Duisburg Zoo
Gorilla Bush

Peter Rasbach, Carlyn Worstell, Monika Fiby (authors)
Achim Winkler (editor for Duisburg Zoo)

Published 16 May 2003



Mülheimer Strasse 273
47058 Duisburg
Phone: +49 203 30559
URL: http://www.zoo-duisburg.de


barriers, enrichment, herbs, mixed species


Family:Species:Common Name:Capacity:
Cercopithecidae Cercopithecus neglectus De Brazza's Monkey
Pongidae Gorilla gorilla gorilla Western Lowland Gorilla 8


The ape house (Equatorium) of Zoo Duisburg was unique worldwide in 1962. Since its construction, Zoo Duisburg has kept lowland gorillas. Thanks to scientific findings on gorilla behavior, the requirements for keeping these primates have changed, and the building did not comply with the new standards over the years. Thus, in 2001 reconstruction of the old "Equatorium" started with a first upgrading phase. The outer walls of the original building were retained. With "Gorilla Bush" Zoo Duisburg again raised the bar for primate keeping.

Barriers of the outdoor enclosures include planted dry and water moats, timber poles placed vertically and tightly together to form a fence (which is accessible by the gorillas and, thus, hot-wired along the top), natural hard Devonian lime stone, artificial rock and electric fence on the inside of the barriers. An existing stand of trees was preserved and supplemented with oak trunks and interconnected ropes.

Indoor facilities include an exhibit for the gorillas, another one for DeBrazza's monkeys and - currently - three holding rooms for the gorillas. Future plans call for the De Brazza's monkeys to share the outdoor space with the gorillas.

The roof is made from multiple synthetic slabs which allows natural light cycles. Flooring is a quartz grit with a resin binder which prevents water penetration. Wall heating is controlled by a thermostat.



An indoor exhibit of 40 m² and 5 m height is available for the gorillas, a similar one for the DeBrazza's monkeys. Three more indoor spaces are connected to each other offering each animal 4 by 5 meters and 4 to 4.5 m height. An indoor exhibit of 40 m² and 5 m height is provided for the gorillas, another similar one for DeBrazza's monkeys. Three additional holding rooms are interconnected and provide each animal 4x5 m and 4 to 4.5 m height. The water moat occupies 189.74 m², so this area is not accessible to the gorillas.

Space allocation in square meters:

Use:Indoors:Outdoors:Total Exhibit:



Gorilla Bush is a donation of Sparkasse Duisburg.

EUR 1,073,713 including 22% for design.



28 May 2002


Beginning: June 2001


Beginning: January 2002

  • Artificial Rock Work: Atelier Artistique du Beton, Mormant, France
  • Project Management: GEBAG, Duisburg, Germany
  • Statics: Helmert & Schumacher Engineering Office, Duisburg, Germany


walter.gif This is a climatic diagram for the closest weather station.



A stand of American red oak, maple and ash were preserved on the site. The live trees are protected by hot-wire around the bottom which is placed 1-2 meters above ground. The following plants were introduced with initial landscaping: 700 bamboo plants, 200 berberis shrubs, 800 perennials and 700 m² of grass. It has been observed that gorillas break and eat the bamboo, but it thrives. The grass is never cut, but allowed to grow lush. There are plans to add wild strawberry vines to the exhibit, because they are fast-growing and will be of interest to the gorillas. Five grate-covered flower beds offer herbs for browsing (see features for animals).

The plant list specifies the Latin names of the plants used for this exhibit.


Dead oak trunks, up to 10 m high, were retained on the site (from exisiting oak trees) and connected with 240 m of Spleitex ropes. The trunks are expected to last 8 years minimum.

Two artificial caves with heated floors provide the gorillas with shelter from the weather. The two caves offer privacy for the animals when they prefer to get out of each others view.

Two artificial termite mounds are used by keepers for feeding-enrichment. They put honey, nuts, raisins, etc. inside for the gorillas to dig out with a stick. Five herb gardens of about 1.5 x 1.5 m and 20 cm deep are covered by a bolted-down metal grate, which prevents the gorillas from pulling the plants at the roots. As the plants grow up through the metal grates, the animals can pick at the new growth on top. The herb gardens were placed at a distance to the public, so as not to hinder the natural appearance of the exhibit by metal grates, but close enough to provide a good view of the gorillas.

The outdoor exhibit has a varying topography, with a hill in the center for viewing around. There are areas of both sun and shade at any given time of day. A netting is fixed under the water edge for security. In case a gorilla falls into the water it could hold onto the net to get out.

The indoor holding areas have a transparent ceiling, allowing natural light and day/night cycles. Some of the panels in the ceiling open to let in fresh air.



Each indoor animal space has at least two hydraulic doors. All of the doors are controlled by a hand-held, wireless remote control. There is a kitchen in a temporary building near the main building.

The mesh roofs of the indoor exhibit and holding rooms are accessible to keepers by a ladder, so they can place food on top of the cages and encourage climbing and manipulation of the food by the animals to get it into the cage.



Two blinds offer views in the Gorilla-Bush through 30 mm thick glass panels. In order to bring the animals to the visitors the floor in the hides is heated on the animal side.

Each view is prevented from cross-viewing by the other views by topography and planting.



Two signs with pictures of gorillas in the wild and in the zoo inform about the biology of these animals.



A technical equipment room houses the electrohydraulic control, central heating control, water and electricity supply control and a high-pressure cleaner. Heating of the building is partly via wall-heating.

The water in the moat is not circulated, however it is a great volume of water and stays rather clean. Because the water is not circulated, the moat is more prone to freezing. When it is frozen, the gorillas cannot go outside for fear of escape via the ice.

The indoor holding areas don't easily allow for two groups to be kept. While there are no intentions to hold two groups, the current collection involves individuals best kept separate.



A several month study by the British student, Sonya Warne, involved observations of the gorillas in their old and new exhibits. Results confirm first impressions that the gorillas displayed only reduced behaviors in their old enclosure and were clearly less active than in Gorilla Bush.



The Lowland gorillas at Duisburg Zoo are part of the European Endangered Species Program (EEP).





© Zoo Duisburg, 2000


Site Plan

Site Plan

© Rasbach, 2002


Western Lowland Gorilla

Western Lowland Gorilla

© Zoo Duisburg, 2002


Lookout on the Hill

1. Lookout on the Hill

© Rasbach, 2002


Approach to Gorilla Bush

2. Approach to Gorilla Bush

© Rasbach, 2002


View from Cave

3. View from Cave

© Monika Fiby, 2003


Glass Panel

4. Glass Panel

© Monika Fiby, 2003


Gorillas' Cave

5. Gorillas' Cave

© Carlyn Worstell, 2003



6. Barriers

© Rasbach, 2002


View from Path

7. View from Path

© Carlyn Worstell, 2003


Plants Prevent Cross-Viewing

8. Plants Prevent Cross-Viewing

© Carlyn Worstell, 2003


Timber Pole Fence

9. Timber Pole Fence

© Monika Fiby, 2003


Close-up View

10. Close-up View

© Monika Fiby, 2003


Oaks for Climbing

11. Oaks for Climbing

© Carlyn Worstell, 2003


Trees up to 10 Meters High

12. Trees up to 10 Meters High

© Monika Fiby, 2003


Hot-Wired Trees

13. Hot-Wired Trees

© Carlyn Worstell, 2003


Herb Garden

14. Herb Garden

© Carlyn Worstell, 2003


Second Cave

15. Second Cave

© Carlyn Worstell, 2003


View to Exhibit Over Lemur Island and Moat

16. View to Exhibit Over Lemur Island and Moat

© Carlyn Worstell, 2003


Educational Signage

17. Educational Signage

© Monika Fiby, 2003


Access Door

18. Access Door

© Carlyn Worstell, 2003


Holding Area

19. Holding Area

© Carlyn Worstell, 2003


Sectional View of Outdoor Enclosure

20. Sectional View of Outdoor Enclosure

© Rasbach, 2002