How does one sprout a lush rain forest with native jungle plant materials in a semi-arid ecosystem parched in its fifth year of drought? That's the water conservation challenge faced by Gorilla Tropics architects and horticulturists - to replicate the sights and sounds of an African rain forest, where plants receive 100 plus inches of rainfall annually, in the middle of the arid San Diego Zoo. The key to the success of the exhibit lies in the efforts to create the most authentic environment as possible.

"To save water in Gorilla Tropics we employed xeriscaping principles you might expect to see in a cactus garden," said Chuck Coburn, the zoo's horticulturist. "We designed a largely automated water system that delivers precise amounts of water exactly where we want it and when we want it."

Water conservation started with the design of the planting beds, built to retain moisture for the plants to use, thus minimizing waste. Micro-irrigation and drip irrigation systems direct water to target plant groups. The exhibit irrigates only at night to limit evaporation loss. Heavy mulching also helps hold water.

The refurbishing of the 68 year old Scripps Aviary included an overhaul of its water systems which will save 750,000 gallons each year. A converted jacuzzi pump collects water at the bottom of the cavernous walk through aviary and sends it back up 90 feet to the top of the exhibit.

Waterfalls in the gorilla enclosure use recycled water. Their rate of flow can be adjusted to limit evaporation loss on extremely hot days. Pools within the exhibit have independent valves and can be cleansed separately, without draining the entire system. The waterfalls are turned off at night.

"As our rain forest grows, it improves its own habitat - adding to its own mulch base, shading its own roots," Coburn states. "In significant ways the Gorilla Tropics plants will in-crease their own water efficiency."

A sign of the times and an advisory to today's water con-scious public is the series of water saving graphic panels posted throughout the zoo's new rain forest. The signs highlight Gorilla Tropics' moisture sensitive design elements.

Sound Immersion

An intricate system of 144 speakers hidden along the Gorilla Tropics walkways transmits a variety of rain forest sounds - insects, birds, wind, animals, rain and waterfalls - heard by animals and zoo visitors alike. Broad-cast fidelity comes from state of the art compact discs that were specially mixed and pro-duced for the Gorilla Tropics from a series of actual field recordings taken in African rain forests.

The sound immersion goes beyond the repetitive playing and replaying of a single recor-ded track. Installed at a cost of $200,000, the computer con-trolled sound system operates 20 compact disc players, allo-wing various tracks to be played in a completely random fashion throughout the day with sounds appropriate to the time of day. Additional vari-ety is achieved through timing devices and 24 strategically placed micro-wave sensors that are activated by the flight of birds or the motion of passing zoo visitors.

The system, designed by the Australian firm Sound Design, is operated by a personal com-puter, not unlike the popular PC systems found in an increasing number of households. The computer analyzes the information col-lected and instantly com-pensates by selectively boosting or lowering volume levels, area by area.

Gorillas Eat Their Environment

Bamboos, fig trees and banana plants inside the gorilla en-closure give the apes the option of eating their environment and nothing would make the zoo horticulturists happier. Thousands of replacement plants are ready in case the resident apes decide to dine on the green, leafy decor.

Gorilla Tropics visitor areas are heavily planted to immerse zoo goers in the layers of the rain forest canopy. In the Scripps Aviary and three other flight cages, a variety of trees and shrubs provide shelter, nesting material and food for some 75 species of colorful African Birds.

Each garden area is different by design, according to Coburn. This difference finds expression in plant selections made, in the ultimate mix of species, and in the strategic placement of the botanical elements. The tropical African plants used in the garden came from a variety of sources, including commercial growers, plant collectors, and botanic gardens in Africa and America, as well as collections made by field researchers in the wilds of Gabon, Rwanda, and the Central African Republic.

The attention to detail keeps visitors flocking back to the Gorilla Tropics. This attraction is a must see for those interested in our primate friends and state of the art exhibits. From a sound system that imitates the jungle to indigenous plant materials and efficient irrigation system, the San Diego Zoo remains on the cutting edge of zoo exhibition designs.LASN