widespread official corruption. The Kenyatta family, which ruled the country for years, was alleged to be involved in the lucrative ivory trade. The World Bank reportedly held up a $17 million loan in an effort to oust John K. Mutinda, a high Kenyan wildlife official accused of protecting poachers. However, Mutinda remained in place and the loan, to beef up anti-poaching forces, was approved. Kenya recently closed souvenir shops which fostered illegal trade, but poaching for export continues.

The wildlife trade in South America has become a major political controversy. "One of the reasons some of our countries are bankrupt is due to the fact that our natural resources are extracted in such a way that we soon shall have nothing left," said Felipe Benavides, a Peruvian conservationist.

Peruvian officials recently confiscated 12 Humboldt penguins as they were being shipped from the airport for West Germany. Benavides believes as many as 300,000 pelts of guanacos, a liama-like animal, have been exported to West Germany.

"Every day we have Germans trying to buy their way to obtain caiman (alligator) skins through any means," Benavides said. "The bribery that goes on is shocking, but what is more shocking is that most of the bribers come from West Germany, Belgium and Holland."

Gabriel Seisdedos, a Chilean wildlife official, estimates that 15,000 fox, otter and other skins are illegally smuggled into Argentina every year. In Chile's remote Southern islands, he said, "the poachers threaten the inspectors with guns, so the inspectors run away."

At the most recent meeting of the Convention on International Trade in Endangered Flora and Fauna, held in Costa Rica in March, Surinam and Brazil sharply criticized West Germany and Great Britain for importing thousands of ocelot, margay and other cat skins smuggled out of the Amazon region.

"The developed countries which allow these illegal products have been notified of the illegality of this trade," protested the Surinam delegation in an official statement, "and yet these products continue to be imported."

West German officials and British customs siad they are "looking into the matter."

Third world countries are not opposed to all animal killing, but when species are overexploited, they cease to be a commodity that can be harvested for continuous economic return. Brazil would eventually like to export crocodiles, but not when the species is threatened with extinction. In the case of Africa, tourism at the game parks, a major source of revenue, is adversely affected when there are no rhinos and zebras to be seen.

In the Far Eastern trading centers of Japan, Hong Kong and Singapore, wild animals are thought to have curative powers. In a Chinese medicine store, one can buy gall bladders of Malayan sun bears for liver problems, tiger bones to boil for a rheumatism potion, burned elephant skin to treat skin ulcers and deer antlers to enhance virility.

For many, animal smuggling raises issues beyond the conservation of species. "There's an immense amount of suffering," said Shirley McGreal, head of the International Primate Protection League in South Carolina. "To get baby monkeys you have to shoot the mother. The babies fall out of the trees and half the time they are killed."

Animals are transported in tiny crates, frequently without enough food or water. They often arrive diseased and injured, according to Jean-Yves Domalain, a former animal trader. He estimates that a third of the live animals traded die during their trips across continents and oceans to the zoos and pet stores of wealthy nations.

Spokesmen for the pet industry say the figures are exaggerated and that the animals are too valuable to be mistreated. The International Convention in Costa Rica, however, passed strict shipping standards to combat inhumane treatment.

While the animal trade has received the most international attention, a multimillion-dollar market for endangered plants is wiping out many species of flora around the world, biologists say.

Collectors will pay as much as $2,000 for a rare orchid. Arizona hires "cactus guards" to protect its desert saguaros. A West German tour company has sponsored collectors, trips to Mexico, during which entire hillsides are stripped bare of cacti.

Although the International Convention requires countries to monitor traffic in endangered plants, U.S. trade is virtually unregulated because the Agriculture Department has denied funding for port inspectors. More than 400,000 pounds of ginseng, considered an aphrodisiac in Oriental countries, left the U.S. in 1977. Only 4,000 pounds had legal permits, despite the fact the plant, which grows wild in Appalachia and is cultivated in the Midwest, has been severely depleted, according to the Natural Resources Defense Council.

It may be hard to work up a lather about ginseng. Or even about crocodiles. Elephants, rhinos, leopards, they have a certain romance about them - but cacti? That's the problem. We can get schoolchildren to write their congressmen to save the whales, but their mothers don't think twice about buying a Hawksbill tortoise shell hair comb. The road ahead seems to lead to more extinctions on the altar of consumerism. CAPTION: Picture 1, The worldwide, multimillion-dollar trade in animals has brought hundreds of species to the brink of extinction. Americans and Europeans want hunting trophies, such as this lion's head (left), photographed in a Nairobi taxidermy studio, as well as handbags, shoes and belts made from Amazonian caiman skins (above). Wolfgang Bayer/Bruce Coleman Inc.; Picture 2, Many species, such as mink, alligators, certain lizards, muskrats and some foxes (above) are plentiful enough that restrictions on their trading have not been necessary, but demand for wildlife products, especially in America and Europe, is decimating other species. D.J. Lyons/Bruce Coleman Inc.; Picture 3, The annual fur seal harvest in Alaska's Pribilof Islands (above) and in Canada's Newfoundland province have sparked protests by animal lovers worldwide.Although the seals are not in dnager of extinction, their death at the end of a club is typical of a wholesale global slaughter: in Rwanda native poachers sever the hands and heads of rare mountain gorillas for the tourist trade; in Peru the government is authorizing the slaughter of thousands of gentle vicuna for their precious wool Wolfgang Bayer/Bruce Coleman Inc.; Picture 4, in the western United States eagle killers who cash in on the feather trade are still being caught and prosecuted. Man's fertile commercial mind has invented thousands of "users" for wildlife: sea turtle eggs are eaten to endow virility; elephant feet can turn into coffee tables; leopard skin has been used to make steering wheel covers and, in Bangkok, a tiger skull was fashioned into an ashtray (right). C.D. Frith/Bruce Coleman Inc.; Picture 5, Arizona hires cactus guards to protect these rare desert saguaros from the multimillion-dollar plant market. Keith Gunnar/Bruce Coleman Inc.