The animal nursery at the San Diego Zoo is a marvel. Strolling past carpeted playrooms, you are suddenly confronted by the startling sight of a baby tiger snoozing on top of a teddy bear, a second glance necessary to make sure that the tiger isn't just another realistic toy.

On a high cabinet nearby, a television set broadcasts the afternoon news at low volume, as if this were an ordinary room in a human hospital and you were the patient's next of kin. In another room, baby orangutans and marmosets also cling to stuffed toys, with their names, birthdates and current diet entered on chalkboards above the big windows.

No modern American zoo has ever promoted itself more imaginatively. A pioneer in the use of television and touch-the-animal enclosures, the San Diego Zoological Society looks for new targets of opportunity -- more animals, more visitors, more money -- with eyes as keen as the California condors it is now helping to save.

The heart of the zoo remains its 100 acres of gardens, hills and cascading streams in Balboa Park, a few blocks from downtown. It began in 1916 with a few stray animals left by the promoters of a defunct international exposition.

Today, it receives 3 million visitors a year. They wander among the attractions near the main gate, such as the koalas and the Children's Zoo. Then they take buses down the steep hills into the canyons where other animals dwell in large open enclosures. Some hardy souls travel the whole park on foot, finding surprises at every turn in a jungle of South American, African and Asian species.

With the money coming in from careful management and inspired public relations, the zoo plans to reorganize its exhibits in the next 30 years, dividing the park into bioclimatic zones from tropical forest to tundra.

The society's new frontier is the Wild Animal Park, 30 miles north in the blown-dry San Pasqual Valley. In its sprawling 1,800-acre expanse, which opened in 1972, zoologists are studying the reproductive patterns of cheetahs, breeding endangered species like the white rhinoceros and lowland gorilla, and providing a hatchery for California condor eggs snatched from cliffs in the mountains northwest of Los Angeles. A 50-minute monorail ride takes visitors on a five-mile route through the park.

The society now has more than 125,000 members, making it the largest in the world. Its growth is a credit to sound finances, the enormous publicity from goodwill ambassador (and former animal attendant) Joan Embrey's frequent appearances with animals on "The Tonight Show" and the generosity of wealthy San Diegans like Ellen Browning Scripps.

The condors have added to the popular interest in the zoo, although they are kept in a special hillside enclosure out of sight and some distance away from daily visitors. A videotape within the Wild Animal Park shows condors hatching and growing into adulthood in spacious, fenced-off kennels.

Despite the Wild Animal Park's special attractions, however, its older, smaller sister downtown attracts twice as many visitors. The koalas are still there -- "They are koalas, not koala bears," our guide warned us -- perhaps the zoo's major attraction. (The Wild Animal Park now has them, too, but they have been a downtown attraction so long that the bond is fixed in the public mind.)

I chose to see most of the downtown zoo by bus. The hills appeared too much of a challenge for a man in a business suit wearing stiff leather shoes. It annoyed me that I could not get on and off the bus to explore interesting spots along the way. But we moved slowly enough during the hour-long trip to see and savor a great deal.

The driver's disc jockey patter was not as helpful as it might have been, but I noticed that many of the written descriptions of the animals displayed at each enclosure were also short. I concluded I would not have gotten much more information on foot, and the ride, after all, takes in 80 percent of the park.

Once off the bus, a visitor may, for an extra fee, stroll into the Children's Zoo near the main entrance -- the highlight of the visit even for a wide-eyed 40-year-old. The petting enclosure inside the Children's Zoo deftly combines elements of fear and high comedy. An assortment of sheep and goats look for an easy handout, but tolerate hardy pats and rough handling from budding zoologists.

And near the animal nursery, in an open-air pen in one corner, lives Marcus, an effervescent baby pigmy hippopotamus. Marcus, who resembles a 150-pound oblong medicine ball, was a mere 10 pounds the day of his birth, Super Bowl Sunday, Jan. 22, 1984. He was named after the Southern California running back who spent much of that day racing through the defensive line of the Washington Redskins.

Washingtonians may shudder at this unpleasant memory, but Marcus the pigmy hippo remains a charming creature. He favors some audiences with small grunts as he dips into his private pond. His attendant, Carole Gerard, said that one visitor could not resist presenting Marcus with a football last year, "but the only thing he found it was good for was as a head rest."

In another part of the Children's Zoo, the Animal Garden, a large sign asks "How high is an elephant's eye?" Visitors may measure themselves against life-size replicas of a giraffe, a kangaroo and even, for short people, an aardvark (one foot, 11 inches).

Adults looking for more complex delights need only stroll out of the Children's Zoo and nose about the exotic plants labeled along the walkways wherever one turns. This mid-city zoo boasts one of the best botanical collections in the world. And for the rest of us who are just here to look at cute or unusual animals, the good burghers of San Diego are doing their best to ensure we have our fill.

In an era when the Chinese giant panda reigns as the Michael Jackson of popular zoology, the San Diego Society has been treating the Chinese government (which controls the panda market) and its leading zookeepers with all the skill of a Confucian scholar in the Ming court. Favors are given, rites are observed, one's ambitions are kept well in the background until the moment is right.

San Diego has established a sister zoo relationship with Chengdu, capital of the southwest province where most of the world's surviving pandas still live. In the last five years it has sent to China 28 emus, 11 Amazon parrots, four spider monkeys, three orangutans, three hippopotamuses, four white rhinoceroses and six rattlesnakes. It has received several obscure Chinese animals, such as the Francois' leaf monkey and the dhole (a wild dog), with warm thanks and has been eager to show how well they are cared for in San Diego.

Now the zoo is entertaining a pair of Chinese golden monkeys with a high-profile blitz of advertising and press releases -- including notice that donations will be collected at the golden monkey exhibit "to rescue giant pandas faced with starvation." With a little luck, one or two of the grateful black and white creatures should be here before long, nuzzling Johnny Carson and keeping the zoo coffers full to pay for even more exotic acquisitions. CAPTION: Pictures 1 and 2, Guru at the Wild Animal Park, with the monorail in the background. Koales at the San Diego Zoo. Photos Copyright (c) San Diego Zoological Society.