The Bronx Zoo's Congo Gorilla Forest accurately recreates habitat.

The Congo Gorilla Forest covers 6.5 acres in New York City.
One of New York City's most intriguing home improvement projects covers 6.5 acres in the Bronx Zoo. The Congo Gorilla Forest recreates a segment of a Central African rain forest in an exhibit that has become home to more than 300 animals of over 60 species.

Highlighted by North America's largest breeding populations of Western lowland gorillas, the new “Forest” also is home to mandrills, okapi and other African mammals, as well as a population of plants, amphibians, reptiles, fish, invertebrates and birds that co-habit the world's second largest rain forest in central and western Africa's Congo River basin.

The indoor-outdoor exhibit includes a 37,000-square-foot structure, which houses the animals at night and during the winter. Also housed within the structure, hidden from visitors, is a special teacher-training center. Classrooms overlook the outdoor Mandrill Forest, the indoor aviary and guenon exhibit, as well as the outside gorilla habitat.

Outdoors, up to 22 gorillas now find themselves in an extraordinary re-creation of their ancestral homelands. Key elements - including more than 20,000 plants representing 400 species - feature shady forests, treetop lookouts, rock promontories, bamboo thickets, sunny meadows, forested pathways, wading pools and thundering waterfalls.

Powering the waterfalls are six ITT Flygt 5-HP Model CS 3102 submersible pumps.

Key to Reality

What makes the new exhibit particularly special, and provides a much more accurate depiction of the gorilla's home environment, is the employment of technology that creates scaled-down natural phenomenon in an area that's otherwise devoid of them. With a bit of help from some modern pumps, and clever disguising by the Zoo's corps of expert exhibit designers and engineers, eight waterfalls within the $40 million exhibit flow whenever the exhibit is open (10 a.m. to 5 p.m. daily).

The waterfalls are much more than just decorative. They provide a natural people/animal barrier, particularly effective since gorillas don't swim well and generally don't like to be immersed in water.

Powering the waterfalls are six ITT Flygt 5 HP Model CS 3102 submersible pumps, which are designed to operate underwater. Since they are located out of any of the animals' reach, close encounters of the mechanical or electrical kind are eliminated.

The waterfalls are created by the pumps' 4-inch diameter discharge lines leading up and spilling into a common overflow tank at a high elevation. There, the water pours over the edge of a rock formation in sheets and begins cascading downward in torrents. Controlled by valves, water volume is kept very high in order to maintain the torrents of water that come crashing down. The runoff feeds streams and brooks, and all water then is gravity-fed back to the pump wells for recirculation.

The exhibit provides an extremely accurate depiction of the gorilla's natural home environment.

And Never the Twain …

In order to maintain a natural environment, steps had to be taken to assure that the animals and pumps do not meet. Two pumps are located under a bridge; one is in a grated enclosure in a streambed in the mandrill and red river hog habitat; and the other three are at the bottom of the moat into which the waterfalls crash.

Water used in the Congo exhibit waterfalls continually recycles. Upon leaving the exhibit, overflow water proceeds to other Zoo aquatic settings, passing through wildflower marshes that act as a bio-filtration system, and eventually wends into the Bronx River.

It took nearly eight years for the idea of moving the Zoo's two families of lowland gorillas into state-of-the-art quarters to proceed from inception to reality. Now, it is anticipated that more than a third of the Zoo's 2.1 million annual visitors will experience this re-created eco-system.

Conservation is Key

According to Lee Ehmke of the Bronx Zoo, “the exhibit's primary goal is to get people to understand and care about an eco-system that is many thousands of miles away from where they live. We need to get them interested in the preservation of the Central African rain forest and the animals that live there.” The best way to do this, Ehmke insists, is to create the most gripping and realistic portrayal of such habitats, a portrayal that is bounded only by concerns for the health and safety of both animals and observers.

Ehmke says, “It's the second largest rain forest in the world after the Amazon. But it is much less studied and much less known to the public. There is increasing pressure upon this natural habitat, pressure emanating from population growth as well as frequent political instability. Therefore, we need to raise interest levels among Zoo visitors - most of whom will never visit the actual territory we are showing - so that costly preservation efforts can be maintained and enhanced. The more realistic our exhibit appears, the more likely we will succeed with our goal.”

The Bronx Zoo attracts 2.1 million visitors annually.

Aiding Eyes and Ears

Part of that aesthetic mission falls to the exhibit's water elements. Not only do the waterfalls add visual authenticity, their sounds also squelch noise both from streets just a couple of hundred feet away, as well as airplanes flying overhead.

Ehmke also notes that the extensive irrigation system needed to maintain tropical plant replication also ties into a system that creates ground fog, simulating humidity in an actual rain forest. The exhibit's atmosphere also contributes toward making the gorillas and other animals feel more at home. That, Ehmke emphasizes, could lead to increased breeding. He explains, “Now, the gorillas have a much more interesting lifestyle than in the past, plus much greater opportunities for normal interaction. These are intelligent, social animals that respond positively to stimulus. This exhibit was designed with that need for stimulus in mind.”