Question: What government complex in Washington has more than 3,500 trees on 163 acres, a hospital, a staff of 325 persons tending to 3,000-plus patients and a weekly grocery list of 375 pounds of oranges, 1,200 pounds of fish, 2,100 crickets, 800 live mice and -- hint, hint -- 280 pounds of bamboo?

Answer: The National Zoological Park. Home of the giant pandas.

Yes, the star-crossed panda couple is the best-known and most popular attraction at the National Zoo, and it may seem at times as if Ling-Ling and Hsing-Hsing are its only claim to fame, especially during mating season. But Michael Robinson, the zoo's director, is more than willing to disabuse people of that notion.

"It's unfortunate that there's been so much concentration on those big black and white teddy bears," said Robinson, who is partial to otters and sea lions. "Being vegetarians, the pandas don't really do very much, just sit and eat bamboo and occasionally ham it up for the public."

For Robinson, who spent 18 years as a field biologist in South America and Africa before assuming the directorship three years ago, there is a lot more happening at the zoo than what goes on in the Panda House. He suggests checking out the red pandas, the bobcats and the baby rhinos as well as the giant octopus and the cuttlefish now on view at the zoo's new invertebrate exhibit.

"The North American bobcats are charming, but instead of going to look at their kittens, people go and stare at the pandas," Robinson said. "And the baby cuttlefish are amazing. Some people mistakenly call them cuddlefish -- a perfect description."

The National Zoo, part of the Smithsonian Institution, is unique among the country's nearly 200 zoos because it is federally funded, receiving about $12 million a year for animal care, research and property maintenance and another $5 million for capital improvements, according to Vince Doyle, the zoo's chief budget officer. Sales of gifts and food account for another $1 million.

Other major zoos have bigger budgets -- the Bronx Zoo, $20 million; the San Diego Zoo, $35 million. But other zoos charge admission.

At the San Diego Zoo, for example, adults pay $7.95 just to get in the gate. Admission to the National Zoo, much to the delight of its 3 million visitors each year, is free.

Feeding the animals and keeping track of their health, mating habits and other behavior is all-consuming. So, too, is shopping for them.

Consider, for instance, the elephant. According to one study, it eats in a year's time 1,600 loaves of bread, 5,000 assorted fruits and vegetables, 12,000 pounds of dried alfalfa and, of course, 100,000 pounds of hay. It also drinks 15,500 gallons of water.

Moses Benson, in charge of the zoo commissary, spends close to $500,000 a year on groceries. He buys his perishables -- fruits and vegetables -- twice a week from the Florida Avenue Market in Northeast Washington. He buys his dry bird feed quarterly on contract from Purina. He gets his crickets for the birds from a cricket farm in Virginia. And he buys his live mice, rats and baby chicks -- which are "euthanized" at the zoo and later fed to the reptiles -- from the federal government.

The zoo long ago scrapped feeding just plain horsemeat to its big cats. Now they get a commercially prepared mixture of beef, horsemeat, fish, eggs and vitamin and mineral supplements, which is cheaper and more nutritionally balanced.

By the same token, Benson buys 1,200 pounds of mixed frozen fish a week from a Baltimore supplier for the zoo's bears, seals and sea lions. Having squid, mackerel and pan trout on hand, he said, "gives the animal a choice."

The zoo will celebrate its centennial in 1989, much changed from the past and, according to Robinson, with a different mission for the future.

"We've gone from being consumers of wildlife to being producers of wildlife," said Robinson, noting that more than two-thirds of all the animals now on exhibit can be bred in zoos.

There is such a surplus of some animals, in fact, that there are birth control programs for certain species. Robinson reports that the zoo's California sea lions are "on the pill" (a contraceptive implant, actually) and that there is no longer any need to breed Bengal tigers or the ordinary African lion.

"When you've got a finite amount of space, you don't want to have a lot of babies around that you can't find homes for," he said.

But while the world has watched unsuccessful efforts to breed a surviving panda cub, the zoo has bred thousands of other babies, many of them "as important as the pandas for the future of the earth," Robinson said.

The red panda "is absolutely delightful, and we were one of the first zoos in the world to breed them," he said. "The Chinese have not matched that at all." Similarly, the zoo has welcomed the offspring of Sumatran tigers, an endangered species, and the golden lion tamarins, who move freely about the zoo's woodland in order to hone their survival skills for the wilds.

Also, the zoo recently produced the first test tube kittens, which Robinson calls an important step toward conservation of the whole cat family, including some facing extinction.

When zoos can't produce a particular breed for their collections, they turn to the "Animal Exchange," a shopping list of surplus and "wanted" animals. As of June, for example, the Columbus (Ohio) Zoo was in the market for a red kangaroo and trying to sell Thomson's gazelles, $3,750 a pair. The National Zoo was desperate for a North American porcupine and trying to unload some surplus black-tailed prairie dogs, $15 each.

But Robinson has another wish list for the future and a vision for the zoo of tomorrow.

"I think we're in a state now of a major change in our philosophy, and I hope that the National Zoo will lead the whole zoo community into a new phase of development," Robinson said.

What Robinson wants to see is a biological park that no longer separates animals from plants and terrestial animals from aquatic animals. Plants and animals, he said, should exist side by side just as they do in the real world. And the zoo should "show the glorious past that led up to the present," which could mean putting a dinosaur skeleton in the park.

The director also hopes to open a new exhibit by 1990, one that would recreate the aquatic life of the Amazon River region, complete with brightly colored freshwater fishes, aquatic reptiles, birds that swim under water and giant 60-pound otters that swim together in packs.

Such plans cost money, though. Robinson said he expects the zoo and other Smithsonian operations will look increasingly to the private sector to help fund "the enormous responsibility of preserving the natural and man-made treasures of this country and the world."

The director, who enjoys conducting VIP tours "because it gives me a chance to feed carrots to the elephants," said he is sure the zoo will have its share of supporters.

"We have a constituency here which doesn't give to anybody else: people who are hopelessly and inextricably entranced with plants and animals."