Quick -- what's the greatest threat to the golden lion tamarin?

You are playing a hot game of Tropical Pursuit at the National Zoo's Summerfest 1985 this weekend, and if you know the answer -- that man is destroying the tiny monkey's habitat -- you also know the theme of the two-day festival. It's a celebration of tropical forests, rich ecosystems that are threatened by farming, logging and capturing of animals for pets.

The free festival -- filled with music, movies and mime -- runs from 11 to 4 Saturday and Sunday in the upper part of the zoo near the Connecticut Avenue entrance. The game of Tropical Pursuit will be played all day both days outside the Education Building, while inside the building there will be continuous films on tropical forests and their residents. Just across from the Education Building, under the glckenspiel, children will be able to get their faces painted as tropical creatures and pose for photos in a cardboard cutout of a tropical forest. B.Y.O. camera.

Since elephants are the weightiest inhabitants of tropical forests, many of the activities will take place in or around the Elephant House. Inside, there will be continuous storytelling. Just outside will be a wire frame of an elephant that visitors can flesh out by sculpting with a bubble-gum-like clay, plus elephant training demonstrations at 11 and 2 both days in the Elephant Yard. Right next to the Elephant Yard, in the Giraffe Yard, there will be dance performances. The Baltimore Dance Theater, for example, will perform an elephant dance -- Saturday at 1 and 2 and Sunday at 2:30 -- with the real elephants looking on.

Many tropical birds are endangered, not only because their homes are being cut down but also because people hunt them for the pet trade. The Echo Mime Company will portray some of these endangered birds, with audience participation, in the Bird House each day from 11 to 1. A Bird House keeper will give a demonstration talk with a cockatoo each day at 1 and 3. Visitors will also be invited to help paint a tropical bird mural.

There will also be folk singers, musical groups, the Navy Band and -- the more serious side of the festival -- information about what can be done to help save tropical forests and the animals that live there.

"Tropical forests are the homes of the really attractive animals kids are going to be turned on by," says zoo director Michael Robinson, who has spent many happy years in tropical forests all over the world in search of spiders and insects. "When the forests are gone, there will be no homes for these animals."

To a limited extent, Robinson says, zoos have been able to serve as Noah's Arks for endangered animals. For example, the National Zoo, in collaboration with other groups, has successfully bred golden lion tamarins in captivity. And in 1984, 13 of the captive-bred creatures, known for their distinctive lion-like manes, were released in a forest preserve in Brazil, their natural habitat. The colony appears to be thriving and has so far produced three offspring in the wild.

"But in terms of sheer space, we can't save many animals in zoos," cautions Robinson. "In the last analysis, the only wave to save these animals is to save the forests."

You can start this weekend at the National Zoo Summerfest.

SAVORING SUMMERFEST -- Summerfest 1985 will take place from 11 to 4 Saturday and Sunday. In case of rain, some events will be moved indoors. Everything is free except parking, which costs $3. Parking lots fill up quickly, and visitors are encouraged to take Metro's Red Line to the Woodley Park-Zoo stop.